1. IPCP Core C Activities Aprepitant Dose-exposure Relationship in the Monkey Jeffrey S. Barrett, Ph.D., FCP The Children’s Hospital of Philadelphia Division of Clinical Pharmacology and Therapeutics The University of Pennsylvania Medical School Department of Pediatrics

2. IPCP Core C Activities Outline Background –Relevance of PK, PK/PD and M&S to IPCP –Overall grant strategy – M&S –M&S Integration with Decision Making Aprepitant Review –PK Signature –Dose-selection rationale for CINV –PK Assessment – Suggestions for CDP Current Core C Efforts –Analytical Methods –CFAR Pilot PK Results Collaborative Efforts –SIV Dose Prediction –SIV Dose Prediction  SIV PK/PD  Projection to HIV –Analytical Effort –“Druggability” / Screening Criteria

3. IPCP Core C Activities Background – What we promised... 1.An evaluation of the correlation between single agent activity experiments and druggability properties theorized to benefit HAART. 2.An evaluation of the ability to generalize activity based on structural similarities of investigated agents. 3.Correlation of non-human primate to human pharmacokinetics via allometric modeling in order to guide clinical dosing based on pharmacokinetic considerations. Correlation of drug exposure to specific agent toxicities in non-human primates. 4.Construction of human PK/PD models built from in vitro, animal PK/PD and assumptions about human activity (efficacy and toxicity). 5.Correlation of non-human primate to patient exposure-response relationships. 6.Clinical trial simulation models to evaluate trial design sensitivities, drug combination and dosing scenarios and population characteristic dependencies.

4. IPCP Core C Activities Background – What we promised... Cross-validate aprepitant LC/MS/MS method (Constanzer et. al., 2004) PK (NCA) of aprepitant in HIV-infected patients (2-stage approach) Individual predicted pop-PK from final model (MAP Bayesian) PD: Exposure-response Psychologic Disturbances (Categorical Analysis) PD: Exposure-Response Viral Dynamics (NLMEM) PD: Exposure-Response NK response (NLMEM) PD: Exposure-response Safety Indices (Logistic Regression) Population PK Model (NLMEM) Structural Model Covariate Model Error Model Validation (data splitting or bootstrapping) Clinical Trial Simulation Model for Proof-of-Concept Phase IIA Trial

5. IPCP Core C Activities Relevance of PK, PK/PD and M&S to IPCP

6. IPCP Core C Activities Overall Strategy -- M&S

7. Aprepitant Background

8. Aprepitant PK Characteristics Absorption Mean absolute oral bioavailability of aprepitant is approximately 60 to 65% Mean peak plasma concentration (Cmax) at approximately 4 hours (Tmax). The pharmacokinetics of aprepitant are non-linear across the clinical dose range. Increase in AUC0-∞ was 26% greater than dose proportional between 80-mg and 125-mg single doses administered in the fed state. Distribution Aprepitant is greater than 95% bound to plasma proteins. The mean apparent volume of distribution at steady state (Vdss) is approximately 70 L in humans. Metabolism Aprepitant undergoes extensive metabolism. Metabolized primarily by CYP3A4 with minor metabolism by CYP1A2 and CYP2C19. Metabolism is largely via oxidation at the morpholine ring and its side chains. No metabolism by CYP2D6, CYP2C9, or CYP2E1 detected. Seven metabolites of aprepitant (weakly active) identified in human plasma. Excretion Aprepitant is eliminated primarily by metabolism; not renally excreted. The apparent plasma clearance of aprepitant ranged from approximately 62 to 90 mL/min. The apparent terminal half-life ranged from approximately 9 to 13 hours

9. Aprepitant PK Characteristics 125 mg80 mg Time Postdose (hr) N=12

10. Aprepitant Dose Selection CINV Indication Correlation of aprepitant plasma trough concentration with binding of aprepitant to striatal NK1 receptors (each point represents an individual subject)

11. Analytical Methods SFBC analysis / method – Monkey Plasma Constanzer method (Merck); no IS LOQ = 10 ng/mL * CHOP / LAPKPD method for Monkey CSF

12. LC-MS/MS CSF Method * API 4000 mass spectrometry coupled w/ Alliance Waters HPLC * Electrospray ionization source * Positive ion mode * C 18 Hypersil Column * Mobile phase (MP) a gradient MP of methanol and H 2 O with 0.1% formic acid * Multiple reaction monitoring at m/z 535.3 and 277.3 for aprepitant * Lowest of detection limit - 20 pg/mL

13. Pilot Study Results: Aprepitant in Rhesus Macaque Monkeys (n=3) TimeDG23DF42CB18 4/26/051.040.170.221 5/3/050.6660.3680.931 CSF Levels (ng/mL)

14. Future Efforts: * Integrated model for aprepitant plasma – CSF exposure * Simulation PK/PD model to study regimens in SIV (cellular PD used as input to define target) * PK/PD in SIV * Scaling of SIV / HIV based on PK/PD * Implement FDA HIV disease model * Validate human analytical method at CHOP / LAPKPD

15. Recent FDA Discussion:

21. Recent FDA Discussion Take Home Message * Tipranavir has more “warts” than aprepitant * Viral load reduction modest at best * FDA assisted with trial design, analysis and interpretation * Indication is focused on special population – treatment-resistant * Exposure-response indicates narrow therapeutic window * Many DDIs * Viability established on after numerous clinical evaluations