The Peptide Primer

A peptide is a short chain of amino acids. That chain can be both structural and a signal.

Amino acids link together into chains. Now, when one of those chains is relatively short we call it a peptide, but when it's long we call it a protein. There is no official cutoff. Somewhere around 50 amino acids most people switch vocabulary, and insulin sits at 51 and gets called both, so that tells you how firm that line really is. Here in the US, due to some regulatory shenanigans at the FDA, we use 40 as a cutoff. But that's a different topic for another day.

Here's the part that matters more than the chemistry. Your body already runs on peptides as one of the languages it uses to talk to itself. When your pancreas needs to tell your liver that food has arrived, it sends a peptide. When your stomach wants your brain to know you're full, it sends a peptide. When your adrenals tell your kidneys to get to work, that's the result of a peptide too. Billions of these messages go out every day and you never notice a single one.

So peptide therapy rests on a fairly simple idea. If your body already uses these molecules as instructions, what if you could send the instructions yourself?

Insulin is a peptide. First isolated in 1921, peptide medicine turned a hundred years old before most of the internet had heard of it.

For example, Vasopressin, stocked in hospital pharmacies across the country for shock and blood pressure support, is a peptide. Leuprolide, one of the standard treatments for advanced prostate cancer since the 1980s, is also a peptide. If you're a parent, you might be interested to know that what hospitals use to induce labor, Oxytocin, is also a peptide.

The question was never whether peptides work as drugs. That got settled a century ago. What changed is the ambition.

For most of pharmaceutical history, drug discovery meant looking outward. Plants, molds, soil bacteria, marine organisms. Penicillin came from a mold on a petri dish. Aspirin traces to willow bark. Metformin traces to French lilac. The model was to go find the molecule somewhere in nature and then figure out what happens when we give it to a person.

GLP-1s reversed the direction. Semaglutide, tirzepatide, and retatrutide are all built off a hormone your own gut releases after you eat. Nobody discovered them in a rainforest (technically they were found in a Gila monster), but once researchers realized that GLP-1 was a native peptide found in us, the race was on.

And pharma noticed.

Those numbers are not a bet on weight loss drugs. They're a bet on an entire category. The industry has decided that the next generation of medicine is going to come from inside the human body, and it's putting its money where its mouth is.

Also peptides. Same chemistry. Just completely different paperwork.

Every drug in your local CVS got there by running a very specific and grueling gauntlet: preclinical work, then Phase I, then Phase II, then Phase III, then an application, then approval. That's what Novo Nordisk did with Semaglutide. But it cost them somewhere north of a decade of development and hundreds of millions of dollars. And that must be repeated every time for every mass-market drug.

But nobody ever did that for BPC-157. Same story for TB-500, GHK-Cu, and MOTS-c. Not because they were tested and failed. But because nobody ever filed.

Most of these compounds, because of their structure and a quirk of US patent law, have no path to meaningful patent protection and no clear commercial owner. Unfortunately, that means no pharma company will ever have a financial reason to spend half a billion dollars proving one out.

So these peptides made it into patients' hands through a very different path. Compounding pharmacies are licensed facilities that prepare customized medications from a personalized prescription. Imagine an antique pharmacy from a classic movie like It's A Wonderful Life where a pharmacist makes a prescription by hand for a given patient. That's akin to a modern compounding pharmacy, except most modern compounding pharmacies are identical to their pharma company counterparts in sophistication and quality.

And for the better part of a decade, licensed compounding pharmacies in this country prepared these peptides for patients who had a doctor and a personalized script.

Then, in 2023, the FDA reclassified 19 of these compounds into what's called Category 2, meaning substances that raise significant safety risks. Preparing them became an enforcement risk overnight, and legitimate pharmacies stopped. It's worth noting that the FDA had no evidence these compounds ever hurt anyone, a fact they were later forced to admit both in court and in July's recent peptide hearing.

When the FDA pulled these compounds out of pharmacies in 2023, they did not reduce the number of people taking them. Patients just started getting their medicine somewhere else. Demand went straight to websites selling vials stamped “for research use only, not for human consumption,” which is, at best, a legal sleight-of-hand that nobody believes.

That's the outcome the FDA didn't plan for. Take a drug out of the pharmacy and you don't get rid of it. You just remove the physicians and pharmacists from the equation.

So I've spent the last two years working on that problem. On July 23rd and 24th of 2026, I testified in front of the FDA's Pharmacy Compounding Advisory Committee at their White Oak campus, alongside other physicians and pharmacists making the case that these compounds belong back in licensed pharmacies with quality control, a doctor, and a script attached.

The committee reviewed seven peptides over two days and voted to recommend six of them for inclusion on the 503A Bulks List, which is the roster of ingredients compounding pharmacies are permitted to work with.

It's worth remembering that this vote was a non-binding recommendation from an independent committee advising the FDA. The FDA itself recommended against approving any of these peptides. It also failed to include any of the science that was submitted to them supporting the safety and efficacy of these peptides. When asked about this during the hearing, FDA representatives first claimed no such data was submitted. When evidence to the contrary was presented, the FDA representatives changed their tune and instead claimed they just ‘didn't have time’ to review everything.

The committee voting in favor of these six peptides being made legal once more was an open rejection of the FDA's argument that they shouldn't.

Unfortunately, nothing is legal today that wasn't legal at the beginning of July. Like I said earlier, the advisory committee vote is a recommendation. It is not binding and it is not approval. Here is what still has to happen:

1. 1

   The FDA decides whether to act.

   The FDA still writes the rulebook. A favorable vote does not obligate them to do anything.

2. 2

   The FDA publishes a proposed rule.

   This is a formal document spelling out which substances it intends to add and under what conditions.

3. 3

   A public comment period opens.

   This is usually 60 to 90 days, but it can be shorter. Pharmacies, physicians, and patients all get to put their position on the record.

4. 4

   The FDA publishes a final rule.

   Only then can a compounding pharmacy legally prepare these peptides from bulk.

Historically that sequence runs twelve to twenty-four months, sometimes longer. Realistically we're likely looking at 2027 at the earliest.

And a favorable rule may not look the way people are picturing it. The agency can attach conditions in the proposed rule, and the most consequential one is route of administration. That isn't hypothetical. The committee openly discussed whether KPV should be permitted for topical use only. If that's how the rule lands, injectable and oral KPV stay off the table, which would rule out some of the most common ways it gets used today, including for the gut conditions many people use it for in the first place.

The vote was a huge win. But it is not the finish line.

When that comment period opens, it's the single best moment for anyone reading this to actually influence the outcome, and I'll tell you the day it happens.

Slightly the wrong question. The better one is: what am I trying to accomplish?

I am a firm believer in goal-based therapy. I don't believe anyone should take a medication without a clear reason, a way to assess whether it's working, and a plan for what happens if it isn't. “I want to try peptides” isn't a goal. “I want to get back into the gym to lose weight and get healthier despite my sore knee” absolutely is.

With that context, here's roughly what the six recommended compounds were put forward to address. Read this as the problem each one was nominated for, not as a promise or a defined indication for therapy. None of them are approved, and the evidence behind them ranges from reasonable to thin.