Td corrigé Doc - the Population Approach Group in Europe pdf

Doc - the Population Approach Group in Europe

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PAGE 2013 Oral ProgramTuesday June 1115:00-18:30Registration18:30-19:30Welcome reception at the Old Fruitmarket located on Candleriggs in the Merchant City area, close to the city centre. Please see the map on  HYPERLINK "http://www.glasgowconcerthalls.com/maps" http://www.glasgowconcerthalls.com/maps Wednesday June 1208:00-08:45Registration08:45-09:00Welcome and introduction09:00-10:20Model-based approaches in benefit-risk assessment and decision makingchair: Oscar Della Pasqua 09:00-09:40Dyfrig HughesQuantitative benefit-risk analysis based on linked PKPD and health outcome modelling 09:40-10:00Jonathan FrenchCan methods based on existing models really aid decision making in non-small-cell lung cancer (NSCLC) trials?10:00-10:20Jonas Bech Møller Optimizing clinical diabetes drug development – what is the recipe? 10:20-11:45Coffee break, poster and software session I HYPERLINK "http://www.page-meeting.org/default.asp?keuze=abstracts&id=37&t=programItem&m=Posters%20I:%20Wednesday%20morning" Posters in Group I (with poster numbers starting with I-) are accompanied by their presenter11:45-12:25Animal health (I)chairs: Alison Thomson & Jonathan Mochel 11:45-12:25Jim RiviereFood safety: the intersection of pharmacometrics and veterinary medicine12:25-13:50Lunch13:50-14:50Animal health (II)chairs: Alison Thomson & Jonathan Mochel 13:50-14:20George Gettinby Two models for the control of sea lice infections using chemical treatments and biological control on farmed salmon populations14:20-14:50Daniel HaydonFrom epidemic to elimination: density-vague transmission and the design of mass dog vaccination programs14:50-16:20Tea break, poster and software session II HYPERLINK "http://www.page-meeting.org/default.asp?keuze=abstracts&id=37&t=programItem&m=Posters%20II:%20Wednesday%20afternoon" Posters in Group II (with poster numbers starting with II-) are accompanied by their presenter16:20-17:40Modelling and evaluation methods with (potential) application to infectious diseaseschair: Leon Aarons16:20-16:40Wojciech KrzyzanskiPhysiologically structured population model of intracellular hepatitis C virus dynamics
16:40-17:00Martin BergstrandModeling of the concentration-effect relationship for piperaquine in preventive treatment of malaria 17:00-17:20Matt HutmacherA Visual Predictive Check for the evaluation of the hazard function in time-to-event analyses 17:20-17:40Celine LaffontNon-inferiority clinical trials: a multivariate test for multivariate PD  Thursday June 1308:45-10:05Lewis Sheiner student sessionchairs: Lena Friberg, Philippe Jacqmin & Leon Aarons 08:45-09:10Abhishek Gulati Simplification of a multi-scale systems coagulation model with an application to modelling PKPD data 09:10-09:35Nelleke Snelder Mechanism-based PKPD modeling of cardiovascular effects in conscious rats - an application to fingolimod 09:35-10:00Nadia TerranovaMathematical models of tumor growth inhibition in xenograft mice after administration of anticancer agents given in combination 10:00-10:05Presentation of awards10:05-11:35Coffee break, poster and software session III HYPERLINK "http://www.page-meeting.org/default.asp?keuze=abstracts&id=37&t=programItem&m=Posters%20III:%20Thursday%20morning" Posters in Group III (with poster numbers starting with III-) are accompanied by their presenter11:35-12:35Mechanistic modellingchair: Nick Holford 11:35-11:55James LuApplication of a mechanistic, systems model of lipoprotein metabolism and kinetics to target selection and biomarker identification in the reverse cholesterol transport (RCT) pathway11:55-12:15Rollo HoareA novel mechanistic model for CD4 lymphocyte reconstitution following paediatric haematopoietic stem cell transplantation 12:15-12:35Huub Jan KleijnUtilization of tracer kinetic data in endogenous pathway modeling: example from Alzheimer’s disease12:35-14:05Lunch14:05-14:55Reproducibility and translationchair: Katya Gibiansky 14:05-14:35Niclas Jonsson and Justin WilkinsTutorial: Reproducible pharmacometrics 14:35-14:55Nick Holford (on behalf of DDMoRe) MDL - The DDMoRe modelling description language 14:55-16:20Tea break, poster and software session IV HYPERLINK "http://www.page-meeting.org/default.asp?keuze=abstracts&id=37&t=programItem&m=Posters%20IV:%20Thursday%20afternoon" Posters in Group IV (with poster numbers starting with IV-) are accompanied by their presenter16:20-17:20New methods for population analysischair: France Mentré 16:20-16:40Vittal Shivva Identifiability of population pharmacokinetic-pharmacodynamic models 16:40-17:00Leonid Gibiansky Methods to detect non-compliance and minimize its impact on population PK parameter estimates 17:00-17:20Julie BertrandPenalized regression implementation within the SAEM algorithm to advance high-throughput personalized drug therapy Social evening Friday June 1409:00-10:00Development and application of models in oncologychair: Marylore Chenel09:00-09:20Shelby WilsonModeling the synergism between the anti-angiogenic drug sunitinib and irinotecan in xenografted mice09:20-09:40Amy CheungUsing a model based approach to inform dose escalation in a Ph I Study by combining emerging clinical and prior preclinical information: an example in oncology09:40-10:00Sonya TateTumour growth inhibition modelling and prediction of overall survival in patients with metastatic breast cancer treated with paclitaxel alone or in combination with gemcitabine10:00-10:10Preview of PAGE 201410:10-10:50Coffee break10:50-12:10Stuart Beal methodology sessionchair: Steve Duffull 10:50-11:10Chuanpu HuLatent variable indirect response modeling of continuous and categorical clinical endpoints11:10-11:30Anne-Gaelle DosneApplication of Sampling Importance Resampling to estimate parameter uncertainty distributions11:30-11:50Hoai Thu ThaiBootstrap methods for estimating uncertainty of parameters in mixed-effects models11:50-12:10Celia BarthelemyNew methods for complex models defined by a large number of ODEs: application to a glucose/insulin model 12:10-12:20Closing remarks12:20-12:40Audience input for the PAGE 2014 program

