NIH to Stop Classifying BESH Studies as Clinical Trials in 2026
NIH said it will no longer classify BESH studies as clinical trials for grant applications due on or after May 25, 2026. The change removes ClinicalTrials.gov registration and reporting requirements for those studies.
The National Institutes of Health recently announced a significant policy shift: it will no longer classify Basic Experimental Studies Involving Humans (BESH) as clinical trials. Effective for grant applications due on or after May 25, 2026, BESH studies will no longer be subject to clinical trial requirements, meaning that mandatory registration and results reporting on ClinicalTrials.gov will no longer be required.
The decision, detailed in Notice NOT-OD-26-032 released on January 29, 2026, follows years of debate over the broad definition of clinical trials that the agency adopted in 2014. The 2014 policy change aimed to enhance transparency and accountability in NIH-funded human research, but unintentionally included many basic-science projects within the clinical trial classification.
The previous definition categorized studies as clinical trials if they prospectively assigned human participants to interventions to evaluate health-related biomedical or behavioral outcomes, and required that such studies be registered on ClinicalTrials.gov with results reported there. A clinical trial is a carefully designed study that evaluates new drugs, devices or care strategies in eligible patients who choose to participate. A clinical trial typically compares a new approach with the current standard of care to determine whether it leads to better outcomes.
BESH studies, while involving human participants, focus on uncovering fundamental aspects of biology or behavior—such as the basic mechanisms of psychology, neuroscience, or cognition—without the primary goal of improving health outcomes or changing clinical practice. Examples include experiments that explore how the brain processes information or how individuals make decisions in controlled settings, rather than testing therapies.
Each phase of clinical trials serves a distinct purpose. Phase I focuses on safety, helping researchers determine whether a new treatment can be used safely in people. Phase II evaluates whether the treatment shows signs of effectiveness, often by comparing before and after images or blood test results. Phase III tests whether the treatment improves patient outcomes and is required for U.S. Food and Drug Administration approval. Phase IV trials occur after FDA approval and involve larger populations to monitor long-term safety and effectiveness, including the identification of any side effects.
Additionally, NIH plans to retire BESH-specific funding opportunities after this date, allowing related research to be submitted under "Clinical Trials Not Allowed" announcements. Existing BESH projects will continue to operate under their current award terms, with interim flexibilities from a prior notice still in effect. As the May 2026 deadline approaches, the NIH will provide further instructions regarding application systems and funding announcements.
For researchers planning human-participant studies, the NIH recommends consulting the revised decision tools available on its website and reaching out to program officers for guidance on how this change will affect specific projects. Overall, registered studies at ClinicalTrials.gov are about 42,969 new studies posted as part of the cumulative total reaching 563,835 by the end of 2025, and in 2026, over 7,000 additional studies have been registered.