Amycretin Side Effects: What Studies Report

What the published record on amycretin covers

Amycretin has been described in the literature as a unimolecular peptide that activates both the GLP-1 receptor and the amylin receptor, an approach reviewers framed as combining two appetite-regulating pathways in a single molecule (PMID 41850421). A 2026 review of amylin receptors as therapeutic targets placed amycretin among a broader group of peptide-based strategies aimed at obesity and related cardiometabolic disease (PMID 41344603). Because the compound is investigational, the safety information available in the peer-reviewed record comes from early-phase trials and from narrative reviews summarising those trials rather than from post-marketing surveillance.

This page summarises what researchers reported about tolerability and adverse events. It does not describe how any compound is used, and it does not provide protocols. A separate PeptideU course covers amycretin's mechanism, trial design and pharmacology in more depth; this page is limited to side-effect and safety intent.

Gastrointestinal Adverse Events: What Studies Report

Across the published amycretin trials, the dominant adverse-event category reported was gastrointestinal. In the first-in-human phase 1 trial of oral amycretin, the study reported that adverse events were predominantly gastrointestinal in nature and mostly mild to moderate in severity, with nausea, vomiting and decreased appetite among the events recorded in participants with overweight or obesity (PMID 40550229). The phase 1b/2a study of subcutaneous amycretin similarly reported gastrointestinal events as the most common treatment-emergent findings, described by the researchers as largely transient and concentrated during periods of dose escalation (PMID 40550231).

Reviewers of the co-agonist class placed those observations in context, noting that nausea, vomiting, diarrhoea and constipation were the adverse events most consistently reported for incretin-based co-agonists as a group, and that tolerability was generally managed in trials through gradual dose escalation rather than through the emergence of unexpected organ toxicity (PMID 40949933). A 2026 review of long-acting amylin-related peptides made a similar point, describing gastrointestinal effects as the principal tolerability constraint for amylin-pathway agents in clinical development (PMID 41747885).

First-in-Human Oral Trial Findings: What Studies Report

The first-in-human trial was published as a double-blind, randomised, placebo-controlled phase 1 study of orally administered amycretin, and its stated objectives were safety, tolerability, pharmacokinetics and pharmacodynamics rather than efficacy endpoints (PMID 40550229). In that design, single and multiple ascending dose cohorts were used, an approach the researchers described as allowing tolerability to be assessed stepwise before higher exposures were evaluated (PMID 40550229). The study reported reductions in body weight at the higher oral dose levels evaluated over the multiple-dose period alongside the gastrointestinal adverse events described above (PMID 40550229).

Reviews summarising that trial emphasised its small size and short duration, characterising it as hypothesis-generating with respect to safety rather than definitive (PMID 41850421). A phase 1 programme is not powered to detect uncommon adverse events, a limitation reviewers of next-generation obesity pharmacotherapy repeatedly flagged when discussing early multi-receptor agonist data (PMID 41948476).

Subcutaneous Phase 1b/2a Findings: What Studies Report

The subcutaneous programme was reported as a randomised controlled phase 1b/2a study of once-weekly amycretin in adults with overweight or obesity, with treatment continuing for 36 weeks in the longest cohorts (PMID 40550231). The study reported dose-dependent reductions in body weight across the dose range tested, with the largest mean reduction of roughly 24% observed at the highest weekly dose level at week 36 (PMID 40550231). On the safety side, the researchers reported that adverse events were mostly mild to moderate, that gastrointestinal events predominated, and that no new safety signals beyond those anticipated for GLP-1 and amylin receptor agonism were identified in that dataset (PMID 40550231).

Commentary published afterwards treated the subcutaneous results as the most substantial human safety dataset available for the molecule, while noting that a phase 1b/2a sample cannot characterise rare events, cardiovascular outcomes or effects over years of exposure (PMID 41850421).

Reported adverse-event categories at a glance

Dose escalation and how it related to tolerability

Both amycretin trials used stepwise escalation designs, and the researchers reported that gastrointestinal events were most apparent as doses increased rather than at steady maintenance exposure (PMID 40550231). Reviews of amylin-pathway pharmacology explained this pattern mechanistically, describing amylin and GLP-1 receptor signalling as slowing gastric emptying and acting on hindbrain satiety circuits, effects that overlap with the sensations participants reported as nausea (PMID 41344603). A 2026 review of amylin-related peptides made the same connection, noting that the therapeutic and the unwanted effects arise from the same signalling pathways (PMID 41747885).

Related phase 2 trials in type 2 diabetes

Two 2026 phase 2 trials reported on zenagamtide, described in both papers as a novel unimolecular GLP-1 and amylin receptor agonist, in adults with type 2 diabetes. The once-weekly subcutaneous dose-finding trial reported efficacy and safety outcomes across multiple dose levels against placebo (PMID 42532080), and a parallel trial evaluated a once-daily oral formulation in the same population using a comparable randomised, double-blind, placebo-controlled dose-finding design (PMID 42532079). Readers comparing sources should note that trial reports for this receptor combination have appeared under more than one compound name, which affects how safety data can be located and cross-referenced.

