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FDA warning letters reject 'research use only' labels on online GLP-1 peptide sales

Regulatory

In warning letters dated August 24, 2026, the FDA told online sellers that products such as retatrutide, tirzepatide, semaglutide, survodutide, mazdutide, bremelanotide (PT-141), tesamorelin and tesamorelin-ipamorelin blends were unapproved new drugs. The agency rejected 'for laboratory, research, and analytical use' disclaimers, citing therapeutic claims, bacteriostatic water for reconstitution and a dosing calculator as evidence of intended human use. Similar letters went to other peptide sellers earlier in 2026, including in March.

Sources

  1. 01Warning Letter 733652, August 24, 2026(opens the source in a new tab) U.S. Food and Drug Administration
  2. 02Warning Letter 721806, March 31, 2026(opens the source in a new tab) U.S. Food and Drug Administration
  3. 03FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss(opens the source in a new tab) U.S. Food and Drug Administration

Peptides involved

  1. In clinical trialsRetatrutideGIP, GLP-1 and glucagon receptor triple agonist39 WADA banned
  2. ApprovedTirzepatideDual GIP and GLP-1 receptor agonist39
  3. ApprovedSemaglutideGLP-1 receptor agonist31
  4. In clinical trialsSurvodutideGlucagon and GLP-1 receptor dual agonist29 WADA banned
  5. Approved elsewhereMazdutideGlucagon and GLP-1 receptor dual agonist (oxyntomodulin analog)34
  6. ApprovedBremelanotideMelanocortin receptor agonist7
  7. ApprovedTesamorelinGrowth hormone-releasing factor (GHRF) analogue44 WADA banned
  8. Not approvedIpamorelinGrowth hormone secretagogue (ghrelin receptor agonist)5 WADA banned