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Pharmacokinetic Information Submitted to Support Valganciclovir Use in Maintenance Therapy for CMV Retinitis. Robert O. Kumi, Ph.D. Reviewer, Pharmacokinetics Food and Drug Administration, Office of Clinical Pharmacology and Biopharmaceutics, Division of Pharmaceutical Evaluation III.
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Pharmacokinetic Information Submitted to Support Valganciclovir Use in Maintenance Therapy for CMV Retinitis Robert O. Kumi, Ph.D. Reviewer, Pharmacokinetics Food and Drug Administration, Office of Clinical Pharmacology and Biopharmaceutics, Division of Pharmaceutical Evaluation III
Outline: Valganciclovir Pharmacokinetics • Background • Studies and Analyses Conducted • Summary of Study Results • Conclusions
Ganciclovir Delivery Systems • Intravenous and oral ganciclovir formulations available for maintenance therapy • Oral capsule has poor bioavailability (F):F < 10 % in the presence of food • Valganciclovir hydrochloride NDA under review
Valganciclovir- Prodrug of Ganciclovir • VALGAN is rapidly and extensively converted to GCV and valine • Following VALGAN administration, GCV bioavailability in presence of food is approximately 60 % • Low Systemic Availability of VALGAN: VALGAN Exposure < 5 % of GCV Exposure
VALGAN Use in Maintenance Therapy: Studies and Analyses Conducted • Exposure-Response (PK/PD) Analysis (GANS 2226) Applicant concluded that AUCavg was the best predictor of time to first photographic progression • Pharmacokinetic comparisons of GCV delivery systems
Ganciclovir PK/PD Analysis • Objective • to determine if any GCV PK parameter (s) predict response (time to first photographic progression) during maintenance therapy • Methodology • three oral GCV dose regimens and one IV GCV dose regimen • PK parameter estimates obtained using population approach • Population PK parameter estimates were used to evaluate PK/PD relationship
Limitations of GCV PK/PD Analysis • Errors in PK parameter estimates anticipated due to insufficient dosing time records • Accuracy of individual parameter estimates unknown, because of the sampling scheme used • Population pharmacokinetic analysis results could not be used for further PK/PD analysis
Pharmacokinetic Comparisons: Alternative to PK/PD Analysis Plasma concentration-time profile comparisons • three ganciclovir delivery systems at recommended and proposed doses • IV GCV, VALGAN, and Oral GCV
Ganciclovir Plasma Concentration-Time Profiles in HIV+/CMV+ Patients
Ganciclovir Plasma Concentration-Time Profiles in HIV+/CMV+ Patients
Ganciclovir Plasma Concentration-Time Profiles in HIV+/CMV+ Patients
Conclusions • GCV Plasma concentration-time profile comparisons of VALGAN to two approved GCV regimens support the use of VALGAN for CMV retinitis maintenance therapy • PK/PD model is not needed to support VALGAN use during maintenance therapy
Acknowledgements • Valganciclovir Review Team • Sue-Chih Lee, Ph.D., Pharmacometrics Reviewer