Amycretin: One Molecule, Amylin and GLP-1

One thing that happens when a drug class starts working is that everyone in it tries to fit more of the working parts into fewer molecules. The drug called amycretin is a tidy example. It is a single peptide built to activate the GLP-1 receptor (the target behind the current generation of weight-loss drugs) and the amylin receptor (the target of a second satiety hormone). In early trials it produced 13.1% weight loss at 12 weeks when taken by mouth and 24.3% weight loss over 36 weeks when injected under the skin.

Those are the headline numbers, and they come from early studies of different lengths using different routes of administration, so they are not a scoreboard. What the available facts do not settle is just as important. They do not say when, or whether, it will be approved, and they do not give a phase 3 result. They also leave open something stranger: whether “amylin and GLP-1” is even a complete description of what the molecule does.

What amycretin is, in plain terms

A review titled “Amycretin in obesity: Mechanisms, clinical efficacy, and …” describes it as a “unimolecular GLP-1 and amylin receptor agonist.” Translated: it is one chain of amino acids that turns on two kinds of appetite receptors. “Unimolecular” is doing all the work in that phrase. It means the two activities are not two drugs sharing a syringe. They are one drug that happens to fit two locks.

This is the same design idea behind tirzepatide, which the site covers elsewhere and which one paper says earned the nickname “twincretin” (pharmacology has a weakness for portmanteaus). Tirzepatide hits GIP and GLP-1. Retatrutide hits GLP-1, GIP and glucagon. Amycretin swaps the gut-hormone partner for amylin, which is a pancreatic hormone that also tells the brain you are full. So the shape is familiar. Only the partner changes.

Why not just mix two drugs together?

Here is the sensible reaction. If you want amylin activity and GLP-1 activity, you can take an amylin drug and a GLP-1 drug. That has already been done. CagriSema is, in the words of its sources, “a fixed-dose combination of semaglutide (a GLP-1 receptor agonist) and cagrilintide (an amylin analogue),” and in the REDEFINE 1 trial published in NEJM it produced 22.7% mean weight reduction at the 2.4 mg / 2.4 mg dose. Two well-characterized molecules, one injection, a big number. Why build a new hybrid when the mixture works?

To be fair, that objection is basically correct as far as it goes. A combination lets you tune each half separately, and each half arrives with its own history. On the other hand, a single molecule has one manufacturing process, one set of pharmacokinetics (how the drug moves through and leaves the body) and one thing for regulators to evaluate, instead of two things plus their interaction. And it may be a more natural candidate for a pill, which is where this gets interesting. It is far from clear you can make two separate peptides survive the stomach together on the same schedule. Amycretin has oral data at all, which tells you someone thought one peptide was a more tractable oral problem than two.

Everyone in this story is acting reasonably. The chemist wants one clean molecule because one molecule is easier to make and to study. The company wants a product that differs from its neighbors, because a crowded field rewards anything that does. The regulator wants to know what every active ingredient does, and fewer ingredients means fewer questions. I mean, nobody set out to make this more complicated.

And yet it is.

The third receptor nobody put in the name

The outlet Metabolic Care Today describes amycretin as “a unimolecular peptide agonist of GLP-1, amylin, AND calcitonin receptors,” capital letters theirs, and counts “three receptor targets.” So the drug marketed in conversation as an amylin/GLP-1 dual is, by at least one description, a triple. The calcitonin receptor sort of comes along for the ride.

This is not unique to amycretin. Structure Therapeutics has an oral small molecule, ACCG-2671, described as a dual amylin and calcitonin receptor agonist (a “DACRA”) with high binding affinity at the calcitonin receptor and at an amylin receptor subtype called AMY3R. In obese rats it produced dose-dependent weight loss, with additive effects when combined with semaglutide. So amylin-side drug design seems to travel with calcitonin activity as a matter of course. Why those two keep showing up together is a receptor biology question, and the facts here do not explain it. I assume the medicinal chemists find this less surprising than I do.

The naming, then, reflects what people care about rather than everything the molecule touches. That is common. It is also how you end up with a field whose drug names are a running count of receptors, plus a footnote.

Reading the early oral and injectable amycretin data

The two numbers are 13.1% at 12 weeks orally and 24.3% over 36 weeks by subcutaneous injection. The tempting move is to compare them and conclude the injection is about twice as good. That is the wrong comparison. The injectable study ran three times as long, and weight loss on these drugs generally keeps accumulating over months, so a 12-week figure is a snapshot of something still moving. The facts available do not give doses, trial sizes, placebo arms or dropout rates for either study, so the honest position is that the oral figure is promising for a short trial, the injectable figure is large, and neither is a head-to-head result.

For scale, and only for scale: tirzepatide produced 19.5% and 20.9% mean weight reduction at 10 mg and 15 mg in SURMOUNT-1, a phase 3 trial. A review in Annals of Internal Medicine pooling 26 randomized trials in 15,491 adults without diabetes put retatrutide at 24.2% at 12 mg weekly, ahead of tirzepatide (17.8%) and subcutaneous semaglutide (13.9%). Amycretin’s 24.3% sits right next to those numbers. But it comes from an earlier, smaller-looking evidence base, and cross-trial comparison is the thing everyone in this field agrees not to do and then does anyway (I am doing it right now, in a paragraph about not doing it).

Here is an invented scenario, offered only to show where the logic leads. A program finds that two receptors beat one, so it adds a third. The third beats two, so someone in a meeting says, “Hey, what if we also hit the receptor for, like, feeling satisfied after a good sandwich?” Eventually there is one molecule that activates every satiety receptor in the body, and its name is an alphabet. It is the drug-design version of Everything Everywhere All at Once, and its development team needs a whiteboard the size of a tennis court. That is not where amycretin is. It is roughly where the incentive points.

Where it sits in a crowded pipeline

One review identifies three main directions for next-generation incretin drugs: dual and triple receptor agonists, “biased agonist design,” and oral formulations. That last phrase means building a drug that switches on only some of a receptor’s signaling pathways rather than all of them. Amycretin touches two of the three directions at once. It is a multi-agonist, and it has an oral version.

The oral lane is not empty, though. Orforglipron, Eli Lilly’s small-molecule (non-peptide) GLP-1 pill, is described as the first oral small-molecule GLP-1 agonist to successfully complete a phase 3 trial, and Lilly positions it as potentially the first oral GLP-1 approved specifically for obesity. Aleniglipron and HRS-7535 are other small-molecule oral GLP-1 agonists with published trial data. Those are small molecules aimed at one receptor. Amycretin is a peptide aimed at two or three. A 2024 systematic review counted 14 ongoing phase 3 obesity trials, including CagriSema, retatrutide, orforglipron, survodutide, mazdutide, etc. In that list, amycretin had no phase 3 entry.

So the bet is specific. Amycretin’s developer is wagering that a single peptide carrying amylin activity can compete with a two-drug amylin combination on the injectable side and with GLP-1-only pills on the oral side. If it works, it is one molecule covering both markets. I would rather not think about what the marketing department has planned for that.

What comes next is the part the facts leave blank: longer trials, larger trials, direct comparisons, and the tolerability data that decides whether a big number becomes a drug people stay on. All of that is still ahead. The early results establish that the design idea is not crazy. They do not establish that it wins.

Eventually every weight-loss drug will be several weight-loss drugs.