Beyond GLP-1: why drugmakers are suddenly racing over muscle
On August 24 Roche's Genentech paid 190 million dollars upfront, with up to about 2.3 billion dollars on the table in total, for a molecule that has never been tested for effectiveness in a single human being. It is called HM17321, it comes from the South Korean company Hanmi, and it is in Phase 1. The striking part is what it is being bought for. Its selling point is not that it takes off more weight than Wegovy or Zepbound. Its selling point is that it aims to take off weight while leaving your muscle where it is. That is worth spelling out, because it says something about where this whole field is heading.
Here is the problem the money is chasing. When anyone loses a significant amount of weight, by any method at all, including plain dieting, part of what goes is not fat but lean tissue, which is mostly muscle. This is not a defect unique to GLP-1 drugs; it is how the body behaves. Estimates of how much vary a lot depending on the trial and on how body composition was measured, roughly somewhere between a quarter and 40 percent of the weight lost. Why it matters is more practical than it sounds. Muscle is what lets you get out of a chair, carry shopping, keep your balance and not break a hip at seventy. It also burns energy at rest, so losing it makes keeping the weight off harder. And if the weight comes back, which it often does after stopping treatment, it tends to come back as fat, not as the muscle you lost.
So the industry is now building in three directions at once. The first is molecules that work somewhere entirely different from the incretin system that GLP-1 drugs use. HM17321 is one of those: it acts on a receptor called CRFR2, a pathway nobody has commercialised in obesity. The second is amylin, a different gut hormone, which several companies are betting will produce solid weight loss with gentler side effects. Roche is in that race too, with a drug called petrelintide developed with Zealand Pharma. The third is add-on agents intended to be taken alongside a GLP-1 specifically to hold onto muscle. What the Hanmi deal tells you is that Roche has now placed two separate bets on the same idea: that muscle preservation is not a footnote to obesity treatment but a market of its own.
Now the part that matters if you are reading this as a patient rather than an investor. HM17321 is in Phase 1. A Phase 1 study asks whether a drug is safe and what the body does with it. It does not ask whether it works. The claim about preserving muscle rests, at this stage, on laboratory and animal work, not on people. Hanmi will finish the Phase 1 study and Genentech takes over from Phase 2, which has not started. Even if everything goes right from here, a drug at this stage is realistically years from a pharmacy, closer to the end of the decade than to next year. Big licensing numbers are a signal that experienced people think something is promising. They are not evidence that it works.
There is something you can do about muscle today, and it does not require waiting for any of this. Two things have actual evidence behind them and both are free or nearly so: resistance training and eating enough protein while you are losing weight. Resistance training does not mean a gym membership and a barbell; it means loading your muscles against something, which can be body weight, resistance bands or simply carrying and standing up more. The protein side matters because during rapid weight loss the body will take what it needs from wherever it can find it. The best time to raise both of these is at the start of treatment, not after a year, when the loss has already happened. It is worth asking your doctor about both at the visit where the prescription is written, because it often does not come up on its own.
We are tracking this because it is a good example of how the obesity field actually changes. The headline story stays the same for months, that Novo and Lilly are fighting over who sells the most weight loss, and then a deal like this one shows that a third large company has quietly decided the competition will be over something else entirely. Whether HM17321 ever reaches anyone is genuinely unknown. That Roche has now paid twice to be in the muscle conversation is a fact, and it is the more useful one. This is general information, not medical advice.