Abstract
The present study intended to confirm the in vivo relevance of the BiPHa+ biphasic dissolution assay using a single set of assay parameters. Herein, we evaluated five commercial drug products formulated by various enabling formulation principles under fasted conditions using the BiPHa+ assay. The in vitro partitioning profiles in the organic phase were compared with human pharmacokinetic data obtained from literature. In the first part, a meaningful in vitro dose of the formulations was assessed by determining the maximum drug concentration in the artificial absorption sink during dissolution (organic 1-decanol layer, C(dec,max)). Then, the maximum concentration of the partitioned drug in the organic layer was correlated with the in vivo fraction absorbed, which was derived from published human pharmacokinetic data. Fraction absorbed represents the percentage, which is absorbed from the intestine without considering first pass. It was found that the maximum drug concentration in the organic phase obtained from an in vitro dose of ten milligrams, which is equivalent to 15-25 µmol of the respective drug, led to the highest congruency with the fraction absorbed in vivo. In the second part, the in vivo relevance of the BiPHa+ dissolution data was verified by establishing a shared in vitro/in vivo relationship including all formulations. Based on the in vitro kinetics of the BiPHa+ experiments human in vivo plasma profiles were predicted using convolutional modelling approach. Subsequently, the calculated pharmacokinetic profiles were compared with in vivo performance of the studied drug products to assess the predictive power of the BiPHa+ assay. The BiPHa+ assay demonstrated biorelevance for the investigated in vitro partitioning profiles using a single set of assay parameters, which was verified based on human pharmacokinetic data of the five drug products.