The US Food and Drug Administration (FDA) has issued notices to more than 2,200 medical product companies and researchers, urging them to comply with mandatory requirements to submit clinical trial results to ClinicalTrials.gov. The move is part of efforts to address persistent gaps in publicly available clinical data and improve transparency in the healthcare system.

According to an internal FDA analysis, nearly 29.6 percent of studies that are likely subject to mandatory reporting requirements have not submitted results information to ClinicalTrials.gov. These include interventional studies involving FDA-regulated products with a US nexus that have surpassed their reporting deadlines, excluding early-stage phase I and device feasibility studies.

The regulator highlighted that failure to report negative or unfavourable trial outcomes contributes to publication bias, distorting the overall understanding of drug safety and efficacy. Such gaps can mislead clinicians, researchers and patients by overrepresenting successful outcomes while underreporting failures.

On March 30, 2026, the FDA sent communications linked to more than 3,000 registered clinical trials, including some publicly funded studies, where results information had not been submitted or had not completed the National Library of Medicine’s quality control review process. The agency is currently seeking voluntary compliance before considering further regulatory action, which could include formal notices of noncompliance.

Officials emphasised that clinical trial sponsors are legally required to report results within one year of trial completion. The initiative is intended to strengthen accountability and ensure that critical data is made accessible to support informed medical decision-making.

The FDA stated that improving compliance will enhance patient safety, provide a clearer picture of treatment risks and benefits and support evidence-based healthcare practices. The agency, part of the US Department of Health and Human Services, continues to play a key role in safeguarding public health through oversight of drugs, medical devices and clinical research.