600 FDA Studies Are Overdue. Your Drug May Be One

Nearly 600 follow-up studies that drug and device makers owe the Food and Drug Administration are behind schedule, according to an analysis of federal records by KFF Health News, published last week. The delayed FDA studies cover almost 350 medicines and devices, many of which patients are still being prescribed and implanted while the research meant to answer open safety questions sits unfinished.

More than 250 of the overdue FDA studies had final reports due before July 31, and about one third of all ongoing studies in the FDA database were listed as behind schedule, the analysis found. Separate FDA databases for medical devices listed dozens more studies as overdue.

To get treatments to patients faster, the FDA often approves a product on the condition that the manufacturer completes more research after it reaches the market. Some of these postmarket studies are mandatory requirements; others are commitments a company agrees to voluntarily. Products granted accelerated approval must also confirm they deliver real clinical benefit.

The word delayed has a specific meaning at the agency: a study behind its original schedule, which can mean off track or already overdue. The FDA has granted extensions in some cases and denied them in others. In a statement, HHS spokesperson Emily Hilliard said delays can happen for legitimate reasons and should be judged case by case. A delay should not be treated as evidence of an unresolved safety or effectiveness issue, she said.

The vasculitis drug the FDA wants off the market

Tavneos, a drug from Amgen for a group of blood vessel diseases known as ANCA-associated vasculitis, was approved in 2021 on the condition that the company run a safety study of 300 patients, each followed for five years. As of July 24, only 49 patients had enrolled, according to Amgen.

The FDA has since cited 76 cases of drug-induced liver injury tied to Tavneos, including eight deaths, and proposed withdrawing the drug's approval. The agency also alleges that results from the trial used to support approval were manipulated, a claim Amgen disputes. The company says the drug's benefits outweigh its risks.

Tavneos remains available in the United States while the dispute plays out. The European Union has already revoked its approval. The drug can cost more than two hundred twenty thousand dollars per year of treatment, and Amgen estimates American patients have taken it for more than 6,500 patient-years. Tavneos generated 459 million dollars in global sales last year.

Amgen told KFF Health News that recruiting for the required study is difficult: once an approved treatment exists, patients are reluctant to enroll in a trial where they might receive a placebo. In June, the New England Journal of Medicine retracted a supporting study of the drug.

Other studies that never caught up

Sarepta Therapeutics' Duchenne muscular dystrophy drug Exondys 51 had a final study report due in May, five years ago, and it is still listed as delayed. The study has been fully enrolled since 2023, according to Sarepta spokesperson Tracy Sorrentino, and the company plans to share initial data late this year. The drug generated 538 million dollars in sales last year.

Other examples reach very different patients. A study of the COVID-19 treatment Paxlovid in pregnant women missed its completion and final report deadlines, and Pfizer says it remains committed to submitting results. A pediatric study of the CustomFlex Artificial Iris enrolled no patients even though its protocol was accepted nine years ago. A study of the Scandinavian Total Ankle Replacement system enrolled 142 of its planned 500 patients, and nearly half of those patients experienced an adverse event, documents show.

Other recent medical research has moved in the opposite direction, with trials delivering results rather than delays. Scientists have reported a new way to fight the Zika virus, and researchers studying the gut have uncovered a link between gut bacteria and sleep.

Why the stakes are rising

Researchers say the growing backlog of overdue FDA studies is harder to ignore as the agency speeds up approvals. In February, agency leaders wrote in the New England Journal of Medicine that a single pivotal clinical trial, rather than two, would become the default requirement for clearing a new drug. Aaron Kesselheim, a professor at Harvard Medical School, told KFF Health News that the change puts more pressure on follow-up research to catch problems.

The money involved is large. The HHS Office of Inspector General estimated in 2022 that Medicare and Medicaid spent more than 18 billion dollars over three years on accelerated-approval drugs whose confirmatory trials were past their planned completion dates.

People with rare diseases may feel the gap most, researchers said. Small patient populations make recruitment hard and approved alternatives are few. Pregnant patients, children, and people taking costly specialty drugs are also waiting on evidence that is still being gathered.

What patients can do

Anyone can look up a medicine's study status in the FDA's public postmarket requirements and commitments database by searching the drug's name. KFF Health News suggests asking a prescriber whether a medicine received accelerated approval, whether its follow-up studies are complete, and what monitoring is recommended. Suspected side effects can be reported to the agency's MedWatch program.

No one should stop taking a prescribed medicine because a study is delayed. Abrupt changes carry their own risks, and patients with questions should speak with a qualified clinician first.

The FDA has not said which delayed studies it considers most concerning. The next milestones to watch, according to the analysis: the Tavneos withdrawal proceedings and Sarepta's expected data release.