ANTICANCER DRUG DEVELOPMENT AT LILLY-RESEARCH-LABORATORIES

Background: The discovery and clinical development of new drugs to treat cancer at Lilly Research Laboratories has undergone significant change during the past 15 years. During the early 1980s drug discovery relied heavily on a panel of syngeneic murine solid tumour models to identify new agents for clinical trial. New classes of oncolytic agents identified by this methodology include the difluoronucleoside antimetabolites, diarylsulfonylureas, and a series of folate-based enzyme inhibitors. Within the folate-based discovery programme at Lilly, a broad understanding of the structure activity relationships of folate antimetabolites and the biochemical basis of folate transport, processing, and enzyme inhibition has enabled a more rational approach for drug discovery. Current studies: Folate receptor binding properties are being studied to predict tumour sensitivities and tissue toxicities. This information, together with knowledge of a compound's ability to undergo polyglutamation via the enzyme folylpolyglutamate synthase, assist in the more rational selection of agents with designed cellular selectivities. Ultimately, the complex metabolic pathways involving folate metabolism provide numerous targets for-enzyme inhibition. Inhibitors of purine biosynthesis and thymidylate synthesis have demonstrated broad activity in preclinical models of disease including several human tumour xenografts, and are undergoing clinical testing. The folate-based drug discovery programme serves as a model for other biochemically based drug discovery programs including those based in drug resistance, signal transduction and cell cycle control.