NIH Funding Cuts Halt 383 Clinical Trials — Nearly 1 in 30, Study Finds

A new study published in JAMA Internal Medicine reports that 383 clinical trials — nearly one in every 30 NIH-funded trials during the review window — were interrupted after the National Institutes of Health (NIH) cut or terminated grant funding. The disruptions affected more than 74,000 enrolled patients and halted research across major areas including cancer, infectious disease, cardiovascular, mental health and reproductive health.

Key findings

The research team examined all clinical trials that received NIH funding between Feb. 28, 2025 (the date of the first reported grant termination), and Aug. 15, 2025. Of roughly 11,008 trials funded in that period, 383 experienced interrupted funding.

Of the interrupted trials, more than 36% have since completed; 35% were recruiting when funding stopped; 11% were active but not recruiting; 14% were active but not yet recruiting; and the remainder were enrolling by invitation. Trials classified as "active and not recruiting" — where participants may have been receiving interventions — accounted for a total of 74,311 enrolled patients.

Which studies were affected?

Trials conducted outside the U.S. were disproportionately impacted, and within the United States the Northeast had the highest rate of interrupted studies. More than 115 cancer trials and 97 infectious disease trials were interrupted. Other affected areas included cardiovascular disease, mental health and reproductive health research. Interrupted trials tended to have higher expected enrollment than trials that were not affected.

"The types of trials that are affected are among the most rigorous way that we generate scientific evidence: randomized clinical trials," said Dr. Anupam B. Jena, study co-author and professor at Harvard Medical School. "Clinical trials aren't light switches. You can't just flip them off without consequences."

Consequences and context

Investigators warned that terminating grants midstream creates avoidable waste, jeopardizes participant safety, and could undermine public trust and future willingness to enroll in research. The authors noted that systematic data are lacking on how often funding lapses pause or interrupt clinical trials, and that federal grant terminations were "exceedingly rare" before 2025.

The interruptions followed more than $2 billion in canceled NIH grant funding earlier in the year, part of President Trump's broader effort to downsize federal spending through the Department of Government Efficiency, according to the reporting. Agency operations were also slowed and roughly 1,300 employees were dismissed. The NIH is the largest funder of biomedical research in the United States, and thousands of universities and institutions rely on its grants.

Former NIH director Dr. Francis Collins told CBS News in April 2025 that every dollar the NIH awarded in 2024 "is estimated to have returned $2.46 just in a year," and warned that abruptly ending long-term clinical studies — such as those for Alzheimer's disease or cancer — risks patients' lives.

The NIH had not responded to requests for comment at the time of the study's publication. The authors call for better tracking of funding-related interruptions and policies to protect participants and preserve scientific value when funding is disrupted.