PAGE2013 Abstracts

 TOC \o "1-3" \h \z \u  HYPERLINK \l "_Toc358384867" Oral presentations Wednesday  PAGEREF _Toc358384867 \h 15
 HYPERLINK \l "_Toc358384868" Dyfrig Hughes A-05 Quantitative benefit-risk analysis based on linked PKPD and health outcome modelling  PAGEREF _Toc358384868 \h 15
 HYPERLINK \l "_Toc358384869" Jonathan French A-06 Can methods based on existing models really aid decision making in non-small-cell lung cancer (NSCLC) trials?  PAGEREF _Toc358384869 \h 16
 HYPERLINK \l "_Toc358384870" Jonas Bech Møller A-07 Optimizing clinical diabetes drug development – what is the recipe?  PAGEREF _Toc358384870 \h 18
 HYPERLINK \l "_Toc358384871" Jim Riviere A-09 Food safety: the intersection of pharmacometrics and veterinary medicine  PAGEREF _Toc358384871 \h 20
 HYPERLINK \l "_Toc358384872" George Gettinby A-11 Two models for the control of sea lice infections using chemical treatments and biological control on farmed salmon populations  PAGEREF _Toc358384872 \h 22
 HYPERLINK \l "_Toc358384873" Dan Haydon A-12 From Epidemic to Elimination: Density-Vague Transmission and the Design of Mass Dog Vaccination Programs  PAGEREF _Toc358384873 \h 24
 HYPERLINK \l "_Toc358384874" Wojciech Krzyzanski A-14 Physiologically Structured Population Model of Intracellular Hepatitis C Virus Dynamics  PAGEREF _Toc358384874 \h 25
 HYPERLINK \l "_Toc358384875" Martin Bergstrand A-15 Modeling of the concentration-effect relationship for piperaquine in preventive treatment of malaria  PAGEREF _Toc358384875 \h 27
 HYPERLINK \l "_Toc358384876" Matt Hutmacher A-16 A Visual Predictive Check for the Evaluation of the Hazard Function in Time-to-Event Analyses  PAGEREF _Toc358384876 \h 29
 HYPERLINK \l "_Toc358384877" Celine M. Laffont A-17 Non-inferiority clinical trials: a multivariate test for multivariate PD  PAGEREF _Toc358384877 \h 30
 HYPERLINK \l "_Toc358384878" Oral presentations Thursday  PAGEREF _Toc358384878 \h 31
 HYPERLINK \l "_Toc358384879" Abhishek Gulati A-18 Simplification of a multi-scale systems coagulation model with an application to modelling PKPD data  PAGEREF _Toc358384879 \h 31
 HYPERLINK \l "_Toc358384880" Nelleke Snelder A-19 Mechanism-based PKPD modeling of cardiovascular effects in conscious rats - an application to fingolimod  PAGEREF _Toc358384880 \h 34
 HYPERLINK \l "_Toc358384881" Nadia Terranova A-20 Mathematical models of tumor growth inhibition in xenograft mice after administration of anticancer agents given in combination  PAGEREF _Toc358384881 \h 36
 HYPERLINK \l "_Toc358384882" James Lu A-23 Application of a mechanistic, systems model of lipoprotein metabolism and kinetics to target selection and biomarker identification in the reverse cholesterol transport (RCT) pathway  PAGEREF _Toc358384882 \h 38
 HYPERLINK \l "_Toc358384883" Rollo Hoare A-24 A Novel Mechanistic Model for CD4 Lymphocyte Reconstitution Following Paediatric Haematopoietic Stem Cell Transplantation  PAGEREF _Toc358384883 \h 40
 HYPERLINK \l "_Toc358384884" Huub Jan Kleijn A-25 Utilization of Tracer Kinetic Data in Endogenous Pathway Modeling: Example from Alzheimer’s Disease  PAGEREF _Toc358384884 \h 41
 HYPERLINK \l "_Toc358384885" Justin Wilkins A-27 Reproducible pharmacometrics  PAGEREF _Toc358384885 \h 42
 HYPERLINK \l "_Toc358384886" Nick Holford A-28 MDL - The DDMoRe Modelling Description Language  PAGEREF _Toc358384886 \h 43
 HYPERLINK \l "_Toc358384887" Vittal Shivva A-30 Identifiability of Population Pharmacokinetic-Pharmacodynamic Models  PAGEREF _Toc358384887 \h 44
 HYPERLINK \l "_Toc358384888" Leonid Gibiansky A-31 Methods to Detect Non-Compliance and Minimize its Impact on Population PK Parameter Estimates  PAGEREF _Toc358384888 \h 45
 HYPERLINK \l "_Toc358384889" Julie Bertrand A-32 Penalized regression implementation within the SAEM algorithm to advance high-throughput personalized drug therapy  PAGEREF _Toc358384889 \h 46
 HYPERLINK \l "_Toc358384890" Oral presentations Friday  PAGEREF _Toc358384890 \h 47
 HYPERLINK \l "_Toc358384891" Shelby Wilson A-34 Modeling the synergism between the anti-angiogenic drug sunitinib and irinotecan in xenografted mice  PAGEREF _Toc358384891 \h 47
 HYPERLINK \l "_Toc358384892" S. Y. Amy Cheung A-35 Using a model based approach to inform dose escalation in a Ph I Study by combining emerging clinical and prior preclinical information: an example in oncology  PAGEREF _Toc358384892 \h 48
 HYPERLINK \l "_Toc358384893" Sonya Tate A-36 Tumour growth inhibition modelling and prediction of overall survival in patients with metastatic breast cancer treated with paclitaxel alone or in combination with gemcitabine  PAGEREF _Toc358384893 \h 49
 HYPERLINK \l "_Toc358384894" Chuanpu Hu A-39 Latent variable indirect response modeling of continuous and categorical clinical endpoints  PAGEREF _Toc358384894 \h 50
 HYPERLINK \l "_Toc358384895" Anne-Gaelle Dosne A-40 Application of Sampling Importance Resampling to estimate parameter uncertainty distributions  PAGEREF _Toc358384895 \h 51
 HYPERLINK \l "_Toc358384896" Hoai Thu Thai A-41 Bootstrap methods for estimating uncertainty of parameters in mixed-effects models  PAGEREF _Toc358384896 \h 52
 HYPERLINK \l "_Toc358384897" Celia Barthelemy A-42 New methods for complex models defined by a large number of ODEs. Application to a Glucose/Insulin model  PAGEREF _Toc358384897 \h 54
 HYPERLINK \l "_Toc358384898" Poster session I: Wednesday morning 10:05-11:40  PAGEREF _Toc358384898 \h 55
 HYPERLINK \l "_Toc358384899" Andrijana Radivojevic I-01 Enhancing population PK modeling efficiency using an integrated workflow  PAGEREF _Toc358384899 \h 55
 HYPERLINK \l "_Toc358384900" Gauri Rao I-02 A Proposed Adaptive Feedback Control (AFC) Algorithm for Linezolid (L) based on Population Pharmacokinetics (PK)/Pharmacodynamics (PD)/Toxicodynamics(TD)  PAGEREF _Toc358384900 \h 56
 HYPERLINK \l "_Toc358384901" Sylvie Retout I-03 A drug development tool for trial simulation in prodromal Alzheimer’s patient using the Clinical Dementia Rating scale Sum of Boxes score (CDR-SOB).  PAGEREF _Toc358384901 \h 57
 HYPERLINK \l "_Toc358384902" Philippe Jacqmin I-04 Constructing the disease trajectory of CDR-SOB in Alzheimer’s disease progression modelling  PAGEREF _Toc358384902 \h 58
 HYPERLINK \l "_Toc358384903" Rachel Rose I-05 Application of a Physiologically Based Pharmacokinetic/Pharmacodynamic (PBPK/PD) Model to Investigate the Effect of OATP1B1 Genotypes on the Cholesterol Synthesis Inhibitory Effect of Rosuvastatin  PAGEREF _Toc358384903 \h 59
 HYPERLINK \l "_Toc358384904" Elisabeth Rouits I-06 Population pharmacokinetic model for Debio 1143, a novel antagonist of IAPs in cancer treatment  PAGEREF _Toc358384904 \h 60
 HYPERLINK \l "_Toc358384905" Alberto Russu I-07 Second-order indirect response modelling of complex biomarker dynamics  PAGEREF _Toc358384905 \h 61
 HYPERLINK \l "_Toc358384906" Teijo Saari I-08 Pharmacokinetics of free hydromorphone concentrations in patients after cardiac surgery  PAGEREF _Toc358384906 \h 63
 HYPERLINK \l "_Toc358384907" Tarjinder Sahota I-09 Real data comparisons of NONMEM 7.2 estimation methods with parallel processing on target-mediated drug disposition models  PAGEREF _Toc358384907 \h 64
 HYPERLINK \l "_Toc358384908" Maria Luisa Sardu I-10 Tumour Growth Inhibition In Preclinical Animal Studies: Steady-State Analysis Of Biomarker-Driven Models.  PAGEREF _Toc358384908 \h 65
 HYPERLINK \l "_Toc358384909" Emilie Schindler I-11 PKPD-Modeling of VEGF, sVEGFR-1, sVEGFR-2, sVEGFR-3 and tumor size following axitinib treatment in metastatic renal cell carcinoma (mRCC) patients  PAGEREF _Toc358384909 \h 66
 HYPERLINK \l "_Toc358384910" Alessandro Schipani I-12 Population pharmacokinetic of rifampicine in Malawian children.  PAGEREF _Toc358384910 \h 67
 HYPERLINK \l "_Toc358384911" Henning Schmidt I-13 The “SBPOP Package”: Efficient Support for Model Based Drug Development – From Mechanistic Models to Complex Trial Simulation  PAGEREF _Toc358384911 \h 68
 HYPERLINK \l "_Toc358384912" Stephan Schmidt I-14 Mechanistic Prediction of Acetaminophen Metabolism and Pharmacokinetics in Children using a Physiologically-Based Pharmacokinetic (PBPK) Modeling Approach  PAGEREF _Toc358384912 \h 69
 HYPERLINK \l "_Toc358384913" Rik Schoemaker I-15 Scaling brivaracetam pharmacokinetic parameters from adult to pediatric epilepsy patients  PAGEREF _Toc358384913 \h 71
 HYPERLINK \l "_Toc358384914" Yoon Seonghae I-16 Population pharmacokinetic analysis of two different formulations of tacrolimus in stable pediatric kidney transplant recipients  PAGEREF _Toc358384914 \h 72
 HYPERLINK \l "_Toc358384915" Catherine Sherwin I-17 Dense Data - Methods to Handle Massive Data Sets without Compromise  PAGEREF _Toc358384915 \h 73
 HYPERLINK \l "_Toc358384916" Giovanni Smania I-18 Identifying the translational gap in the evaluation of drug-induced QTc interval prolongation  PAGEREF _Toc358384916 \h 74
 HYPERLINK \l "_Toc358384917" Alexander Solms I-19 Translating physiologically based Parameterization and Inter-Individual Variability into the Analysis of Population Pharmacokinetics  PAGEREF _Toc358384917 \h 75
 HYPERLINK \l "_Toc358384918" Hankil Son I-20 A conditional repeated time-to-event analysis of onset and retention times of sildenafil erectile response  PAGEREF _Toc358384918 \h 77
 HYPERLINK \l "_Toc358384919" Heiner Speth I-21 Referenced Visual Predictive Check (rVPC)  PAGEREF _Toc358384919 \h 78
 HYPERLINK \l "_Toc358384920" Michael Spigarelli I-22 Title: Rapid Repeat Dosing of Zolpidem - Apparent Kinetic Change Between Doses  PAGEREF _Toc358384920 \h 79
 HYPERLINK \l "_Toc358384921" Christine Staatz I-23 Dosage individulisation of tacroliums in adult kidney transplant recipients  PAGEREF _Toc358384921 \h 80
 HYPERLINK \l "_Toc358384922" Gabriel Stillemans I-24 A generic population pharmacokinetic model for tacrolimus in pediatric and adult kidney and liver allograft recipients  PAGEREF _Toc358384922 \h 81
 HYPERLINK \l "_Toc358384923" Elisabet Størset I-25 Predicting tacrolimus doses early after kidney transplantation - superiority of theory based models  PAGEREF _Toc358384923 \h 82
 HYPERLINK \l "_Toc358384924" Fran Stringer I-26 A Semi-Mechanistic Modeling approach to support Phase III dose selection for TAK-875 Integrating Glucose and HbA1c Data in Japanese Type 2 Diabetes Patients  PAGEREF _Toc358384924 \h 83
 HYPERLINK \l "_Toc358384925" Eric Strömberg I-27 FIM approximation, spreading of optimal sampling times and their effect on parameter bias and precision.  PAGEREF _Toc358384925 \h 84
 HYPERLINK \l "_Toc358384926" Herbert Struemper I-28 Population pharmacokinetics of belimumab in systemic lupus erythematosus: insights for monoclonal antibody covariate modeling from a large data set  PAGEREF _Toc358384926 \h 86
 HYPERLINK \l "_Toc358384927" Elin Svensson I-29 Individualization of fixed-dose combination (FDC) regimens - methodology and application to pediatric tuberculosis  PAGEREF _Toc358384927 \h 87
 HYPERLINK \l "_Toc358384928" Eva Sverrisdóttir I-30 Modelling analgesia-concentration relationships for morphine in an experimental pain setting  PAGEREF _Toc358384928 \h 89
 HYPERLINK \l "_Toc358384929" Maciej Swat I-31 PharmML – An Exchange Standard for Models in Pharmacometrics  PAGEREF _Toc358384929 \h 90
 HYPERLINK \l "_Toc358384930" Amit Taneja I-32 From Behaviour to Target: Evaluating the putative correlation between clinical pain scales and biomarkers.  PAGEREF _Toc358384930 \h 91
 HYPERLINK \l "_Toc358384931" Joel Tarning I-33 The population pharmacokinetic and pharmacodynamic properties of intramuscular artesunate and quinine in Tanzanian children with severe falciparum malaria; implications for a practical dosing regimen.  PAGEREF _Toc358384931 \h 92
 HYPERLINK \l "_Toc358384932" David Ternant I-34 Adalimumab pharmacokinetics and concentration-effect relationship in rheumatoid arthritis  PAGEREF _Toc358384932 \h 94
 HYPERLINK \l "_Toc358384933" Adrien Tessier I-35 High-throughput genetic screening and pharmacokinetic population modeling in drug development  PAGEREF _Toc358384933 \h 95
 HYPERLINK \l "_Toc358384934" Iñaki F. Trocóniz I-36 Modelling and simulation applied to personalised medicine  PAGEREF _Toc358384934 \h 96
 HYPERLINK \l "_Toc358384935" Nikolaos Tsamandouras I-37 A mechanistic population pharmacokinetic model for simvastatin and its active metabolite simvastatin acid  PAGEREF _Toc358384935 \h 97
 HYPERLINK \l "_Toc358384936" Sebastian Ueckert I-38 AD i.d.e.a. – Alzheimer’s Disease integrated dynamic electronic assessment of Cognition  PAGEREF _Toc358384936 \h 99
 HYPERLINK \l "_Toc358384937" Wanchana Ungphakorn I-39 Development of a Physiologically Based Pharmacokinetic Model for Children with Severe Malnutrition  PAGEREF _Toc358384937 \h 101
 HYPERLINK \l "_Toc358384938" Elodie Valade I-40 Population Pharmacokinetics of Emtricitabine in HIV-1-infected Patients  PAGEREF _Toc358384938 \h 102
 HYPERLINK \l "_Toc358384939" Georgia Valsami I-41 Population exchangeability in Bayesian dose individualization of oral Busulfan  PAGEREF _Toc358384939 \h 103
 HYPERLINK \l "_Toc358384940" Sven van Dijkman I-42 Predicting antiepileptic drug concentrations for combination therapy in children with epilepsy.  PAGEREF _Toc358384940 \h 104
 HYPERLINK \l "_Toc358384941" Coen van Hasselt I-43 Design and analysis of studies investigating the pharmacokinetics of anti-cancer agents during pregnancy  PAGEREF _Toc358384941 \h 106
 HYPERLINK \l "_Toc358384942" Anne van Rongen I-44 Population pharmacokinetic model characterising the influence of circadian rhythm on the pharmacokinetics of oral and intravenous midazolam in healthy volunteers  PAGEREF _Toc358384942 \h 107
 HYPERLINK \l "_Toc358384943" Marc Vandemeulebroecke I-45 Literature databases: integrating information on diseases and their treatments.  PAGEREF _Toc358384943 \h 108
 HYPERLINK \l "_Toc358384944" Nieves Velez de Mendizabal I-46 A Population PK Model For Citalopram And Its Major Metabolite, N-desmethyl Citalopram, In Rats  PAGEREF _Toc358384944 \h 109
 HYPERLINK \l "_Toc358384945" An Vermeulen I-47 Population Pharmacokinetic Analysis of Canagliflozin, an Orally Active Inhibitor of Sodium-Glucose Co-Transporter 2 (SGLT2) for the Treatment of Patients With Type 2 Diabetes Mellitus (T2DM)  PAGEREF _Toc358384945 \h 110
 HYPERLINK \l "_Toc358384946" Marie Vigan I-48 Modelling the evolution of two biomarkers in Gaucher patients receiving enzyme replacement therapy.  PAGEREF _Toc358384946 \h 111
 HYPERLINK \l "_Toc358384947" Paul Vigneaux I-49 Extending Monolix to use models with Partial Differential Equations  PAGEREF _Toc358384947 \h 112
 HYPERLINK \l "_Toc358384948" Winnie Vogt I-50 Paediatric PBPK drug-disease modelling and simulation towards optimisation of drug therapy: an example of milrinone for the treatment and prevention of low cardiac output syndrome in paediatric patients after open heart surgery  PAGEREF _Toc358384948 \h 113
 HYPERLINK \l "_Toc358384949" Max von Kleist I-51 Systems Pharmacology of Chain-Terminating Nucleoside Analogs  PAGEREF _Toc358384949 \h 116
 HYPERLINK \l "_Toc358384950" Camille Vong I-52 Semi-mechanistic PKPD model of thrombocytopenia characterizing the effect of a new histone deacetylase inhibitor (HDACi) in development, in co-administration with doxorubicin.  PAGEREF _Toc358384950 \h 117
 HYPERLINK \l "_Toc358384951" Katarina Vu
ievi I-53 Total plasma protein and haematocrit influence on tacrolimus clearance in kidney transplant patients - population pharmacokinetic approach  PAGEREF _Toc358384951 \h 119
 HYPERLINK \l "_Toc358384952" Bing Wang I-54 Population pharmacokinetics and pharmacodynamics of benralizumab in healthy volunteers and asthma patients  PAGEREF _Toc358384952 \h 120
 HYPERLINK \l "_Toc358384953" Jixian Wang I-55 Design and analysis of randomized concentration controlled  PAGEREF _Toc358384953 \h 121
 HYPERLINK \l "_Toc358384954" Franziska Weber I-56 A linear mixed effect model describing the expression of peroxisomal ABCD transporters in CD34+ stem cell-derived immune cells of X-linked Adrenoleukodystrophy and control populations  PAGEREF _Toc358384954 \h 122
 HYPERLINK \l "_Toc358384955" Sebastian Weber I-57 Nephrotoxicity of tacrolimus in liver transplantation  PAGEREF _Toc358384955 \h 123
 HYPERLINK \l "_Toc358384956" Mélanie Wilbaux I-58 A drug-independent model predicting Progression-Free Survival to support early drug development in recurrent ovarian cancer  PAGEREF _Toc358384956 \h 124
 HYPERLINK \l "_Toc358384957" Dan Wright I-59 Bayesian dose individualisation provides good control of warfarin dosing.  PAGEREF _Toc358384957 \h 125
 HYPERLINK \l "_Toc358384958" Klintean Wunnapuk I-60 Population analysis of paraquat toxicokinetics in poisoning patients  PAGEREF _Toc358384958 \h 126
 HYPERLINK \l "_Toc358384959" Rujia Xie I-61 Population PK-QT analysis across Phase I studies for a p38 mitogen activated protein kinase inhibitor – PH-797804  PAGEREF _Toc358384959 \h 127
 HYPERLINK \l "_Toc358384960" Shuying Yang I-62 First-order longitudinal population model of FEV1 data: single-trial modeling and meta-analysis  PAGEREF _Toc358384960 \h 128
 HYPERLINK \l "_Toc358384961" Jiansong Yang I-63 Practical diagnostic plots in aiding model selection among the general model for target-mediated drug disposition (TMDD) and its approximations  PAGEREF _Toc358384961 \h 129
 HYPERLINK \l "_Toc358384962" Rui Zhu I-64 Population-Based Efficacy Modeling of Omalizumab in Patients with Severe Allergic Asthma Inadequately Controlled with Standard Therapy  PAGEREF _Toc358384962 \h 130
 HYPERLINK \l "_Toc358384963" Poster session II: Wednesday afternoon 14:50-16:20  PAGEREF _Toc358384963 \h 132
 HYPERLINK \l "_Toc358384964" Thomas Dorlo II-01 Miltefosine treatment failure in visceral leishmaniasis in Nepal is associated with low drug exposure  PAGEREF _Toc358384964 \h 132
 HYPERLINK \l "_Toc358384965" Anne Dubois II-02 Using Optimal Design Methods to Help the Design of a Paediatric Pharmacokinetic Study  PAGEREF _Toc358384965 \h 133
 HYPERLINK \l "_Toc358384966" Cyrielle Dumont II-03 Influence of the ratio of the sample sizes between the two stages of an adaptive design: application for a population pharmacokinetic study in children  PAGEREF _Toc358384966 \h 134
 HYPERLINK \l "_Toc358384967" Thomas Dumortier II-04 Using a model-based approach to address FDA’s midcycle review concerns by demonstrating the contribution of everolimus to the efficacy of its combination with low exposure tacrolimus in liver transplantation  PAGEREF _Toc358384967 \h 136
 HYPERLINK \l "_Toc358384968" Mike Dunlavey II-05 Support in PML for Absorption Time Lag via Transit Compartments  PAGEREF _Toc358384968 \h 137
 HYPERLINK \l "_Toc358384969" Charles Ernest II-06 Optimal design of a dichotomous Markov-chain mixed-effect sleep model  PAGEREF _Toc358384969 \h 138
 HYPERLINK \l "_Toc358384970" Christine Falcoz II-07 PKPD Modeling of Imeglimin Phase IIa Monotherapy Studies in Type 2 Diabetes Mellitus (T2DM)  PAGEREF _Toc358384970 \h 139
 HYPERLINK \l "_Toc358384971" Floris Fauchet II-08 Population pharmacokinetics of Zidovudine and its metabolite in HIV-1 infected children: Evaluation doses recommended  PAGEREF _Toc358384971 \h 140
 HYPERLINK \l "_Toc358384972" Eric Fernandez II-09 drugCARD: a database of anti-cancer treatment regimens and drug combinations  PAGEREF _Toc358384972 \h 142
 HYPERLINK \l "_Toc358384973" Martin Fink II-10 Animal Health Modeling & Simulation Society (AHM&S): A new society promoting model-based approaches for a better integration and understanding of quantitative pharmacology in Veterinary Sciences  PAGEREF _Toc358384973 \h 143
 HYPERLINK \l "_Toc358384974" Sylvain Fouliard II-11 Semi-mechanistic population PKPD modelling of a surrogate biomarker  PAGEREF _Toc358384974 \h 145
 HYPERLINK \l "_Toc358384975" Nicolas Frances II-12 A semi-physiologic mathematical model describing pharmacokinetic profile of an IgG monoclonal antibody mAbX after IV and SC administration in human FcRn transgenic mice.  PAGEREF _Toc358384975 \h 146
 HYPERLINK \l "_Toc358384976" Chris Franklin II-13 : Introducing DDMoRe’s framework within an existing enterprise modelling and simulation environment.  PAGEREF _Toc358384976 \h 148
 HYPERLINK \l "_Toc358384977" Ludivine Fronton II-14 A Novel PBPK Approach for mAbs and its Implications in the Interpretation of Classical Compartment Models  PAGEREF _Toc358384977 \h 149
 HYPERLINK \l "_Toc358384978" Aline Fuchs II-15 Population pharmacokinetic study of gentamicin: a retrospective analysis in a large cohort of neonate patients  PAGEREF _Toc358384978 \h 151
 HYPERLINK \l "_Toc358384979" Aurelie Gautier II-16 Pharmacokinetics of Canakinumab and pharmacodynamics of IL-1² binding in cryopyrin associated periodic fever, a step towards personalized medicine  PAGEREF _Toc358384979 \h 152
 HYPERLINK \l "_Toc358384980" Ronette Gehring II-17 A dynamically integrative PKPD model to predict the efficacy of marbofloxacin treatment regimens for bovine Mannheimia hemolytica infection  PAGEREF _Toc358384980 \h 153
 HYPERLINK \l "_Toc358384981" Peter Gennemark II-18 Incorporating model structure uncertainty in model-based drug discovery  PAGEREF _Toc358384981 \h 154
 HYPERLINK \l "_Toc358384982" Eva Germovsek II-19 Age-Corrected Creatinine is a Significant Covariate for Gentamicin Clearance in Neonates  PAGEREF _Toc358384982 \h 155
 HYPERLINK \l "_Toc358384983" TJ Carrothers II-20 Comparison of Analysis Methods for Population Exposure-Response in Thorough QT Studies  PAGEREF _Toc358384983 \h 156
 HYPERLINK \l "_Toc358384984" Parviz Ghahramani II-21 Population PKPD Modeling of Milnacipran Effect on Blood Pressure and Heart Rate Over 24-Hour Period Using Ambulatory Blood Pressure Monitoring in Normotensive and Hypertensive Patients With Fibromyalgia  PAGEREF _Toc358384984 \h 157
 HYPERLINK \l "_Toc358384985" Ekaterina Gibiansky II-22 Immunogenicity in PK of Monoclonal Antibodies: Detection and Unbiased Estimation of Model Parameters  PAGEREF _Toc358384985 \h 158
 HYPERLINK \l "_Toc358384986" Leonid Gibiansky II-23 Monoclonal Antibody-Drug Conjugates (ADC): Simplification of Equations and Model-Independent Assessment of Deconjugation Rate  PAGEREF _Toc358384986 \h 159
 HYPERLINK \l "_Toc358384987" Pascal Girard II-24 Tumor size model and survival analysis of cetuximab and various cytotoxics in patients treated for metastatic colorectal cancer  PAGEREF _Toc358384987 \h 160
 HYPERLINK \l "_Toc358384988" Sophie Gisbert II-25 Is it possible to use the plasma and urine pharmacokinetics of a monoclonal antibody (mAb) as an early marker of efficacy in membranous nephropathy (MN)?  PAGEREF _Toc358384988 \h 161
 HYPERLINK \l "_Toc358384989" Timothy Goggin II-26 Population pharmacokinetics and pharmacodynamics of BYL719, a phosphoinositide 3-kinase antagonist, in adult patients with advanced solid malignancies.  PAGEREF _Toc358384989 \h 162
 HYPERLINK \l "_Toc358384990" Roberto Gomeni II-27 Implementing adaptive study design in clinical trials for psychiatric disorders using band-pass filtering approach  PAGEREF _Toc358384990 \h 164
 HYPERLINK \l "_Toc358384991" JoseDavid Gomez Mantilla II-28 Tailor-made dissolution profile comparisons using in vitro-in vivo correlation models.  PAGEREF _Toc358384991 \h 165
 HYPERLINK \l "_Toc358384992" Ignacio Gonzalez II-29 Simultaneous Modelling Of Fexofenadine In In Vitro Cell Culture And In Situ Experiments  PAGEREF _Toc358384992 \h 166
 HYPERLINK \l "_Toc358384993" Sathej Gopalakrishnan II-30 Towards assessing therapy failure in HIV disease: estimating in vivo fitness characteristics of viral mutants by an integrated statistical-mechanistic approach  PAGEREF _Toc358384993 \h 167
 HYPERLINK \l "_Toc358384994" Verena Gotta II-31 Simulation-based systematic review of imatinib population pharmacokinetics and PK-PD relationships in chronic myeloid leukemia (CML) patients  PAGEREF _Toc358384994 \h 169
 HYPERLINK \l "_Toc358384995" Bruce Green II-32 Clinical Application of a K-PD Warfarin Model for Bayesian Dose Individualisation in Primary Care  PAGEREF _Toc358384995 \h 170
 HYPERLINK \l "_Toc358384996" Zheng Guan II-33 The influence of variability in serum prednisolone pharmacokinetics on clinical outcome in children with nephrotic syndrome, based on salivary sampling combined with translational modeling and simulation approaches from healthy adult volunteers  PAGEREF _Toc358384996 \h 171
 HYPERLINK \l "_Toc358384997" Monia Guidi II-34 Impacts of environmental, clinical and genetic factors on the response to vitamin D supplementation in HIV-positive patients  PAGEREF _Toc358384997 \h 173
 HYPERLINK \l "_Toc358384998" Vanessa Guy-Viterbo II-35 Tacrolimus in pediatric liver recipients: population pharmacokinetic analysis during the first year post transplantation  PAGEREF _Toc358384998 \h 175
 HYPERLINK \l "_Toc358384999" Chihiro Hasegawa II-36 Modeling & simulation of ONO-4641, a sphingosine 1-phosphate receptor modulator, to support dose selection with phase 1 data  PAGEREF _Toc358384999 \h 176
 HYPERLINK \l "_Toc358385000" Michael Heathman II-37 The Application of Drug-Disease and Clinical Utility Models in the Design of an Adaptive Seamless Phase 2/3 Study  PAGEREF _Toc358385000 \h 177
 HYPERLINK \l "_Toc358385001" Emilie Hénin II-38 Optimization of sorafenib dosing regimen using the concept of utility  PAGEREF _Toc358385001 \h 178
 HYPERLINK \l "_Toc358385002" Eef Hoeben II-39 Prediction of Serotonin 2A Receptor (5-HT2AR) Occupancy in Man From Nonclinical Pharmacology Data. Exposure vs. 5-HT2AR Occupancy Modeling Used to Help Design a Positron Emission Tomography (PET) Study in Healthy Male Subjects.  PAGEREF _Toc358385002 \h 180
 HYPERLINK \l "_Toc358385003" Taegon Hong II-40 Usefulness of Weibull-Type Absorption Model for the Population Pharmacokinetic Analysis of Pregabalin  PAGEREF _Toc358385003 \h 182
 HYPERLINK \l "_Toc358385004" Andrew Hooker II-41 Platform for adaptive optimal design of nonlinear mixed effect models.  PAGEREF _Toc358385004 \h 183
 HYPERLINK \l "_Toc358385005" Daniel Hovdal II-42 PKPD modelling of drug induced changes in thyroxine turnover in rat  PAGEREF _Toc358385005 \h 185
 HYPERLINK \l "_Toc358385006" Yun Hwi-yeol II-43 Evaluation of FREM and FFEM including use of model linearization  PAGEREF _Toc358385006 \h 186
 HYPERLINK \l "_Toc358385007" Ibrahim Ince II-44 Oral bioavailability of the CYP3A substrate midazolam across the human age range from preterm neonates to adults  PAGEREF _Toc358385007 \h 188
 HYPERLINK \l "_Toc358385008" Lorenzo Ridolfi II-45 Predictive Modelling Environment - Infrastructure and functionality for pharmacometric activities in R&D  PAGEREF _Toc358385008 \h 189
 HYPERLINK \l "_Toc358385009" Masoud Jamei II-46 Accounting for sex effect on QT prolongation by quinidine: A simulation study using PBPK linked with PD  PAGEREF _Toc358385009 \h 190
 HYPERLINK \l "_Toc358385010" Alvaro Janda II-47 Application of optimal control methods to achieve multiple therapeutic objectives: Optimization of drug delivery in a mechanistic PK/PD system  PAGEREF _Toc358385010 \h 191
 HYPERLINK \l "_Toc358385011" Nerea Jauregizar II-48 Pharmacokinetic/Pharmacodynamic modeling of time-kill curves for echinocandins against Candida.  PAGEREF _Toc358385011 \h 192
 HYPERLINK \l "_Toc358385012" Roger Jelliffe II-49 Multiple Model Optimal Experimental Design for Pharmacokinetic Applications  PAGEREF _Toc358385012 \h 193
 HYPERLINK \l "_Toc358385013" Sangil Jeon II-50 Population Pharmacokinetics of Piperacillin in Burn Patients  PAGEREF _Toc358385013 \h 194
 HYPERLINK \l "_Toc358385014" Guedj Jeremie II-51 Modeling Early Viral Kinetics with Alisporivir: Interferon-free Treatment and SVR Predictions in HCV G2/3 patients  PAGEREF _Toc358385014 \h 195
 HYPERLINK \l "_Toc358385015" Claire Johnston II-52 A population approach to investigating hepatic intrinsic clearance in old age: Pharmacokinetics of paracetamol and its metabolites  PAGEREF _Toc358385015 \h 196
 HYPERLINK \l "_Toc358385016" Niclas Jonsson II-53 Population PKPD analysis of weekly pain scores after intravenously administered tanezumab, based on pooled Phase 3 data in patients with osteoarthritis of the knee or hip  PAGEREF _Toc358385016 \h 197
 HYPERLINK \l "_Toc358385017" Marija Jovanovic II-54 Effect of Carbamazepine Daily Dose on Topiramate Clearance - Population Modelling Approach  PAGEREF _Toc358385017 \h 198
 HYPERLINK \l "_Toc358385018" Rasmus Juul II-55 Pharmacokinetic modelling as a tool to assess transporter involvement in vigabatrin absorption  PAGEREF _Toc358385018 \h 199
 HYPERLINK \l "_Toc358385019" Matts Kågedal II-56 A modelling approach allowing different nonspecific uptake in the reference region and regions of interest – Opening up the possibility to use white matter as a reference region in PET occupancy studies.  PAGEREF _Toc358385019 \h 200
 HYPERLINK \l "_Toc358385020" Ana Kalezic II-57 Application of Item Response Theory to EDSS Modeling in Multiple Sclerosis  PAGEREF _Toc358385020 \h 201
 HYPERLINK \l "_Toc358385021" Takayuki Katsube II-58 Pharmacokinetic/pharmacodynamic modeling and simulation for concentration-dependent bactericidal activity of a bicyclolide, modithromycin  PAGEREF _Toc358385021 \h 203
 HYPERLINK \l "_Toc358385022" Irene-Ariadne Kechagia II-59 Population pharmacokinetic analysis of colistin after administration of inhaled colistin methanesulfonate.  PAGEREF _Toc358385022 \h 204
 HYPERLINK \l "_Toc358385023" Ron Keizer II-60 cPirana: command-line user interface for NONMEM and PsN  PAGEREF _Toc358385023 \h 205
 HYPERLINK \l "_Toc358385024" Frank Kloprogge II-61 Population pharmacokinetics and pharmacodynamics of lumefantrine in pregnant women with uncomplicated P. falciparum malaria.  PAGEREF _Toc358385024 \h 206
 HYPERLINK \l "_Toc358385025" Gilbert Koch II-62 Solution and implementation of distributed lifespan models  PAGEREF _Toc358385025 \h 207
 HYPERLINK \l "_Toc358385026" Kanji Komatsu II-63 Modelling of incretin effect on C-Peptide secretion in healthy and type 2 diabetes subjects.  PAGEREF _Toc358385026 \h 208
 HYPERLINK \l "_Toc358385027" Julia Korell II-64 Gaining insight into red blood cell destruction mechanisms using a previously developed semi-mechanistic model  PAGEREF _Toc358385027 \h 209
 HYPERLINK \l "_Toc358385028" Poster session III: Thursday morning 10:05-11:35  PAGEREF _Toc358385028 \h 210
 HYPERLINK \l "_Toc358385029" Stefanie Kraff III-01 Excel®-Based Tools for Pharmacokinetically Guided Dose Adjustment of Paclitaxel and Docetaxel  PAGEREF _Toc358385029 \h 210
 HYPERLINK \l "_Toc358385030" Andreas Krause III-02 Modeling the two peak phenomenon in pharmacokinetics using a gut passage model with two absorption sites  PAGEREF _Toc358385030 \h 211
 HYPERLINK \l "_Toc358385031" Elke Krekels III-03 Item response theory for the analysis of the placebo effect in Phase 3 studies of schizophrenia  PAGEREF _Toc358385031 \h 212
 HYPERLINK \l "_Toc358385032" Anders Kristoffersson III-04 Inter Occasion Variability (IOV) in Individual Optimal Design (OD)  PAGEREF _Toc358385032 \h 213
 HYPERLINK \l "_Toc358385033" Cédric Laouenan III-05 Modelling early viral hepatitis C kinetics in compensated cirrhotic treatment-experienced patients treated with triple therapy including telaprevir or boceprevir  PAGEREF _Toc358385033 \h 215
 HYPERLINK \l "_Toc358385034" Anna Largajolli III-06 An integrated glucose-insulin minimal model for IVGTT  PAGEREF _Toc358385034 \h 217
 HYPERLINK \l "_Toc358385035" Robert Leary III-07 A Fast Bootstrap Method Using EM Posteriors  PAGEREF _Toc358385035 \h 219
 HYPERLINK \l "_Toc358385036" Donghwan Lee III-08 Development of a Disease Progression Model in Korean Patients with Type 2 Diabetes Mellitus(T2DM)  PAGEREF _Toc358385036 \h 220
 HYPERLINK \l "_Toc358385037" Joomi Lee III-09 Population pharmacokinetics of prothionamide in Korean tuberculosis patients  PAGEREF _Toc358385037 \h 221
 HYPERLINK \l "_Toc358385038" Junghoon Lee III-10 Modeling Targeted Therapies in Oncology: Incorporation of Cell-cycle into a Tumor Growth Inhibition Model  PAGEREF _Toc358385038 \h 222
 HYPERLINK \l "_Toc358385039" Tarek Leil III-11 PK-PD Modeling using 4²-Hydroxycholesterol to Predict CYP3A Mediated Drug Interactions  PAGEREF _Toc358385039 \h 223
 HYPERLINK \l "_Toc358385040" Annabelle Lemenuel-Diot III-12 How to improve the prediction of Sustained Virologic Response (SVR) for Hepatitis C patients using early Viral Load (VL) Information  PAGEREF _Toc358385040 \h 224
 HYPERLINK \l "_Toc358385041" Joanna Lewis III-13 A homeostatic model for CD4 count recovery in HIV-infected children  PAGEREF _Toc358385041 \h 226
 HYPERLINK \l "_Toc358385042" Yan Li III-14 Modeling and Simulation to Probe the Likely Difference in Pharmacokinetic Disposition of R- and S-Enantiomers Justifying the Development of Racemate Pomalidomide  PAGEREF _Toc358385042 \h 227
 HYPERLINK \l "_Toc358385043" Lia Liefaard III-15 Predicting levels of pharmacological response in long-term patient trials based on short-term dosing PK and biomarker data from healthy subjects  PAGEREF _Toc358385043 \h 228
 HYPERLINK \l "_Toc358385044" Karl-Heinz Liesenfeld III-16 Pharmacometric Characterization of the Elimination of Dabigatran by Haemodialysis  PAGEREF _Toc358385044 \h 229
 HYPERLINK \l "_Toc358385045" Otilia Lillin III-17 Model-based QTc interval risk assessment in Phase 1 studies and its impact on the drug development trajectory  PAGEREF _Toc358385045 \h 230
 HYPERLINK \l "_Toc358385046" Hyeong-Seok Lim III-18 Pharmacokinetics of S-1, an Oral 5-Fluorouracil Agent in Patients with Gastric Surgery  PAGEREF _Toc358385046 \h 232
 HYPERLINK \l "_Toc358385047" Andreas Lindauer III-19 Comparison of NONMEM Estimation Methods in the Application of a Markov-Model for Analyzing Sleep Data  PAGEREF _Toc358385047 \h 234
 HYPERLINK \l "_Toc358385048" Jesmin Lohy Das III-20 Simulations to investigate new Intermittent Preventive Therapy Dosing Regimens for Dihydroartemisinin-Piperaquine  PAGEREF _Toc358385048 \h 235
 HYPERLINK \l "_Toc358385049" Dan Lu III-21 Semi-mechanistic Multiple-analyte Population Model of Antibody-drug-conjugate Pharmacokinetics  PAGEREF _Toc358385049 \h 236
 HYPERLINK \l "_Toc358385050" Viera Lukacova III-22 Physiologically Based Pharmacokinetic (PBPK) Modeling of Amoxicillin in Neonates and Infants  PAGEREF _Toc358385050 \h 237
 HYPERLINK \l "_Toc358385051" Panos Macheras III-23 On the Properties of a Two-Stage Design for Bioequivalence Studies  PAGEREF _Toc358385051 \h 238
 HYPERLINK \l "_Toc358385052" Merran Macpherson III-24 Using modelling and simulation to evaluate potential drug repositioning to a new therapy area  PAGEREF _Toc358385052 \h 239
 HYPERLINK \l "_Toc358385053" Paolo Magni III-25 A PK-PD model of tumor growth after administration of an anti-angiogenic agent given alone or in combination therapies in xenograft mice  PAGEREF _Toc358385053 \h 240
 HYPERLINK \l "_Toc358385054" Mathilde Marchand III-26 Population Pharmacokinetics and Exposure-Response Analyses to Support Dose Selection of Daratumumab in Multiple Myeloma Patients  PAGEREF _Toc358385054 \h 242
 HYPERLINK \l "_Toc358385055" Eleonora Marostica III-27 Population Pharmacokinetic Model of Ibrutinib, a BTK Inhibitor for the Treatment of B-cell malignancies  PAGEREF _Toc358385055 \h 243
 HYPERLINK \l "_Toc358385056" Hafedh Marouani III-28 Dosage regimen individualization of the once-daily amikacin treatment by using kinetics nomograms.  PAGEREF _Toc358385056 \h 244
 HYPERLINK \l "_Toc358385057" Amelie Marsot III-29 Population pharmacokinetics of baclofen in alcohol dependent patients  PAGEREF _Toc358385057 \h 245
 HYPERLINK \l "_Toc358385058" María Isabel Mas Fuster III-30 Stochastic Simulations Assist to Select the Intravenous Digoxin Dosing Protocol in Elderly Patients in Acute Atrial Fibrillation  PAGEREF _Toc358385058 \h 246
 HYPERLINK \l "_Toc358385059" Pauline Mazzocco III-31 Modeling tumor dynamics and overall survival in patients with low-grade gliomas treated with temozolomide.  PAGEREF _Toc358385059 \h 247
 HYPERLINK \l "_Toc358385060" Litaty Céphanoée Mbatchi III-32 A PK-PGx study of irinotecan: influence of genetic polymorphisms of xenoreceptors CAR (NR1I3) and PXR (NR1I2) on PK parameters  PAGEREF _Toc358385060 \h 248
 HYPERLINK \l "_Toc358385061" Sarah McLeay III-33 Population pharmacokinetics of rabeprazole and dosing recommendations for the treatment of gastro-esophageal reflux disease in children aged 1-11 years  PAGEREF _Toc358385061 \h 249
 HYPERLINK \l "_Toc358385062" Christophe Meille III-34 Modeling of Erlotinib Effect on Cell Growth Measured by in vitro Impedance-based Real-Time Cell Analysis  PAGEREF _Toc358385062 \h 250
 HYPERLINK \l "_Toc358385063" Olesya Melnichenko III-35 Characterizing the dose-efficacy relationship for anti-cancer drugs using longitudinal solid tumor modeling  PAGEREF _Toc358385063 \h 252
 HYPERLINK \l "_Toc358385064" Enrica Mezzalana III-36 A Target-Mediated Drug Disposition model integrated with a T lymphocyte pharmacodynamic model for Otelixizumab.  PAGEREF _Toc358385064 \h 253
 HYPERLINK \l "_Toc358385065" Iris Minichmayr III-37 A Microdialysate-based Integrated Model with Nonlinear Elimination for Determining Plasma and Tissue Pharmacokinetics of Linezolid in Four Distinct Populations  PAGEREF _Toc358385065 \h 254
 HYPERLINK \l "_Toc358385066" Jonathan Mochel III-38 Chronobiology of the Renin-Angiotensin-Aldosterone System (RAAS) in Dogs: Relation to Blood Pressure and Renal Physiology  PAGEREF _Toc358385066 \h 255
 HYPERLINK \l "_Toc358385067" Dirk Jan Moes III-39 Evaluating the effect of CYP3A4 and CYP3A5 polymorphisms on cyclosporine, everolimus and tacrolimus pharmacokinetics in renal transplantation patients.  PAGEREF _Toc358385067 \h 256
 HYPERLINK \l "_Toc358385068" John Mondick III-40 Mixed Effects Modeling to Quantify the Effect of Empagliflozin Exposure on the Renal Glucose Threshold in Patients with Type 2 Diabetes Mellitus  PAGEREF _Toc358385068 \h 257
 HYPERLINK \l "_Toc358385069" Morris Muliaditan III-41 Model-based evaluation of iron overload in patients affected by transfusion dependent diseases  PAGEREF _Toc358385069 \h 258
 HYPERLINK \l "_Toc358385070" Flora Musuamba-Tshinanu III-42 Modelling of disease progression and drug effects in preclinical models of neuropathic pain  PAGEREF _Toc358385070 \h 259
 HYPERLINK \l "_Toc358385071" Kiyohiko Nakai III-43 Urinary C-terminal Telopeptide of Type-I Collagen Concentration (uCTx) as a Possible Biomarker for Osteoporosis Treatment; A Direct Comparison of the Modeling and Simulation (M&S) Data and those Actually Obtained in Japanese Patients with Osteoporosis Following a Three-year-treatment with Ibandronic Acid (IBN)  PAGEREF _Toc358385071 \h 260
 HYPERLINK \l "_Toc358385072" Thu Thuy Nguyen III-44 Mechanistic Model to Characterize and Predict Fecal Excretion of Ciprofloxacin Resistant Enterobacteria with Various Dosage Regimens  PAGEREF _Toc358385072 \h 261
 HYPERLINK \l "_Toc358385073" Thi Huyen Tram Nguyen III-45 Influence of a priori information, designs and undetectable data on individual parameters estimation and prediction of hepatitis C treatment outcome  PAGEREF _Toc358385073 \h 263
 HYPERLINK \l "_Toc358385074" Xavier Nicolas III-46 Steady-state achievement and accumulation for a compound with bi-phasic disposition and long terminal half-life, estimation by different techniques  PAGEREF _Toc358385074 \h 265
 HYPERLINK \l "_Toc358385075" Ronald Niebecker III-47 Are datasets for NLME models large enough for a bootstrap to provide reliable parameter uncertainty distributions?  PAGEREF _Toc358385075 \h 266
 HYPERLINK \l "_Toc358385076" Lisa O'Brien III-48 Implementation of a Global NONMEM Modeling Environment  PAGEREF _Toc358385076 \h 267
 HYPERLINK \l "_Toc358385077" Kayode Ogungbenro III-49 A physiological based pharmacokinetic model for low dose methotrexate in humans  PAGEREF _Toc358385077 \h 269
 HYPERLINK \l "_Toc358385078" Jaeseong Oh III-50 A Population Pharmacokinetic-Pharmacodynamic Analysis of Fimasartan in Patients with Mild to Moderate Essential Hypertension  PAGEREF _Toc358385078 \h 270
 HYPERLINK \l "_Toc358385079" Fredrik Öhrn III-51 Longitudinal Modelling of FEV1 Effect of Bronchodilators  PAGEREF _Toc358385079 \h 271
 HYPERLINK \l "_Toc358385080" Andrés Olivares-Morales III-52 Qualitative prediction of human oral bioavailability from animal oral bioavailability data employing ROC analysis  PAGEREF _Toc358385080 \h 272
 HYPERLINK \l "_Toc358385081" Erik Olofsen III-53 Simultaneous stochastic modeling of pharmacokinetic and pharmacodynamic data with noncoinciding sampling times  PAGEREF _Toc358385081 \h 274
 HYPERLINK \l "_Toc358385082" Sean Oosterholt III-54 PKPD modelling of PGE2 inhibition and dose selection of a novel COX-2 inhibitor in humans.  PAGEREF _Toc358385082 \h 275
 HYPERLINK \l "_Toc358385083" Ignacio Ortega III-55 Application of allometric techniques to predict F10503LO1 PK parameters in human  PAGEREF _Toc358385083 \h 276
 HYPERLINK \l "_Toc358385084" Jeongki Paek III-56 Population pharmacokinetic model of sildenafil describing first-pass effect to its metabolite  PAGEREF _Toc358385084 \h 277
 HYPERLINK \l "_Toc358385085" Sung Min Park III-57 Population pharmacokinetic/pharmacodynamic modeling for transformed binary effect data of triflusal in healthy Korean male volunteers  PAGEREF _Toc358385085 \h 278
 HYPERLINK \l "_Toc358385086" Zinnia Parra-Guillen III-58 Population semi-mechanistic modelling of tumour response elicited by Immune-stimulatory based therapeutics in mice  PAGEREF _Toc358385086 \h 279
 HYPERLINK \l "_Toc358385087" Ines Paule III-59 Population pharmacokinetics of an experimental drug’s oral modified release formulation in healthy volunteers, quantification of sensitivity to types and timings of meals.  PAGEREF _Toc358385087 \h 281
 HYPERLINK \l "_Toc358385088" Sophie Peigne III-60 Paediatric Pharmacokinetic methodologies: Evaluation and comparison  PAGEREF _Toc358385088 \h 282
 HYPERLINK \l "_Toc358385089" Nathalie Perdaems III-61 A semi-mechanistic PBPK model to predict blood, cerebrospinal fluid and brain concentrations of a compound in mouse, rat, monkey and human.  PAGEREF _Toc358385089 \h 284
 HYPERLINK \l "_Toc358385090" Chiara Piana III-62 Optimal sampling and model-based dosing algorithm for busulfan in bone marrow transplantation patients.  PAGEREF _Toc358385090 \h 285
 HYPERLINK \l "_Toc358385091" Sebastian Polak III-63 Pharmacokinetic (PK) and pharmacodynamic (PD) implications of diurnal variation of gastric emptying and small intestinal transit time for quinidine: A mechanistic simulation.  PAGEREF _Toc358385091 \h 286
 HYPERLINK \l "_Toc358385092" Angelica Quartino III-64 Evaluation of Tumor Size Metrics to Predict Survival in Advanced Gastric Cancer  PAGEREF _Toc358385092 \h 288
 HYPERLINK \l "_Toc358385093" Poster session IV: Thursday afternoon 14:55-16:20  PAGEREF _Toc358385093 \h 290
 HYPERLINK \l "_Toc358385094" Khaled Abduljalil IV-01 Prediction of Tolerance to Caffeine Pressor Effect during Pregnancy using Physiologically Based PK-PD Modelling  PAGEREF _Toc358385094 \h 290
 HYPERLINK \l "_Toc358385095" Rick Admiraal IV-02 Exposure to the biological anti-thymocyte globulin (ATG) in children receiving allogeneic-hematopoietic cell transplantation (HCT): towards individualized dosing to improve survival  PAGEREF _Toc358385095 \h 291
 HYPERLINK \l "_Toc358385096" Wafa Alfwzan IV-03 Mathematical Modelling of the Spread of Hepatitis C among Drug Users, effects of heterogeneity.  PAGEREF _Toc358385096 \h 292
 HYPERLINK \l "_Toc358385097" Sarah Alghanem IV-04 Comparison of NONMEM and Pmetrics Analysis for Aminoglycosides in Adult Patients with Cystic Fibrosis  PAGEREF _Toc358385097 \h 293
 HYPERLINK \l "_Toc358385098" Nidal Al-huniti IV-05 A Nonlinear Mixed Effect Model to Describe Placebo Response in Children and Adolescents with Major Depressive Disorder  PAGEREF _Toc358385098 \h 294
 HYPERLINK \l "_Toc358385099" Hesham Al-Sallami IV-06 Evaluation of a Bayesian dose-individualisation method for enoxaparin  PAGEREF _Toc358385099 \h 295
 HYPERLINK \l "_Toc358385100" Oskar Alskär IV-07 Modelling of glucose absorption  PAGEREF _Toc358385100 \h 296
 HYPERLINK \l "_Toc358385101" Helena Andersson IV-08 Clinical relevance of albumin concentration in patients with Crohn’s disease treated with infliximab for recommendations on dosing regimen adjustments  PAGEREF _Toc358385101 \h 298
 HYPERLINK \l "_Toc358385102" Franc Andreu Solduga IV-09 Development of a Bayesian Estimator for Tacrolimus in Kidney Transplant Patients: A Population Pharmacokinetic approach.  PAGEREF _Toc358385102 \h 299
 HYPERLINK \l "_Toc358385103" Yasunori Aoki IV-10 PopED lite an easy to use experimental design software for preclinical studies  PAGEREF _Toc358385103 \h 300
 HYPERLINK \l "_Toc358385104" Eduardo Asín IV-11 Population Pharmacokinetics of Cefuroxime in patients Undergoing Colorectal Surgery  PAGEREF _Toc358385104 \h 301
 HYPERLINK \l "_Toc358385105" Ioanna Athanasiadou IV-12 Simulation of the effect of hyperhydration on urine levels of recombinant human erythropoietin from a doping control point of view  PAGEREF _Toc358385105 \h 302
 HYPERLINK \l "_Toc358385106" Guillaume Baneyx IV-13 Modeling Erlotinib and Gefitinib in Vitro Penetration through Multiple Layers of Epidermoid and Colorectal Human Carcinoma Cells  PAGEREF _Toc358385106 \h 304
 HYPERLINK \l "_Toc358385107" Aliénor Bergès IV-14 Dose selection in Amyotrophic Lateral Sclerosis: PK/PD model using laser scanning cytometry data from muscle biopsies in a patient study  PAGEREF _Toc358385107 \h 305
 HYPERLINK \l "_Toc358385108" Shanshan Bi IV-15 Population Pharmacokinetic/Pharmacodynamic Modeling of Two Novel Neutral Endopeptidase Inhibitors in Healthy Subjects  PAGEREF _Toc358385108 \h 307
 HYPERLINK \l "_Toc358385109" Bruno Bieth IV-16 Population Pharmacokinetics of QVA149, the fixed dose combination of Indacaterol maleate and Glycopyrronium bromide in Chronic Obstructive Pulmonary Disease (COPD) patients  PAGEREF _Toc358385109 \h 308
 HYPERLINK \l "_Toc358385110" Roberto Bizzotto IV-17 Characterization of binding between OSM and mAb in RA patient study: an extension to TMDD models  PAGEREF _Toc358385110 \h 309
 HYPERLINK \l "_Toc358385111" Marcus Björnsson IV-18 Effect on bias in EC50 when using interval censoring or exact dropout times in the presence of informative dropout  PAGEREF _Toc358385111 \h 311
 HYPERLINK \l "_Toc358385112" Karina Blei IV-19 Mechanism of Action of Jellyfish (Carukia barnesi) Envenomation and its Cardiovascular Effects Resulting in Irukandji Syndrome  PAGEREF _Toc358385112 \h 312
 HYPERLINK \l "_Toc358385113" Michael Block IV-20 Predicting the antihypertensive effect of Candesartan-Nifedipine combinations based on public benchmarking data.  PAGEREF _Toc358385113 \h 314
 HYPERLINK \l "_Toc358385114" Michael Block IV-21 Physiologically-based PK/PD modeling for a dynamic cardiovascular system: structure and applications  PAGEREF _Toc358385114 \h 316
 HYPERLINK \l "_Toc358385115" Irina Bondareva IV-22 Population Modeling of the Time-dependent Carbamazepine (CBZ) Autoinduction Estimated from Repeated Therapeutic Drug Monitoring (TDM) Data of Drug-naïve Adult Epileptic Patients Begun on CBZ-monotherapy  PAGEREF _Toc358385115 \h 318
 HYPERLINK \l "_Toc358385116" Jens Borghardt IV-23 Characterisation of different absorption rate constants after inhalation of olodaterol  PAGEREF _Toc358385116 \h 319
 HYPERLINK \l "_Toc358385117" Karl Brendel IV-25 How to deal properly with change-point model in NONMEM?  PAGEREF _Toc358385117 \h 320
 HYPERLINK \l "_Toc358385118" Frances Brightman IV-26 Predicting Torsades de Pointes risk from data generated via high-throughput screening  PAGEREF _Toc358385118 \h 321
 HYPERLINK \l "_Toc358385119" Margreke Brill IV-27 Population pharmacokinetic model for protein binding and subcutaneous adipose tissue distribution of cefazolin in morbidly obese and non-obese patients  PAGEREF _Toc358385119 \h 322
 HYPERLINK \l "_Toc358385120" Brigitte Brockhaus IV-28 Semi-mechanistic model-based drug development of EMD 525797 (DI17E6), a novel anti-±v integrin monoclonal antibody  PAGEREF _Toc358385120 \h 323
 HYPERLINK \l "_Toc358385121" Vincent Buchheit IV-29 A drug development tool for trial simulation in prodromal Alzheimer s patient using the Clinical Dementia Rating scale Sum of Boxes score (CDR-SOB  PAGEREF _Toc358385121 \h 324
 HYPERLINK \l "_Toc358385122" Vincent Buchheit IV-30 Data quality impacts on modeling results  PAGEREF _Toc358385122 \h 325
 HYPERLINK \l "_Toc358385123" Núria Buil Bruna IV-31 Modelling LDH dynamics to assess clinical response as an alternative to tumour size in SCLC patients  PAGEREF _Toc358385123 \h 326
 HYPERLINK \l "_Toc358385124" Martin Burschka IV-32 Referenced VPC near the Lower Limit of Quantitation.  PAGEREF _Toc358385124 \h 327
 HYPERLINK \l "_Toc358385125" Theresa Cain IV-33 Prediction of Rosiglitazone compliance from last sampling information using Population based PBPK modelling and Bayes theorem: Comparison of prior distributions for compliance.  PAGEREF _Toc358385125 \h 328
 HYPERLINK \l "_Toc358385126" Vicente G. Casabo IV-34 Modification Of Non Sink Equation For Calculation The Permeability In Cell Monolayers  PAGEREF _Toc358385126 \h 329
 HYPERLINK \l "_Toc358385127" Anne Chain IV-35 Not-In-Trial Simulations: A tool for mitigating cardiovascular safety risks  PAGEREF _Toc358385127 \h 330
 HYPERLINK \l "_Toc358385128" Kalayanee Chairat IV-36 A population pharmacokinetics and pharmacodynamics of oseltamivir and oseltamivir carboxylate in adults and children infected with influenza virus A(H1N1)pdm09  PAGEREF _Toc358385128 \h 331
 HYPERLINK \l "_Toc358385129" Quentin Chalret du Rieu IV-37 Hematological toxicity modelling of abexinostat (S-78454, PCI-24781), a new histone deacetylase inhibitor, in patients suffering from solid tumors or lymphoma: influence of the disease-progression on the drug-induced thrombocytopenia.  PAGEREF _Toc358385129 \h 333
 HYPERLINK \l "_Toc358385130" Phylinda Chan IV-38 Industry Experience in Establishing a Population Pharmacokinetic Analysis Guidance  PAGEREF _Toc358385130 \h 335
 HYPERLINK \l "_Toc358385131" Pascal Chanu IV-39 Simulation study for a potential sildenafil survival trial in adults with pulmonary arterial hypertension (PAH) using a time-varying exposure-hazard model developed from data in children  PAGEREF _Toc358385131 \h 336
 HYPERLINK \l "_Toc358385132" Christophe Chassagnole IV-40 Virtual Tumour Clinical: Literature example  PAGEREF _Toc358385132 \h 337
 HYPERLINK \l "_Toc358385133" Chao Chen IV-41 A mechanistic model for the involvement of the neonatal Fc receptor in IgG disposition  PAGEREF _Toc358385133 \h 338
 HYPERLINK \l "_Toc358385134" Chunli Chen IV-42 Design optimization for characterization of rifampicin pharmacokinetics in mouse  PAGEREF _Toc358385134 \h 339
 HYPERLINK \l "_Toc358385135" Nianhang Chen IV-43 Comparison of Two Parallel Computing Methods (FPI versus MPI) in NONMEM 7.2 on complex popPK and popPK/PD Models  PAGEREF _Toc358385135 \h 340
 HYPERLINK \l "_Toc358385136" Marylore Chenel IV-44 Population Pharmacokinetic Modelling to Detect Potential Drug Interaction Using Sparse Sampling Data  PAGEREF _Toc358385136 \h 341
 HYPERLINK \l "_Toc358385137" Jason Chittenden IV-45 Practical Application of GPU Computing to Population PK  PAGEREF _Toc358385137 \h 342
 HYPERLINK \l "_Toc358385138" Yu-Yuan Chiu IV-46 Exposure-Efficacy Response Model of Lurasidone in Patients with Bipolar Depression  PAGEREF _Toc358385138 \h 343
 HYPERLINK \l "_Toc358385139" Steve Choy IV-47 Modelling the Effect of Very Low Calorie Diet on Weight and Fasting Plasma Glucose in Type 2 Diabetic Patients  PAGEREF _Toc358385139 \h 344
 HYPERLINK \l "_Toc358385140" Oskar Clewe IV-48 A Model Predicting Penetration of Rifampicin from Plasma to Epithelial Lining Fluid and Alveolar Cells  PAGEREF _Toc358385140 \h 346
 HYPERLINK \l "_Toc358385141" Teresa Collins IV-49 Performance of Sequential methods under Pre-clinical Study Conditions  PAGEREF _Toc358385141 \h 348
 HYPERLINK \l "_Toc358385142" Francois Combes IV-50 Influence of study design and associated shrinkage on power of the tests used for covariate detection in population pharmacokinetics  PAGEREF _Toc358385142 \h 349
 HYPERLINK \l "_Toc358385143" Emmanuelle Comets IV-51 Additional features and graphs in the new npde library for R  PAGEREF _Toc358385143 \h 351
 HYPERLINK \l "_Toc358385144" Camille Couffignal IV-52 Population pharmacokinetics of imipenem in intensive care unit patients with ventilated-associated pneumonia  PAGEREF _Toc358385144 \h 353
 HYPERLINK \l "_Toc358385145" Damien Cronier IV-53 PK/PD relationship of the monoclonal anti-BAFF antibody tabalumab in combination with bortezomib in patients with previously treated multiple myeloma: comparison of serum M-protein and serum Free Light Chains as predictor of Progression Free Survival  PAGEREF _Toc358385145 \h 354
 HYPERLINK \l "_Toc358385146" Zeinab Daher Abdi IV-54 Analysis of the relationship between Mycophenolic acid (MPA) exposure and anemia using three approaches: logistic regression based on Generalized Linear Mixed Models (GLMM) or on Generalized Estimating Equations (GEE) and Markov mixed-effects model.  PAGEREF _Toc358385146 \h 355
 HYPERLINK \l "_Toc358385147" Elyes Dahmane IV-55 Population Pharmacokinetics of Tamoxifen and three of its metabolites in Breast Cancer patients  PAGEREF _Toc358385147 \h 357
 HYPERLINK \l "_Toc358385148" Adam Darwich IV-56 A physiologically based pharmacokinetic model of oral drug bioavailability immediately post bariatric surgery  PAGEREF _Toc358385148 \h 358
 HYPERLINK \l "_Toc358385149" Camila De Almeida IV-57 Modelling Irinotecan PK, efficacy and toxicities pre-clinically  PAGEREF _Toc358385149 \h 359
 HYPERLINK \l "_Toc358385150" Willem de Winter IV-58 Population PK/PD analysis linking the direct acute effects of canagliflozin on renal glucose reabsorption to the overall effects of canagliflozin on long-term glucose control using HbA1c as the response marker from clinical studies  PAGEREF _Toc358385150 \h 360
 HYPERLINK \l "_Toc358385151" Joost DeJongh IV-59 A population PK-PD model for effects of Sipoglitazar on FPG and HbA1c in patients with type II diabetes.  PAGEREF _Toc358385151 \h 362
 HYPERLINK \l "_Toc358385152" Paolo Denti IV-60 A semi-physiological model for rifampicin and rifapentine CYP3A induction on midazolam pharmacokinetics.  PAGEREF _Toc358385152 \h 363
 HYPERLINK \l "_Toc358385153" Cheikh Diack IV-61 An indirect response model with modulated input rate to characterize the dynamics of A²-40 in cerebrospinal fluid  PAGEREF _Toc358385153 \h 365
 HYPERLINK \l "_Toc358385154" Laura Dickinson IV-62 Population Pharmacokinetics of Twice Daily Zidovudine (ZDV) in HIV-Infected Children and an Assessment of ZDV Exposure Following WHO Dosing Guidelines  PAGEREF _Toc358385154 \h 366
 HYPERLINK \l "_Toc358385155" Christian Diedrich IV-63 Using Bayesian-PBPK Modeling for Assessment of Inter-Individual Variability and Subgroup Stratification  PAGEREF _Toc358385155 \h 367
 HYPERLINK \l "_Toc358385156" Christian Diestelhorst IV-64 Population Pharmacokinetics of Intravenous Busulfan in Children: Revised Body Weight-Dependent NONMEM® Model to Optimize Dosing  PAGEREF _Toc358385156 \h 369
 HYPERLINK \l "_Toc358385157" Aris Dokoumetzidis IV-65 Bayesian parameter scan for determining bias in parameter estimates  PAGEREF _Toc358385157 \h 370
 HYPERLINK \l "_Toc358385158" Software Demonstration  PAGEREF _Toc358385158 \h 371
 HYPERLINK \l "_Toc358385159" Gregory Ferl S-01 Literate Programming Methods for Clinical M&S  PAGEREF _Toc358385159 \h 371
 HYPERLINK \l "_Toc358385160" Bruce Green S-02 DoseMe - A Cross Platform Dose Individualised Program  PAGEREF _Toc358385160 \h 373
 HYPERLINK \l "_Toc358385161" Roger Jelliffe S-03 The MM-USCPACK Pmetrics research software for nonparametric population PK/PD modeling, and the RightDose clinical software for individualizing maximally precise dosage regimens.  PAGEREF _Toc358385161 \h 375
 HYPERLINK \l "_Toc358385162" Niclas Jonsson S-04 Reproducible pharmacometrics  PAGEREF _Toc358385162 \h 377
 HYPERLINK \l "_Toc358385163" List of Abstracts sorted by abstract category  PAGEREF _Toc358385163 \h 378
 Oral presentations Wednesday
Oral: Other Topics

