FDA warns peptide vendors selling retatrutide as a 'research' GLP-1

The FDA issued warning letters to research-peptide sellers — among them Prime Sciences and Gram Peptides — offering products labeled 'GLP-1-R', 'GLP1-S' and 'GLP1-T' that the agency identified as retatrutide, an investigational drug with no approved product that cannot lawfully be compounded. The letters cite unapproved-new-drug and misbranding violations for promoting the peptides for human use behind 'research use only' labeling, part of a broader 2026 enforcement push against GLP-1 and peptide sellers that also produced dozens of letters to telehealth firms marketing compounded GLP-1s.