This post was written by Paul Sheives. FDA is authorized to approve applications based on clinical trials that demonstrate a new drug’s impact on a “surrogate endpoint,” or laboratory measure or physical sign used as a substitute for a clinical endpoint. When FDA approves a drug based on a surrogate endpoint under an accelerated approval process, a sponsor must, as a condition of approval, conduct postmarketing confirmatory studies to validate that a drug’s impact on a surrogate endpoint also leads to clinical benefits. Responding to concerns raised about FDA’s reliance on surrogate endpoints and its oversight of postmarketing studies, the GAO issued a report that (1) identified drugs approved based on surrogate endpoints; (2) obtained the status of related postmarketing studies; and (3) reviewed FDA’s oversight of a sample of 35 studies it required under its accelerated approval process, selected to include studies at varying levels of completion.  According to the GAO, although FDA has authority to expedite the withdrawal of a drug from the market if a sponsor does not complete a required confirmatory study with due diligence, or if a study fails to confirm a drug’s clinical benefit, it has not specified the conditions that would prompt it to do so. The GAO notes that this authority has never been exercised by the agency, even when such study requirements have gone unfulfilled for nearly 13 years. The GAO report recommends that FDA clarify the conditions under which it would utilize its authority to expedite the withdrawal of drugs under its accelerated approval process, but FDA disagreed with the need to develop such clarifying guidance.