Dyfrig Hughes A-05 Quantitative benefit-risk analysis based on linked PKPD and health outcome modelling
Dyfrig Hughes Centre for Health Economics and Medicines Evaluation, Bangor University
Objectives: Health outcomes modelling, conventionally used in health technology assessment, is based on disease progression models with the probabilities of benefit and harm for health states based on epidemiological and clinical trial evidence, and the health state preferences based on utility estimates. During early phases of clinical drug development, and where randomised controlled trials may not be possible, outputs from PKPD models may serve as inputs to health outcome models to inform the balance of harms and benefits based on the quality-adjusted life-year (QALY).  Here, a comparison is made of the net clinical benefits of genotype-guided warfarin with both standard, clinically-dosed warfarin and three new oral anticoagulants (dabigatran, rivaroxaban and apixaban).
Methods: A clinical trial simulation based on a PKPD model of S-warfarin was used to predict differences in time within therapeutic range (TTR) between genotype guided and clinically dosed warfarin. A meta-analysis of trials linking TTR with outcomes was conducted to obtain relative risks of different clinical events. A discrete event simulation model representative of the AF population in the UK was used to extrapolate event risks to a lifetime horizon. Modelled outputs included clinical outcomes and QALYs.
Results: In the base case analysis, genotype guided-warfarin, rivaroxaban, apixaban and dabigatran extended life by 0.003, 1.11, 2.06 and 1.47 months, respectively, compared with clinical algorithm dosed warfarin. The corresponding incremental net benefits were 0.0031 (95% central range [CR] -0.1649 to 0.1327), 0.0957 (95% CR -0.0510 to 0.2431), 0.1298 (95% CR -0.0290 to 0.2638) and 0.1065 (95% CR -0.0493 to 0.2489) QALYs. In pairwise comparisons, using clinical algorithm dosed warfarin as the comparator, genotype guided warfarin, rivaroxaban, apixaban and dabigatran were associated with a positive incremental net health benefit in 57%, 83%, 90% and 85% of the simulations respectively.
Conclusion: Clinical trial simulations based on pharmacological models offer a new way to obtain estimates of net benefit in circumstances where trial data are not available. Based on our simulations, apixaban appears to be associated with the highest net benefit.

Oral: Drug/Disease modelling

Jonathan French A-06 Can methods based on existing models really aid decision making in non-small-cell lung cancer (NSCLC) trials?
Jonathan L French (1), Daniel G Polhamus (1), and Marc R Gastonguay (1) (1) Metrum Research Group, Tariffville, CT, USA
Objectives: The need for more efficient drug development in oncology is widely recognized. Wang et al [1] propose the use of % change in tumor size at 8 weeks (PTR8) as a marker of efficacy to aid decision making in NSCLC drug development. Sharma et al. [2] advocate M&S in oncology drug development through the use of adaptive Phase II-III trials. In this work we compare 3 approaches to using M&S for making decisions based on accruing data in a Phase II clinical trial.
Methods:We simulated clinical trials with 400 NSCLC patients randomized 1:1 to 2 groups receiving first-line treatment. We assume a recruitment period of 6 months with an additional 9 month follow-up period. Overall survival (OS) and PTR8 data were simulated using the NSCLC model of Wang et al. [1]. For each simulated trial, 3 interim analyses (IAs) were performed: 8 weeks after (1) 80 pts enrolled (~10 events), (2) 280 pts enrolled (~50 events), and (3) 400 pts enrolled (~90 events).
Two drug effect scenarios were evaluated. The first had a median difference in PTR8 of 40%, a difference in median OS of 100 days, and expected hazard ratio of 0.67. The second had no difference in PTR8 or OS.
We compared decision rules based on difference in PTR8 to Bayesian rules based on the posterior predictive distribution for the log hazard ratio (logHR) at the end of the study. For the Bayesian rules, the relationship between PTR8 and OS was updated using the accruing data in the trial and prior distributions centered at the estimates from [1]. We also evaluated rules based on the estimated logHR using a Cox model. Decision rules were compared using ROC analysis (true positive rate, TPR, and false positive rate, FPR).
Simulation and analysis were performed using R 2.15.1 and OpenBUGS 3.2.1.
Results: Under scenario 1, all rules performed poorly at IA1. At IA2, the best Bayes rule performed notably better (TPR=.67, FPR=.29) than either the best PTR8 rule (TPR=.56, FPR=.46) or Cox rule (TPR=.65, FPR=.37). At IA3, the best Bayes and Cox rules (TPR~.75, FPR~.25) performed better than the best PTR8 rule (TPR=.55, FPR=.33). Scenario 2 showed similar results.
Conclusions: Model-based approaches can aid decision making in NSCLC trials. However, IA decision rules based on PTR8 alone have little ability to predict the outcome of positive or negative studies, consistent with recently published results [3]. The model-based Bayesian decision rules evaluated here performed notably better.
References: [1] Wang Y. et al. Elucidation of relationship between tumor size and survival in non-small-cell lung cancer patients can aid early decision making in clinical drug development. Clin Pharmacol Ther. 86, 167--174 (2009). [2] Sharma MR, Maitland ML, and Ratain MJ. Models of Excellence: Improving Oncology Drug Development. Clin Pharmacol Ther. 92, 548--550 (2012). [3] Claret L. et al. Simulations using a drug-disease modeling framework and phase II data predict phase III survival outcome in first-line non-small-cell lung cancer. Clin. Pharmacol. Ther. 92, 631--634 (2012).

Oral: Clinical Applications

Jonas Bech Møller A-07 Optimizing clinical diabetes drug development – what is the recipe?
Jonas B Møller (1), Rune V Overgaard (1), Maria C Kjellsson (2), Niels R Kristensen (1), Søren Klim (1), Steen H Ingwersen (1), Mats Karlsson (2) (1) Quantitative Clinical Pharmacology, Novo Nordisk A/S, Søborg, Denmark (2) The Pharmacometrics Group, Uppsala University, Uppsala, Sweden;
Objectives: A key challenge in diabetes drug development is to extrapolate the results from early clinical efficacy assessments (clamp studies or glucose provocation tests) to late phase efficacy outcomes such as HbA1c. With the increasing need for investigating anti-diabetic medicine in special populations (e.g. paediatrics), another challenge is to use available data to extrapolate from one population to another. These challenges call for a library of quantitative models to link and predict key endpoints in diabetes trials during the different phases of drug development. The objective of this presentation is to show how specific pharmacometric diabetes models, alone or in combination, can be applied to optimize clinical diabetes drug development.
Methods: By combining a PK model with a model for glucose homeostasis [1], a link between drug concentration and drug effect on plasma glucose can be established, as previously shown for an oral anti-diabetic (OAD) or insulin treatment  [2,3]. By subsequently applying a model linking glucose to HbA1c [4], the predicted plasma glucose response can be used for prediction of late phase efficacy outcome. Clearly, assessment of treatment dependence on the link between glucose and HbA1c is crucial, and thus we applied individual data from 4 clinical trials covering 12 treatment arms (OADs, GLP-1 agonist, and insulins) to test our approach.
Results: The performance of the proposed framework is illustrated through a case study where trial outcome wrt. HbA1c for each treatment arm was predicted. The HbA1c predictions were successful with a mean absolute error ranging from 0.0% to 0.24% across treatment arms. Calculations of the mean "HbA1c vs. comparator and the corresponding confidence intervals were shown to provide identical conclusions based on predictions and observations at end-of-trial.
Conclusions: In this presentation we outlined and applied models for linking early phase assessments and late phase treatment outcomes within clinical diabetes drug development. Implementation and validation of these models were driven by a consistent focus on the ability to predict future trial outcomes and link data from different stages of clinical development. We find this a key ingredient in the recipe for optimizing diabetes drug development.
Acknowledgements: This work was part of the DDMoRe project.
References: [1] Jauslin PM et. al: An integrated glucose-insulin model to describe oral glucose tolerance test data in type 2 diabetics, 2007 [2] Jauslin PM et. al: Identification of the mechanism of action of a glucokinase activator from oral glucose tolerance test data in type 2 diabetic patients based on an integrated glucose-insulin model, 2011 [3] Roege RM et. al.: PAGE poster n. l-61, 2012: Integrated model of glucose homeostasis including the effect of exogenous insulin [4] Moeller et. al.: ADOPT (A Dynamic HbA1c EndpOint Prediction Tool) - A framework for predicting primary endpoint in Phase 3 diabetes trials, abstract accepted for ACOP 2013


Oral: Animal Health

Jim Riviere A-09 Food safety: the intersection of pharmacometrics and veterinary medicine
Jim E. Riviere Institute of Computational Comparative Medicine, College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
Food animal veterinarians bear numerous responsibilities, not only to their sick patients, but also to the producers and consumers of animal food products, as well as the environment. A fundamental difference between food animal veterinary and human medicine relates to the fact that animals treated with drugs are often consumed as food after treatment is completed.
Unlike for humans where the physician isn't concerned about drug left in the patient after treatment, in food animal medicine the veterinarian must be sure an effective dose of drug is given (appropriate PK-PD regimen) and also that no potentially adverse levels of drug persist in the edible tissues and products (e.g. milk, eggs) of treated animals. A second difference is that drugs are administered to large populations of animals as disease is often diagnosed and treated on a herd basis.
Animals may be dosed in feed, water or dips, creating uncertainty in dose level and interval. Uncontrollable environmental covariates like temperature and humidity can further increase variability. These factors must be considered to insure that a safe food animal product free of toxic or allergic chemicals reaches the consumer. The regulatory determination of such tissue withdrawal times is performed in control groups of healthy animals. Although the pharmacometric approaches to the calculation of such parameters in various regulatory jurisdictions may differ, the experimental design of such trials is similar. Once approved, drugs are then used in natural clinical populations where diseases processes for which the drug is labeled to treat are present, and concomitant medications are also often administered. This has resulted in a regulatory system with a reasonable degree of reproducibility relative to determination of the withdrawal time metric, but a lack of direct relationship to drug disposition processes seen in clinical populations of animals treated under diverse conditions.
Various authors have amply reviewed the impact of disease processes on the primary drug pharmacokinetic parameters, with focus being on drug elimination and distribution pathways and processes as they affect blood concentration-time profiles as a function of drug efficacy. However, the effect of such factors on very low residue-level concentrations (PPM, PPB) of drugs and their metabolites in edible tissues has rarely been addressed or even considered. Similarly, residue depletion trials are often conducted in homogeneous groups of animals using controlled dosing regimens in order to reduce animal numbers while still arriving at a statistical solution to the withdrawal time algorithm; yet variability in the actual treated populations relative to breed, production and environmental factors alone easily violates this assumption. This is particularly true when the withdrawal time algorithm is attempting to estimate behavior in 1-5% of the population with 95% confidence. Situations where concern arises include when the disease process alters the normal ratio of parent drug to marker residue produced by altered biotransformation processes, when a product of the disease process binds to and modifies the drug residue depletion profile in a target tissue, or when disposition processes fundamentally alter pharmacokinetic patterns.
Advances in population (mixed effect) pharmacokinetic modeling open up approaches to study, model and predict these factors; in many cases directly based on the mechanism of the interaction.  Mixed effect models allow disease related and potentially pharmacogenomic factors to be directly estimated and modeled. Such considerations become increasingly important if global regulatory jurisdictions set residue tolerances based on the limits of analytical detection, which of late continually drops to levels where minor interactions at the molecular tissue level become important for model predictions and violations of tissue tolerances, but are totally irrelevant to their toxicological impact on human food safety.


Oral: Animal Health

George Gettinby A-11 Two models for the control of sea lice infections using chemical treatments and biological control on farmed salmon populations
George Gettinby (1), Maya Groner (2), Ruth Cox (2), Chris Robbins (3) and Crawford Revie (2) (1) University of Strathclyde, Glasgow, Scotland, (2) University of Prince Edward Island, Canada, (3) Grallator Ltd, UK
Objectives: To formulate models to inform how best to manage the control of sea lice populations which are a major threat to aquaculture and salmon production worldwide.
Methods: Two types of models are used to investigate the interaction between sea lice and salmon populations.  In the first model changes in lice population stages are represented using four differential-delay equations. Time dependent solutions are obtained using algorithms embedded in the Sea Lice Difference Equation Simulator software.   This enables treatment regimens under different geographical and environmental conditions to be investigated.   The second model adopts a different approach to facilitate the introduction of a further fish population i.e. wrasse. Wrasse along with several other fish species are increasingly being used as "cleaner" fish because they feed on lice which are attached to salmon [1][2].   Using an individual-based modelling approach  and simulations  implemented using proprietary modelling software  the density relationship between wrasse and salmon populations was investigated.
Results: Early work using the population modelling approach provided a parsimonious mathematical representation of the growth of the sea lice population [3] [4].  Using numerical methods it was possible to obtain solutions to the differential equations which reflected day-to-day changes in sea lice counts per salmon.  The model identified when to apply treatments  that would be less costly and more effective.   The model lacked flexibility, stochasticity and did not take cognisance  of sea water temperature and its effect on development and survival time of the lice stages.   Experiences of adapting the model in Scotland and Norway [5] showed that it was not always stable and small changes in parameters could produce very different outcomes.  The introduction of biological control and the use of cleaner fish led to investigating an individual-based modelling (IBM) approach [6][7][8].  A simple IBM which takes account of biological development rates associated with water temperature [9] showed that the use of wrasse fish to graze on sea lice in salmon production units can provide an effective way forward for salmon aquaculture.    
Conclusion: Sea lice are a major threat worldwide  to the sustainability of  farmed and wild salmons stocks.   They are affected by a large number of factors on salmon farms.  Mathematical modelling offers a way  of assessing  the simultaneous impact of these factors.
References: [1] Treasurer JW.  Prey selection and daily food consumption by a cleaner fish, Ctenolabrus rupestris (L.), on farmed Atlantic salmon, Salmo salar L. Aquaculture (1994) 122:269-277. [2] Treasurer JW.  Wrasse (Labridae) as cleaner-fish of sea lice on farmed Atlantic salmon in west Scotland. In: Wrasse: Biology and Use in Aquaculture (ed by MDJ  Sayer, JW  Treasurer & MJ Costello), (1996)  pp. 185-195. Fishing News Book, Oxford. [3] Revie CW, Robbins C, Gettinby G, Kelly L, Treasurer JW.  A mathematical model of the growth of sea lice, Lepeophtheirus salmonis, populations on farmed Atlantic salmon, Salmo salar L., in Scotland and its use in the assessment of treatment strategies. J. Fish Dis. (2005) 28: 603-613. [4] Robbins C, Gettinby G, Lees L, Baillie M, Wallace C, Revie CW, Assessing topical treatment interventions on Scottish salmon farms using a sea lice (Lepeophtheirus salmonis) population model. Aquaculture (2010) 306: 191-197.  [5] Gettinby G, Robbins C, Lees F, Heuch PA, Finstad B, Malkenes R and Revie CW.  Use of a mathematical model to describe the epidemiology of Lepeophtherius salmonis on farmed Atlantic salmon Salmo salar in the Hardangerfjord, Norway. Aquaculture (2011) 320: 164-170. [6] Cox R, Groner M, Gettinby G, Revie CW.   Modelling the efficacy of cleaner fish for the biological control of sea lice in farmed salmon. Proceedings of the 13th ISVEE Conference, Aug 20-24, 2012, Maastricht, Netherlands. [7] Groner M, Cox R, Gettinby G, Revie CW.  Individual-based models: A new approach to understanding the biological control of sea lice. Proceedings of the 9th International Sea Lice conference, May 21-23, 2012, Bergen, Norway. [8] Groner ML, Cox R, Gettinby G and Revie CW.  Use of agent-based modelling to predict benefits of cleaner fish in controlling sea lice, Lepeophtheirus salmonis, infestations on farmed Atlantic salmon, Salmo salar L. Journal of Fish Diseases (2012) doi:10.1111/jfd.12017. [9] Stien A, Bjørn PA, Heuch  PA, Elston D. Population dynamics of salmon lice Lepeophtheirus salmonis on Atlantic salmon and sea trout. Mar. Ecol. Prog. Ser. (2005) 290:263-275.

