GLP-1 + Amylin Combination: What the Research Shows

GLP-1 receptor agonists work by mimicking a gut hormone that tells your brain you're full, slows down gastric emptying, and boosts insulin secretion when blood sugar's high. But there's another hormone — amylin — that does something similar through different receptors, and the two pathways aren't redundant. They're complementary.

Amylin is co-secreted with insulin from pancreatic beta cells — which means people with impaired beta-cell function have less of both. It acts on the area postrema in the brainstem, triggering satiety signals that are distinct from GLP-1's CNS effects. It also delays gastric emptying (through a different mechanism than GLP-1) and suppresses glucagon secretion.

The research rationale is to test whether activating both pathways produces additive or synergistic effects. That is a hypothesis to measure, not evidence that lower doses remove adverse effects; tolerability and safety remain specific to each combination and study model.

Two approaches have emerged in clinical research. Novo Nordisk combined cagrilintide — a dual amylin and calcitonin receptor agonist (DACRA) — with semaglutide, in the investigational CagriSema combination. Eli Lilly developed eloralintide, described as a selective amylin receptor agonist. The compounds have different receptor profiles and have not been compared head to head in the cited evidence.

CagriSema is a once-weekly fixed-dose combination of cagrilintide 2.4 mg and semaglutide 2.4 mg. Two Phase 3 trials published in NEJM in June 2025 — REDEFINE 1 and REDEFINE 2 — showed what this dual-pathway approach can do.

REDEFINE 1 — adults without diabetes

3,417 participants with BMI ≥30 (or ≥27 with at least one obesity-related complication) were randomised 21:3:3:7 to CagriSema, semaglutide alone, cagrilintide alone, or placebo. At 68 weeks, the estimated mean weight loss was:

In the treatment-adherent analysis, CagriSema hit −22.7%. More striking: 40.4% of adherent CagriSema participants lost at least 25% of their body weight. More than half of participants (50.7%) moved from having obesity to a BMI below the obesity threshold — compared to just 10.2% on placebo.

GI side effects were common — 79.6% in the CagriSema group reported at least one GI event, versus 39.9% with placebo. Nausea, diarrhoea, and vomiting were the most frequent, though the paper describes them as "mainly transient and mild-to-moderate in severity."

REDEFINE 2 — adults with type 2 diabetes

1,206 participants with BMI ≥27 and HbA1c 7–10% were randomised 3:1 to CagriSema or placebo. The results were more modest, which you'd expect in a T2D population: −13.7% with CagriSema versus −3.4% with placebo (full adherence: −15.7%). But the glycemic data were impressive — 73.5% of CagriSema patients hit an HbA1c of ≤6.5%, versus 15.9% on placebo.

The GI tolerability was similar to REDEFINE 1: 72.5% in the CagriSema group reported GI events (34.4% placebo). No new safety signals emerged.

What these numbers suggest: the combination clearly beats either monotherapy, but the effect size shrinks in people with diabetes, and tolerability remains the main practical constraint.

A Nature Metabolism study published in September 2026 directly examined cagrilintide with retatrutide in diet-induced obese male rats. This differs from CagriSema: retatrutide activates GLP-1, GIP, and glucagon receptors, while cagrilintide adds amylin and calcitonin receptor activity.

The authors reported dose-dependent reductions in body weight and food intake with the combination. In the studied rat model, these effects exceeded the equimolar monotherapies and comparator combinations pairing cagrilintide with semaglutide or tirzepatide. The study also assessed metabolic markers, pair-feeding, and tissue-level molecular responses.

This is direct evidence for the pairing, but it is preclinical evidence from one animal model. It does not establish safety, efficacy, tolerability, or dosing in people, and it should not be used to infer a human protocol. No human outcome trial of the cagrilintide-retatrutide combination is cited here.

Lilly took a different pharmacological tack with eloralintide. Instead of a dual amylin/calcitonin agonist like cagrilintide, eloralintide is described as a selective amylin receptor agonist, with greater activity at amylin receptor targets than at the calcitonin receptor in laboratory assays. This does not mean calcitonin receptor activity is absent, nor does it establish a tolerability advantage in people.

The Phase 2 data were published in The Lancet in November 2025. 263 participants with obesity or overweight (mean BMI 39.1, mean weight 109.1 kg) were randomised across six dosing arms — 1 mg, 3 mg, 6 mg, 9 mg, and two dose-escalation schemes (6→9 mg and 3→6→9 mg) — versus placebo.

Results at 48 weeks (efficacy estimand):

The results varied across the trial arms. Comparisons with separate tirzepatide or CagriSema trials are not head-to-head evidence because the studies used different participants and designs.

