Modeling & Simulation in Pediatric Patients: Top down, Bottom Up, and What it All Means Clinically Alexander A. Vinks, PharmD, PhD, FCP Professor, Pediatrics and Pharmacology University of Cincinnati, College of Medicine Director, Division of Clinical Pharmacology
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Modeling & Simulation in Pediatric Patients: Top down, Bottom Up, and What it All Means Clinically
Alexander A. Vinks, PharmD, PhD, FCP
Professor, Pediatrics and Pharmacology
University of Cincinnati, College of Medicine
Director, Division of Clinical Pharmacology
Outline
• Describe how growth and maturation of relevant processes are predictive of pediatric drug disposition
• Highlight how pharmacometrics can facilitate the development of informative pediatric clinical studies
• Describe examples of the application of modeling and simulation and Physiologically-Based Pharmacokinetics (PBPK)
Vicini & van der Graaf. Clinical Pharmacology & Therapeutics (2013); 93 5, 379–381
Systems Pharmacology for Drug Discovery and Development: Paradigm Shift or Flash in the Pan?
Why Pediatric Pharmacometrics?
• To develop informative models based on pharmacology, physiology and disease for quantitative analysis of interactions between drugs and patients
• To collect informative PK, PD, PG data with a focus on variability across populations
• To better predict and control exposure and response in individual patients
• Achieve paradigm shift in way we perform clinical trials and individualized therapeutics in children
Barrett J. et al., 2012 Clin Pharmacol Ther 92(1):40-9. Johnson T. et al., 2010 Pediatric Anesthesia. Edginton A. et al., 2006 Clin Pharmacokinet 45(10):1013-34; Barrett J. et al., 2008 J Clin Pharmacol 48(5):632-49
Clinical trials provide evidence of efficacy and safety at usual doses in populations
Physicians treat individual patients who can vary widely in their response to drug therapy
+ =
+ =
Continuing Paradox of Drug Development
Efficacious & Safe
Efficacious & Safe
No Response
Adverse Drug Reaction
Courtesy: Dr. Guido Filler, London, Ontario, Canada
Descriptive Population Analysis & Modeling
Clinical data Population PK/PD & covariate exploration
• Percentages of patients with steady-state teduglutide exposure within the targeted window of efficacy • Dose reductions of 55, 65, 75, and 85% in the 0–1-, 1–2-, 2–3-, and 3–6-month age groups, vs. the optimal
dosing regimen in the 6–12-month age group.
Mouksassi S. et al. Clin. Pharmacol. Ther. 2009, 86:667-71
0
20
40
60
80
100
Kidney
MP
A A
UC
(m
ghr/
L)
0
20
40
60
80
100
120
Heart
MP
A A
UC
(m
ghr/
L)
0
20
40
60
80
100
120
140
160
180
200
220
240
260
Liver
MP
A A
UC
(m
ghr/
L)
MMF Dose, 1 g BID
Shaw LM, et al, Am J Transplantation, 2003; Fukuda T. et al., J Clin Pharmacol, 2011
Target Target
Mycophenolates - One Dose Does Not Fit All Large variability at standard doses
MPA: Mycophenolic acid AUC: Area under the concentration-time curve
Dose, 1000 mg twice a day
Consensus papers: Van Gelder et al. 2006; Kuypers et al.2011
Rationale for Developing of a Bayesian Estimator
• Large between patient variability
• Substantial within patient variability – Complex absorption process
– Enterohepatic recycling
• Clearance changes first 3-6 months post-transplant
• Pre-dose concentration does not allow accurate estimation of drug exposure
Fukuda T. et al. 2011 J Clin Pharmacol 51: 309-20. BCS Class II substance with strong pH-dependent solubility profile
Descriptive Modeling of PK variability
Dong M. et al. 2014 Population PK/PD of mycophenolic acid in pediatric renal transplant recipients. Br J Clin Pharmacol.
Final model prediction: R²=0.27 Posthoc Bayesian estimates: R²=0.70
GastroPlusTM 8.0 - Physiochemical properties with ADMET Predictor™ 6.0 Metabolism parameters based on in vitro UGT1A9 data - EHC process included
G.I. Tract (MPAG->MPA)
Liver (MPA MPAG)
Circulation (MPA)
Enterohepatic Recycling (EHC)
Hydrolysis
Sherwin C. et al. 2011 The evolution of models to describe the EHC of mycophenolic acid. Clin Pharmacokinet 50(1):1-24. Stemkens R. et al. 2013 13th International Congress IATDMCT, Salt Lake City. Data from: Burllingham et al. 1996: 1.5g MMF (IV infusion and oral administration in 12 healthy volunteers)
Empirical approaches Population PK-PD & covariate exploration
Dosing scenario 3
Applying Pharmacometrics in Pediatrics
Mechanistic approaches In vitro-in vivo extrapolation (IVIVE) & Physiologically-based pharmacokinetics (PBPK)
Top-down
p< 0.03
p< 0.01
p< 0.03
IVIVC confirmation of ontogeny
N=4
N=3
N=2
N=8
Emoto C. et al. 2014 submitted
In vivo data In vitro data
Substrate depletion assay with human microsomes and recombinant CYP3A7: CYP3A4, CYP3A5, CYP3A7 and CYP2C8; montelukast and ketoconazole as inhibitors.
Age group (years)
Sirolimus metabolic pathways in children
Filler G. & Christians U. Pediatr Transplant. 2009;13(1):44-53 Emoto C. et al. 2014 submitted.
Pediatric PBPK model development
Adapted from Leong et al with some modifications.
Adult PBPK model
Drug-
dependent
parameters
Systems-
dependent
parameters
(Adults)
Develop and verify an adult PBPK model
Pediatric PBPK model
Drug-
dependent
parameters
Systems-
dependent
parameters
(Pediatric)
• Perform sensitivity analysis to characterize
residual clearance with available pediatric data
• Update ontogeny profiles for each CYP3A isoform
Lipscomb JC et al
Type Neutral
MW 914
Log Po:w 4.3
B/P 35.6
fu,p 0.08
Caco-2 3.1×10-6 cm/s
CLint,3A4
9.33
µL/min/pmol
CLint,3A5
3.96
µL/min/pmol
CLint,2C8
0.25
µL/min/pmol
fu,m 0.43
Drug dependent parameters
for Sirolimus
Emoto C. et al. 2013 Development of a PBPK Model for Sirolimus. CPT-PSP 2:e59
Simcyp Peds, Version 13
Rowland, Peck, and Tucker 2011. Physiologically-Based Pharmacokinetics in Drug Development and Regulatory Science. Annu. Rev. Pharmacol. Toxicol. 51:45–73.
Vision of PBPK models in candidate selection and drug development
Momper and Wagner. TDM as a component of personalized medicine: applications in pediatric drug development. Clin Pharmacol Ther 2014, 95(2): 138-140.
Concluding remarks • Top-down statistics-based approaches alone are insufficient as
they do not provide mechanistic basis for extrapolation
• Despite the promise of PBPK as a powerful tool, there still are significant knowledge gaps, and a great amount of work will need to go into developing fully predictive pediatric PBPK models – DME and transporter ontogeny profiles
• Given the limited pool of experts in PBPK modeling and the lack of formal comparisons of existing PBPK software, it would be desirable to develop guidance or best practice documents for PBPK modeling using existing experience and databases
• But - “It is here and it can only get better” (Malcolm Rowland)