FDA warns Gram Peptides and Prime Sciences over "research use only" peptide sales
The FDA says the two online sellers marketed peptides as research chemicals while describing weight loss, blood sugar and appetite effects that make them unapproved drugs.
The FDA sent warning letters dated March 31, 2026, to two online sellers of research-labeled peptides, telling both firms they are marketing unapproved new drugs for human use [1][2]. The letters went to Gram Peptides of Rancho Santa Fe, California, and Prime Sciences of Scottsdale, Arizona, and were issued by the Center for Drug Evaluation and Research [1][2].
FDA said it reviewed grampeptides.com and prime-sciences.com between January and March 2026 [1][2]. Gram Peptides offered "Retatrutide," which it also called "GLP-1-R peptide," "Tirzepatide," which it called "GLP-2 peptide," and "Bacteriostatic Water for Injection" [1]. Prime Sciences offered "Cagrilintide," "GLP1-R," "GLP1-S," "GLP1-T," "Mazdutide" and "BAC water" [2].
Both sites carried disclaimers. Gram Peptides labeled its products "Research Use Only" and "not intended for human consumption, medical use, or veterinary use" [1]. Prime Sciences used "laboratory research purposes only" and similar wording [2]. FDA said that language did not settle the question. The agency said other statements on the same sites showed the products were intended to treat disease or to affect the structure or function of the body, which makes them drugs under federal law [1][2].
FDA quoted examples. Gram Peptides described retatrutide as influencing "appetite suppression, insulin sensitivity, thermogenesis, and fat-oxidation models" and as showing "significant potential for reducing body weight, improving glucose handling, and enhancing lipid metabolism" [1]. Prime Sciences said cagrilintide produced weight loss of 25% or more in 40.4% of patients in one study, compared with 16.2% for semaglutide alone [2]. It said retatrutide showed average weight reduction of up to 28% in trials, against around 15% for semaglutide or tirzepatide [2]. The site also cited a 15.2% average weight loss for semaglutide, a 20% body weight reduction for tirzepatide, and up to 14.8% for mazdutide in the phase 3 GLORY-1 trial, along with a report of up to an 80% reduction in liver fat in some participants [2].
FDA also treated the water products as drugs. Gram Peptides sold bacteriostatic water for injection alongside peptides that require reconstitution [1]. Prime Sciences sold a reconstitution kit containing BAC water and a syringe next to its peptides, which FDA said showed the water was intended for injection [2].
FDA said the products are "new drugs" because they are not generally recognized as safe and effective for the uses described in their labeling, and that no approved applications are in effect for them [1][2]. The letters also said injectable products bypass some of the body's defenses against toxins and microorganisms, which can lead to serious and life-threatening conditions [1][2].
Why it matters for patients
The letters address a common claim in the gray market: that a peptide is a research chemical rather than a drug, and therefore outside FDA's drug rules. FDA's position here is that how a product is marketed, not the disclaimer on the label, decides whether it is a drug [1][2].
Products sold as research chemicals have not gone through FDA review for safety, effectiveness, purity or manufacturing quality. FDA said no approved applications are in effect for any of the products named in the two letters [1][2]. That includes retatrutide, cagrilintide and mazdutide, which are described in the letters as unapproved products sold by these firms [1][2].
A warning letter is not a recall or a court order. It states the agency's view, gives the firm a chance to answer, and warns that failure to correct the issues could lead to seizure or injunction [1][2]. The letters do not say whether either company has stopped selling the products, and it has not been reported whether the sites have changed [1][2].
What happens next
Both letters ask for a written response within 15 working days of receipt, describing the steps taken to correct the violations, how the firm will prevent them from recurring, and supporting documents. Responses go to FDA's Office of Unapproved Drugs and Labeling Compliance [1][2]. Firms that believe they are not violating the law may send their reasoning instead [1][2]. FDA said failure to adequately address the matter may lead to regulatory or legal action, including seizure and injunction [1][2].
Neither letter states whether the companies have replied. As of the letters' date, no recall, product seizure or court action against either firm has been disclosed [1][2].
Sources
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