A NEW IN-VITRO MODEL TO PREDICT THE IN VIVO BEHAVIOR OF DRUGS BASED ON PARALLEL ARTIFICIAL MEMBRANE AND PLASMA PROTEIN BINDING

Biopharmaceutical properties of drug candidates are commonly taken into account at early stage in the drug discovery process to lower the attrition rate in later clinical development stages and reduce the overall time and cost of the development of new drugs [1]. Lipophilicity and Plasma Protein Binding of a candidate drug molecule are important parameters influencing pharmacokinetic and metabolic properties [2,3]. At present, several assays exist to determine these two fundamental parameters individually [4,5], but there is no approach to assess simultaneously the two parameters and their reciprocal influence. So the main objective of this work is to develop an in vitro model to investigate the influence of a lipidic membrane on the protein binding of drugs, and to obtain a rank ordering of them. Compatibly with the needs of the modern drug discovery process, a highly automated process has been developed, allowing the rapid turnaround of in vitro data using LC-MS/MS methods to assess widely diverse compounds. The assay runs in a 96-well format using commercially available parts [6]. The protein used in this assay is Human Serum Albumin; it is not immobilized on any surface. The lipophilic distribution of drugs is guaranteed by use of an artificial lipidic membrane coated on a porous filter plate. A series of highly protein-bound compounds (PPB> 95%) having high membrane retention in PAMPA assay (>90%) were selected and tested. Distribution kinetics between lipidic membrane and HSA were measured. A different behavior of these compounds has allowed their rank ordering. Compounds with these features are not ranked by current assays, so this new approach would help early discovery process predicting better the in vivo behavior of candidate drugs from in vitro data. The impact of nonspecific binding was also investigated. REFERENCES [1] Kerns EH. J. Pharm. Sci. 2001, 90, 1838-1858 [2] Caron G, Ermondi G, Lorenti M.. J. Med. Chem. 2004, 47, 3949-3961. [3] Testa B, Crivori P, Reinst M, Carrupt PA. Kluvert Academic Publisher: Norwell, MA, 2000, pp 179-211. [4] Schuhmecher J, Buhner K, Witt-laido A. J Pharm Sci, 2000, 89, 1008-1021. [5] Loidl-Stahlhofen A, Hartmann T, Schottner M, Rohring C, Brodowsky H, Schmitt J, Keldenich J. Pharmaceutical Research, 2001, 18, 12, 1782-1788. [6] Elisabet Lazaro, Philip J. Lowe, Xavier Briand, Bernard Faller. J. Med. Chem. 2008, 51, 2009-2017.