Bioanalytical Support for Both In Vitro and In Vivo Assays Across Drug Discovery and Drug Development

Bioanalysis in a drug metabolism environment can be defined as the analytical techniques utilized to assay various samples that are the result of in vitro or in vivo studies of one or more new chemical entities (NCEs). Bioanalysis has continued to evolve in response to the needs of the drug discovery and drug development teams, as well as the continuing improvement of the analytical technology that is used for the various assays. This chapter provides an overview of the various assays that are commonly used in various stages of drug discovery and drug development. The chapter is divided into three main sections: bioanalytical strategies, in vitro assays, and in vivo assays. For most of the assays discussed in this chapter, the analytical tool is high performance liquid chromatography (HPLC) combined with tandem mass spectrometry (MS/MS). It is common to have different levels of analytical acceptance criteria that become stricter as one moves from the early lead optimization arena into the development arena. By using this strategy, the higher throughput assays that are used in the screening stage would have minimal standards needed as part of the assay. As one goes to the higher levels, relatively smaller numbers of compounds are being assayed and the number of samples per compound is higher. There are multiple in vitro assays that are used for drug discovery screening of NCEs. The basic strategy for utilizing these various in vitro assays is to use them to screen NCEs in order to select those that have druglike properties. These tests are commonly used as part of the absorption, distribution, metabolism, and excretion (ADME) optimization phase of new drug discovery. The most commonly used assays are designed to measure one of the following parameters: permeability, metabolic stability, enzyme inhibition, or metabolism. Each of these assay types are described in this chapter as a subtopics. In a drug discovery setting, in vivo assays are similar to in vitro assays in terms of the need for providing the results in a timely manner. The main difference between in vitro assays and in vivo assays is that in vivo assays are often more challenging because the sample matrix is more complex. Most in vivo assays rely on some form of HPLC-MS/MS for the analytical step. The main in vivo topics covered in this chapter are PK screening, PK studies, and metabolite identification. Keywords: mass spectrometry; drug discovery; bioanalytical; HPLC-MS/MS; in vitro assays