Over the past 10 or more years, the drug development paradigm has shifted radically as a consequence of the availability of generic formulations for many important drugs and the growing influence of major payers in controlling reimbursement of new medicines. The demand for health care in an aging and increasingly information-seeking population is steadily outstripping society's ability to pay for all possible treatments. Regulatory approval of new drugs is necessary but no longer sufficient for market access in many countries, including the United States.