Pharmacology and drug discovery

There are two general approaches to drug discovery. The oldest is the empirically-driven in vivo identification of a drug candidate, with little or no consideration given to identifying the active constituent. The alternative is mechanism-based, a process that entails the in vitro screening of purified chemical compounds to identify those that interact specifically with a selected biological target, after which they are tested for therapeutic potential. A major difference between these approaches is the extent to which the principles of pharmacology are employed to demonstrate safety and efficacy and to enable improvements in the therapeutic properties of the product. As a thorough pharmacological analysis of the pharmacokinetics and pharmacodynamics of a test agent requires that it be a stable, single, purified substance, such testing is more difficult with unpurified samples containing multiple compounds as compared to single agents. A lack of pharmacological information compromises the clinical utility of a test substance by leaving open questions about its bioavailability, metabolism, and mechanisms of therapeutic actions and toxicities. Although drug discovery success has be achieved with both the empirically-driven and mechanism-based approaches, the proper application of pharmacological techniques in the drug discovery process maximizes efficacy, safety and the chance for regulatory approval. In addition, pharmacological data provides information needed for improving the therapeutic properties of an agent, enhancing its clinical utility, and extending the product lifespan.