Oral: Animal Health

Dan Haydon A-12 From Epidemic to Elimination: Density-Vague Transmission and the Design of Mass Dog Vaccination Programs
Daniel T Haydon, Sunny Townsend, Sarah Cleaveland, Katie Hampson Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow
Objectives: Rabies is one of the most important zoonotic diseases in the world, causing an estimated 55,000 human deaths each year, primarily in Asia and Africa.  Momentum is building towards development of a strategy for the global elimination of canine rabies, which has recently been identified as a priority by WHO, OIE and FAO as well as other international human and animal health agencies.  This presentation will address several critical issues relating to the design of mass dog vaccination campaigns for the cost-effective control and elimination of canine rabies.
Methods: Our findings are based on the analysis of data generated from a high-profile and well-studied outbreak in Bali, Indonesia, and the on the results of a closely parameterized spatially explicit computer simulation of the dynamics of rabies outbreaks.
Results: We present three main findings.  The first is that although dog densities on Bali are at least an order of magnitude higher than other populations in which rabies has been studied, our estimate for the basic reproduction number (R0) of ~ 1.2 is similar to other populations with much lower dog densities, which suggests that, counter to expectations, R0 for rabies is essentially density independent. 
The second result follows directly from these consistent values of R0: across a wide range of settings, and even in very high-density dog populations, control and elimination of canine rabies by dog vaccination is an entirely feasible control option.  Additional measures to reduce dog population density are not likely to be necessary.
Our third result is that the effectiveness of vaccination depends primarily upon reaching a sufficient vaccination coverage (70%) across the population in successive campaigns, and does not improve with more complex, reactive or synchronized campaigns.  However, even small ‘gaps' in vaccination coverage can significantly impede prospects of elimination, and therefore regional coordination and participation in such campaigns is critical.
Conclusions: This study has enabled us to evaluate the impact of different vaccination strategies on human deaths averted and the time it will take for rabies to be eliminated from Bali under a range of plausible scenarios.  Modeling can be used to develop simple, pragmatic and operational guidelines for regional rabies vaccination campaign that will be of immediate practical relevance for developing strategies for the global elimination of canine rabies.


Oral: Methodology - New Modelling Approaches

Wojciech Krzyzanski A-14 Physiologically Structured Population Model of Intracellular Hepatitis C Virus Dynamics
Wojciech Krzyzanski (1), Xavier Woot de Trixhe (2), Filip De Ridder (2), An Vermeulen (2) (1) University at Buffalo, NY, USA; (2) Janssen Research & Development, a division of Janssen Pharmaceutica NV, Beerse, Belgium
Objectives: To develop a physiologically structured population model capable of describing intracellular dynamics of viral RNA and its integration with observable circulating HCV RNA levels.
Methods: The standard model of viral dynamics [1] consists of target cells (T), infected cells (I), and viral load (V). The circulating virus levels are determined by the production (pI) and elimination rate (cV). The drug inhibits the viral production rate. To explain the discrepancy in the estimates of the half-life of the circulating HCV RNA, the standard cellular infection (CI) model was expanded by including the drug effects on intracellular processes of viral RNA production and virion assembly [2]. The central part of this model is the intracellular level of HCV RNA (R). The link between the intracellular and cellular infection (ICCI) model and CI model has been achieved by replacing the constant p with a time dependent p(t) = rR(t). To account for the time scale of intracellular processes, the time from infection a was introduced [3].  a was interpreted as an individual cell characteristic (structure) and an a-structured population model was applied.We propose a new physiologically structured population (PSP) model where R rather than a is the individual cell structure. The production rate for circulating HCV RNA is expressed as rRtot(t), where the total intracellular viral RNA is a new link between ICCI and CI models. The drug effect is dose dependent [4].The p-state equations of the PSP model were integrated resulting in a CI model augmented by a new variable Rtot(t). The model parameters were obtained from [3]. Simulations were performed to compare the time courses of V(t) with the results presented in [3]. Additional simulations were done to study the impact of dose on V(t). All simulations were performed using MATLAB R2012b.
Results: The circulating levels of HCV RNA predicted by the R-structured population model overlap with that for the a-structured model. The dose effect on V(t) exhibits a critical dose Dosecrit. For Dose > Dosecrit, V(t) vanish for larger times implicating virus eradication. For Dose < Dosecrit, those variables approach new steady-states that are dose dependent.
Conclusion: The R-structured population model describes the drug effect on the intracellular processes and allows integration with the cell infection model. The viral load time courses predicted by the PSP model are similar to the time courses generated by the standard CI model.
References: [1] Neumann AU, Lam NP, Dahari H, Greatch DR, Wiley TE, Mika B, Perelson AS, Hepatitis C viral dynamics in vivo and the antiviral efficacy of interferon-alpha therapy. Science (1998) 282:103-107. [2] Guedj J, Neumann AU, Understanding hepatitis C viral dynamics with direct-acting antiviral agents due to the interplay between intracellular replication and cellular infection dynamics. J. Theor. Biol. (2010) 267:330-340. [3] Guedj J, Dahari H, Rong L, Sansone ND, Nettles RE, Cotler SJ, Layden TJ, Uprichard SL, Perelson AS, Modeling shows that the NS5A inhibitor daclatasvir has two modes of action and yields a shorter estimate of the hepatitis C virus half-life. PNAS (2013) 110: 3991-6. [4] Snoeck E, Chanu P, Lavielle M, Jacqmin P, Jonsson EN, Jorga K, Goggin T, Grippo J, Jumbe NL, Frey N, A comprehensive hepatitis C viral kinetic model explaining cure. Clin. Pharmacol. Ther. (2010) 87:706-713.

Oral: Drug/Disease modelling

Martin Bergstrand A-15 Modeling of the concentration-effect relationship for piperaquine in preventive treatment of malaria
Martin Bergstrand (1), François Nosten (2,3,4), Khin Maung Lwin (4), Mats O. Karlsson (1), Nicholas White (2,3), Joel Tarning (2,3) (1) Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden. (2) Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. (3) Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK. (4) Shoklo Malaria Research Unit (SMRU), Mae Sod, Thailand.
Objectives: A randomized, placebo controlled trial conducted on the Northwest border of Thailand compared monthly to bi-monthly treatment with a standard 3-day treatment regimen of dihydroartemisinin-piperaquine [1]. A total of 1000 healthy adult male subjects were followed up weekly for 9 months of treatment. This project aimed to characterize the concentration-effect relationship for the malaria preventive effect of piperaquine and utilize it for simulations of dosing in vulnerable populations and in areas with piperaquine resistance.
Methods: Seasonal variations in baseline risk of malaria infection were investigated by applying one or two surge functions to a constant baseline hazard for placebo treated subjects. A mixture model was used to differentiate between a high- and low-risk subpopulation [2]. Monthly observations of piperaquine plasma concentrations were modeled using a frequentist prior [3] based on a published PK model [4]. A joint PKPD model was subsequently applied to explore the effect of piperaquine plasma concentration on malaria infection hazard. The model was sequentially extended to account for the effect of dihydroartemisinin and the delay between the malaria diagnosis and the crucial point of prevention failure.
Results: One significant seasonal peak in malaria transmission was identified from May throughout June during when the hazard was increased with 217% (RSE 27%). The concentration-effect relationship was best characterized with a sigmoidal Emax relationship where concentrations of 7 ng/mL (RSE 13%) and 20 ng/ml were found to reduce the hazard of acquiring a malaria infection by 50% (i.e. IC50) and 95% (IC95), respectively.
Simulations of monthly dosing, based on the final model and literature information about PK, suggested that the one year incidence of malaria infections could be reduced by 70% with a recently suggested dosing regimen compared to the manufacture recommendations for children with a body weight of 8-12 kg [5]. Pregnant women were predicted to have a 12.5% higher incidence compared to non-pregnant.
Conclusions: For the first time a concentration-effect relationship for the malaria preventive effect of piperaquine was established. The established model has been useful in translating observed results from a healthy male population to that expected in other populations.
References: [1] K. M. Lwin et al., Randomized, double-blind, placebo-controlled trial of monthly versus bimonthly dihydroartemisinin-piperaquine chemoprevention in adults at high risk of malaria. Antimicrobial Agents and Chemotherapy 56, 1571 (2012). [2] Farewell, V.T., The use of mixture models for the analysis of survival data with long-term survivors. Biometrics, 1982. 38(4): p. 1041-1046. [3] Gisleskog, P.O., M.O. Karlsson, and S.L. Beal, Use of prior information to stabilize a population data analysis. J Pharmacokinet Pharmacodyn, 2002. 29(5-6): p. 473-505. [4] Tarning, J., et al., Population pharmacokinetics of dihydroartemisinin and piperaquine in pregnant and nonpregnant women with uncomplicated malaria. Antimicrobial Agents and Chemotherapy, 2012. 56(4): p. 1997-2007. [5] Tarning, J., et al., Population pharmacokinetics and pharmacodynamics of piperaquine in children with uncomplicated falciparum malaria. Clinical Pharmacology and Therapeutics, 2012. 91(3): p. 497-505.
 

Oral: Methodology - New Modelling Approaches

Matt Hutmacher A-16 A Visual Predictive Check for the Evaluation of the Hazard Function in Time-to-Event Analyses
Matthew M Hutmacher Ann Arbor Pharmacometrics Group (A2PG)
Objectives: To present methods for performing visual predictive checks (VPCs) specifically for evaluating the hazard function while modeling time-to-event (TTE) data. Binned and smoothed hazard estimators will be discussed for continuous single-event TTE data.
Methods: Pharmacometricians are becoming more involved in determining exposure-response relationships for efficacy and safety TTE endpoints. because these can be the most clinically informative for certain indications. Determining the hazard, or instantaneous risk, of an event has great utility. Changes in the absolute risk of an event over time contain information for supporting dosing or titration strategies. Methods for TTE analyses are being discussed ([1],[2]) and presented more frequently (for example, see [3]). However, little can be found for simulation-based model evaluation (or VPC) other than using Kaplan-Meier (KM) curves [1]. KM based methods evaluate the model through the survival function, which is an exponential function of the integrated (cumulative) hazard. Thus, hazard evaluation using KM curves does not provide a direct assessment of the hazard's features. It may also lack sufficient sensitivity in some cases [4]. A binned hazard estimate (BHE) approach is presented first. The method essentially considers a piecewise constant hazard for each bin and uses a simple hazard estimator for the bin. Conceptually straightforward extensions can be made using running line smoothers (RLS) with further smoothing using kernel regression. However, going back to Watson and Leadbetter (1964) [5], kernel smoothers (KS) can be directly applied. This method is more complex conceptually. Literature in this area is quite rich.
Results: Simulations were performed for various hazard functions. The BHE, RLS, and KS methods described above are introduced, implementation and considerations for their use are discussed, and the methods are contrasted to the KM method typically used.
Conclusions: Hazard-based VPCs provide a direct evaluation of the hazard function and provide a valuable simulation-based diagnostic tool for development of TTE models.
Reverences: [1] Holford N, Lavielle M. A tutorial on time to event analysis for mixed effects modellers. PAGE 20 (2011) Abstr 2281 [www.page-meeting.org/?abstract=2281] [2] Hu C, Szapary P, Yeilding N, Zhou N. Informative dropout and visual predictive check of exposure-response model of ordered categorical data. PAGE 20 (2011) Abstr 1991 [www.page-meeting.org/?abstract=1991] [3] Frobel AK, et. al. A time-to-event model for acute rejections in paediatric renal transplant recipients treated with ciclosporin A. PAGE 21 (2012) Abstr 2374 [www.page-meeting.org/?abstract=2374] [4] Hutmacher MM, Krishnaswami K, Lamba M, French JL. A diagnostic plot of evaluating time-to-event models. Abstract presented at ACCP 2011 [5] Watson GS, Leadbetter MR. Hazard analysis I. Biometrika (1964) 51-175-183

Oral: Methodology - New Tools

Celine M. Laffont A-17 Non-inferiority clinical trials: a multivariate test for multivariate PD
Laffont C. M.(1), Fink M(2) and Concordet D(1) (1) INRA, UMR 1331, Toxalim, F-31027 Toulouse, France. Université de Toulouse, INPT, ENVT, UPS, EIP, F-31076 Toulouse, France; (2) Novartis Pharma AG, Basel, Switzerland
Objectives: Composite PD endpoints are a common feature of clinical trials. This multiplicity poses a challenge for the statistical comparison of two treatments, generally the non-inferiority of a drug to a reference. Several strategies are possible. One is to test each endpoint separately but the risk is to have different conclusions and to fail to demonstrate non-inferiority because we have to correct for the multiplicity of the tests (loss of power). A second strategy is to derive a single variable from the multiple endpoints (either binary: responder/non-responder, or linear combination) and perform a single test. In that case, we lose part of the information. We have seen in previous works1,2,3 that it is possible to model all endpoints simultaneously. In that context, we propose a multidimensional statistical test which exploits all the information and is a priori more powerful.
Methods: We assume that a multivariate population model is available where treatment differences are coded as ratio parameters on the PD parameters of interest. We define the statistical hypotheses of the test in a multidimensional framework. As previously discussed4, several definitions are possible based on intersection/union principles. We propose a decision rule which can be interpreted geometrically as follows: the null hypothesis H0 is rejected when the confidence region of the vector of ratio parameter estimates has no common point with H0. Based on several simulation studies, we explore the advantages of this test over separate univariate tests. We then apply the test to real clinical data where the efficacy of NSAIDs on chronic osteoarthritis is evaluated using four ordinal responses. 
Results: We found that there is a balance between the dimension (the number of endpoints), the correlation between estimates, and the size of the dataset. When applied to real clinical data, non-inferiority was demonstrated with the multivariate test. When no correction was applied to account for the multiplicity of the tests, it was also demonstrated on each response separately. In contrast, when the multiplicity of the tests was accounted for as it should, non-inferiority could not be demonstrated for any response.
Conclusion: Multivariate testing definitely raises some challenges for the scientists and regulatory authorities (definition of null hypothesis, non-inferiority margin) but needs to be explored as it can be a powerful tool to increase power and thus reduce clinical costs.
References: [1] Laffont CM and Concordet D. How to analyse multiple ordinal scores in a clinical trial? Multivariate vs. univariate analysis. PAGE 20 (2011) Abstr 2157. [2] Laffont CM, Fink M, Gruet P, King JN, Seewald W and Concordet D. Application of a new method for multivariate analysis of longitudinal ordinal data testing robenacoxib in canine osteoarthritis. PAGE 21 (2012) Abstr 2548. [3] Ueckert S, Plan EL, Ito K, Karlsson MO, Corrigan B and Hooker AC. Application of Item Response Theory to ADAS-cog Scores Modelling in Alzheimer's Disease. PAGE 21 (2012) Abstr 2318. [4] Hasler M and Hothorn LA. Simultaneous confidence intervals on multivariate non inferiority. Statistics in Medicine, 2012 online.
Oral presentations Thursday
Oral: Lewis Sheiner Student Session

Abhishek Gulati A-18 Simplification of a multi-scale systems coagulation model with an application to modelling PKPD data
Abhishek Gulati (1), Geoffrey K Isbister (2, 3), Stephen B Duffull (1) (1) School of Pharmacy, University of Otago, Dunedin, New Zealand; (2) Department of Clinical Toxicology and Pharmacology, Calvary Mater Newcastle, NSW, Australia; (3) School of Medicine and Public Health, University of Newcastle, NSW, Australia
Background
A comprehensive systems pharmacology model of the coagulation network was recently shown to describe the time course of changes in coagulation factors in response to Australian elapid envenoming [1]. The model consists of 62 ordinary differential equations (ODEs) and 178 parameters with multiple inputs and outputs. Based on any given set of available data relating to a specific input-output process, it is possible that some compartments are either less important or have no influence at all. Fixing the parameters that are not informed by the data would solve the issue of identifiability but not resolve model complexity. In this work, we describe the simplification of a multiscale systems coagulation model and its application to describe the recovery of fibrinogen concentrations postsnake bite. Available data includes timed fibrinogen concentrations in patients with complete venominduced consumption coagulopathy resulting from Brown snake envenomation [2]. The patients (N=61) were recruited to the Australian Snakebite Project from over 100 hospitals in Australia between January 2004 and May 2008.
Aims
The overall aim of this work was to explore a simplification of a coagulation systems pharmacology model for use in modelling pharmacokinetic-pharmacodynamic (PKPD) data. Four specific objectives were identified: (1) to create a simplified model for exploring fibrinogen recovery after envenomation that mechanistically aligns with the coagulation systems pharmacology model, (2) to extract the simplified model for use for estimation purposes, (3) to assess structural identifiability of the simplified model based on the inputs and outputs available in the dataset and (4) to develop a population PKPD model for fibrinogen concentration-time data based on the mechanisms apparent in the simplified model.
Methods
(1) Simplification of the coagulation systems pharmacology model: The technique of proper lumping, based on a previously published method [3], was used to simplify the 62 compartment ("original") model. Fibrinogen and Brown snake venom absorption and plasma compartments were left unlumped. For each of the remaining 59 lumpable compartments, the compartments were lumped randomly and a lumping matrix constructed. This lumping matrix was used to transform the full state parameter vector to the lumped state vector ("lumped" model). The simulated time courses of fibrinogen post Brown snake bite were compared among the lumped and original models to assess for loss of predictive performance. Simulations were carried out using MATLAB® R2011a. (2) Extraction of the simplified model: ODEs of the lumped model were "extracted" from the ODEs of the original model by eliminating the "unwanted" reactions that did not have any influence on the fibrinogen profile. ODEs of the lumped compartments that were formed as a result of merging of various compartments from the original model had to be explicitly written as if they had been unlumped compartments. The clotting factor that was most relevant to the Brown snake venomfibrinogen relationship represented its respective lumped compartment. (3) Identifiability of the simplified model: The structural identifiability of the extracted model was assessed using an Information Theoretic Approach [4]. A criterion that consisted of two predefined conditions, as per [4], had to be met for a model to be structurally identifiable. Population OPTimal (POPT) design software was used for the analysis. (4) Modelling the fibrinogen concentration time data using the simplified model: A full population approach was carried out to analyze the fibrinogen data using NONMEM® v7.2. The extracted model was used as the structural model and no further changes were made to the structure of the model. The unidentifiable parameters obtained from Methods (3) were fixed. BSV was considered for parameters that were identifiable. The models with BSV on one or more structural parameters were assessed for significance using the likelihood ratio test that required a decrease in the objective function value of at least 3.84. A visual predictive check (VPC) to evaluate the final model was performed by simulating 1000 replicates from the model and comparing the observed data and the prediction intervals derived from the simulated data graphically.
Results
(1) Simplification of the coagulation systems pharmacology model: The original 62 compartment model was lumped to a 5 compartment model that described the Brown snake venomfibrinogen relationship. An in silico Brown snake venom bite followed by an in silico antivenom administration at 4 hours resulted in a similar consumption-recovery profile for fibrinogen using the lumped and original models. Lumping the compartments further significantly reduced the predictive performance of the lumped model. (2) Extraction of the simplified model: Extraction of the ODEs of the lumped model resulted in reduction of the total number of parameters to 11 compared to 178 in the original model. A Brown snake bite using the extracted model resulted in the nadir of fibrinogen depletion to 0.025 g/L compared to 0.018 g/L with the original model. (3) Identifiability of the simplified model: Assessment of identifiability of the extracted model using POPT found that 9 parameters out of the total 11 parameters were identifiable. The remaining two parameters were fixed. (4) Modelling the fibrinogen concentration time data using the simplified model: The decline and eventual recovery of fibrinogen after Brown snake envenomation was described by the 5 compartment model. A VPC showed that the model explained the observed data well. The half-life of fibrinogen was estimated to be 40 hrs (1.5 days) post Brown snake envenomation which was close to a half-life of 1 day observed in patients post Taipan snake bites [5]. The half-life of Brown snake venom was estimated to be equal to 55 minutes and refers to the procoagulant toxin in the venom and not the venom itself.
Conclusions
The technique of proper lumping was able to simplify a complicated systems pharmacology model to a much simpler model that retained a clear physical interpretation of the input-output relationship as seen in the original model. Coagulation factors - prothrombin and thrombin seemed to play the most important role in the Brown snake venom-fibrinogen relationship. The technique of structural identifiability analysis identified the parameters that could be estimated precisely after fixing the unidentifiable parameters. The techniques used in this study can be applied to other multi-scale pharmacology models.
References [1] Gulati A, Isbister GK, Duffull SB. Effect of Australian elapid venoms on blood coagulation: Australian Snakebite Project (ASP-17). Toxicon. 2013;61:94-104. [2] Isbister GK, Scorgie FE, O'Leary MA, Seldon M, Brown SG, Lincz LF. Factor deficiencies in venom-induced consumption coagulopathy resulting from Australian elapid envenomation: Australian Snakebite Project (ASP-10). J Thromb Haemost. 2010;8(11):2504-13. [3] Dokoumetzidis A, Aarons L. Proper lumping in systems biology models. IET systems biology. 2009;3(1):40-51. [4] Shivva V, Korell J, Tucker IG, Duffull SB. Identifiability of Population Pharmacokinetic-Pharmacodynamic Models.  Population Approach Group in Australia and New Zealand (PAGANZ); University of Queensland, Brisbane, Australia. 2013. [5] Tanos PP, Isbister GK, Lalloo DG, Kirkpatrick CM, Duffull SB. A model for venom-induced consumptive coagulopathy in snake bite. Toxicon. 2008;52(7):769-80.

Oral: Lewis Sheiner Student Session

Nelleke Snelder A-19 Mechanism-based PKPD modeling of cardiovascular effects in conscious rats - an application to fingolimod
N. Snelder (1,2), B.A. Ploeger (1), O. Luttringer (3), D.F. Rigel (4), F. Fu (4), M. Beil (4), D.R. Stanski (3) and M. Danhof (1,2) (1) Division of Pharmacology, Leiden Academic Centre for Drug Research, Leiden, The Netherlands; (2) LAP&P Consultants BV, Leiden, The Netherlands; (3) Modeling and simulation department, Novartis, Basel, Switzerland; (4) Cardiovascular and Metabolism Research, Novartis Institutes for BioMedical Research, Novartis Pharmaceuticals Corporation, East Hanover, New Jersey, USA
Objectives
Fingolimod (FTY720; Gilenya (trade name)) is a sphingosine 1-phosphate (S1P) receptor modulator, which is effective in the treatment of multiple sclerosis[1]. In 2010 fingolimod was approved for treatment of patients with relapsing forms of multiple sclerosis at a dose of 0.5 mg. However, early in clinical development a dose-dependent mild increase in blood pressure of 5-6 mmHG was observed at the supra-therapeutic doses of 1.25 and 5 mg. The mechanism of action (MoA) underlying this effect was not fully understood. In general, cardiovascular safety issues in drug development occur often. In this context, an adequate understanding of the cadiovascular system (CVS) which regulates blood pressure in both preclinical species and human is pivotal to efficiently anticipate clinical effects of drugs on blood pressure and ultimately improve translational drug research. The development of such a translational pharmacodynamic (PD) model requires a mechanistic understanding of blood pressure regulation. The physiological principles of the CVS including BP regulation are well characterized and the homeostatic principles of the CVS are thoroughly understood. Briefly, mean arterial pressure (MAP) equals the product of cardiac output (CO) and total peripheral resistance (TPR) and CO equals the product of heart rate (HR) and stroke volume (SV). However, drug effects on this interrelationship have not been analyzed in a mechanism-based and quantitative manner. This investigation aimed 1) to describe, in a mechanism-based and quantitative manner, the effects of drugs with different MoA on the interrelationship between BP, TPR, CO, HR and SV and 2) to describe the effect of fingolimod on the CVS and to get a better understanding of mechanisms leading to blood pressure changes following administration of fingolimod using the developed drug-independent model.
Methods
The cardiovascular effects of 8 drugs with diverse MoA's, (amlodipine, fasudil, enalapril, propranolol, hydrochlorothiazide, prazosin, amiloride and atropine) following a single administration of a range of different doses were characterized in spontaneously hypertensive (SHR) and normotensive (WKY) rats. In addition, the effect of fingolimod following multiple administrations (maximal 4 weeks) of doses of 0, 0.1, 0.3, 1, 3 and 10 mg/kg were characterized in SHR and WKY rats. The rats were chronically instrumented with ascending aortic flow probes and/or aortic catheters/radiotransmitters for continuous recording of BP, HR and SV. Data were analyzed in conjunction with independent information on the time course of drug concentration using a mechanism-based PKPD modeling approach. The interrelationship between MAP, TPR, CO, HR and SV is expressed by the formulas 1) MAP=CO*TPR and 2) CO=HR*SV. Previously, we have developed a mechanism-based linked turnover model to describe the inter-relationship between MAP, CO and TPR[2]. This model consisted of two differential equations, one for CO and one for TPR, which were linked by negative feedback through MAP. Following a top-down modeling approach this model was extended in two ways. I) HR and SV were included in the model. The extended model consisted of three linked turnover equations involving the basic parameters of the CVS, TPR, HR and SV all linked by negative feedback through MAP. II) the circadian rhythm, which was observed in all 5 parameters of the CVS, was described by two cosine functions, one influencing HR and one influencing TPR. Linear, log-linear, power, Emax and Sigmoid Emax models were evaluated to describe the drug effects on TPR, HR or SV. Subsequently, the developed drug-independent model was applied to identify the site of action of fingolimod and to describe the effect of fingolimod on the 5 parameters of the CVS. To this extend the system-parameters were fixed and only drug-specific parameters were estimated.
Results
By simultaneous analysis of the effects of 8 different compounds with diverse MoA's, the dynamics of the interrelationship between BP, TPR, CO, HR and SV were quantified. System-specific parameters could be distinguished from drug-specific parameters (all correlations < 0.95) indicating that the developed model is drug-independent. Model based hypothesis testing on the basis of the developed mechanism-based CVS model revealed that the increase in BP in rats, which was observed after treatment with fingolimod, is mediated by a primary effect of fingolimod on TPR. The effect of fingolimod on TPR was described by a combination of a fast (effect on the production rate of TPR (Kin_TPR) and slow effect on TPR (disease modifying effect on the dissipation rate of TPR (kout_TPR). Both effects were found to be proportional to the baseline and the slow effect resulted in a permanent increase in BP as compared to the baseline at start of treatment. The slow effect was dependent on disease state (baseline TPR). This explains why the slow effect does not occur in WKY rats, which have a lower baseline TPR. Through the feedback-mechansims the drug effect on TPR results in an increase in MAP and TPR and a decrease in CO, HR and SV.
Conclusions
A system-specific model characterizing the interrelationship between BP, TPR, CO, HR and SV in rats has been obtained, which was used to quantify and predict cardiovascular drug effects and to elucidate the MoA for the effect of fingolimod. Ultimately, the proposed PKPD model may allow prediction of BP effects in humans based on preclinical evaluations of drug effect. It should be noted that the identified set of system parameters is specific for SHR and WKY rats. Consequently, applications of the developed model, using the identified set of system parameters, are limited to SHR and WKY rats. However, an advantage of a mechanism-based model is that it allows accurate extrapolation between different rat strains and from one species to another[3,4] as the structure of the model is expected to be the same in all species. Therefore, future research will include the application of the developed drug-independent model to predict the clinical response based on preclinical data for fingolimod and other compounds. To this end the developed drug-independent model will be scaled to human and validated on human MAP and CO measurements.
References [1] Cohen JA, Barkhof F, Comi G, Hartung HP, Khatri BO, Montalban X (2010). Oral fingolimod or intramuscular interferon for relapsing multiple sclerosis. N Engl J Med. 362(5): 402-15. [2] Snelder N, Ploeger BA, Luttringer O, Rigel DF, Webb RL, Feldman D, Fu F, Beil M, Jin L, Stanski DR and Danhof M. PKPD modeling of the interrelationship between mean arterial blood pressure, cardiac output and total peripheral resistance in conscious rats (Submitted for publication) [3] Danhof M, de Lange EC, Della Pasqua OE, Ploeger BA, Voskuyl RA (2008). "Mechanism-based pharmacokinetic-pharmacodynamic (PK-PD) modeling in translational drug research." Trends Pharmacol Sci. 29(4): 186-191. [4] Ploeger BA, van der Graaf PH, Danhof M (2009). "Incorporating receptor theory in mechanism-based pharmacokinetic-pharmacodynamic (PK-PD) modeling." Drug Metab Pharmacokinet. 24(1): 3-15.

