Intelligence for peptide industry operators.

In a week that materially reshapes the peptide enforcement landscape, the FDA’s Center for Drug Evaluation and Research issued thirty warning letters against compounding pharmacies and online vendors operating under the “research use only” framework. The action arrives alongside ongoing review of which peptides will remain available through 503A compounding — a decision that will determine the supply structure of an estimated $500M–$1B grey market.

The warning letters, posted in a single afternoon to the agency’s online enforcement database, name a mix of established vendors operating since 2019 and newer entrants that appeared during the GLP-1 supply crunch of 2024–2025. Five of the letters specifically cite therapeutic claims published on vendor websites; the remaining twenty-five focus on undeclared active pharmaceutical ingredients identified through targeted laboratory testing.

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