An amylin drug used on its own cut weight up to 8.6% in phase 1

Petrelintide, a long-acting analogue of the gut hormone amylin, reduced bodyweight by up to 8.6% after 16 weeks in two early-stage trials and was well tolerated, with mostly mild gastrointestinal side-effects [s1]. The result is a phase 1 signal in small groups of mostly healthy volunteers, not proof that the drug works for obesity, and it comes without any comparison against the GLP-1 drugs that now dominate weight-loss treatment [s1].

The reason a drug like this is being tested at all is that the current class has a tolerability ceiling. GLP-1-based medicines produce large weight loss but also nausea, vomiting and diarrhoea that lead some people to stop taking them; amylin analogues are being pursued as a class that might match some of the effect with fewer of those effects, alone or combined with a GLP-1 drug [s2].

What was tested

The manufacturer, Zealand Pharma, ran two randomised, double-blind, placebo-controlled trials: a single-ascending-dose study and a multiple-ascending-dose study [s1]. The single-dose trial gave subcutaneous petrelintide at doses from 0.04 mg to 2.4 mg, plus a 0.35 mg intravenous dose [s1]. The multiple-dose trial had two parts: six once-weekly subcutaneous doses of 0.6 mg and 1.2 mg in the first part, and in the second, 16 once-weekly doses escalated every two weeks to target doses of 2.4 mg, 4.8 mg and 9.0 mg [s1].

Who was enrolled matters for how the weight numbers should be read. The single-dose study and the first part of the multiple-dose study enrolled adults of normal weight or overweight; only the second part enrolled adults with overweight or obesity [s1]. Phase 1 trials are designed primarily to establish safety, tolerability and how the drug behaves in the body, and weight change here is an early pharmacodynamic readout rather than a proper efficacy endpoint [s1].

What it showed

Petrelintide was slowly absorbed and had a half-life of about 10 days, consistent with once-weekly dosing, and its exposure rose in proportion to dose at steady state [s1]. Over 16 weeks it reduced bodyweight by up to 8.6% [s1].

On tolerability, there were no serious or severe treatment-emergent adverse events in either trial [s1]. The most common side-effects were gastrointestinal and mostly mild, and a single participant discontinued because of them [s1]. Nausea, the most frequent gastrointestinal event, occurred in 16.7% to 33.3% of participants receiving petrelintide in the second part of the multiple-dose trial, against 16.7% on placebo; diarrhoea was rare and vomiting occurred only in the one participant who stopped treatment [s1].

How much this tells us

The honest summary is that this is a first look. An 8.6% reduction over 16 weeks is a real pharmacodynamic effect and a promising one for an amylin drug given on its own, but three cautions sit on top of it [s1].

First, the design. These are phase 1 trials in small cohorts, several of them not selected for obesity, and short — 16 weeks is a fraction of how long weight-loss drugs are taken [s1]. Second, there is no active comparator. Nothing in these trials measures petrelintide against semaglutide or tirzepatide, so any claim that it is better tolerated than a GLP-1 drug is a hypothesis these data raise, not one they test [s1]. The nausea figures show gastrointestinal events still occur; whether they occur less than with a GLP-1 drug at matched weight loss is exactly the question a head-to-head trial would have to answer. Third, the trials were run and funded by the company developing the drug [s1].

The wider context is that amylin has become one of the most active areas in obesity drug development, with several analogues and amylin-plus-GLP-1 combinations in trials, on the theory that adding an amylin mechanism could improve either the amount of weight lost or how well treatment is tolerated [s2]. Petrelintide is one entrant in that field, and these results are the kind that move a drug into larger trials rather than the kind that settle anything.

What to watch

The meaningful tests are still ahead: phase 2 and phase 3 trials in people with obesity, run long enough to show whether the weight loss deepens and holds, and ideally against or alongside an established GLP-1 drug so the tolerability claim can be checked rather than assumed. Until then, petrelintide is an early-stage candidate with an encouraging safety readout and a weight signal that needs to be reproduced at scale.

This article describes early-phase trial results and is informational only. It is not medical advice and does not recommend any drug. Petrelintide is investigational and not approved for use.