Longhorn Vaccines And Diagnostics LLC – FDA Warning Letter, Oct 30, 2025

The FDA issued a Warning Letter to Longhorn Vaccines and Diagnostics LLC following an inspection from October 20-30, 2025, regarding its PrimeStore® MTM device. The device, intended for stabilizing and inactivating specific virus RNA and bacterial DNA in nasal washes and sputum, was found to be adulterated and misbranded due to significant violations of medical device regulations. Major issues included widespread non-conformity with Quality System regulations, particularly the failure to establish and maintain fundamental procedures for complaint handling, including documenting and investigating device failures or adverse events like leakage, ingestion, or cyanide release. There was also a critical lack of robust corrective and preventive action (CAPA) processes and comprehensive design control procedures covering all stages of development, verification, and validation. Furthermore, the firm lacked adequate controls for nonconforming products, rework, supplier management, management review, and quality audits. Additionally, the PrimeStore® MTM device was deemed misbranded and unapproved because Longhorn Vaccines and Diagnostics LLC marketed it for expanded indications beyond its original FDA authorization. This included claims on their website and brochures for stabilizing and inactivating numerous additional microorganisms and specimen types, as well as detecting antimicrobial resistance genes, without obtaining necessary premarket clearance or approval. The FDA requires Longhorn Vaccines and Diagnostics LLC to promptly address all identified violations and submit a written response within fifteen business days detailing specific corrective actions, a preventative plan, and an implementation timetable. Failure to comply may lead to further regulatory actions, including seizure or injunctions.