Lantheus Holdings, Inc. (NASDAQ: LNTH) said the U.S. Food and Drug Administration has issued a Complete Response Letter (CRL) for its New Drug Application for LNTH-2501 (Gallium 68 edotreotide), a PET diagnostic imaging agent targeting somatostatin receptor-positive neuroendocrine tumors.

The FDA said it could not approve the application by the Prescription Drug User Fee Act action date of June 29, 2026, citing unresolved manufacturing-related conditions at a third-party facility responsible for drug product manufacturing. The agency said resolution of the facility inspection-related conditions is required before the application can be approved.

The CRL did not identify concerns with the data Lantheus submitted in support of the application, nor did it cite issues related to the safety or efficacy of LNTH-2501.

"The feedback received from the FDA relates solely to our third-party manufacturer, and not to the clinical performance of the product," said Mary Anne Heino, Executive Chairperson and Chief Executive Officer of Lantheus. "We are working closely with our partner and the Agency to address these facility manufacturing-related conditions and advance the program."

LNTH-2501 is an investigational radioactive diagnostic kit for use with positron emission tomography for localization of neuroendocrine tumors in adult and pediatric patients. The product is not currently approved by the FDA and is not available for sale in the United States.