Therapeutic ratings and end-of-phase II conferences: initiatives to accelerate the availability of important new drugs

J Clin Pharmacol. 1991 Jan;31(1):17-24. doi: 10.1002/j.1552-4604.1991.tb01882.x.


To facilitate the availability of important new therapeutic agents, the Food and Drug Administration (FDA) in the mid-1970s began assigning therapeutic ratings to investigational new drugs and holding end-of-phase II conferences with drug sponsors. To determine whether these initiatives are associated with faster approvals, we examined new drug application (NDA) review times of new chemical entities (NCEs) approved during the 12-year period 1978 through 1989. Mean NDA review time for 1A drugs (22.5 months) was 22% shorter than that for 1B drugs (28.7 months), which in turn was 25% shorter than that for 1C drugs (38.4 months). For drugs approved during the recent 4-year period 1986 through 1989, however, the gap between 1A and 1C review times has narrowed considerably from 19 to 9 months. When drugs were grouped by FDA reviewing division, 1A drugs had the shortest mean review time in each division except the Cardio-Renal Division; in that division, 1B drugs had the shortest mean review time. Mean NDA review time for drugs that had end-of-phase II conferences (28.6 months) was 15% shorter than that for drugs without such conferences (33.7 months). These results suggest that NCEs that receive 1A or 1B ratings and are the subject of end-of-phase II conferences benefit by having shorter review times.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Drug Evaluation / standards*
  • Drugs, Investigational* / classification
  • Humans
  • Program Evaluation
  • Time Factors
  • United States
  • United States Food and Drug Administration*


  • Drugs, Investigational