The tolerability story matters here. Nausea rates ranged across the eloralintide arms, from 11% to 64%; it was 25% in the 3→6→9 mg escalation arm and 14% with placebo. Fatigue ranged from 0–46% across eloralintide arms, compared with 12% for placebo. The trial shows variation between study groups; it does not establish tolerability relative to cagrilintide.

In September 2026, Lilly also announced Phase 2b results for EloraTZP, a separate combination of eloralintide and tirzepatide. The sponsor-reported findings are not peer-reviewed monotherapy results; see the eloralintide research guide for the evidence and caveats.

Cagrilintide and eloralintide both target the amylin system, but the pharmacology differs in ways that might matter for research.

Cagrilintide is a dual amylin and calcitonin receptor agonist (DACRA). The calcitonin receptor component adds an extra signalling pathway — calcitonin receptors are expressed in bone, kidney, and certain CNS regions. Whether this contributes to efficacy or just adds side effects isn't fully settled. The REDEFINE data suggest the combination is effective, but the GI side effect burden is substantial.

Eloralintide is described as a selective amylin receptor agonist. In its Phase 2 trial, nausea was reported by 25% of participants in one dose-escalation group and 14% of placebo participants. There has been no head-to-head clinical trial against cagrilintide, so the available evidence does not establish that receptor selectivity gives eloralintide a tolerability advantage.

The head-to-head comparison we don't have is CagriSema versus eloralintide combined with a GLP-1. The evidence bases also differ: CagriSema has Phase 3 combination data, while the eloralintide evidence cited here is Phase 2 monotherapy data. Comparing headline percentages across separate trials does not establish that the treatments are equivalent.

For UK researchers, the relevant distinction is whether the question concerns dual-pathway combination pharmacology or selective amylin receptor pharmacology. See our eloralintide research guide for a focused review of its human study evidence and current development.

The REDEFINE and eloralintide trials answered a lot, but plenty of questions remain:

Durability. Both trials ran for 48–68 weeks. We don't know how these effects hold up over 2–5 years, or whether weight regain kinetics differ from GLP-1 monotherapy. The amylin system may have different compensatory mechanisms than GLP-1.

Optimal combination partners. CagriSema uses semaglutide, while the 2026 rat study directly tested cagrilintide with the GLP-1/GIP/glucagon agonist retatrutide. Whether those preclinical findings translate to people, or how this pairing compares in a human trial, remains unknown.

Calcitonin receptor effects. Cagrilintide activates calcitonin receptors. What does that mean for bone metabolism, calcium handling, or renal function over the long term? The calcitonin receptor is expressed in osteoclasts — chronic activation could theoretically affect bone turnover. No signal yet, but the trials weren't powered for that.

Selectivity vs breadth. Is selective amylin agonism (eloralintide) better than dual amylin/calcitonin agonism (cagrilintide)? The compounds have not been compared head to head in the cited clinical evidence, so their different receptor profiles do not establish a tolerability or efficacy advantage for either one.

Combination with triple agonists. Retatrutide already activates GLP-1, GIP, and glucagon receptors. The new rat study provides a starting point for studying added amylin signalling, but it does not answer the safety, tolerability, or efficacy questions in humans.

Which patients benefit most. The REDEFINE 2 data showed smaller effects in T2D. Is that an inherent limitation of the amylin-GLP-1 combination in diabetes, or a dose optimisation issue?

For UK research laboratories working on metabolic disease, the GLP-1 + amylin combination space offers several reference compounds:

• Semaglutide — the GLP-1 component of CagriSema, available as a standalone reference material for in vitro research
• Tirzepatide — dual GLP-1/GIP agonist, a comparator for studies examining whether dual incretin agonism outperforms GLP-1 alone in amylin combination models
• Retatrutide — triple GLP-1/GIP/glucagon agonist, useful for studying how amylin signalling might interact with multi-receptor metabolic pathways
• Cagrilintide — long-acting amylin and calcitonin receptor co-agonist supplied as a research reference material for in vitro work

Hati supplies cagrilintide as a research reference material and plans to stock eloralintide as a research reference material. Check the catalogue for current availability. Availability does not change the research-only boundary: these materials are not licensed medicines and are not for human or animal use.

The key research questions UK labs can address right now include:

• Does amylin receptor activation produce additive effects to GLP-1, GIP, and glucagon in cellular signalling assays?
• What's the dose-response relationship for amylin-mediated satiety signalling in CNS-derived cell models?
• How does chronic amylin exposure affect beta-cell function and insulin secretion in islet culture models?
• Can amylin receptor ligands be used to study receptor-RAMP interactions and subtype selectivity in transfected cell systems?

All standard UK peptide research regulations apply. These peptides are not controlled substances under the Misuse of Drugs Act. For laboratory research only — no human or animal use.