BIOANALYTICAL STRATEGIES TO SUPPORT A DISCOVERY RESEARCH-PROGRAM

To facilitate the selection of drug candidates from a discovery resear ch programme, a strategy was developed to assess the preliminary metab olism and pharmacokinetics of numerous chemical entities. A three-leve l ''screening funnel'' was set up, using both in-vitro and in-vivo tec hniques, requiring bioanalytical methods for the determination of pare nt compound. Simple high performance liquid chromatography (HPLC)/UV a ssays with minimal sample workup were adequate for the initial high th roughput in-vitro screen used to assess in-vitro metabolic stability b ut a more selective sample extraction method was required for the seco nd level of the screen. Here; rats were infused with drug to steady-st ate concentrations and whole blood, plasma, and brain tissue homogenat e were analysed to assess clearance and to investigate blood/brain bar rier penetration. Generally, HPLC/UV was adequate as only moderate sen sitivities were required. However, the final level of the screen, a ra t PO/IV bioavailability study, needed far more sensitive assays and of ten presented significant analytical challenges.