Oral: Lewis Sheiner Student Session

Nadia Terranova A-20 Mathematical models of tumor growth inhibition in xenograft mice after administration of anticancer agents given in combination
Nadia Terranova (1), Massimiliano Germani (2), Francesca Del Bene (2), Paolo Magni (1). (1) Dipartimento di Ingegneria Industriale e dell'Informazione, Università degli Studi di Pavia, Italy; (2) PK & Modeling, Accelera srl, Nerviano (MI), Italy.
Objectives In clinical oncology, combination treatments are widely used and increasingly preferred over single drug administrations. Therefore, the R&D process is nowadays focused on the development of new compounds that can be successfully administered in combination with drugs already on the market. To this aim, preclinical studies are routinely performed, even if they are only qualitatively analyzed, on xenograft mice for the assessment of new combination therapies. The ability of deriving from single drug experiments a reference response to a joint administration, assuming no interaction, and comparing it to real response would be the key to recognize synergic and antagonist compounds. This work is aimed at deriving quantitative information from standard experiments. In particular, the definition of no interaction between drug effects has been provided by means of a new mathematical model. On this basis, we have also developed a new combination model able to predict the tumor growth inhibition (TGI) in combination regimens and provide a quantitative measurement of the nature and the strength of the pharmacological drug interaction as well.
Methods Experimental Methods The experimental setting is that of a typical in vivo study routinely performed within several drug development projects using human carcinoma cell lines on xenograft mice [1]. The typical combination experiment involves the control arm, the single agent arms and the combination arms. Average data of tumor weight of control and treated groups were considered. The PKs are evaluated in separated studies. The no interaction model Starting from a minimal set of basic assumptions at cellular level that include and extend those formulated for the single drug administration [2], a minimal model able to define and simulate the no interacting behavior of an arbitrary number of co-administered antitumor drugs has been formulated. The tumor growth dynamics is described by an ordinary and several partial differential equations. Under suitable assumptions, the model reduces to a lumped parameter model that represents the extension of the very popular Simeoni TGI model [3] to the combined administration of two non-interacting drugs. The TGI minimal model parameters relative to the tumor growth and to the drugs action were estimated from experimental data coming from single-drug administrations and used to simulate combination regimens under the hypothesis of no interaction. Fitting was performed by nonlinear least squares as implemented in the lsqnonlin routine of MATLAB 2007b suite with analytical computation of the Jacobian. Each residual was weighted proportionally to the inverse of the related measurement. The combination model Starting from the TGI minimal model, we have also developed a new PK-PD model able to predict tumor growth after the co-administration of two anticancer agents, assessing the nature and the strength of interaction as well. The tumor growth rate assessed in untreated mice is decreased by two terms proportional to drug concentrations and decreased-increased by one interaction term proportional to their product. In order to provide an understandable measure of the strength of the interaction, two indexes (called synergistic/antagonistic combination index) were defined. PK and PD models were implemented in WinNolin 3.1 for the analysis of several experiments. Model identification was performed by using the nonlinear weighted least squared algorithm (with weights equal to the inverse of the related measurement). As for the minimal model the tumor-related parameters and the drug-related parameters were estimated by fitting the Simeoni TGI model on the single agent arms. Then, fixing these parameters to the estimated values, the new proposed TGI model was fitted against the combination arms to obtain the value of the interaction term.
Results The no interaction model The minimal TGI model specialized for the case of two non-interacting drugs has been applied to analyze the study of irinotecan CPT-11 in combination with two different dosages of a novel compound (here call Drug B) on the HT29 human colon adenocarcinoma cell line. The validity of the no interaction hypothesis was then assessed by a suitable statistical test [4]. CPT-11 and Drug B showed a negative interaction, namely a (slight) antagonistic behavior in both combination arms. The combination model The model was successfully applied to four novel anticancer candidates, synthesized by Nerviano Medical Sciences, Nerviano, co-administered with four drugs already available on the market for the treatment of three different tumor cell lines. In total, six experiments, testing 11 different combination treatments involving more than 230 mice, were led. The estimation of the interaction term allowed an easy evaluation of the nature of the interaction. The combination indexes were then evaluated for the combination treatment in order to have an absolute measure of the strength of interaction. The model has also shown very good capabilities in predicting different combination regimens in which the same drugs were administered at different doses/schedules.
Conclusions Starting from a minimal set of assumptions formulated at cellular level, the proposed minimal TGI model has been defined to describe the case of no interaction between co-administered drugs, in order to provide a theoretical definition of interaction. The model defines a general class of models and at least in one of its specialized form, can be used for the evaluation of drug combinations by exploiting simulations, providing a rigorous alternative to the subjective and qualitative visual comparison of experimental data. Starting from the concepts, a new PK-PD model has been developed and implemented aiming to be an approach of practical use in assessing combination therapy in standard xenograft experiments as well as identifying synergistic drug combinations. The relevance and applicability of the combination model were demonstrated analyzing several studies. This model can be considered an indispensable tool in the preclinical drug development and a crucial advance in the knowledge as it integrates the previous information to improve the decision making. This work was supported by the DDMoRe project (www.ddmore.eu).
References [1] M. Simeoni, G. De Nicolao, P. Magni, M. Rocchetti, and I. Poggesi. Modeling of human tumor xenografts and dose rationale in oncology. Drug Discovery Today: Technologies, 2012. [2] P. Magni, M. Germani, G. De Nicolao, G. Bianchini, M. Simeoni, I. Poggesi, and M. Rocchetti. A mininal model of tumor growth inhibition. IEEE Trans. Biomed. Eng., 55(12): 2683-2690, 2008. [3] M. Simeoni, P. Magni, C. Cammia, G. De Nicolao, V. Croci, E. Pesenti, M. Germani, I. Poggesi, and M. Rocchetti. Predictive pharmacokinetic-pharmacodynamic modeling of tumor growth kinetics in xenograft models after administrations of anticancer agents. Cancer Res., 64: 1094-1101, 2004. [4] M. Rocchetti, F. Del Bene, M. Germani, F. Fiorentini, I. Poggesi, E. Pesenti, P. Magni, and G. De Nicoalo. Testing additivity of anticancer agents in pre-clinical studies: A PK/PD modelling approach. Eur. J of Cancer, 45(18):3336-3346, 2009.

Oral: Drug/Disease modelling

James Lu A-23 Application of a mechanistic, systems model of lipoprotein metabolism and kinetics to target selection and biomarker identification in the reverse cholesterol transport (RCT) pathway
James Lu(1), Katrin Hübner(2), M. Nazeem Nanjee(3), Eliot A. Brinton(4), Norman Mazer(1) (1) Clinical Pharmacology, F. Hoffman-La Roche Ltd., Basel, Switzerland; (2) Department of Modeling Biological Processes, BioQuant, University of Heidelberg, Heidelberg, Germany; (3) Division of Cardiovascular Genetics, University of Utah, Salt Lake City, UT, USA; (4) Atherometabolic Research, Utah Foundation for Biomedical Research, Salt Lake City, UT, USA
Objectives: The inverse association between the levels of high density lipoprotein cholesterol (HDL-C) with cardio-vascular (CV) risk has led to the "HDL-cholesterol hypothesis" whereby interventions raising HDL-C are expected to decrease CV risk [1]. However, the recent failures of HDL-C raising compounds (e.g., CETP inhibitors/modulators [2]) to reduce CV risk have prompted a revision of this hypothesis. The "HDL flux hypothesis" has been proposed [1]: interventions should aim to promote cholesterol efflux into the reverse cholesterol transport (RCT) pathway, leading to plague regression. This new conceptual framework calls for a re-evaluation of targets and biomarkers.  
Methods: In contrast to the stochastic, particle-based model previously presented [3], the current work utilizes a coarse-grained model that describes the dynamics of cholesterol and apoA-I pools by a system of ODEs. Importantly, the cyclic process of HDL particle maturation and re-generation is described, employing geometrical concepts [4]. HDL re-generation results in a feedback loop linking the clearance rate of HDL-C back to the RCT input rate. The 17 parameters in the model are estimated using the maximum a posteriori approach: prior estimates of key parameters are taken from published flux values in normal subjects, which are subsequently informed by the calibration data. "Virtual populations" are created by sampling model parameters from a multivariate normal distribution around the mean to understand epidemiological relationships. Using correlation and principal component analyses of simulation outputs, biomarkers are examined and selected based on further mathematical analysis.
Results: Our model predicts that CETP inhibitors raise HDL-C due to a reduction in its clearance rate, but do not increase the RCT input rate. We believe this provides an explanation for their lack of CV benefit. In contrast, we identify targets that increase both HDL-C and RCT: e.g., ABCA1. Using the model, we further predict that the ratio of lipoprotein parameters pre-b/apoA-I is a biomarker of therapeutic response under ABCA1 upregulation.
Conclusions: A challenge in understanding the effects of perturbations to the RCT pathway is the presence of a feedback loop due to the cyclic nature of HDL metabolism. To meet this challenge, a systems model has been built to help select targets and identify biomarkers. The model shows that only some targets which increase HDL-C are associated with increases in RCT.
References: [1] D.B. Larach, E. M. deGoma, D. J. Rader. Targeting high density lipoproteins in the prevention of cardiovascular disease? Curr Cardiol Rep (2012) 14:684-691.   [2] G. S. Schwartz et al. Effects of dalcetrapib in patients with a recent acute coronary syndrome. The New England Journal of Medicine (2012) 367:2089-2099. 3] J. Lu, K. Hübner, N. Mazer. Refining the mechanism of CETP mediated lipid transfer in a stochastic model of lipoprotein metabolism and kinetics (LMK model). PAGE abstract 2386 (2012). [4] N.A. Mazer, F. Giulianini, N.P. Paynter, P. Jordan, S. Mora. A comparison of the theoretical relationship between HDL size and the ratio of HDL cholesterol to apolipoprotein A-I with experimental results from the Women's Health Study. Clin Chem, (2013).

Oral: Drug/Disease modelling

Rollo Hoare A-24 A Novel Mechanistic Model for CD4 Lymphocyte Reconstitution Following Paediatric Haematopoietic Stem Cell Transplantation
Rollo L Hoare (1,2), Robin Callard (1,2), Paul Veys (1,3), Nigel Klein (1,3), Joseph F Standing (1,2,3) (1) Institute of Child Health, University College London, 30 Guilford St, London, UK; (2) Centre for Mathematics and Physics in the Life Sciences and Experimental Biology, University College London, Gower St, London, UK; (3) Great Ormond Street Hospital NHS Foundation Trust, Great Ormond St, London, UK
Objectives: Before a haematopoietic stem cell transplant (HSCT), a child will usually be given a conditioning regimen to reduce or ablate the host immune system in order to prevent graft rejection. Following HSCT, long-term successful outcomes and short-term complications are associated with the rate and extent of recovery in the child's immune system. Studying immune reconstitution in children presents a huge challenge as the rapidly developing immune system means that expected CD4 T cell counts (a key subset of lymphocytes) for age can vary by as much as three-fold [1]. This work presents a new mechanistic model that has been developed which describes the reconstitution of total body CD4 T cell count with time in children who have had an HSCT.
Methods: The fundamental model of the CD4 cell count has three parameters representing, the initial total body CD4 cell count, thymic output of CD4 cells, and the net loss rate of CD4 cells. The model is made more mechanistic in three ways: (1) accounting for age-related changes in the thymus with a functional form for thymic output [2]; (2) allowing for thymic output not recovering production immediately after the HSCT; (3) including the effects of competition for homeostatic signals leading to changes in the net loss rate with cell quantities. We apply this model to longitudinal data collected in the bone marrow transplant unit in Great Ormond Street Hospital.
Results: Adding the effects of reduced thymic function and competition both significantly improved model fit, and the final model had good descriptive and simulation properties.  In the long term, the modelled population average returned to, or very near to, the total body CD4 count expected for a healthy child. The dynamics of the thymus returning to full production agree well with experimental evidence [3].
Conclusions: A novel mechanistic model for the immune reconstitution of CD4 cells after HSCTs in children has been developed. The model brings together many ideas about the immune system in children, including the changes in the thymus with age, and appears to show clearly the necessity of including both the effects of reduced thymic function post HSCT, and of competition for homeostatic signals by CD4 cells in the body. It is now possible to carry out a multivariate analysis and find which parts of the immune system are affected by covariates such as disease type, drug pre-conditioning, and graft-versus-host disease prophylaxis.
References: [1] S Huenecke et al. Age-matched lymphocyte subpopulation reference values in childhood and adolescence: application of exponential regression analysis. Eur J Haematol 2008; 80(6): 532-39 [2] I Bains et al. Quantifying thymic export: combining models of naive T cell proliferation and TCR excision circle dynamics gives an explicit measure of thymic output. J Immunol 2009; 183: 4329-36 [3] PR Fallen et al. Factors affecting reconstitution of the T cell compartment in allogeneic haematopoietic cell transplant recipients. Bone Marrow Transplant 2003; 32: 1001-14

Oral: Drug/Disease modelling

Huub Jan Kleijn A-25 Utilization of Tracer Kinetic Data in Endogenous Pathway Modeling: Example from Alzheimer’s Disease
Huub Jan Kleijn, Tom Bradstreet, Mary Savage, Mark Forman, Matthew Kennedy, Arie Struyk, Rik de Greef, Julie A. Stone Merck Research Laboratories, Whitehouse Station, NJ, US
Objectives: Tracer kinetic studies can be a valuable tool to gain understanding on the dynamics of protein pathways. However, results interpretation is difficult and requires a model-based evaluation to take full advantage of the data. In this example, timecourse data on CSF tracer and ELISA-based total CSF A² were obtained under unaltered, mild and potent production inhibition with a BACE inhibitor in healthy human to inform understanding of the amyloid pathway, which is central to plaque formation in Alzheimer's Disease. Our goal was to establish a mechanistic pathway model that describes the total A², fraction labeled A², and newly generated A² with a single drug action (inhibition of BACE) to enhance understanding of the utility and interpretation of tracer kinetic data.
Methods: Subjects (n=5/arm) received single doses of placebo, low or high dose BACE inhibitor with 13C-labeled leucine infused from 5 to 15 hours post-dose. Serial plasma and CSF samples were obtained for assessment of drug concentration, total A², and fraction of leucine and A² labeled. Data were fit to a compartmental model reflecting brain pools for precursor protein, BACE cleavage product C99, gamma secretase cleavage product A² and distribution to the lumbar CSF sampling site. Duplicate pathways were needed, informed by the timecourse of fraction 13C-labeled leucine, to separately describe the labeled and unlabeled fractions. BACE inhibition was modeled as an Emax function on the production rate of C99.
Results: The model was able to simultaneously describe the time courses of total A², fraction labeled A², and newly generated A² with a single drug action. Rate constants related to steps in the amyloid pathway could be separated from delays related to distributional processes. Simulations indicated that timing of 13C-leucine infusion relative to dosing of the BACE inhibitor is key in obtaining informative data on the underlying system.
Conclusions: Tracer kinetic approaches together with mechanistic modeling enhance the understanding of endogenous pathway dynamics. A model-based analysis allowed to distinguish between steps in the amyloid pathway and distributional processes. This framework enables a more physiologically based approach to account for effects of A² oligomers and/or plaque pool in Alzheimer's disease. Finally, model-based simulations inform on improvements of the experimental design that will maximize derived knowledge on the underlying system pharmacology of the amyloid pathway.

Oral: Tutorial

Justin Wilkins A-27 Reproducible pharmacometrics
Justin J. Wilkins (1), E. Niclas Jonsson (2) (1) SGS Exprimo NV, Mechelen, Belgium; (2) Pharmetheus AB, Uppsala, Sweden
Reproducibility is the cornerstone of scientific research, but is nonetheless a challenging area in pharmacometric data analysis. The large number of intermediate steps required, often involving multiple versions of datasets, combined with a mixture of software tools and the substantial quantity of results that must be tracked and summarized renders traceability an onerous and time-consuming business. 
The concept of “reproducible research” is that the final product of scientific research is not just the text of a report or research article, but should also include the full computational environment used to produce the results, including all the associated code and data – and that this bundle of data and scripts should be shared with others who wish to reproduce these results. Although this is not often possible in pharmacometrics, given that data are usually confidential and that it may not be practical to reproduce hundreds of model fits, we can apply the process of reproducible research to our activities as far as possible to ensure that traceability is maintained. 
Although there are many approaches that may be taken to adopting this principle, we shall focus on the combination of R, knitr and LaTeX. These tools together enable the end-to-end scripting of data file creation, capture of results from external software tools and subsequent analyses, and can automate the creation of publication-quality reports, articles and slide decks.
We shall demonstrate that applying techniques such as these is not particularly difficult, especially now that they are coming into general use and support from software tools is maturing. We shall discuss the substantial benefits of doing so, which include increased accuracy, efficiency, reliability and credibility, elimination of transcription errors, built-in traceability, and the ability to reproduce an analysis, including article or report, in its entirety years later. A live demonstration will be available during the poster sessions.

Oral: Methodology - New Tools

Nick Holford A-28 MDL - The DDMoRe Modelling Description Language
Nick Holford (1), Mike Smith (2) on behalf of DDMoRe WP3 contributors 1. Department of Pharmaceutical Biosciences, Uppsala University, Sweden 2. Dept Statistical Pharmacometrics, Pfizer Global Research & Development, United Kingdom
Objectives: Definition of a modelling description language (MDL) is a key deliverable from the Innovative Medicines Initiative Drug Disease Modelling Resource (DDMoRe) project [1]. The MDL aims to provide a new standard in describing pharmacometric models consistently across software tools and brings together features of various existing modelling languages. It is intended to be flexible, extensible, easy to code, understand and use. Together with the associated computer-readable markup language, PharmML, the aim is to facilitate automated translation of models and modelling tasks into target application scripts for NONMEM, Monolix, Phoenix NLME, BUGS, R and Matlab.
Methods: A DDMoRe work-package group comprising members from European universities, small to medium enterprises (SME) and the pharmaceutical industry have collaborated for 2 years to develop the MDL. A draft MDL description was proposed and refined through review and input from colleagues across the project. Example models (Use Cases) have been proposed which test the ability of the language to describe a variety model features succinctly and unambiguously.
Results: A MDL specification document has been written that describes the structure and properties of the language. There are two components 1) the Model Coding Language (MCL) which is declarative and describes the mathematical model, parameters, data and task properties. 2) the Task Execution Language which is procedural and defines the workflow of modelling tasks using a R like language which may include (but is not limited to) estimation, simulation, diagnostics, modelling summaries and data generation. Close integration with R is desirable to leverage existing and established modelling and simulation packages. Automated translation from NM-TRAN to MDL [2] and from MDL to NM-TRAN has been demonstrated for simple models. A "Rosetta Stone" has been constructed to assess whether key attributes within the target languages have been adequately expressed within the MCL and to identify how translation of MDL to the other target languages can be achieved.
Conclusions:  It is expected that conversion to the remaining target application scripts will occur rapidly now that the feasibility of using NM-TRAN has been confirmed. Public release of the language specification will occur by June 2013. This work is presented on behalf of the DDMoRe project.
References: [1] The DDMoRe project, www.ddmore.eu Accessed 14 March 2013 [2] Holford NHG. nt2mdl - an automated NM-TRAN to MDL translator.  HYPERLINK "http://nmtran-to-mdl.mango-solutions.com/" http://nmtran-to-mdl.mango-solutions.com/ Accessed 14 March 2013
 


Oral: Methodology - New Modelling Approaches

Vittal Shivva A-30 Identifiability of Population Pharmacokinetic-Pharmacodynamic Models
Vittal Shivva(1)*, Julia Korell(1,2), Ian G Tucker(1), Stephen B Duffull(1) (1)School of Pharmacy, University of Otago, Dunedin, New Zealand (2)Department of Pharmaceutical Biosciences, Uppsala University, Sweden
Background: Mathematical models are routinely used in clinical pharmacology to study the time course of concentration and effect of a drug in the body. Identifiability of these models is an essential prerequisite for the success of these studies [1]. Identifiability is classified into two types, structural identifiability related to the structure of the mathematical model and deterministic identifiability which is related to the study design. Though various approaches are available for assessment of structural identifiability of fixed effects models, no specific approaches are proposed to formally assess population models.
Aim & Objectives: In this study we developed a unified numerical approach for simultaneous assessment of both structural and deterministic identifiability for fixed and mixed effects pharmacokinetic (PK) or pharmacokinetic-pharmacodynamic models. The approach was based on an information theoretic framework [2]. The approach was applied to both simple PK models to explore known identifiability properties and also to a parent-metabolite PK model [3] to illustrate its utility.
Methods & Results: One compartment first order input PK models (Bateman & Dost) were assessed as fixed effects and mixed effects models using the criteria developed in this study. Results from the assessment of mixed effects models revealed that the bioavailable fraction F and its between subject variability (BSV) parameter ÉF were unidentifiable in the Dost model, whereas only F was unidentifiable in the Bateman model. A parent-metabolite model that described the oral PK of ivabradine and its metabolite was assessed for identifiability of both fixed and mixed effects. Assessment of the model revealed that Vm2 (volume of distribution of the metabolite in the central compartment) and FI (bioavailable fraction of the parent) were unidentifiable in the model. All BSV parameters were identifiable in the mixed effects model of ivabradine.
Discussion & Conclusions: Results from the analysis of simple and more complicated (multiple response) PK models have demonstrated the ability of this approach to assess structural identifiability of population models. This method also enables the assessment of deterministic identifiability by examining the diagonal elements of the inverse of the Fisher Information Matrix for a candidate design. The current approach can serve as a unified method for assessing both structural and deterministic identifiability of population models.
References: [1]. Godfrey, K.R., Jones, R.P. & Brown, R.F. Identifiable pharmacokinetic models: The role of extra inputs and measurements. Journal of Pharmacokinetics and Biopharmaceutics 8, 633-648 (1980). [2]. Mentré, F., Mallet, A. & Baccar, D. Optimal Design in Random-Effects Regression Models. Biometrika 84, 429-442 (1997). [3]. Evans, N.D., et al. An identifiability analysis of a parent-metabolite pharmacokinetic model for ivabradine. Journal of Pharmacokinetics and Pharmacodynamics 28, 93-105 (2001).

Oral: Methodology - New Modelling Approaches

Leonid Gibiansky A-31 Methods to Detect Non-Compliance and Minimize its Impact on Population PK Parameter Estimates
Leonid Gibiansky (1), Ekaterina Gibiansky (1), Valerie Cosson (2), Nicolas Frey (2), Franziska Schaedeli Stark (2) (1) QuantPharm LLC, North Potomac, MD, US; (2) F. Hoffmann-La Roche Ltd, Basel, Switzerland
Objectives: To develop and evaluate methods to detect non-compliance and obtain unbiased parameter estimates in a population pharmacokinetic (PK) analysis.
Methods: Data sets emulating clinical studies with different duration, sampling schemes and levels of compliance to a once daily oral dosing regimen were simulated using a 2-compartment model with first-order absorption and elimination and significant drug accumulation. Non-compliance was simulated as drug holidays preceding some observations in 20 to 80% of subjects. For each dataset, the original model was fit assuming full compliance to evaluate precision and bias on the parameter estimates. Two methods (CM1, CM2) to account for non-compliance were tested. CM1 introduced a random effect (ETAerr) on the magnitude of the residual error and re-estimated PK parameters with increasing fractions of subjects with high ETAerr removed from the data set. CM2 is the generalization of the idea proposed in [1]. It relied on rich data obtained immediately before and after an observed dose in the clinic, while trough PK samples related to unobserved doses outside the clinic (outpatient doses) were ignored. To account for possible non-compliance, individual relative bioavailability of the outpatient doses was introduced, estimated, and associated to individual compliance.
Results: When assuming full compliance, the PK parameter estimates were significantly biased. By introducing ETAerr in CM1 the bias was reduced and non-compliant subjects could be associated with a high ETAerr. Incremental removal of subjects with high ETAerr further reduced the bias until the parameter estimates converged to the true values, while the variance of the ETAerr decreased towards zero. However, precision of the obtained parameter estimates decreased with increasing number of subjects removed to obtain unbiased parameter estimates. CM2 yielded unbiased PK parameter estimates for the datasets with any fraction of non-compliant subjects. Non-compliant subjects could be associated with a low bioavailability estimate for the outpatient doses. However, the method heavily relies on the availability of rich data following an observed dose in the clinic.
Conclusions: The proposed methods offer ways to identify subjects with non-compliance and reduce or eliminate bias on PK parameter estimates based on rich or sparse PK sampling data in populations with prevalent non-compliance.
References:  [1] Gupta P, Hutmacher MM, Frame B, Miller R, An alternative method for population pharmacokinetic data analysis under noncompliance. J Pharmacokinet Pharmacodyn. 2008;35(2):219-33.

Oral: Methodology - New Modelling Approaches

Julie Bertrand A-32 Penalized regression implementation within the SAEM algorithm to advance high-throughput personalized drug therapy
Julie Bertrand (1), Maria De Iorio (2), David J. Balding (1) (1) Genetics Institute, University College London, London, UK, (2) Department of Statistical Science, University College London, London, UK
Context: In a previous study, we have shown that penalized regression approaches (such as Lasso) in combination with a model-based population analysis were computationally and statistically efficient to explore a large array of single nucleotide polymorphisms (SNPs) in association with drug pharmacokinetics (PK) [1]. However, these approaches use two stages in which the effect of a SNP on model parameters is assessed after those parameters are estimated.
Objectives: To develop an integrated approach to simultaneously estimate the PK model parameters and the genetic size effects and compare its performance to a penalized regression on Empirical Bayes Estimates (EBEs) and a classical stepwise procedure.
Methods: At each iteration of the Stochastic Approximation (SA) Expectation Maximization algorithm, a penalized regression is realized on the values of the individual parameters issued from the SA to update the vector of fixed effects. In the Lasso procedure, the penalty function is the double-exponential (DE) probability density. Hoggart et al. [2] proposed the HyperLasso, a generalization of the Lasso, to allow the penalty function to have flatter tails and a sharper peak. HyperLasso uses the normal-exponential Gamma (NEG) distribution, which is the DE with the rate parameter drawn from a Gamma distribution. The shape parameter of the NEG was here set to 1 and the scale using a formula ensuring a given family wise error rate (FWER) [2] rather than permutations as in [1].
Our simulated PK model is based on a real-case study but with a design selected to ensure reasonable precision of parameter estimates of 300 subjects and 6 sampling times. The simulated array includes 1227 SNPs in 171 genes. Under the alternative, H1, we randomly picked 6 SNPs per simulated data set which together explain 30% of the variance in the logarithm of the apparent clearance of elimination.
Results: The penalized regression on EBEs and the stepwise procedure obtained a FWER not significantly different from the target value of 0.2, while the integrated approach was more conservative with an empirical FWER of 0.1. Nevertheless, all three approaches obtain similar power estimates to detect each of the 6 causal SNPs with the integrated approach detecting almost no false positives. The integrated approach computing times were longer under the null and under H1, 1.8 and 2.8h compared to 0.08 and 0.12h for the penalized regression on EBEs and 0.08 and 0.73h for the stepwise procedure.
References:  [1] Simultaneous analysis of all SNPs in genome-wide and re-sequencing association studies. Hoggart CJ, Whittaker JC, De Iorio M, Balding DJ. PLoS Genet. 2008, 4(7): e1000130 [2]Multiple single nucleotide polymorphism analysis using penalized regression in nonlinear mixed-effect pharmacokinetic models. Bertrand J, Balding DJ. Pharmacogenet Genomics. 2013, 23(3): 167-74

Oral presentations Friday
Oral: Drug/Disease modelling

Shelby Wilson A-34 Modeling the synergism between the anti-angiogenic drug sunitinib and irinotecan in xenografted mice
S. Wilson, E. Grenier, M. Wei, V. Calvez, B. You, M. Tod, B. Ribba INRIA Grenoble Rhone-Alpes, Numed Project Team, 655 avenue de l’Europe, 38330 Montbonnot-Saint-Martin, France
Objectives: We aim to evaluate a potential synergistic effect between sunitinib, an anti-angiogenic agent, when given in combination with irinotecan, a cytotoxic agent, in preclinical settings using tumor inhibition models.
Methods: We analyze a data set consisting of longitudinal tumor size measurements (1,371 total observations) in 90 colorectal tumor-bearing mice. Mice received single or combination administration of sunitinib and/or irinotecan. We model this data with a system of non-linear ordinary differential equations that describe tumor growth and angiogenesis. Sunitinib is modeled as acting by reducing the carrying capacity of the tumor, while irinotecan directly reduces the tumor bulk by inducing progressive cell death through transit compartments. Model parameters corresponding to tumor growth and monotherapy are estimated in a mixed-effect manner using Monolix (Lixoft) while parameters corresponding to drug synergism are estimated in a fixed-effect manner using a Nelder-Mead Simplex Method. We then evaluate the hypothesis that sunitinib and irinotecan interact synergistically when administered together.
Results: Through a chi-squared test on the residuals generated by the single and combination arm simulations, we conclude that there must be a synergistic interaction between these drugs (p0.05).
Conclusions:  In this chronopharmacology study in 12 healthy volunteers, an influence of circadian rhythm was identified for oral bioavailability of midazolam representing a maximum reduction of 23% at night. Further research using physiologically-based modelling should elucidate which subprocess contributes to this circadian variability in bioavailability.

