Novo Nordisk A/S (NYSE:NVO) shares declined 2.8% on Tuesday after the company disclosed it had received a warning letter from the U.S. Food and Drug Administration related to shortcomings in postmarketing adverse event reporting.
The FDA issued the letter on March 5, 2026, following an inspection of Novo Nordisk Inc. conducted between January 13 and February 7, 2025. Regulators said the review uncovered significant violations tied to the reporting of adverse drug experiences associated with products including semaglutide, liraglutide, nedosiran sodium and estradiol.
According to the agency, the company did not maintain adequate written procedures governing the monitoring, collection, evaluation and reporting of adverse drug experiences after products had entered the market. Investigators found that Novo Nordisk and certain contractors failed to submit reports of serious and unexpected adverse events to the FDA within the mandated 15-day reporting window.
The warning letter also noted that the company’s procedures permitted some adverse event reports to be rejected or cancelled when reporters believed the event was not linked to the product, a practice the FDA said conflicts with regulatory requirements. During its review, the agency identified several cases in which serious adverse events—including stroke, death and suicidal ideation—were either reported late or invalidated even though valid patient identifiers were present.
Regulators further stated that Novo Nordisk did not consistently investigate adverse events requiring 15-day alert reports in a timely manner. In some instances, follow-up was delayed because the company required consent from reporters before conducting additional investigation.
Novo Nordisk has submitted several responses to the FDA between March 2025 and January 2026 outlining corrective measures. These included updating internal procedures, conducting retrospective reviews of reported cases and shifting safety case intake to specialized in-house patient safety personnel.
However, the FDA said the responses did not provide enough detail to confirm that the corrective actions would effectively prevent similar issues in the future.
The agency has requested that Novo Nordisk submit a detailed response within 15 business days describing the steps it will take to address the violations and prevent them from recurring.