Maximising use of in vitro ADMET tools to predict in vivo bioavailability and safety.

The drastic increase in the costs for discovering and developing a new drug and the high attrition rate of development candidates led to shifting of drug discovery strategy to parallel assessment of comprehensive drug properties along with efficacy. The article reviews the benefits and caveats of implementing comprehensive in vitro tools in early drug discovery and their impact on addressing in vivo ADMET issues. With the proposal of four-barrier profiling paradigm and employment of integrated risk assessment, one can exponentially enhance the predictive power of those in vitro tools by taking into consideration the interplays among those profiling parameters. An 'Exposure Cube' is proposed to promote collective employment of solubility/dissolution, permeability and metabolic clearance to address in vivo exposure and to direct optimization of new chemical entities in drug discovery.