Nearly 70% Of New Drugs Now Win FDA Approval With Just One Study

How FDA Drug Approval Standards Quietly Slipped Over Nine Years

When a new prescription lands on a pharmacy counter, the assumption is that it went through years of testing, checked and rechecked before ever reaching a shelf. That assumption isn’t as safe as it used to be. A new analysis of every novel drug the Food and Drug Administration approved between 2016 and 2024 found that most reached the market on the strength of a single clinical study, a sharp break from years earlier when the agency typically wanted evidence from three or more trials.

Researchers built a database covering 6,763 studies tied to FDA drug approvals over the nine-year period, publishing their findings in the journal PLOS One. The numbers show an agency relying on fewer studies, leaning more heavily on industry-funded evidence, and operating within a system where results often take years to reach the public. In 2016, 59.1% of approved drugs had backing from three or more trials; by 2024 that figure had fallen to 5.6%, while 69.4% of drugs approved that year made it through on a single study.

None of this points to one drug slipping through the cracks. The trend unfolded during the years following the 21st Century Cures Act, a 2016 law that gave the FDA more flexibility in how much proof it demands, though the researchers are careful to note their study can’t prove the law caused the decline. A shift toward oncology and rare-disease drugs, changing trial norms, and the pandemic may have played a role too.

The Average Drug Approval Relied on Just 1.4 Studies by 2024

Researchers pulled records for every new drug the FDA approved from 2016 through 2024, matching each against the National Library of Medicine’s ClinicalTrials.gov database to track how many studies backed each drug, who paid for them, and how quickly results went public.

Two trends stand out. The average number of studies supporting each approval dropped steadily, from 3.41 in 2016 to 1.39 in 2024. A brief uptick in 2023 was a fluke caused by one drug, a diabetes medication called Brenzavvy backed by nine trials; remove it and the 2023 average falls back to 1.85, in line with the trend. Who paid for those trials shifted just as sharply. Industry funding covered less than half of all studies in 2016 but paid for more than 80% by 2024, while NIH-funded studies shrank to a sliver of the total, falling from just under 3% in 2016 to under half a percent by 2023, even as the NIH’s overall budget remained level or increased.

Three-or-More-Trial Approvals Fell From 59% to Under 6%

Requiring at least two independent trials before approving a drug isn’t just bureaucratic caution. It rests on a simple idea: repeat the experiment and see if the result holds. A second study confirming the first makes it far less likely the finding was a fluke or the product of hidden bias. That principle has guided drug approval since the 1960s, and it had already been eroding for decades before this study even began. This new data shows the erosion accelerating hard after 2016.

Fewer trials doesn’t automatically mean drugs are less safe. Trial size, design, disease type, and overall evidence strength all factor in, and the study’s authors are careful to say their analysis doesn’t prove current practices are putting patients at greater risk. What it does show is a safety net with far less redundancy built in.

Trial Results Often Took More Than Two Years to Become Public

A second part of the study looked at how quickly results tied to approved drugs were made public once a study wrapped up. Under a 2017 law, sponsors must post results within a year or face fines up to $10,000 a day, capped at $1 million, but enforcement has been almost nonexistent. By 2021, the FDA had issued only four notices of noncompliance and hadn’t collected a dollar, even though uncollected penalties could total roughly $19 billion, more than five times the FDA’s entire budget for fiscal year 2025.

Actual delays back up the concern. For clinical trials completed in 2016, results took an average of 840.7 days to appear publicly, more than two years, and the wait only got longer, peaking at 1,226 days in 2020. Delays eased after that but never came close to the one-year limit.

Less Evidence, More Industry Money

These two trends reinforce each other. As the number of studies required for approval kept shrinking, the studies that remained were increasingly paid for by the same companies whose products were being tested, and earlier research has found industry-funded trials are more likely to favor the sponsor’s drug. Most pivotal evidence still came from late-stage trials, run just before a drug reaches the market, and the pattern suggests fewer of those trials were conducted or submitted per approval, rather than cheaper early-stage studies swapping in for confirmatory ones.

That combination, fewer studies and more industry money behind them, held steady across nine straight years, just as Congress weighs a follow-up law, sometimes called Cures 2.0, that could push the system further toward speed over volume of evidence. A drug reaching shelves faster sounds like good news until the question turns to how much proof stood behind it, and that proof has been shrinking for the better part of a decade.

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Disclaimer: This article summarizes findings from a peer-reviewed observational study and is intended for general informational purposes. It is not medical advice. Anyone with questions about a specific medication should consult a doctor or pharmacist.

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