Poster: Other Drug/Disease Modelling

Marc Vandemeulebroecke I-45 Literature databases: integrating information on diseases and their treatments.
Vandemeulebroecke M, Demin I, Luttringer O, McDevitt H, Ramakrishna R, Sander O Novartis
Objectives: Quantitative knowledge about the clinical efficacy of approved drugs makes it possible to interpret the efficacy of a candidate drug in light of the competitive landscape. This can be used when setting the desired efficacy profile of a new drug candidate, for example in proof of concept, dose finding or inlicensing. In this context, our objective is to build comprehensive literature-based databases on selected indications and their major treatments, containing longitudinal data and covariates to facilitate dynamic modeling.
Methods: Motivated by a case example in Rheumatoid Arthritis, we present the range of applications to date, and a new generic database infrastructure that was developed to further ramp up these efforts.
Results: Eight drug-disease databases have been built, and two are in development. The range of successful applications spans from dose selection to supporting Go/Nogo milestones. The generic database solution has an easy-to-use front end and allows quick extraction of relevant information, while still retaining the full complexity of a relational database in the background.
Conclusions: Great value can be derived from investing time and effort into building literature-based drug-disease databases.
References: [1] Demin et al.: Longitudinal model-based meta-analysis in rheumatoid arthritis: an application toward model-based drug development, Clin Pharmacol Ther 2012. [2] Ito et al.: Disease progression meta-analysis model in Alzheimer's disease, Alzheimer's & Dementia 2010. [3] Mandema et al.: Model-based development of gemcabene, a new lipid-altering agent, AAPS J 2005. [4] McDevitt et al.: Infrastructure development for building, maintaining and modeling indication-specific summary-level literature databases to support model-based drug development, PAGE 2009.

Poster: Absorption and Physiology-Based PK

Nieves Velez de Mendizabal I-46 A Population PK Model For Citalopram And Its Major Metabolite, N-desmethyl Citalopram, In Rats
Nieves Velez de Mendizabal (1, 2), Kimberley Jackson (3), Brian Eastwood (4), Steven Swanson (5), David M. Bender (5), Stephen Lowe (6), Robert R. Bies (1, 2) (1) Indiana Clinical and Translational Sciences Institute (CTSI), Indianapolis, IN, USA; (2) Department of Medicine, Division of Clinical Pharmacology, Indiana University School of Medicine, Indianapolis, USA; (3) Global PK/PD/Trial Simulation, Eli Lilly and Company, Windlesham UK; (4) Global Statistical Sciences, Eli Lilly and Company, Windlesham UK; (5) Lilly Corporate Center, Eli Lilly and Company, Indianapolis, Indiana, USA; (6) Lilly-NUS Centre for Clinical Pharmacology, Eli Lilly and Company, Singapore, Singapore
Objectives: To develop a population PK model able to simultaneously describe citalopram and N-desmethyl citalopram plasma concentrations in rats after IV and PO administration of citalopram.
Methods: Citalopram was administered intravenously (IV) and orally (PO) to Sprague-Dawley rats (mean weight: 285 grams) at different doses: 0.3, 1, 3, and 10-mg/kg IV and 10-mg/kg PO. Plasma samples were collected for citalopram and N-desmethyl citalopram. Data below the limit of quantification BLQ were reported for both compounds at 0.1 ng/mL. All analyses were performed by using NONMEM 7.2 software. BLQ values were included in the analyses and treated as censored information using the M3 method [1]. The Laplacian numerical estimation method was used for parameter estimation. Citalopram and its metabolite were simultaneously modeled for all doses and administration routes. The model was then extended to Wistar rats (mean weight: 497 grams) at different oral doses: 0.3, 1, 3, 10, 30 and 60-mg/kg. Several absorption models were explored (e.g. first, zero order and combined absorptions, Michaelis-Menten, lag time) in combination with dose and/or time covariate effects.
Results: Disposition of citalopram and of its major metabolite was described by a 5-compartment model: a 3-compartment model for citalopram and a 2-compartment for the metabolite. Citalopram clearance and metabolite formation rate were adequately described as linear processes. Metabolite clearance was best described using a Michaelis-Menten clearance. When the Wistar data were included (over a large range of oral doses), the absorption process revealed its complexity.
Conclusions: As far as we are aware, this is the first combined citalopram and metabolite population PK model to describe IV as well as oral data in rats in the literature. A complex absorption model was required to adequately describe the disposition of citalopram and N-desmethyl citalopram over the large dose range studied herein.
References: [1] Beal SL. Ways to fit a PK model with some data below the quantification limit. J Pharmacokinet Pharmacodyn. 2001 Oct;28(5):481-504.

Poster: Other Drug/Disease Modelling

An Vermeulen I-47 Population Pharmacokinetic Analysis of Canagliflozin, an Orally Active Inhibitor of Sodium-Glucose Co-Transporter 2 (SGLT2) for the Treatment of Patients With Type 2 Diabetes Mellitus (T2DM)
E. Hoeben (1), W. De Winter (1), M. Neyens (1), A. Vermeulen (1) and D. Devineni (2) (1) Janssen Research and Development, Model Based Drug Development, Turnhoutseweg 30, B-2340 Beerse, Belgium; (2) Janssen Research and Development, Clinical Pharmacology, 920 Route 202, Raritan, New Jersey, USA
Objectives: Canagliflozin, an orally active inhibitor of SGLT2, is currently in development for the treatment of patients with T2DM. The objective of this analysis was to develop a population pharmacokinetic (PK) model, including relevant covariates as source of inter-individual variability (IIV), with the aim to describe Phase 1, 2 and 3 PK data of canagliflozin in healthy subjects and in patients with T2DM.
Methods: Data were obtained from 1616 subjects enrolled in 9 Phase 1, 2 Phase 2 and 3 Phase 3 trials. Nonlinear mixed effects modeling of pooled data was conducted using NONMEM®[1.2]. IIV was evaluated using an exponential error model and residual error described using an additive model in the log domain. The FOCE method with interaction was applied and the model was parameterized in terms of rate constants. Covariate effects were explored graphically on empirical Bayes estimates of PK parameters, as shrinkage was low. Clinical relevance of statistically significant covariates on model parameters was evaluated. The model was evaluated internally (visual and numerical predictive check) and externally (bias and precision)[3].
Results: The population PK model was first developed using richly sampled Phase 1 data. Gender, age and WT on Vc/F, BMI on ka and BMI and over-encapsulation on Tlag were identified as the most significant covariates affecting the absorption and distribution characteristics of canagliflozin. The absorption and distribution parameters from the final Phase 1 model, including their covariate and random effects, were fixed and the model was re-run on a combined Phase 1, 2 and 3 dataset. A two-compartment PK model with lag-time and sequential zero- and first order absorption was found to provide an adequate description of the observed study data. Further covariate evaluation on ke, estimated in the final model, demonstrated that eGFR, dose and genetic polymorphism (carriers of UGT1A9*3 allele) were statistically significant. The model passed internal and external evaluation and was considered valid from an accuracy and precision point of view.
Conclusions: The developed population model successfully described the PK of canagliflozin in healthy subjects and in patients with T2DM. Although the effects of gender, age and WT on Vc/F and eGFR, dose and genetic polymorphism on ke were statistically significant, given the small magnitude of these effects, they were considered not to be of clinical relevance.
References: [1] NONMEM 7.1.0 Users Guides (1989-2009). Beal SL, Sheiner LB, Boeckmann AJ, and Bauer RJ (eds). Icon Development Solutions, Ellicott City, MD. [2] FDA (1999) Guidance for Industry: Population Pharmacokinetics, U.S. Food and Drug Administration, 1999. [3] Sheiner LB, Beal SL. Some suggestions for measuring predictive performance. J Pharmacokinet Biopharm. 1981; 9:503-512.

Poster: Other Drug/Disease Modelling

Marie Vigan I-48 Modelling the evolution of two biomarkers in Gaucher patients receiving enzyme replacement therapy.
M. Vigan(1), J. Stirnemann(2,3), C. Caillaud (2,4), R. Froissart (5), A. Boutten (6), B. Fantin (7), N. Belmatoug (2,7), F. Mentré(1) (1) INSERM, UMR 738, Univ Paris Diderot, Sorbonne Paris Cité, Paris, France; (2) Referral Center for Lysosomal Diseases, Paris, France; (3) Division of General Internal Medicine, Faculty of Medicine, Geneva University Hospital, Geneva, Switzerland; (4) Laboratoire de Biochimie, Hôpital Cochin, Paris, France; (5) Laboratory of Inborn Errors of Metabolism, Hospices Civils de Lyon, Bron, France; (6) Laboratoire de Biochimie A, Hôpital Bichat, Assistance Publique-Hôpitaux de Paris, 46 rue Henri Huchard, 75018 Paris, France; (7) Service de Médecine Interne, Hôpital Beaujon, AP–HP, Clichy, France.
Objectives: Gaucher disease (GD) [1] is a rare recessively inherited disorder due to the deficiency of lysosomal enzyme glucocerebrosidase. Several biomarkers are significantly increased during this disease, such as ferritin and chitotriosidase. GD can be treated by enzyme replacement therapy (ERT), imi/al-glucerase, but no physiological model was proposed to analyse the evolution of biomarkers during ERT [2,3]. The aim of this study was to develop a drug-disease model explaining the response of biomarkers to ERT and to analyse the influence of several covariates.
Methods: We analysed patients from the French Registry of GD [4] who were treated by ERT (N=238). The accumulation of glucosylceramide in their macrophages leads to an increased production of ferritin and chitotriosidase. Therefore, we modelled that ERT participates in the decrease of these biomarkers and, neglecting their half-life, the turnover models were simplified to exponential drug-disease models. We analysed separately the evolution of both biomarkers using all measurements since initiation of ERT to stop of ERT (more than 6 months) or end of follow-up. Several covariates were tested including age at initiation of ERT, splenectomy and sex. Estimations were performed with MONOLIX 4.2.0 [5].
Results: Median time of follow-up during ERT was 9 [1-19] years. Median age at the initiation of ERT was 22 [1-67] years (18%60% from baseline was believed to show the efficacy on the endpoint (number of lesions obtained with magnetic resonance imaging) [4]. The simulation results using the developed model indicated that ONO-4641 dose more than 0.1 mg produced the decrease. The suppression with lower doses was mild to moderate (30-45%), but the efficacy on the number of lesions was unknown. Further, the simulation results indicated the mean drop-out rate due to the lymphopenia of at most 3% of total patients in phase 2 trial.
Conclusions: The clinical trial simulation of ALC based on the developed population PK-PD model led to the acquisition of useful information for selecting doses in the future trial.
References: [1] Ohno T, Hasegawa C, Nakade S, et al. The prediction of human response to ONO-4641, a sphingosine 1-phosphate receptor modulator, from preclinical data based on pharmacokinetic-pharmacodynamic modeling. Biopharm Drug Dispos (2010) 31: 396-406. [2] Meno-Tetang GM, Lowe PJ. On the prediction of the human response: a recycled mechanistic pharmacokinetic/pharmacodynamic approach. Basic Clin Pharmacol Toxicol (2005) 96: 182-92. [3] Rohatagi S, Zahir H, Moberly JB, et al. Use of an exposure-response model to aid early drug development of an oral sphingosine 1-phosphate receptor modulator. J Clin Pharmacol (2009) 49: 50-62. [4] Kappos L, Antel J, Comi G, et al. Oral fingolimod (FTY720) for relapsing multiple sclerosis. N Engl J Med (2006) 355: 1124-40.

Poster: Study Design

Michael Heathman II-37 The Application of Drug-Disease and Clinical Utility Models in the Design of an Adaptive Seamless Phase 2/3 Study
Michael Heathman(1), Zachary Skrivanek(1), Brenda Gaydos(1), Mary Jane Geiger(2), Jenny Chien(1) (1)Eli Lilly and Company, Indianapolis, IN, USA; (2)Relypsa, Inc, Redwood City, CA, USA
Objectives: A two-stage, adaptive dose-finding, inferentially seamless Phase 2/3 study was designed to optimize the development of dulaglutide (dula), a new therapeutic for the treatment of type 2 diabetes mellitus.  Integrated models of dula pharmacokinetics and pharmacodynamics (PD) of key clinical and safety measures were developed, leveraging early phase clinical data and literature data of marketed comparators.  These models were used to simulate virtual patients and to evaluate the operating characteristics and probability of success of the trial.
Methods: Data from early phase studies were used to develop models of prospectively selected clinical endpoints for dose determination: a linked model of glucose-HbA1c, a weight loss model with placebo response and circadian rhythm models of blood pressure and heart rate.  Published comparator’s longitudinal data were used to inform the timecourses of PD endpoints.  Virtual patient populations (N=10,000) were simulated to match baseline demographic and disease characteristics of a typical Phase 3 study population for up to a year.  A Bayesian theoretical framework was used to adaptively randomize virtual patients sampled from the dataset in Stage 1 to one of seven dula doses.  At each interim analysis, a multi-attribute clinical utility function was applied to predefined dose selection criteria to support either stopping for futility or selecting up to 2 dula doses to advance to Stage 2.
Results: Dula drug-disease models predicted the most likely doses to demonstrate optimal and competitive glycemic efficacy and safety profiles.  In simulated studies, the adaptive algorithm identified the correct dose 88% of the time, compared to as low as 6% for a fixed-dose design using frequentist decision rules.
Conclusions: Drug-disease models developed using limited Phase 1 and literature data are efficient tools to support the optimization of drug development.  Model-based trial simulations allow systematic and robust evaluation of trial design and assessment of probability of trial success.

Poster: Oncology

Emilie Hénin II-38 Optimization of sorafenib dosing regimen using the concept of utility
Emilie Hénin, Michel Tod EMR HCL/UCBL 3738 CTO, Faculté de Médecine Lyon-Sud, Université de Lyon
Objectives: The utility function allows finding a compromise between drug efficacy and toxicity, balancing the probability of benefit and the probability of risks [1, 2]. Sorafenib is an oral non-specific multi-kinase inhibitor, approved for the treatment of renal and hepatic carcinoma, blocking cell proliferation and angiogenesis by targeting Raf/ERK pathway. Hand-foot Syndrome (HFS) is one of the major dose-limiting toxicity. This work aimed at applying the concept of utility function to determine the optimal regimen of sorafenib, integrating models for efficacy and toxicity.
Methods: Sorafenib-induced efficacy and toxicity in 100 replicates of 100 patients were simulated under various dosing regimen: daily dose ranging between 200 and 2000 mg, fractionated as 1, 2, 3 or 4 occasions. The pharmacokinetics were described by a one-compartment model with first-order elimination and saturable absorption [3]. The efficacy on tumor growth inhibition (TGI) was sigmoidally linked to the area under the unbound concentration curve at steady state [4]. The risk of HFS was characterized by a latent variable model whose kinetics is impacted by sorafenib accumulated plasma concentration and whose levels are translated into HFS probability [5]. The utility was defined as a weighted sum of the probability of benefit and the probability of non-risk, the weights adding to 1. It aimed at maximizing the percentage of patients showing at least 20% TGI (responders) and minimizing the risk for grade 2 or 3 HFS. The sensitivity to the relative contribution of efficacy and toxicity to the utility was also evaluated.
Results: The usual regimen of sorafenib is 400mg twice daily (800mg per day). The non-linear pharmacokinetics of sorafenib result in greater exposure the more the daily dose is fractionated. Considering a 60% efficacy-40% toxicity balance, a maximal plateau in utility is obtained for 200mg to 400mg twice daily. Increasing the contribution of efficacy (or the expected TGI for responders) tends to favor the fractionation of the daily dose: e.g. if the efficacy criterion is the % of responders with TGI > 40% or greater, the utility function favors the four times daily regimen.
Conclusion: The utility is a comprehensible concept for the optimization of dosing regimen, allowing the balance between the required response and acceptable risks. This approach relies on the combination of several PK-PD models, and can be extended to multi-scale models.
References [1] Sheiner, L.B. and K.L. Melmon, The utility function of antihypertensive therapy. Ann N Y Acad Sci, 1978. 304: p. 112-27. [2] Ouellet, D., et al., The use of a clinical utility index to compare insomnia compounds: a quantitative basis for benefit-risk assessment. Clin Pharmacol Ther, 2009. 85(3): p. 277-82. [3] Hornecker, M., et al., Saturable absorption of sorafenib in patients with solid tumors: a population model. Invest New Drugs, 2011. [4] Hoshino-Yoshino, A., et al., Bridging from preclinical to clinical studies for tyrosine kinase inhibitors based on pharmacokinetics/pharmacodynamics and toxicokinetics/toxicodynamics. Drug Metab Pharmacokinet. 26(6): p. 612-20. [5] Hénin, E., et al., A latent-variable model for Sorafenib-induced Hand-Foot Syndrome (HFS) in non-selected patients to predict toxicity kinetics according to sorafenib administrations. PAGE. Abstracts of the Annual Meeting of the Population Approach Group in Europe, 2012. 21: p. Abstr 2494 [www.page-meeting.org/?abstract=2494].  

Poster: CNS

Eef Hoeben II-39 Prediction of Serotonin 2A Receptor (5-HT2AR) Occupancy in Man From Nonclinical Pharmacology Data. Exposure vs. 5-HT2AR Occupancy Modeling Used to Help Design a Positron Emission Tomography (PET) Study in Healthy Male Subjects.
E. Hoeben (1), V. Sinha (2), P. de Boer (3), K. Wuyts (4), H. Bohets (5), E. Scheers (5), X. Langlois (6), P. Te Riele (6), and H. Lavreysen (6) Janssen Research & Development, a Division of Janssen Pharmaceutica NV, Turnhoutseweg 30, B-2340 Beerse Belgium
Objectives: JNJ-mGluR2 PAM, a positive allosteric modulator of the metabotropic glutamate receptor-2 and 5-HT2AR antagonist, is currently in development for the treatment of disorders of the central nervous system [1,2]. To understand the pharmacological profile of JNJ-mGluR2 PAM and to define exposure vs. 5-HT2AR occupancy relationship in man, a PET study was performed in healthy male subjects [3]. To help in designing a PET study, 5-HT2AR occupancies in man were predicted based on in vitro and in vivo nonclinical pharmacology data in the rat.
Methods: In vitro functional and radioligand binding experiments were performed to investigate the in vitro activity and binding of JNJ-mGluR2 PAM and its major metabolite (M47) to human 5-HT2AR. Receptor occupancy assays were conducted in rats to evaluate JNJ-mGluR2 PAM occupancy to 5-HT2AR in vivo. Plasma concentrations vs. 5-HT2AR modeling was performed in rat and used to predict the 5-HT2AR occupancy in man. The relationship between predicted 5-HT2AR occupancy and simulated plasma concentrations in man was used to predict 5-HT2AR occupancy in man at clinical doses of 50 to 700 mg.
Results: In vitro preclinical experiments showed that JNJ-mGluR2 PAM is a weak 5-HT2AR antagonist. In rats, JNJ-mGluR2 PAM is rapidly metabolized to M47 which is a relatively potent and selective 5-HT2AR antagonist. Modeling experiments suggested that M47 significantly contributes to the 5-HT2AR binding in the rat but in humans only limited metabolism to M47 has been observed. Accounting for the different contributions of parent and metabolite and the differences in free fraction in rat vs. man, 5-HT2AR occupancy could be predicted in man based on exposure vs. 5-HT2AR modeling in the rat. At clinical doses of 50 to 700 mg, predicted 5-HT2AR occupancy in man ranged between 5% and 25%. The human PET data confirmed minimal 5-HT2AR occupancy by JNJ-mGluR2 PAM in man, which is not expected to be clinically relevant.
Conclusions: 5-HT2AR occupancy could be predicted in man based on nonclinical pharmacology data in the rat, taking into account the difference in free fraction and the different contributions of parent and metabolite in rat vs. man. At clinical doses, predicted 5-HT2AR occupancy in man was low and in good agreement with observed 5-HT2AR occupancy in man. This modeling work illustrated the "translatability" of in vitro and in vivo preclinical information to 5-HT2AR occupancy in man.
References: [1] Swanson CJ, Bures M, Johnson MP, Linden AM, Monn JA, Schoepp DD. Metabotropic glutamate receptors as novel targets for anxiety and stress disorders. Nat. Rev. Drug. Discov. 2005; 4:131-144. [2] Patil ST, Zhang L, Martenyi F, Lowe SL, Jackson KA, Andreev BV, et al. Activation of mGlu2/3 receptors as a new approach to treat schizophrenia: a randomized Phase 2 clinical trial. Nat. Med. 2007; 13:1102-1107. [3] Ito H, Nyberg S, Halldin C, Lundkvist C, Farde L. PET imaging of central 5-HT2A receptors with carbon-11-MDL 100,907. J. Nucl. Med. 1998; 39(1):208-214.

Poster: Absorption and Physiology-Based PK

Taegon Hong II-40 Usefulness of Weibull-Type Absorption Model for the Population Pharmacokinetic Analysis of Pregabalin
Taegon Hong (1,2), Seunghoon Han (1,2), Jongtae Lee (1,2), Sangil Jeon (1,2), Jeongki Paek (1,2), Dong-Seok Yim (1,2) (1) Department of Pharmacology, College of Medicine, The Catholic University of Korea, (2) Department of Clinical Pharmacology and Therapeutics, Seoul St.Mary's Hospital
Objectives: Pregabalin is an anticonvulsant used for the treatment of neuropathic pain and partial seizure in adults. The aim of this study was to develop a population pharmacokinetic (PK) model to describe the absorption characteristics of pregabalin given fasting or after meals.
Methods: Data from 5 healthy subject PK studies (n = 88) of single or multiple dose pregabalin (150 mg) were used. Pregabalin was administered twice daily, without meals or 30 min after a meal (regular diet or high fat diet) in the morning and 30 min or 4 h after a meal (regular diet) in the evening. Serial plasma samples were collected up to 24 h after the last dose for PK analysis. To find the model that best describes the absorption process, first-order, transit compartment, and Weibull-type absorption models were compared using the non-linear mixed effect method (NONMEM, ver. 7.2).
Results: A two-compartment linear PK model with Weibull-type absorption using its cumulative distribution function was better than the first-order absorption model with lag time. The conditional weighted residuals at Tmax and visual predictive check plots obtained from the Weibull-type absorption model were less biased than those from the first-order absorption model.
Conclusions: We found that the Weibull-type absorption model best described the absorption characteristics of pregabalin regardless of meal status and the absorption model should be carefully chosen based upon the principle of model development and validation, not by following a conventional model for its popularity and simplicity, especially when the PK dataset includes densely sampled data.
References: [1] Bockbrader HN, Radulovic LL, Posvar EL, Strand JC, Alvey CW, Busch JA, Randinitis EJ, Corrigan BW, Haig GM, Boyd RA, Wesche DL. Clinical pharmacokinetics of pregabalin in healthy volunteers. J Clin Pharmacol. 2010 Aug;50(8):941-950

Poster: Study Design

Andrew Hooker II-41 Platform for adaptive optimal design of nonlinear mixed effect models.
Andrew C. Hooker (1), J. G. Coen van Hasselt (2) (1) Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden. (2) Department of Clinical Pharmacology, Netherlands Cancer Institute, Amsterdam, Netherlands.
Introduction: Recent years have seen an increasing interest in adaptive trial design methodologies. With the growing use of nonlinear mixed effect (NLME) models to support clinical development, adaptive optimal design (AOD) approaches have also become increasingly relevant. A recent survey indicated that out of 10 major European pharmaceutical companies, the importance of AOD for NLMEM was ranked, 4 on a scale of 5, on average [1]. The usefulness of AOD approaches for NLME models has been previously demonstrated for PET occupancy studies [2], bridging studies [3] and pediatric PK studies [4].  
Aims: To develop a general computational platform for adaptive optimal study design in the context of NLME models. 
Methods: A general algorithm for implementing AOD methodology was created using the optimal design software package PopED [5,6] which links to NONMEM [7] and Perl speaks NONMEM [8] for the estimation steps. The proposed AOD methodology consisted of the following steps: i) definition of prior NLME model(s); ii) study design optimization of an initial cohort of subjects based on the prior NLME model(s); iii) collection and estimation of a cohort of data using the optimized study design (alternatively, stochastic simulation and re-estimation); iv) updating of the prior NLME model(s) from the estimation step. Steps ii-iv are repeated (and might change between each iteration) until a predefined stopping criteria has been reached.
Results: An initial implementation of the AOD platform was successfully implemented, allowing the evaluation of feasibility and the identification of technical challenges. The AOD platform has a modular setup and a generalized and flexible design, allowing modifications for specific study design characteristics. As proof-of-concept, an application of adaptive optimal design of a pediatric PK bridging study supported by a maturation model [9] was implemented, in which study designs were optimized for age-cohorts and sampling times.
Conclusion: We successfully developed an initial implementation of an AOD computational platform, which will be available as freeware when released.  
References: [1] Mentre et al. "Current use and developments needed for optimal design in pharmacometrics: a study performed amongst DDMoRe's EFPIA members." CPT:PSP, 2013. [2] Zamuner et al. "Adaptive-optimal design in PET occupancy studies." CPT, 2010. [3] Foo, Duffull. "Adaptive Optimal Design for Bridging Studies with an Application to Population Pharmacokinetic Studies." Pharm. Res., 2012. [4] Dumont et al. "Optimal two-stage design for a population pharmacokinetic study in children." PAGE, 2012. [5] Foracchia et al. "POPED, a software for optimal experiment design in population kinetics." CMPB, 2004. [6] Nyberg et al. "PopED: an extended, parallelized, nonlinear mixed effects models optimal design tool." CMPB, 2012. [7] Beal et al. "NONMEM User's Guides." (1989-2009), Icon Development Solutions. [8] Lindbom et al. "Perl-speaks-NONMEM (PsN) - A Perl module for NONMEM related programming." CMPB, 2004. [9] Anderson et al. "Mechanism-based concepts of size and maturity in pharmacokinetics." Annu. Rev. Pharmacol. Toxicol., 2008.

Poster: Endocrine

Daniel Hovdal II-42 PKPD modelling of drug induced changes in thyroxine turnover in rat
D. Hovdal (1) (1) Modelling & Simulation, iMed DMPK CVGI, AstraZeneca R&D Mölndal, Sweden
Objectives: To determine the in vivo potency of drug induced reduction in plasma thyroxine, T4, levels for three different drugs in rat and to explore how in vivo potency correlates with in vitro data.
Methods: A three day toxicological study with a two days washout period in rat was performed. Vehicle and three different compounds were tested at two or three dose levels. The study was designed to monitor the onset and extent of T4 reduction, as well as the return of T4 levels to baseline during washout. In all blood samples collected, the drug exposure and T4 levels were measured. A pharmacokinetic model was developed for each compound. Since all treatment groups share the systems parameters related to the turnover of T4, one PD model in form of a standard turnover model was applied to all T4 data. To identify the effects of the different compounds, the drug induced changes in T4 levels were driven by the individual pharmacokinetic profiles and unique in vivo potency of T4 reduction (IC50) was used for each compound. All analysis was performed using the NMLE module in Phoenix.
Results: The pharmacokinetics of the three drugs could be described by oral one or two compartment models with modified absorption. A drift in the baseline levels of T4 was observed and accounted for in the turnover model. The drug induced changes in T4 levels were successfully modeled by applying an Imax function on the production rate of T4. In contrast to consider one compound at a time, the simultaneous fit of the model to all T4 data allowed determination of the systems parameters of T4 turnover. As a result the potency of the different compound could be determined; despite administration of insufficient dose ranges to appropriately define the full inhibitory function of each compound. The derived in vivo potencies confirmed the ranking the compounds obtained by in vitro data.
Conclusions: Population PKPD modeling of preclinical data allows generation of more robust models (takes into account all available information) and allows conclusions to be drawn when the available information of each data set is insufficient for individual analysis.

