Nearly 600 postmarket studies the FDA required drugmakers and devicemakers to complete after approving their products are behind schedule, according to a Sept. 18 KFF Health News analysis. Some are delayed by more than a decade, and roughly a third of ongoing studies were listed as behind schedule as of an August database download.
The report highlights Tavneos, Amgen’s drug for ANCA-associated vasculitis, as an example. The FDA required a postmarket safety study of 300 patients when it approved the drug in 2021 amid internal concerns about limited safety data, but only 21 patients had enrolled as of last fall. The FDA has since proposed withdrawing Tavneos’ approval, citing 76 cases of drug-induced liver injury, including eight deaths, and alleging that unblinded study personnel manipulated the pivotal trial’s results. Amgen has declined the FDA’s earlier request to voluntarily withdraw the drug and disputes the manipulation allegation. The dispute remains unresolved after a supporting study was retracted by the New England Journal of Medicine in June.
Other examples cited include an eye-implant study for children with zero patients enrolled nine years after its protocol was accepted, a Paxlovid pregnancy safety study that missed its 2024 completion deadline and an ankle-replacement device study that enrolled less than a third of its target population before nearly half of those patients experienced an adverse event. Researchers said the stakes are rising as the FDA moves to accelerate drug approvals.
The report also cited Sarepta’s Duchenne muscular dystrophy drug Exondys 51, whose postmarket confirmatory study missed a May 2021 deadline and remains delayed years later as the drug continues generating hundreds of millions in annual sales. HHS’ Office of Inspector General separately raised concerns in a January 2025 report about weak evidence supporting several accelerated approvals.
An HHS spokesperson told KFF Health News that delays do not necessarily indicate a product has an unresolved safety issue and that assessing any delay “requires a case-specific review.” The HHS Office of Inspector General has separately estimated that Medicare and Medicaid spent more than $18 billion from 2018 to 2021 on accelerated-approval drugs with incomplete confirmatory trials past their original deadlines.
