02/11/14 Update: FDA Commissioner Margaret Hamburg responded to the results of the AMA study.
A recent study in the Journal of the American Medical Association found wide variations in the quality and quantity of trial evidence used by the FDA for drug approvals between 2005 and 2012. The authors reviewed the approval of 188 novel therapeutic agents approved during this period and discovered that over a third of of the agents were approved on the basis of a single trial. The FDA guidance suggests that manufacturers provide at least two trials that independently demonstrate the efficacy of the drug. However, there are also circumstances in which a single trial might be sufficient for FDA approval (e.g., fast-tracking drugs for life-threatening diseases).
The study authors also found variations in trial features, such as duration, endpoints, and patient completion rates. According to Dr. Joseph Ross, the study’s senior author, about 45 percent of trials tested a “surrogate endpoint” rather than the “clinical endpoint” (e.g., the study showed that a drug reduced tumor size, but did not analyze whether the drug improved survival rates for cancer patients). Additionally, over 40 percent of the 188 drugs studied were meant to treat long-term conditions such as asthma and diabetes; however, more than half of these drugs were approved using trials lasting less than six months. Thus, the long term effects are not fully known when the drug enters the market and strong post-marketing surveillance is needed. Overall, variations in the quantity and rigor of evidence needed for FDA approval can have serious implications on prescribers and patients deciding to use newly approved drugs.