Target-based drug discovery, genetic diseases, and biologics

The last fifteen years have witnessed a major strategic shift in drug discovery away from an empiric approach based on incremental improvements of proven therapies, to a more theoretical, target-based approach. This arose as a consequence of three technical advances: (1) generation and interpretation of genome sequences, which facilitated identification and characterization of potential drug targets; (2) efficient production of candidate ligands for these putative targets through combinatorial chemistry or generation of monoclonal antibodies; and (3) high-throughput screening for rapid evaluation of interactions of these putative ligands with the selected targets. The basic idea underlying all three of these technologies is in keeping with Marshall Nirenberg’s dictum that science progresses best when there are simple assays capable of generating large data sets rapidly. Furthermore, practical implementation of target-based drug discovery was enabled directly by technologies that either were originated or nurtured by Marshall, his post-docs and fellows. Chief among these was the genetic code. Also important was adoption of clonal cell lines for pharmacological investigations, as well as the use of hybridomas to generate molecular probes that allowed physical purchase on signaling elements that had previously been only hypothetical constructs. Always the pure scientist, Marshall’s contributions nevertheless enabled fruitful applications in the pharmaceutical industry, several of them by his trainees. Both the successes and the shortcomings of target-based drug discovery are worthy of consideration, as are its implications for the choices of therapeutic goals and modalities by the pharmaceutical industry.