The FDA advisory panel that spent Thursday voting on gray-market peptides did not stop at the two everyone expected. After recommending BPC-157 and KPV, the Pharmacy Compounding Advisory Committee kept going and cleared the two peptides on its day-one list with the thinnest evidence behind them. TB-500 passed 8 to 6, with one member abstaining. MOTS-c passed 7 to 5, with two abstaining. Both are banned in professional sport. Neither has ever been tested in a human trial.
That is the part the headline number missed. Our companion piece ↗ covered the 8-6 vote to add BPC-157 and KPV over the objection of the agency's own scientists. The same panel, in the same session, went on to recommend two more. Adding a substance to the Section 503A Bulks List is what lets compounding pharmacies legally make it. All four of Thursday's peptides are now on track for that pathway, pending a formal FDA rulemaking that the agency says takes six to eighteen months and is free to ignore. The vote is advice, not law. It is also a win for HHS Secretary Robert F. Kennedy Jr., whose deregulation push helped put these seven peptides in front of the committee in the first place.
What the panel waved through
TB-500 is a synthetic fragment of thymosin beta-4, a protein the body uses in wound repair and cell migration. It sells online as a tissue-repair and recovery injectable. MOTS-c is a short peptide that mitochondria make on their own, studied in animals for metabolism and aging. Neither is an approved drug anywhere. What people buy is manufactured for research use and injected off-label.
The FDA's career staff reviewed both against the agency's four-factor test (how well the substance is characterized, its history in compounding, evidence that it works, and evidence that it is safe) and found the same hole in each: no human data at all. Not a small trial. Not a poorly controlled one. None. For BPC-157 and the sleep and cognition peptides later on the docket, staff at least had thin or flawed human studies to weigh. For KPV, TB-500, and MOTS-c, the effectiveness column was empty.
The doping history sharpens the point. Both TB-500 and MOTS-c sit on the World Anti-Doping Agency's prohibited list, TB-500 for its tissue-repair claims and MOTS-c as a metabolic modulator. Athletes cannot use either substance in competition. Yet the committee just recommended both for a legal compounding channel that reaches anyone with a prescription.
The room knew it
The tally drew an audible gasp in the meeting room, according to reporters present. The discomfort was on the record. Josh Mailman of the Neuroendocrine Tumor Research Foundation, who voted no, said he did not know what he was voting on. "It's kind of like a black box to me," he told the committee. Brian Lee of USC, another no vote, pointed at the evidence problem directly, noting that about 30 percent of patients on a placebo report a response, which is roughly the bar these peptides would have to clear to show they do anything.
Even the yes side hedged on characterization. Russell Wesdyk, an FDA official, summed up the identity problem the staff kept running into: "We've never faced a problem of, 'What is it?'" Haleem Mohammed, a physician who runs a men's health clinic and voted yes, framed his vote as harm reduction, arguing his job was to keep patients as safe as possible given that they are already buying these compounds.
Why the molecules matter here
The gap the panel voted past is visible on the science. MOTS-c is a real signaling peptide, and in one 2025 readout it switched on the metabolic pathway it targets and still failed to keep aging stem cells young ↗. Hitting the right target is not the same as a clinical benefit. TB-500's parent molecule, thymosin beta-4, has been in real trials, and the most advanced one, a thymosin eye drop, missed its Phase 3 when the placebo group healed just as well ↗. That is the track record for the family the panel just endorsed for compounding.
The peptidemodel cards for MOTS-c ↗ and TB-500 ↗ both catalog what is known and, more to the point, what is not.
The committee reconvenes Friday for the second half of its slate: delta sleep-inducing peptide (also called emideltide), Semax, and Epitalon. FDA staff recommended against all three, same as the four that already passed. Whether the panel keeps overruling its own scientists is the only open question left in the meeting.