Poster: Covariate/Variability Model Building

Yun Hwi-yeol II-43 Evaluation of FREM and FFEM including use of model linearization
Hwi-yeol (Thomas) Yun, Ronald Niebecker, Elin M. Svensson, Mats O. Karlsson Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
Objectives: In full model approaches, covariate relations are predefined [1]. Attaching covariate relations selectively to only some of the model parameters can lead to selection bias [2,3]. By allowing all covariates of interest to affect all parameters, this risk of selection bias is mitigated. In the present work we evaluate and compare two full model approaches that both allow estimation of all parameter-covariate relations: a full random effects model (FREM [3,4]) and a full fixed effects model (FFEM) saturated with respect to parameter-covariate relations.
Methods: A semi-mechanistic myelosuppression model with four structural parameters and a dataset containing 636 individuals and 3549 observations was used [5]. In addition, two dummy covariates having correlations of 0.5 and 0.75 respectively with a clinically relevant covariate were generated to investigate the performances of correlated covariates in both models. Linearization to decrease run times during model development and evaluation was assessed for both methods [6,7]. The performance was evaluated in terms of model run times, estimates and precision of parameters and ability to identify clinically relevant covariates. Precision was derived from variance-covariance matrix and bootstraps. FOCE-I with NONMEM 7.2 assisted by PsN was used.
Results: Both FREM and FFEM were successfully implemented, also as linearized models with good agreement and several magnitudes shorter run times. FFEM and FREM were found to be similarly precise. Run times for FREM and FFEM were similar. Both methods identified the same parameter-covariate relationships to be clinically relevant. However, in the case of correlated covariates, only FREM was able to identify all clinically relevant parameter-covariate relations. Furthermore, the coefficients were more precisely estimated compared to FFEM.
Conclusions: Although FREM and FFEM performed equally well in this case with an informative dataset and predominantly uncorrelated covariates, FREM has advantages in comparison with FFEM when investigating correlated covariates. This first combination of linearization and FREM/saturated FFEM appears to be promising and should be further evaluated.   
Acknowledgement: This work was supported by the DDMoRe ( HYPERLINK "http://www.ddmore.eu/" www.ddmore.eu) project.
References:
[1] Gastonguay, The AAPS Journal 2004 (6), S1, W4354.
[2] Ivaturi et al, PAGE 20 (2011) Abstr 2228 [www.page-meeting.org/?abstract=2228]
[3] Karlsson, PAGE 21 (2012) Abstr 2455[www.page-meeting.org/?abstract=2455]
[4] Ivaturi et al, WCoP (2012) Abstr WCoP-152
[5] Kloft et al, Clin Cancer Res. 2006;12(18):5481-90
[6] Khandelwal et al, The AAPS Journal 2011; 13(3): 464-72
[7] Svensson et al, PAGE 21 (2012) Abstr 2404 [www.page-meeting.org/?abstract=2404]
 
 
 

Poster: Paediatrics

Ibrahim Ince II-44 Oral bioavailability of the CYP3A substrate midazolam across the human age range from preterm neonates to adults
I. Ince (1,2), S.N. de Wildt (1), M.Y.M. Peeters (3), K. Burggraaf (4), E. Jacqz-Aigrain (5), J.S. Barrett (6), M. Danhof (2), C.A.J. Knibbe (1,2,3) 1.Erasmus MC - Sophia Children's Hospital, Rotterdam, The Netherlands; 2.Leiden/Amsterdam Center For Drug Research, Leiden, The Netherlands; 3.St. Antonius Hospital, Nieuwegein, The Netherlands; 4.Centre for Human Drug Research, Leiden, The Netherlands; 5.University Diderot, Paris, France; 6.Children's Hospital of Philadelphia, Philadelphia, PA, USA
Objectives: A maturation model for midazolam clearance from preterm neonates to adults has been previously developed, analyzing data that were obtained after IV dosing of midazolam across the entire human age range.[1] The aim of this study was to investigate changes in oral bioavailability and absorption rate of midazolam across the pediatric age range upon oral dosing of midazolam. The results can be used for the development of evidence-based dosing of oral midazolam in children.
Methods: Pharmacokinetic (PK) data were obtained from a combined dataset of 7 previously reported studies in 52 preterm infants (26-37 weeks GA, PNA 2-13 days), 305 children (3 months-18 years) and 20 adults, who received IV and/or PO midazolam. Population PK modeling was performed using NONMEM v6.2, and the influence of postnatal age (PNA), bodyweight (BW) and study population was investigated in a systematic covariate analysis.
Results: Oral bioavailability of midazolam with a population estimate of 24% (CV of 7.5%) was negatively influenced by BW in an allometric function, resulting in a value of 67% in a preterm neonate of 0.77 kg to 17% in an adult (70 kg). Previous results on the influence of BW on midazolam CL, characterized using an allometric function with a BW dependent exponent (BDE),[1] were confirmed.
Conclusions: Oral bioavailability of midazolam decreases from preterm neonates to adults, leading to higher systemic availability of midazolam in preterm neonates (67%) compared to older children or adults (17%). While this information may aid for the development of evidence-based dosages of oral midazolam for children of different ages, further physiologically-based modeling should elucidate the exact subprocesses that contribute to the reported age related changes in oral bioavailability of midazolam.
References: [1] Ince et al., PAGE 20 (2011) Abstr 2102 [www.page-meeting.org/?abstract=2102]

Poster: Other Modelling Applications

Lorenzo Ridolfi II-45 Predictive Modelling Environment - Infrastructure and functionality for pharmacometric activities in R&D
Lorenzo Ridolfi (1), Chris Franklin (1), Oscar Della Pasqua (1) (1) Clinical Pharmacology Modelling and Simulation, GlaxoSmithKline, Stockley Park West, Uxbridge, Middlesex UB11 1BT
Objectives:  The Predictive Modelling Environment (PME) supports Clinical Pharmacology Modelling & Simulation, enabling the implementation of M&S activities which are used to facilitate decision making within GSK. The system's architecture has been developed taking into account a pre-defined workflow and the interaction between software packages such as R and NONMEM 7.2.  Here we describe how a server-based tool has been implemented within the regulated R&D environment. Moreover, we show how workflow and software functionalities are integrated to meet the needs of a continuously growing pharmacometric community.
Methods:  Architecture and system requirements to integrate hardware (platforms), software and user interface functionality have been summarised and reviewed against user requirements and workflows for data manipulation, model building, validation and reporting.  An overview of system performance is provided, which includes a GAP analysis and a summary of modelling outputs and typical computation times.
Results:  The current environment provides access to NONMEM 7.2 as executable software in the web and command line (Linux shell), which are linked to a grid engine with PsN, RStudio and R as ancillary tools supporting the pre-defined M&S workflow. Integrated modules have been identified to provide functionality for project management, data warehouse (DCP), data set creation (DEP) as well for analysis and reporting (DMP). In addition, structured user interface features allow efficient access to previously generated files and templates (e.g. reports). Gaps remain in terms of data reuse, as analysis-ready datasets include software- and model-specific syntax. Likewise, workflows may not always be fully transferred across analyses in an automatic manner due to differences in model selection criteria and data set structure.
Conclusions: PME 2.5 is the result of years of internal and external development where the users' needs have been balanced with the industry standards, taking into account the requirements for an integrated workflow. Many of the technical challenges arising from the development and upgrade of modelling and simulation environment are due to differences in the expectation and expertise within the user community, which impose flexibility and consensus on workflows. System modularity, standard processes and grid computing are essential to ensure M&S tools can be upgraded in  a rapidly evolving field.

Poster: Safety (e.g. QT prolongation)

Masoud Jamei II-46 Accounting for sex effect on QT prolongation by quinidine: A simulation study using PBPK linked with PD
Manoranjenni Chetty1, Sebastian Polak1, Pavan Vajjah1,3, Masoud Jamei1, Amin Rostami 1,2 (1) Simcyp Ltd (a Certara Company), Blades Enterprise Centre, John St, Sheffield, S2 4SU; School of Pharmacy and Pharmaceutical Sciences, Manchester University, Manchester; (3) Current affiliation: UCB Celltech, 208, Bath road, Slough, SL13WE; UK
Objectives: To evaluate the sex effects on the potential risk of significant QT prolongation using a physiologically based pharmacokinetic/pharmacodynamic (PBPK/PD) model.
Methods: The Simcyp Population Based Simulator (version 12 release 1) was used to simulate the concentration-time profiles of quinidine in virtual male and female Caucasian healthy volunteers with a full PBPK model and a systemic clearance of quinidine of 20.59 (CV 38%) L/h1. Clinically observed changes in QT prolongation corrected for heart rate (QTc)2 were used to develop the Emax models  with differences in baseline QTc values between males and females obtained from the literature2. Parameter estimation was used to determine the ”Emax (the maximum value of ”QTc) and the concentration of quinidine required to produce 50% of the maximum response (EC50). Following evaluation of the developed models to predict clinically observed data, the models were used to simulate PD profiles in 500 males and females respectively. The proportion of subjects of each sex who showed QTc >500ms and hence probably carried a greater risk of experiencing torsade de pointes3, were then estimated.
Results: Visual predictive checks suggested that the PBPK model recovered the clinical PK profiles adequately and there was no significant difference between the PK profiles in males and females. The estimated parameters for the Emax models were not significantly different with respect to the ” Emax values in males and females (128.9 ms and 130.8 ms respectively) but differed in the values for EC50 (6.28 µM for females and 7.01 µM for males), suggesting a greater sensitivity to change in QT in females. The PBPK/PD model recovered the clinical data adequately. Simulation of QTc in the sexes showed that 56% of females were likely to show maximum QTc > 500ms while the corresponding value for males was 43%.
Conclusions: This PBPK/PD model effectively recovered the higher rate of QT prolongation reported in females and predicted a 1.3 times higher risk of significant QT prolongation in females on quinidine. The estimated sensitivity parameter (EC50) of the PD model suggests a female/male ratio of 0.89. Clinical support for a lower EC50 in Caucasian females comes from the study by Benton and coworkers who reported that at a ‘therapeutic’ concentration of 3µg/mL women are likely to show a 38ms greater increase in QT change than men4. Future PBPK/PD models should include 3-hydroxyquinidine.
References: [1] The Pharmacological basis of therapeutics.11th ed. Brunton LL, Lazo J and Parker KL ed.2006. 2. Shin et al, Br J Clin Pharmac 2006, 63(2):206. 3.Bednar et al, Prog Cardiovas Dis 2001, 43:1. 4.Benton et al, CPT 1994,67:413.

Poster: New Modelling Approaches

Alvaro Janda II-47 Application of optimal control methods to achieve multiple therapeutic objectives: Optimization of drug delivery in a mechanistic PK/PD system
A. Janda (1,2), S. Ardanza-Trevijano (2), E. Romero (1), N. Vélez de Mendizábal (3), I.F. Trocóniz (1) (1) Department of Pharmacy and Pharmaceutical Technology and (2) Department of Physics and Applied Mathematics; University of Navarra, Pamplona, Spain. (3) Indiana University School of Medicine; Indianapolis, IN, USA.
Objectives: Optimizing delivery systems targeting constant drug concentration levels in plasma represents always a challenge, especially for long periods of treatment, and in case of complex non-linear pharmacokinetics/pharmacodynamics (PKPD) systems. Recently we have developed a mechanistic PKPD model for the testosterone (TST) effects of triptoreline (TRP) in prostate cancer patients using data from five different sustained formulations [1]. TST profiles are characterised by an undesired initial flare-up, following by a profound receptor-down regulation eliciting castration (TST
Methods: The analysis has been performed in three steps. First, a population of individual set of disposition PK, PD, and system-related paremeters is generated [1]. Second, using this set of parameters, the optimal drug absorption and TST profiles for each patient are derived by means of optimal control methods implemented by the softwares PSOPT and GPOPS [2,3]. Finally, and to summarize the absorption properties the optimal (non-parametric) absorption profiles are described using standard absorption models considering several simultaneous absorption processes based on zero and first order kinetics. The individual model parameters are estimated by the R package DEoptim which performs global optimization by differential evolution [4].
Results:The optimal TST profiles obtained reveal that the time to castration can be minimized to 21 days (13 – 36) while the increase of TST levels at the flare is only 30% (0,1% – 50%) with respect to baseline (95% interval confidence between parenthesis). The castration time has been evaluated for different doses of TRP and the administration of 20 mg achieve the castration time longer than 9 months for 95% of patients. Additionally, the therapeutic objectives obtained have been compared to those from the formulations reported in [1] showing an important improvement, especially on the flare-up and the castration time.
Conclusions: The application of optimal control methods profiles are useful techniques for the optimization PK/PD profiles. They are more relevant in physiological systems with complex dynamics where simple simulation exercises tuning parameters are not effective. Moreover, the flexibility of the method allows to deal with multiple and tight therapeutic objectives performing real optimization.
References: [1] Romero E et al. Pharmacokinetic/Pharmacodynamic model of the testosterone effects of triptorelin administered in sustained release formulations in patients with prostate cancer. J Pharmacol Exp Ther. 342: 788-98 (2012). [2] Rao A. V. et al. .GPOPS: A MATLAB Software for Solving Multiple-Phase Optimal Control Problems Using the Gauss Pseudospectral Method. ACM Transactions on Mathematical Software. 37 (2): 22-39 (2010). [3] Becerra, V.M. "Solving complex optimal control problems at no cost with PSOPT". Proc. IEEE Multi-conference on Systems and Control, Yokohama, Japan, September 7-10, 1391-1396 (2010). [4] K.M. Mullen et al. DEoptim: An R Package for Global Optimization by Differential Evolution", Journal of Statistical Software (2011), 40 (6): 1- 26.

Poster: Infection

Nerea Jauregizar II-48 Pharmacokinetic/Pharmacodynamic modeling of time-kill curves for echinocandins against Candida.
Sandra Gil-Alonso (1), Nerea Jauregizar (1), Ignacio Ortega (2), Elena Eraso (3) and Guillermo Quindós (3) (1) Department of Pharmacology, Faculty of Medicine, University of the Basque Country (UPV/EHU), Spain. UFI11/25 “Microbios y Salud”. (2) Research Development and Innovation Department, Faes Farma S.A. Leioa. Spain. (3) Department of Immunology, Microbiology and Parasitology, Faculty of Medicine, University of the Basque Country (UPV/EHU), Spain. UFI11/25 “Microbios y Salud”
Objectives: In vitro time-kill studies are commonly used in the assessment of efficacy of antimicrobial agents. The aim of the present study was to develop a general semi-mechanistic pharmacokinetic/pharmacodynamic mathematical model that fits three echinocandins time-kill data against Candida isolates in vitro.
Methods: Time-kill curve data from static in vitro experiments with Candida albicans, Candida glabrata and other emerging species exposed to constant concentrations of three echinocandins (caspofungin, micafungin and anidulafungin) were used for model development. The concentrations ranged from 0.06 to 2 µg/mL and samples for viable counts were taken at time points 0, 2, 4, 6, 24 and 48 h after start of experiments. Data was modeled using NONMEM V7.2.0 [1] with first order conditional estimation method. Diagnostic plots and precision of parameter estimates were evaluated to assess model performance.
Results: Time-kill data were best fit by using an adapted sigmoidal Emax model that corrected for delay in the growth of Candida and the onset of the three drugs activity, steepness of the concentration-response curve, and saturation of the cell number of Candida. Time-kill curves of all investigated strains, drugs and concentrations were well predicted by the model.
Conclusions: The activity of the three echinocandins against Candida isolates can be accurately described using this semi-mechanistic mathematical model. The developed model allowed the estimation of pharmacodynamic parameters (EC50: concentration of echinocandin necessary to produce 50% of maximum effect; Kmax: maximum killing rate constant and delay in the onset of killing) for the comparison of the three echinocandins.
References: [1] Beal SL, Sheiner LB, Boeckmann AJ & Bauer RJ (Eds.) NONMEM Users Guides. 1989-2011. Icon Development Solutions, Ellicott City, Maryland, USA.

Poster: Study Design

Roger Jelliffe II-49 Multiple Model Optimal Experimental Design for Pharmacokinetic Applications
David Bayard and Roger Jelliffe Laboratory of Applied Pharmacokinetics, USC School of Medicine, Los Angeles CA USA
Objective: To develop an experiment design approach for multiple model problems where the population model associated with the Bayesian prior is specified as a finite discrete probability distribution. Such population models are generated routinely by nonparametric population modeling programs such as NPEM and NPAG.
Methods: The multiple model estimation process can be interpreted as a classification problem. As a classification problem, estimator performance can be scored in terms of how well it minimizes the Bayes risk, i.e., the probability of a misclassification. The use of Bayes risk as an experiment design criteria provides an alternative to D-optimality and other criteria based on the asymptotic Fisher Information matrix. Unfortunately, the Bayes risk is difficult to compute. However, a theoretical upper bound on the Bayes risk has recently appeared in the literature (cf., Blackmore, Rajamanoharan and Williams 2008). Because of its clear computational advantages, this poster proposes experiment designs for pharmacokinetic applications based on minimizing the Bayes risk upper bound.
Results: In a simulated example, sampling times were discretized to every 15 minutes rather than continuously. An additive assay error of 0.1 units was assumed. It is not necessary to get one sample for each model parameter.  For a 1 compartment model with parameters V and Kel, and a 1 hour infusion IV, the 1 sample strategy was best at 4.25 hrs, with a cost of 1.6457. The 2 sample strategy was best at 1 hr and 9.5 hrs, with cost of 0.7946. The 3 sample strategy was best at 1, 1, and 10.5 hrs, with cost of 0.5988. The 4 sample strategy was best at 1, 1, 1, and 10.75 hrs, with cost of 0.5062.
Conclusions: Multiple Model Optimal Design (MMOpt) can potentially improve on D-optimal design, as it is based on a true MM formulation of the problem (classification theory), and is optimal with respect to a Bayesian prior. It is applicable to the full assay error polynomial: Sigma_noise=c0 + c1*y + c2*y^2 + c3*y^3. It is based on a recent theoretical overbound on Bayes Risk. In contrast to D-optimal designs, MMOpt discriminates models by using global differences in model response curves rather than local sensitivity to small parameter variations. Also, MMopt experiment designs can handle populations of heterogeneous model types, for example, models having different numbers of compartments. MMOpt will soon be included in the USC RightDose software.
Supported by NIH Grants GM068968 and HD070886

Poster: Infection

Sangil Jeon II-50 Population Pharmacokinetics of Piperacillin in Burn Patients
Sangil Jeon (1), Heungjeong Woo (2), Seunghoon Han (1), Jongtae Lee (1), Taegon Hong (1), Jeongki Paek (1), Hyeongsik Hwang (2), Dong-Seok Yim (1) (1) Department of Clinical Pharmacology and Therapeutics, Seoul St. Mary’s Hospital, The Catholic University of Korea, Seoul, Korea, (2) Department of Internal Medicine, Hangang Sacred Heart Hospital, Hallym University Medical Center, Seoul, Korea
Objectives: Piperacillin-tazobactam is a parenterally administered combination of ²-lactam antibiotic/²-lactamase inhibitor. It shows broad antibacterial activity against Pseudomonas aeruginosa and other pathogens. This combination has been frequently used for the empirical treatment of infection in intensive care patients including burn patients. The purpose of this study was to develop a population pharmacokinetic (PK) model for piperacillin in burn patients.
Methods: Fifty patients with burns ranging from 1% to 81% of total body surface area treated with piperacillin-tazobactam were enrolled. Piperacillin-tazobactam was administered via infusion for about 30 minutes at a dose of 4.5 g every 8 h. Blood samples were collected right before and at 1, 2, 3, 4 and 6 h after more than 5 infusions. The population PK model of piperacillin was developed using a nonlinear mixed effect method (NONMEM, ver 7.2).
Results: The final model was a two-compartment model with first-order elimination. Covariates included in the final model were creatinine clearance (CLCR) on the clearance and sepsis on the central volume of piperacillin. The mean population PK parameters were; clearance (L/h) = 15 × CLCR (mL/min) / 132, V1 (central volume) = 24.6 + 16.3 × presence of sepsis L, V2 (peripheral volume) = 14.6 L, and Q (intercompartmental clearance) = 0.645 L/h with interindividual variability (CV%) of 36.0%, 38.3%, 0%(not estimated) and 93.7%, respectively.
Conclusions: The population PK of piperacillin have been characterized in burn patients after infusion. These results are to be used for further pharmacodynamic modeling and simulation in burn patients.
References: [1] Dowell JA, Korth-Bradley J., Milisci M., Tantillo K., Amorusi P., Tse S. Evaluating possible pharmacokinetic interactions between tobramycin, piperacillin, and a combination of piperacillin and tazobactam in patients with various degrees of renal impairment. J Clin Pharmacol 2001, 41: 979-86. [2] Roberts JA, Kirkpatrick CM, Roberts MS, Dalley AJ, Lipman J: First-dose and steady-state population pharmacokinetics and pharmacodynamics of piperacillin by continuous or intermittent dosing in critically ill patients with sepsis. Int J Antimicrob Agents 2010, 35:156-163.
 

Poster: Other Drug/Disease Modelling

Guedj Jeremie II-51 Modeling Early Viral Kinetics with Alisporivir: Interferon-free Treatment and SVR Predictions in HCV G2/3 patients
Jeremie Guedj, Jing Yu, Micha Levi, Bin Li, Steven Kern, Nikolai V. Naoumov, Alan S. Perelson 1INSERM UMR 738, University Paris Diderot, F-75018 Paris
Objectives: Alisporivir (ALV) is a cyclophilin inhibitor with pan-genotypic activity against hepatitis C virus (HCV). We characterized viral kinetics (VK) in 249 patients infected with HCV genotypes 2 or 3 during treatment with ALV interferon-free regimens for six weeks ±800 mg ribavirin (RBV) daily.
Methods:We used a VK model that integrated pharmacokinetic (PK) and pharmacodynamic effects to analyze patient data as well as to predict the effect of different doses of ALV twice a day with RBV on the sustained virologic response (SVR) rate.
Results: The VK model was able to fit the individual viral load profiles of 214 (86%) patients by assuming that ALV blocked viral production. A mean antiviral effectiveness of 0.93, 0.86 and 0.75 in patients treated with 1000, 800 and 600 mg ALV QD, respectively was estimated. Patients receiving RBV had a significantly faster rate of viral decline, which was attributed in our model to an effect of RBV in increasing the loss rate of infected cells, ´ (mean ´=0.35 d-1 vs 0.21 d-1 in patients +/- RBV, respectively, P=0.0001). The remaining 35 patients (14%) had a suboptimal response (i.e. flat or increasing levels of HCV RNA after week 1), and their viral kinetic profile was not described using the model. The occurrence of this suboptimal response was higher in patients that received ALV monotherapy than those receiving ALV+RBV (21.5 vs 10.5%, P=0.02). Moreover, high body weight and low RBV levels were associated with suboptimal response (in patients receiving RBV). There was a trend for low exposure to ALV to be associated with suboptimal response as well, suggesting that high RBV and ALV exposures are important in reducing the suboptimal response rate. The model predicts 71.5% SVR following 400 mg ALV BID + 400 mg RBV BID for 24 weeks. The predicted SVR rate following response-guided therapy was 79%.
Conclusions: Alisporivir 400 mg BID plus RBV may represent an effective IFN-free treatment that is predicted to achieve high SVR rates in genotypes 2 or 3 patients. Response-guided therapy would further increase SVR. In addition, weight-based RBV dosing should be considered to prevent suboptimal exposure.

Poster: Other Drug/Disease Modelling

Claire Johnston II-52 A population approach to investigating hepatic intrinsic clearance in old age: Pharmacokinetics of paracetamol and its metabolites
Claire Johnston (1,2), Andrew J McLachlan (3,4), Carl M Kirkpatrick (5) and Sarah N Hilmer (1,2) 1. Sydney Medical School, University of Sydney, Sydney, Australia; 2. Department of Clinical Pharmacology, Royal North Shore Hospital, Sydney, Australia; 3. Centre for Education and Research on Ageing, Concord RG Hospital, Sydney, Australia; 4. Faculty of Pharmacy, University of Sydney, Sydney, Australia; 5. Centre for Medicine Use and Safety, Monash University, Melbourne, Australia.
Objectives: The aims of this study were to investigate the pharmacokinetics of paracetamol and its sulfide and glucuronide metabolites in older people. Paracetamol can be used as a marker of hepatic intrinsic clearance and Phase 2 metabolism. This is due to its capacity limited clearance and low protein binding [1]. There is large variability in drug response in older people that is often not explained by chronological age. The investigation of important covariates to pharmacokinetic and pharmacodynamic responses in this population is vital as they are frequently excluded from clinical trials and dosing recommendations may not be appropriate. The concept of frailty as a determining factor of health outcomes in older people is an increasing trend in geriatric medicine [2]. There are only a handful of papers that have investigated the use of frailty in explaining pharmacokinetic changes in old age. To our knowledge this is one of the only studies to use frailty as a covariate in population modeling. We aim to determine the important covariates that can describe the variability seen in paracetamol pharmacokinetics in pain patients aged over 70 years.
Methods: Data from two studies of oral paracetamol were pooled. The first was a study of steady state paracetamol in healthy volunteers with intensive plasma sampling over 6 hours post dose [3]. The second was a large observational study of inpatients over 70 years old, admitted for pain. These patients had residual blood taken from routine blood tests, with 1-25 samples per patient. Frailty was measured using the Reported Edmonton Frailty Scale (REFS), with a score of more then or equal to 8 out of a possible 18 being considered frail [4]. Both the categorical and continuous frailty score will be included in the model. The paracetamol glucuronide and sulfide metabolites were measured for each sample along with the parent drug concentration using HPLC. Population pharmacokinetic analysis was undertaken using NONMEM (version 7.2) and Pirana software. Missing data for weight and height was imputed [5].
Results: The total study population was 219; 20 healthy volunteers and 199 inpatients. The average age of the volunteers was 35.7 years and the inpatients was 84.7 years. There were 139 frail patients and 61 non-frail. The best model was a one-compartment linear model for parent drug and one compartment models for each of the metabolites. There was high variability in both populations.
Conclusions: Decreasing variability in the model will allow for more predictable therapeutic outcomes in older people. Frailty may be an important measure for predicting drug responses in older people.
References: [1]. Bannwarth et al., Drugs 63(2): 5-13 (2003) [2]. Clegg et al., Lancet 381: 752-762 (2013) [3]. Rittau et al., JPP 64(5):705-711 (2012) [4]. Hilmer et al., AJA 28(4):182-188 (2009) [5]. Jackson et al., Biostatistics 10:335-351 (2009)

Poster: Other Modelling Applications

Niclas Jonsson II-53 Population PKPD analysis of weekly pain scores after intravenously administered tanezumab, based on pooled Phase 3 data in patients with osteoarthritis of the knee or hip
E. Niclas Jonsson (1,2), Rosalin Arends (3), Rujia Xie (3) and Scott Marshall (3) (1) Exprimo NV (2) now Pharmetheus AB, (3) Pfizer
Objectives: To characterize the relationship between tanezumab concentrations and weekly pain scores (WPS) over time (measured daily on a 0-10 numerical rating scale) after IV administration in patients with OA of the knee or hip, including covariate relationships and probability of dropout.
Methods: Data were available from four Phase 3 studies (n=2449) for which a population PK model previously had been developed. Separate models for the response and dropout probability after placebo and active treatment were developed. The final PKPD model described the WPS response as the sum of the tanezumab and the placebo effects. The impact of covariates was characterized for all models and simulations, integrated with the PK model, were used to quantify their impact on the clinically relevant endpoint - the baseline and placebo corrected WPS response at week 16, both with and without BOCF imputation.
Results: A set of exponential functions was used to describe the onset of placebo response after the first and subsequent doses. The higher placebo effect with higher baseline pain score and the higher placebo effect in knee compared to hip patients were only evident over the first dosing interval. The rate of placebo onset was faster in two studies investigating patients with more severe osteoarthritis (population not appropriate for NSAID use). The placebo dropout pattern as well as the tanezumab dropout pattern was characterized for the first 3 doses separately using a parametric survival model. An indirect response model was used to link the PK to WPS. The maximal achievable decrease in WPS by tanezumab was higher in females compared to males, higher in patients with OA of the hip and higher in patients with more severe pain at baseline. The potency of tanezumab was lower with higher baseline pain score and higher with higher body weight. The simulations indicated the site of OA (knee or hip) to be the most potentially clinically relevant covariate for the clinical endpoint, followed by weight, baseline pain score and sex.
Conclusions: The established population PKPD model adequately describes the relationship between tanezumab concentration and WPS after IV administration in patients with OA. The most potentially clinically relevant covariate in terms of the endpoint is the site of OA. While other covariates predict additional small differences in the endpoint, all characterized groups gain benefit from treatment with tanezumab.

