Identifying small-molecule lead compounds: the screening approach to drug discovery.

A number of new technologies that enable high-throughput, cost-effective screening of potential drug candidates have been developed in recent years. Such compounds may be derived from the large proprietary collections held by pharmaceutical companies, from new synthetic approaches such as combinatorial chemistry, or from natural sources. The latter remain a major source of new chemicals: many are already used in human treatment and many others are currently undergoing evaluation as the potential medicines of the future.