Comparison with approved weight-management drugs

Because amycretin is investigational, reviewers often compared its early tolerability profile with that of approved agents. A 2025 systematic review comparing semaglutide, liraglutide, orlistat and phentermine reported that gastrointestinal adverse effects were the most commonly documented issues with the GLP-1 receptor agonists, while orlistat was associated with its own gastrointestinal profile (PMID 40206909). A 2026 endocrinology review of future obesity treatments placed dual GLP-1/amylin agents alongside other multi-receptor candidates and reported that the anticipated tolerability issues for these newer molecules resembled those already characterised for incretin monotherapies (PMID 42444567).

Modelling work has also attempted to anticipate how amylin-pathway therapies might perform. A 2025 synthetic target trial emulation and predictive modelling paper generated projected efficacy and safety comparisons for amylin-pathway agents in obesity and type 2 diabetes, an approach the authors framed as a way to bridge gaps before large randomised outcome trials report (PMID 41255585). Modelled estimates are not observed adverse-event rates, and that distinction matters when interpreting claims about the compound.

What the published literature does not report

Several categories of safety information are simply absent from the peer-reviewed record on amycretin, and that absence should be read as absence rather than reassurance:

• Long-term exposure data. The longest published treatment period in the amycretin trials was 36 weeks in the subcutaneous phase 1b/2a study (PMID 40550231); multi-year safety has not been published.
• Rare and serious events. Reviews noted that early-phase samples cannot quantify uncommon adverse events for multi-receptor agonists (PMID 41948476).
• Cardiovascular outcome data. Reviewers of incretin co-agonists reported that dedicated outcome trials were still needed to establish cardiometabolic benefit and risk for newer agents in this class (PMID 40949933).
• Special populations. The published amycretin trials enrolled adults with overweight or obesity, or with type 2 diabetes; pregnancy, paediatric and hepatic or renal impairment data were not part of those reports (PMID 40550229, PMID 42532079).
• Non-trial material. No published study has evaluated the safety of amycretin-labelled material obtained outside a regulated clinical trial, including identity, purity or dose accuracy of such material.

Limitations of the current safety picture

Three limitations shape any reading of amycretin adverse-event data. First, the trials were small and early-phase by design, with safety and tolerability as stated objectives (PMID 40550229). Second, adverse-event reporting in escalation studies is influenced by the escalation schedule itself, which the researchers acknowledged when describing when gastrointestinal events occurred (PMID 40550231). Third, much of what circulates about the compound derives from narrative reviews rather than new data, and reviews such as the 2026 mechanistic and clinical overview explicitly described the clinical evidence base as still developing (PMID 41850421).

Educational note

This page is for educational purposes only and is not medical advice; consult a licensed physician about any question relating to health, medication or investigational therapies. Amycretin has not been approved for general clinical use in the sources cited here, and nothing above describes how any substance should be used. The material summarises what the study reports and what researchers reported in the publications listed below.

References

• Amycretin, a novel, unimolecular GLP-1 and amylin receptor agonist administered subcutaneously: results from a phase 1b/2a randomised controlled study (Lancet, 2025)
• Safety, tolerability, pharmacokinetics, and pharmacodynamics of the first-in-class GLP-1 and amylin receptor agonist, amycretin: a first-in-human, phase 1, double-blind, randomised, placebo-controlled trial (Lancet, 2025)
• Amycretin in obesity: Mechanisms, clinical efficacy, and future perspectives (Metabolism, 2026)
• Long-acting amylin-related peptides as therapies for obesity and type 2 diabetes (Peptides, 2026)
• Amylin receptors as therapeutic targets in obesity: Emerging peptide-based strategies (Vascular Pharmacology, 2026)
• Efficacy and safety of incretin co-agonists: Transformative advances in cardiometabolic healthcare (World Journal of Cardiology, 2025)
• Obesity pharmacotherapy reimagined: The era of multi-receptor agonists and next-generation metabolic modulators, perspectives and controversies (Metabolism Open, 2026)
• Efficacy and safety of once-weekly subcutaneous zenagamtide, a novel unimolecular GLP-1 and amylin receptor agonist, in type 2 diabetes: a phase 2 trial (Lancet, 2026)
• Efficacy and safety of once-daily oral zenagamtide, a novel unimolecular GLP-1 and amylin receptor agonist, in adults with type 2 diabetes: a phase 2 trial (Lancet, 2026)
• Medical Treatments for Obesity: What Does the Future Have in Store? (Journal of Clinical Endocrinology and Metabolism, 2026)
• Synthetic target trial emulation and predictive modeling of amylin-pathway therapies for obesity and type 2 diabetes (Metabolism Open, 2025)
• Comparative Effectiveness of Semaglutide, Liraglutide, Orlistat, and Phentermine for Weight Loss in Obese Individuals: A Systematic Review (Cureus, 2025)