Poster: CNS

Marija Jovanovic II-54 Effect of Carbamazepine Daily Dose on Topiramate Clearance - Population Modelling Approach
M. Jovanovic (1), D. Sokic (2) I. Grabnar (3), T.Vovk (3), M. Prostran (4), K. Vucicevic (1), B. Miljkovic (1) (1) Department of Pharmacokinetics and Clinical Pharmacy, Faculty of Pharmacy, University of Belgrade, Serbia; (2) Clinic of Neurology, Clinical Centre of Serbia, Belgrade; (3) Department of Biopharmaceutics and Pharmacokinetics, Faculty of Pharmacy, University of Ljubljana, Slovenia; (4) Departmant of Pharmacology, Clinical Pharmacology and Toxicology, School of Medicine, University of Belgrade, Serbia.
Objectives: The aim of the study was to investigate influence of carbamazepine (CBZ) on topiramate (TPM) oral clearance (CL/F) in adult patients with epilepsy.
Methods: Data were collected from 78 adult epilepsy patients on mono- or co-therapy of TPM and other antiepileptic drug(s). Daily doses of TPM were in range from 50 - 1200 mg and dosage regimens were once, twice or three times a day. One to two blood samples were taken per patients in steady-state. Patients co-treated with CBZ administered doses in range from 300 - 1600 mg. The population pharmacokinetic (PK) analysis was performed using NONMEM® software (version 7.2).
Results: A one-compartment model with first-order absorption and elimination was used as a structural model. The interindividual variability was evaluated by an exponential model while residual variability was best described by proportional model. Volume of distribution was estimated at 0.575 (0.499 - 0.651) l/kg. TPM CL/F was significantly (p < 0.001) influenced by CBZ daily dose. The estimate of CL/F for a typical patient was 1.534 (1.448 - 1.612) l/h while the interindividual variability in studied population was 16.514% (11.780 - 20.166%). Mean TPM CL/F during CBZ co-therapy was higher for 60.78% than in patients not co-treated with CBZ. The stability of the model was confirmed by bootstrap resampling technique.
Conclusions: Final population PK model quantifies influence of CBZ daily dose on TPM CL/F. The results from the study allow individualization of TPM dosing in routine patient care, especially useful for patients on different CBZ dosing regimens.

Poster: Absorption and Physiology-Based PK

Rasmus Juul II-55 Pharmacokinetic modelling as a tool to assess transporter involvement in vigabatrin absorption
Rasmus Vestergaard Juul (1), Martha Kampp Nøhr (2), Carsten Uhd Nielsen (2), Rene Holm (3) and Mads Kreilgaard (1) (1) Department of Drug Design and Pharmacology and (2) Department of Pharmacy, University of Copenhagen, Denmark, (3) Biologics and Pharmaceutical Science, H. Lundbeck A/S, Valby, Denmark
Objectives: Vigabatrin is an anti-epileptic drug used for the treatment of infantile spams. Vigabatrin has been identified as a substrate of the human proton-coupled amino acid transporter, hPAT1 [1], and in vitro studies suggest that PAT1 mediates the transepithelial transport [2]. The aim of this study was to develop a population-based pharmacokinetic (PK) model of the oral absorption of vigabatrin and to assess the potential involvement of PAT1.
Methods: Vigabatrin plasma concentration-time profiles were obtained from 78 rats dosed either orally (0.3mg/kg, 1mg/kg, 3mg/kg or 30mg/kg) or intravenously (i.v.) (1mg/kg). The involvement of PAT1 was investigated by co-administration of the hPAT1 substrate and inhibitor, proline (100mg/kg) and tryptophan (100mg/kg). PK models were fitted to data using non-linear mixed-effects modelling implemented in NONMEM (V7.2.0.). One to three compartment models with 1st order elimination were investigated to describe disposition of vigabatrin. Oral absorption of vigabatrin was investigated among zero-order, 1st order and saturable (Michaelis-Menten) absorption models encompassing lag-time or transit compartments [2,3]. Models were selected and evaluated based on objective function value, visual goodness of fit, parameter precision, visual predictive checks and bootstraps.
Results: A two-compartment model best described the disposition of vigabatrin after oral and i.v. administration. A transit compartment model with estimated 1.4 compartments and a population mean transit time (MTT) of 4.5 min best described the oral absorption of vigabatrin. An apparent dose dependent absorption was observed, as the MTT of 0.3mg/kg doses were lower (3.0 min) than for other doses. Administration of proline and tryptophan resulted in significantly prolonged MTT of 9.2 min.
Conclusions: The oral absorption of vigabatrin in rat was successfully described by a population PK model with dose-dependent transit that could be prolonged by the PAT1 inhibitors proline/tryptophan. These findings are the first in vivo evidence suggesting that PAT1 could be involved in intestinal vigabatrin absorption.
References: [1] Abbot, E.L., et al., Vigabatrin transport across the human intestinal epithelial (Caco-2) brush-border membrane is via the H+ -coupled amino-acid transporter hPAT1. Br J Pharmacol, 2006. 147(3): p. 298-306. [2] Nøhr, M.K. et al., The absorptive transport of the anti-epileptic drug substance vigabatrin across Caco-2 cell monolayers is carrier-mediated, submitted, Eur J Pharm Biopharm, 2013. [3] Holford, N.H. et al., Models for describing absorption rate and estimating extent of bioavailability: application to cefetamet pivoxil. J Pharmacokinet Biopharm, 1992. 20(5): p. 421-42. [4] Savic, R.M., et al., Implementation of a transit compartment model for describing drug absorption in pharmacokinetic studies. J Pharmacokinet Pharmacodyn, 2007. 34(5): p. 711-26.

Poster: CNS

Matts Kågedal II-56 A modelling approach allowing different nonspecific uptake in the reference region and regions of interest – Opening up the possibility to use white matter as a reference region in PET occupancy studies.
M. Kågedal(1), MO Karlsson(2) AC Hooker(2) (1) AstraZeneca R&D Södertälje, Sweden (2) Department of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
Objectives: Analyses of receptor occupancy studies are often performed using the concentration in a reference region in the brain as input function. These analyses assume identical non-specific binding in the reference region and in the region of interest (ROI). In the present work it is investigated if an apparent difference in occupancy between regions could be explained by different non-specific uptake. In addition it is investigated whether the use of white matter as reference region is possible by estimation of non-specific uptake in the ROI relative to reference. The analysis is based on data from a study published previously (Varnäs et al 2011) [1].
Methods: Nonlinear mixed effects modelling of data from PET scans with the 5-HT1B radioligand [11C] AZ10419369 was applied. Data from all PET-scans and several brain regions of interest were included simultaneously in the analysis. The simplified reference tissue model with cerebellum as reference region was applied as described previously (Zamuner et al) [2] but modified to allow nonspecific uptake to differ between regions. The use of white matter as reference region was also explored. A simulation experiment was performed to assess the ability of the model to pick up a difference in non-specific uptake and the consequence of not accounting for this difference. The study included six healthy subjects with PET-scans at baseline and after different oral doses of the 5-HT1B antagonist AZD3783.
Results:  Based on the likelihood ratio test, regional difference in occupancy was more likely than differences in non-specific uptake. Using white matter as reference region resulted in a similar affinity estimate as that obtained with cerebellum as reference region if the difference in non-specific uptake was accounted for. The simulation experiment, showed a bias in occupancy when differences in non-specific uptake were not accounted for.
Conclusions: In the present case, difference in occupancy rather than in non-specific uptake between regions was concluded. This evaluation was possible by a simultaneous analysis of several regions of interest and all PET-measurements. Estimation of occupancy by the use of white matter is possible by accounting for any difference in non-specific uptake. Results presented show that differences in non-specific binding between the reference region and the regions of interest can markedly bias the occupancy estimate if not accounted for.
References: [1] Dose-dependent binding of AZD3783 to brain 5-HT1B receptors in non-human primates and human subjects: a positron emission tomography study with [11C]AZ10419369. Varnas K.  Nyberg S.  Karlsson P.  Pierson ME.  Kagedal M.  Cselenyi Z.  McCarthy D.  Xiao A.  Zhang M.  Halldin C.  Farde L.  Psychopharmacology.  213(2-3):533-45, 2011 Feb. [2] Estimate the time varying brain receptor occupancy in PET imaging experiments using non-linear mixed effects modelling approach. Stefano Zamuner, Roberto Gomeni, Alan Bye. Nuclear Medicine and Biology 29 (2002) 115-123.

Poster: Other Drug/Disease Modelling

Ana Kalezic II-57 Application of Item Response Theory to EDSS Modeling in Multiple Sclerosis
Ana Kalezic (1), Radojka Savic (2), Alain Munafo (3), Mats O Karlsson (1) (1) Dept of Pharmaceutical Biosciences, Uppsala University, Uppsala, Sweden
Objectives: Traditional approaches to measurement scales generally disregard the underlying nature of the subcomponent data. In contrast, item response theory (IRT) refers to a set of mathematical models that describe, in probabilistic terms, the relationship between a person's response to a survey question and its level of the "latent variable" being measured by the scale [1]. In the area of clinical pharmacology, IRT modeling has previously been applied to ADAS-cog assessments [2]. The objective of this analysis was to apply IRT methodology to the Expanded Disability Status Score (EDSS) [3], a widely used measure of disease disability in multiple sclerosis (MS).
Methods: Data were collected from a 96-week Phase III clinical study with relapsing-remitting MS. For this analysis, 41664 EDSS observations from 1319 patients at baseline or treated with placebo were used. The assumption is that the outcome of each item constituting EDSS depends on an unobserved variable "disability." Unlike most measurement scales, EDSS total score does not result from simple addition of individual items, but instead results from individual components via a decision tree. For each EDSS item, a model was developed in accordance with the nature of data, describing the probability of a given score as a function of disability variable. Sets of parameters characterizing each item were modeled as fixed effects, while the MS disability was modeled as subject-specific random effect with or without time components. All models were fitted using NONMEM 7.2; simulation-based diagnostics for model evaluation also used PsN and R/Xpose4 software.
Results: The final model contained 8 ordered categorical submodels for a total of 54 parameters. Simulations from the IRT model were in good agreement with the observed EDSS and item-level data. The disability variable showed a significant increase (p15% for any monthly regimen.
Conclusions: Simulations with a PKPD model for the malaria preventive effect of DHA-PQ was useful in investigations of alternative dosing regimens. A novel weekly dosing regimen was indicated to outperform the previously suggested monthly regimen especially with regards to being less sensitive to poor compliance.
References: [1] K. M. Lwin et al., Randomized, double-blind, placebo-controlled trial of monthly versus bimonthly dihydroartemisinin-piperaquine chemoprevention in adults at high risk of malaria. Antimicrobial Agents and Chemotherapy 56, 1571 (2012). [2] M Bergstrand et al., Modeling of the concentration-effect relationship for piperaquine in preventive treatment of malaria. PAGE 2013 abstract. [3] J. Tarning et al., Population pharmacokinetics of dihydroartemisinin and piperaquine in pregnant and nonpregnant women with uncomplicated malaria. Antimicrobial Agents and Chemotherapy 56, 1997 (2012).

Poster: Other Drug/Disease Modelling

Dan Lu III-21 Semi-mechanistic Multiple-analyte Population Model of Antibody-drug-conjugate Pharmacokinetics
Dan Lu (1), Jin Yan Jin (1), Priya Agarwal (1), Sandhya Girish (1), Dongwei Li (1), Saileta Prabhu (1), Denise Nazzal (1), Ola Saad (1), Randy Dere (1), Neelima Koppada (1), Chee Ng (2, 3) (1) Genentech, South San Francisco, CA, USA; (2) Children Hospital of Philadelphia, Philadelphia, PA, USA (3) School of Medicine, University of Pennsylvania, Philadelphia, PA
Objectives: Monomethyl auristatin E (MMAE) containing antibody-drug-conjugates (ADCs) are complex mixtures, therefore their pharmacokinetics are assessed by evaluating multiple analytes including total antibody (TAB), antibody-conjugated MMAE (acMMAE) and unconjugated MMAE after ADC dosing. Both TAB and acMMAE concentrations represent mixtures of various drug-to-antibody ratio (DAR) species. The objective of this analysis is to develop a semi-mechanistic multiple-analyte population model to better understand the major pathways of ADC elimination and unconjugated MMAE formation by ADC catabolism.
Methods: The pharmacokinetic (PK) data of multiple analytes for anti-CD79b ADC after a single intravenous dose (0.3, 1, 3 mg/kg) and multiple intravenous doses (1, 3, 5 mg/kg every-three-week for 4 doses), and the PK data of MMAE after a single intravenous dose administration of unconjugated MMAE (0.03 and 0.063 mg/kg) in cynomolgous monkeys were used together for modeling. Multiple semi-mechanistic models were explored to describe the PK of TAB, acMMAE and unconjugated MMAE simultaneously. Parallel hybrid ITS-MCPEM estimation algorithm was used for parameter estimation in S-ADAPT 1.57. The observed below quantification limit data were modeled using M3 method.
Results: ADC elimination clearance pathways are comprised of both deconjugation and proteolytic degradation pathways. A multiple-compartment PK model assuming a sequential deconjugation from high DAR species to low DAR species with a Weibull model for description of the deconjugation rate constant change with the DAR and michaelis-menton kinetics of proteolytic degradation adequately described the PK data of TAB and acMMAE simultaneously. The fraction of formation from the proteolytic degradation pathway to unconjugated MMAE was ~ 66%, while the fraction of formation from the deconjugation pathway was only ~ 2%.
Conclusions: The final model well described the observed TAB, acMMAE and unconjugated MMAE PK data in cynomolgous monkeys simultaneously. The model suggested ADC is eliminated via both the deconjugation pathway and the proteolytic degradation pathway, while the unconjugated MMAE is formed mainly via the proteolytic degradation pathway. This finding suggested that the unconjugated MMAE level after ADC dosing might be modulated by modifying the binding affinity of the ADC to FcRn and/or target and consequently the rate of FcRn and/or target-mediated proteolytic degradation.

Poster: Paediatrics

Viera Lukacova III-22 Physiologically Based Pharmacokinetic (PBPK) Modeling of Amoxicillin in Neonates and Infants
Viera Lukacova, Michael B. Bolger, Walter S. Woltosz Simulations Plus, Inc., Lancaster, CA, USA
Objectives: An amoxicillin PBPK model was previously developed and validated in several adult populations. The purpose of this study was to explore the utility of the model in describing amoxicillin pharmacokinetics (PK) in neonates and infants.
Methods: An absorption/PBPK model for amoxicillin PK in adult populations was previously developed and validated [1-2] using GastroPlus™ 8.0 (Simulations Plus, Inc.). The program’s Advanced Compartmental Absorption and Transit (ACAT™) model described the absorption of the drug, while PK was simulated with its PBPKPlus™ module. Intestinal absorption and tissue distribution accounted for both passive diffusion and carrier-mediated transport. Total clearance consisted of renal (major) and hepatic (minor) components. Physiologies for infants and neonates were based on information collected from literature. These account for body weight, height, tissue sizes and blood flows, as well as rapid changes in extracellular water and renal function during first few weeks of life. Plasma protein and red blood cell binding was adjusted to account for infant plasma protein levels and hematocrit. The PBPK model, along with observed Cp-time profiles after i.v. administration was used to estimate the ontogeny of renal transporters.
Results: The PBPK model for amoxicillin correctly predicted volume of distribution in infants. The age-dependent glomerular filtration rate (GFR) was incorporated as reported in the literature for full-term and pre-term infants [3-4]. Renal transporter expression levels were fitted against observed Cp-time profiles from some studies and validated by using the final model to simulate amoxicillin PK in subjects of similar age from different studies. The differences in scaling for GFR and renal transporters are in line with the reported rates of maturation of GFR and active tubular secretion [5].
Conclusions: Amoxicillin is eliminated primarily by renal secretion. A physiological model that included relevant distribution and clearance mechanisms was previously fitted and validated in different adult populations. In the current work the model was applied to simulations of amoxicillin PK in neonates and infants: (1) to fill-in missing pieces of physiological information (ontogeny of renal transporters) using available in vivo data; and (2) to explore sources of variability in amoxicillin PK and provide insights into the drug’s behavior in populations where large scale clinical studies are not feasible.
References: [1] Lukacova V., Poster presentation (#6366), AAPS Annual Meeting 2012, Chicago IL [2] [2] Lukacova V., Poster presentation (#6367), AAPS Annual Meeting 2012, Chicago IL [3] DeWoskin R.S., Regul Toxicol Pharmacol 2008, 51 : 66-86 [4] Arant B.S., J Pediatr 1978, 92: 705-712 [5] Huisman-de Boer, J.J., Antimicrob Agents Chemother 1995, 39(2): 431-434

Poster: Study Design

Panos Macheras III-23 On the Properties of a Two-Stage Design for Bioequivalence Studies
Vangelis Karalis, Panos Macheras Laboratory of Biopharmaceutics-Pharmacokinetics, Faculty of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece.
Objectives: To introduce and unveil the properties of a two-stage design (TSD) for bioequivalence (BE) studies.
Methods: A TSD with an upper sample size limit (UL) is described and analyzed under different conditions using Monte Carlo simulations. This TSD was split into three branches: A, B1, and B2. The first stage included branches A and B1, while stage two referred to branch B2. Sample size re-estimation at B2 relies on the observed geometric mean ratio (GMR) and variability of the pharmacokinetic parameters at stage 1. The properties studied were % BE acceptance, % uses and % efficiency of each branch, as well as the reason of BE failure.
Results: No inflation of type I error was observed. Each TSD branch exhibits different performance. Branch A exerts the highest ability to declare BE either when variability is low to moderate, or an adequately high number of subjects is recruited.Second stage becomes mainly useful when highly variable drugs are assessed with a low number of subjects (N1) enrolled at stage 1  and/or the two drug products differ significantly. Branch A is more frequently used when variability is low, drug products are similar, and a large N1 is included. BE assessment at branch A exhibits high efficiency to declare BE. On the contrary, branches B1 and B2 are usually less efficient in declaring BE.
Conclusions: BE assessment at branch A exhibits high efficiency to declare BE, while branches B1 and B2 are usually less efficient. Inclusion of a UL is necessary to avoid inflation of type I error.

Poster: Other Modelling Applications

Merran Macpherson III-24 Using modelling and simulation to evaluate potential drug repositioning to a new therapy area
M Macpherson (1), A Viberg (1, 2), R Riley (1) (1) AstraZeneca, UK, (2) qPharmetra, Stockholm, Sweden
Introduction: Two doses of drug x were explored in initial phase IIa trials in over 300 patients. The lower dose was judge to be the minimally efficacious dose based on preclinical data and the other dose was chosen to represent maximum anticipated well tolerated dose. A consequence of target inhibition with drug x, was an increase in serum levels of a biomarker and this biomarker was used as a surrogate for receptor occupancy. A review of internal and external data suggested that this compound/target could be repositioned into another therapy area and, in order to robustly test the hypothesis, the dose required for a clinically relevant response was targeted to achieve e" 90% receptor occupancy in 80% of patients. 
Objectives: Develop a PKPD model from the patients in these trials and investigate the dose required for 90% receptor occupancy in 80% of patients in a new patient population.
Methods: A two-step sequential population pharmacokinetic-pharmacodynamic (PK-PD) analysis was performed using NONMEM 7.2.0. A two-compartment population PK model was fitted to the PK data and subsequently an inhibitory Emax pharmacodynamic model was fitted to the biomarker data accounting for the relationship between drug concentration and effect. Various simulations of the final sequential PK-PD model were performed.
Results: Based on simulations of the final model, it is unlikely that 90% receptor occupancy will be achieved in 80% of patients at the highest investigated dose. A doubling of exposure would be required to approach this target value. In the populations under consideration, this could be achieved through a reduction in CL/F or an increase in dose. It is also likely that variability in exposure may increase in the new target population as a consequence of reduced hepatic and renal function and an indication of this effect was demonstrated.
Conclusions: This analysis demonstrates a range of possible receptor occupancies and the impact patient specific variables may have on this assessment. Given the higher doses required and the additional potential DMPK and safety risks in the target patient population at these doses, an informed decision was made to suspend the project.
References: [1] Beal SL, Sheiner LB, Boeckmann AJ & Bauer RJ (Eds.) NONMEM Users Guides. 1989-2012. Icon Development Solutions, Ellicott City, Maryland, USA

Poster: Oncology

Paolo Magni III-25 A PK-PD model of tumor growth after administration of an anti-angiogenic agent given alone or in combination therapies in xenograft mice
Massimiliano Germani (1), Maurizio Rocchetti, Francesca Del Bene (1), Nadia Terranova (2), Italo Poggesi (3), Giuseppe De Nicolao (2), Paolo Magni (2) (1) PK & Modeling, Accelera srl, Nerviano (MI), Italy, (2) Dipartimento di Ingegneria Industriale e dell'Informazione, Università degli Studi di Pavia, Italy, (3) Johnson & Johnson, c/o Janssen Cilag S.p.A., Via M. Buonarroti 23, 20093, Cologno M.se, MI, Italy.
Objectives: PK–PD models able to predict the action of anticancer compounds in tumor xenografts have an important impact on drug development. In case of antiangiogenic compounds, many of the most common models are inadequate , as they are based on a cell kill hypothesis, while these drugs mainly act on the tumor vascularization, without a direct tumor cell kill effect. For this reason, a PK–PD model able to describe the tumor growth modulation following treatment with a cytostatic therapy, as opposed to a cytotoxic treatment, is proposed here.
Methods: Experimental Methods The experimental setting is that of a typical in vivo study routinely performed within several drug development projects using human carcinoma cell lines on xenograft mice [1]. Bevacizumab (Avasin) was given either alone or in combination with a polo-like kinase 1 (PLK1) inhibitor synthesized by Nerviano Medical Sciences (NMS). Average data of tumor weight of control and treated groups were considered. The mathematical model Untreated tumor growth was described using an exponential growth phase followed by a linear one. The effect of anti-angiogenic compounds was implemented using an inhibitory effect on the growth function. A combination model was also developed under a ‘no-interaction’ assumption [2] to assess the effect of the combination of bevacizumab with a target-oriented agent. Nonlinear regression techniques were used for estimating the model parameters.
Results: The model successfully captured the tumor growth data following different bevacizumab dosing regimens, allowing to estimate experiment-independent parameters. In combination therapies, the observation of a significant difference between model-predicted (under the no-interaction hypothesis) and observed tumor growth curves [3] was suggestive of the presence of a pharmacological interaction that was further accommodated into the model.
Conclusions: This approach can be used for optimizing the design of preclinical experiments and for investigate the best combination treatments. This work was supported by the DDMoRe project (www.ddmore.eu).
References: [1] M. Simeoni, G. De Nicolao, P. Magni, M. Rocchetti, and I. Poggesi. Modeling of human tumor xenografts and dose rationale in oncology. Drug Discovery Today: Technologies, 2012. [2] P. Magni and N. Terranova and F. {Del Bene} and M. Germani and G. {De Nicolao}. A Minimal Model of Tumor Growth Inhibition in Combination Regimens under the Hypothesis of no Interaction between Drugs. IEEE Trans. on Biomed. Eng.59:2161-2170, 2012 [3] M. Rocchetti, F. Del Bene, M. Germani, F. Fiorentini, I. Poggesi, E. Pesenti, P. Magni, and G. De Nicoalo. Testing additivity of anticancer agents in pre-clinical studies: A PK/PD modelling approach. Eur. J of Cancer, 45(18):3336-3346, 2009.

Poster: Oncology

Mathilde Marchand III-26 Population Pharmacokinetics and Exposure-Response Analyses to Support Dose Selection of Daratumumab in Multiple Myeloma Patients
M. Marchand (1), L. Claret (1), N. Losic (2), TA Puchalski (3), R. Bruno (1) (1) Pharsight Consulting Services, Pharsight, a CertaraTM Company, Marseille, France (2) Genmab, Copenhagen, Denmark, (3) Janssen Research & Development, LLC, Spring House, PA, USA
Objectives: Daratumumab is a human CD38 monoclonal antibody with broad-spectrum antitumor activity. The aim of this project was to explore the pharmacokinetics (PK), pharmacodynamic (PD) response and the exposure-response relationship of daratumumab from a Phase I/II study in patients with advanced multiple myeloma (MM).  This information was an integral aspect of dose selection.
Methods: Data were available from 25 MM patients with measurable PK who received daratumumab 0.1 to 16 mg/kg weekly by intravenous infusion (data cut 31 July 2012). A population PK model was developed to derive systemic exposure to daratumumab in patients. A simplified tumor growth inhibition (TGI) model [1] was used to estimate response metrics based on time profiles of M-protein and involved free light chain (FLC) after daratumumab administration. Relationship between these TGI metrics and progression free survival (PFS) were assessed.
Results: A 2-compartment population PK model with parallel linear and Michaelis-Menten eliminations best described daratumumab pharmacokinetics, as often described for monoclonal antibodies targeting receptors [2]. Estimated response metrics, i.e. M-protein and involved FLC time to nadir were correlated with daratumumab exposure (pq?qYqíÛíÍÄÍ®íÍ’ƒ’qƒ’ƒíÛíÍÄÍ[íÍ’ƒ’*jžˆh WØh-]i0JUmHnHu#j!ˆh-]iUmHnHujh-]iUmHnHuh-]imHnHu!h WØh-]i0J6]mHnHu*j¤‡h WØh-]i0JUmHnHuh-]imHnHuh WØh-]i0JmHnHu#hjæh-]iaJmHnHsH tH u$jh WØh-]i0JUmHnHuYqZq[q^q_q`qaqbqcqq€qq‚qŽqVrWrXrrrsrtrwrxryrzr{r|r˜r™ršríÞÓÞÀ®À — Àp ÓÞÓ^ÞÓÞÀ®À — H*j’Šh WØh-]i0JUmHnHu#jŠh-]iUmHnHu!h WØh-]i0J6]mHnHu*j˜‰h WØh-]i0JUmHnHuh-]imHnHuh WØh-]i0JmHnHu#hjæh-]iaJmHnHsH tH u$jh WØh-]i0JUmHnHuh-]imHnHujh-]iUmHnHu#j‰h-]iUmHnHušr›r¬rõrör÷rsssssssss7s8s9s:sJsùsúsûsttttttttt;t©@©B©íÞÓÞÀ®À — Àp ÓÞÓ^ÞÓÞÀ®À — H*jËh WØh-]i0JUmHnHu#j‰Êh-]iUmHnHu!h WØh-]i0J6]mHnHu*j Êh WØh-]i0JUmHnHuh-]imHnHuh WØh-]i0JmHnHu#hjæh-]iaJmHnHsH tH u$jh WØh-]i0JUmHnHuh-]imHnHujh-]iUmHnHu#jÉh-]iUmHnHu*§©iª«ù«â¬•­\®¯Ð¯°N±²¢²]³=´µáµŸ¶>·"¸é¸Ì¹¼º‚»L¼½¾è¾÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷÷edH ÏZgd-]iB©D©t©EªFªGªaªbªcªfªgªhªiªjªkª‡ªˆª‰ªŠª—ªáªâªãªýªþªÿª««««««#«$«íÜÎôâ´Ã´íí·ÎqíÜÎôÃ_´Ã´íí·Î#j}́h-]iUmHnHu*jÌh WØh-]i0JUmHnHuh-]imHnHu#hjæh-]iaJmHnHsH tH u#jƒËh-]iUmHnHujh-]iUmHnHuh-]imHnHuh WØh-]i0JmHnHu!h WØh-]i0J6]mHnHu$jh WØh-]i0JUmHnHu!$«%«&«-«Õ«Ö«×«ñ«ò«ó«ö«÷«ø«ù«ú«û«¬¬¬¬'¬¾¬¿¬À¬Ú¬Û¬Ü¬ß¬à¬ê×Ƹ­ž­Œž­ž×z׸q¸[×Ƹ­ž­Iž­ž#jq΁h-]iUmHnHu*jôÍh WØh-]i0JUmHnHuh-]imHnHu#hjæh-]iaJmHnHsH tH u#jẃh-]iUmHnHujh-]iUmHnHuh-]imHnHuh WØh-]i0JmHnHu!h WØh-]i0J6]mHnHu$jh WØh-]i0JUmHnHu*júÌh WØh-]i0JUmHnHuà¬á¬â¬ã¬ä¬­­­­­q­r­s­­Ž­­’­“­”­•­–­—­³­´­µ­¶­Ä­8®9®:®T®íÛíÍÄÍ®íÍ’ƒ’qƒ’ƒíÛíÍÄÍ[íÍ’ƒ’*jèÏh WØh-]i0JUmHnHu#jkρh-]iUmHnHujh-]iUmHnHuh-]imHnHu!h WØh-]i0J6]mHnHu*jîÎh WØh-]i0JUmHnHuh-]imHnHuh WØh-]i0JmHnHu#hjæh-]iaJmHnHsH tH u$jh WØh-]i0JUmHnHuT®U®V®Y®Z®[®\®]®^®z®{®|®}®®ê®ë®ì®¯¯¯ ¯ ¯
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