Abstract

Purpose: To develop a mechanistic mathematical model for analysis of in vitro permeability assays that accounts for all mechanisms contributing to observed apparent permeability: passive paracellular and transcellular diffusion, carrier-mediated transport, as well as drug accumulation in membranes and some intracellular compartments (e.g., lysosomes). The model was validated by analyzing the effect of competitive inhibition of P-gp by vinblastine on the apparent permeability of indinavir in Caco-2 monolayers.

Methods: MembranePlus™ (Simulations Plus, Inc.) was used to analyze the concentration-time profiles in donor and receiver compartments after apical and basolateral administration of 50 µg/mL (81.5 µM) indinavir alone and co-administration of 50 µg/mL (81.5 µM) indinavir with 70 µM vinblastine [1]. The physicochemical properties of indinavir and vinblastine were predicted by ADMET Predictor™ 6.0 (Simulations Plus, Inc.). The contribution of paracellular diffusion was estimated from drug properties and the experimental setup. Carrier-mediated transport was modeled with Michaelis-Menten kinetics. The indinavir P-gp Vmax/Km ratio, along with parameters accounting for passive transcellular diffusion and membrane accumulation were fitted to the indinavir-alone data. This basic model was then applied to simulate the inhibition of P-gp by vinblastine by fitting the Vmax/Km ratio for indinavir with competitive inhibition of P-gp by vinblastine. The model also includes various effects of major experiment-related parameters (e.g, shaking rate, solvent pH, filter support and sampling effects).

American Association of Pharmaceutical Scientists (AAPS), November 10-14, 2013, San Antonio, TX

By Ke X. Szeto, Viera Lukacova, Walter S. Woltosz, and Michael B. Bolger