FDA warns research-peptide sellers Gram Peptides and Prime Sciences
FDA sent warning letters March 31, 2026 to two online peptide sellers, saying their "research use only" labels don't protect them when the marketing points to human use [1][2].
The FDA's Center for Drug Evaluation and Research issued warning letters on March 31, 2026 to Gram Peptides of Rancho Santa Fe, California, and Prime Sciences of Scottsdale, Arizona, saying the injectable peptides they sell online are unapproved new drugs [1][2]. In both letters, the agency said disclaimers calling the products "research use only" did not change the legal outcome, because the companies' own websites showed the products were intended for use in people [1][2].
What the FDA found
FDA reviewed grampeptides.com from January to March 2026 and found the site offering "Retatrutide" (which the firm also called "GLP-1-R peptide"), "Tirzepatide" (called "GLP-2 peptide"), and "Bacteriostatic Water for Injection" [1]. The agency reviewed prime-sciences.com over the same window and found "Cagrilintide," "GLP1-R" (identified as retatrutide), "GLP1-S" (identified as semaglutide), "GLP1-T" (identified as tirzepatide), "Mazdutide," and "BAC water" [2].
The letters quote the sites' own sales copy as evidence of intended use. Gram Peptides' retatrutide page said the product "influences appetite suppression, insulin sensitivity, thermogenesis, and fat-oxidation models" and "demonstrated significant potential for reducing body weight, improving glucose handling, and enhancing lipid metabolism" [1]. Its tirzepatide page listed "Weight Management" as a benefit, "associated with significant decreases in body weight in both animal and human studies" [1].
Prime Sciences' pages went further, according to FDA. The cagrilintide page claimed "weight loss of 25% or more was achieved in 40.4% of patients receiving Cagri compared to 16.2% with semaglutide alone" [2]. The retatrutide page claimed "an average of up to 28% body weight reduction, compared to around 15% with semaglutide or Tirzapeptide" [2]. The semaglutide page was headlined "Ozempic – Weight Loss Supplement" and said participants "lost an average of 15.2% of their initial body weight" [2]. The tirzepatide page cited a phase 3 trial showing "a 20 percent reduction in body weight," and the mazdutide page cited the GLORY-1 phase 3 trial with "an average body weight reduction of up to 14.8%" [2].
FDA also classified the bacteriostatic water as a drug in both cases. Because it was sold alongside injectable peptides that require reconstitution — and, at Prime Sciences, bundled in a "Reconstitution Kit" with a syringe — the agency said the firms intended it to be used for injection [1][2].
Both letters state that no approved applications under section 505 of the Federal Food, Drug, and Cosmetic Act are in effect for these products, making them unapproved new drugs whose sale in interstate commerce violates sections 301(d) and 505(a) [1][2].
Why it matters for patients
Gray-market peptide sites have grown alongside GLP-1 demand, and many lean on "research use only" or "not for human consumption" language as a legal shield. FDA's position in these two letters is that the disclaimer does not control; the marketing does. At Gram Peptides the label said "Research Use Only" and "not intended for human consumption, medical use, or veterinary use," and at Prime Sciences it said "laboratory research purposes only" — and in both cases FDA said website evidence established the products were intended as human drugs [1][2].
The agency also flagged a specific safety concern with this category: injectable products "are delivered directly into the body, sometimes directly into the bloodstream, and therefore, bypass some of the body's key defenses against toxins and microorganisms that can lead to serious and life-threatening conditions" [1][2].
It is worth noting what these letters do not say. They do not report any testing of the products' contents, purity, sterility or actual dose, and they do not describe any injuries linked to either seller. FDA's stated basis is the legal status of the products and how they were marketed [1][2]. Whether either site's vials contain what the label claims is not addressed in the sources.
Renaming molecules also did not help. FDA identified Gram Peptides' "GLP-2 peptide" as tirzepatide and Prime Sciences' "GLP1-S" as semaglutide and "GLP1-T" as tirzepatide, tying the code names back to the actual compounds [1][2].
What happens next
Both firms have 15 working days from receipt of the March 31, 2026 letters to tell FDA in writing what steps they have taken, or to explain why they believe their products do not violate the law [1][2]. FDA warned that failing to adequately address the matter "may lead to regulatory or legal action including, without limitation, seizure and injunction" [1][2]. Responses go to the Office of Unapproved Drugs and Labeling Compliance, referencing case numbers 721806 for Gram Peptides and 721805 for Prime Sciences [1][2]. Neither company's response was public as of the letters' publication.
Sources
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