Uses of Flow Cytometry in Preclinical Safety Pharmacology and Toxicology

Abstract

During the last decade, commercial bench-top and multilaser flow cytometers have become widely available in academic, industrial, and government research laboratories. These flow cytometers provide a broad range of applications for multilaser and multiparameter analyses with user-friendly software interfaces. The purpose of this chapter is to review currently available and specialized applications of flow cytometry in preclinical pharmacology and toxicology. It is now common for most research and development, safety pharmacology, and safety assessment/toxicology groups to have direct access to flow cytometry instrumentation and technology. Many pharmaceutical companies have developed preclinical research groups that combine certain aspects of pharmacology and toxicology into early stages of drug discovery and development. The reason for this is that many new chemical entities (these are usually xenobiotics, i.e., nonindigenous chemicals) with interesting pharmacologic properties have proved to have unsuspected toxicities, but these effects are often undetected until late in development. Because drug toxicity is often not associated with the pharmacology of chemical agents, it is sometimes possible to select novel chemicals with excellent pharmacologic efficacy with minimal or reduced toxicity or potential for drug interactions. As will be discussed later in this chapter, flow cytometry has many desirable features that allow for high-throughput analysis of xenobiotics, as well as a definition of rare target cells and the measurement of biochemical endpoints. Thus, flow cytometry is finding increasing numbers of applications in preclinical pharmacology and toxicology and is being incorporated into all phases of drug discovery: development, preclinical, and clinical safety evaluation. Because of the longstanding use of flow cytometry in the evaluation of peripheral blood and hematopoietic cells in humans and other species, immunotoxicology was one of the first areas of toxicology to use flow cytometry and to develop routine testing procedures. Therefore, this chapter will largely focus on numerous applications of flow cytometry in immunotoxicity evaluation. Another factor that is driving the use of flow cytometry in immunotoxicology is that new regulations have been implemented in Europe and are being proposed in the United States and Japan to incorporate flow cytometry surface marker evaluation of circulating leukocytes in routine preclinical toxicology testing of pharmaceuticals in animals.