Success rates in the United States drug development system

Drug development in the United States has been characterized by: (1) high attrition and correspondingly low success rates of drug candidates passing through the development sys(2) a steady decline in new chemical entities (NCEs) entering clinical r e~ea rch ,~ -~ and (3) increasingly lengthy and more costly periods required for clinical and regulatory review.3 These characteristics have raised the concern that the number~f NCEs reaching the market in the future might remain low or decline even further unless compensatory increases in NCE success rates s