Letters from The Peptide Column.
Editorial commentary on regulation, research, and access. Each letter is sourced to primary literature and reviewed before publication.
Educational content only. Not medical advice. Substances discussed may not be FDA-approved for the uses described.
Peptide 101: PT-141 (Bremelanotide)
The peptide behind Vyleesi — an FDA-approved injection that works on the brain, not the body, to treat low sexual desire in women. What it does, what the trials really showed, and who it's not for.
PT-141 (bremelanotide) is one of the few peptides we cover with a real FDA approval. It treats low sexual desire in premenopausal women by working on the brain's desire circuitry, not blood flow or hormones. Here's the plain-English version — how it works, what the trials actually showed, and the real trade-offs.
Peptide 101: Tirzepatide (Mounjaro / Zepbound)
A plain-language explainer on tirzepatide — what it is, how it works, and what the evidence actually shows.
This week's Peptide 101 explains tirzepatide start to finish — the dual-hormone, FDA-approved drug behind Mounjaro and Zepbound — and what the trial evidence actually shows.
Peptide 101: BPC-157 (Body Protection Compound-157)
A plain-language explainer on BPC-157 — extensively studied in animals, almost untested in humans — plus where it actually stands with the FDA.
It has a devoted following in recovery and athletic circles and a mountain of animal data — but the human trials have not been done. Here is BPC-157 explained plainly, and a straight account of what we do and don't know.
Peptide 101: Semaglutide — what it is, and what it actually does
The most talked-about molecule in medicine, explained start to finish — plus the FDA's formal 503B notice, and one new review translated.
Everyone has heard of Ozempic. Far fewer can say what semaglutide is, how it works, or what the evidence does and doesn't show. This is the explainer — followed by this week's regulatory news and a new study, in plain English.
What the February announcement actually changed
An HHS Secretary signaled a peptide reclassification. The Federal Register did not.
In February, HHS Secretary RFK Jr. publicly suggested several peptides could move off the FDA's restricted compounding list. We've now had three months to watch the Federal Register. Here is what has — and has not — actually changed.
FDA's 503B GLP-1 exclusion proposal, in plain English
The agency proposed excluding semaglutide, tirzepatide, and liraglutide from the 503B bulks list. Comments close June 29.
On April 30, the FDA proposed adding three GLP-1 receptor agonists to the 503B 'Do Not Compound' list. We break down what 503B is, what the proposal does, who it affects, and how the comment period works.
Six generic semaglutides in 24 hours
Novo Nordisk's Indian patent on semaglutide expired March 20. Six Indian generics filed launches the same day. The implications for U.S. patients are not what most coverage said.
India's patent system, U.S. patent protection, and the global gray market are three different stories. We separate them — and explain what the Indian patent cliff actually means for an American patient looking at semaglutide costs in 2026.
One careful letter every Monday.
Free. Bias-checked. Under 1,200 words. Written for clinicians, patients, and the genuinely curious.
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