What Is Cagrilintide and How Does It Work?

Cagrilintide is a long-acting amylin analogue engineered by Novo Nordisk. Amylin is a peptide hormone co-secreted with insulin from pancreatic beta cells. It slows gastric emptying, suppresses glucagon, and signals satiety through the central nervous system. Native amylin has a very short half-life, so cagrilintide was designed with fatty-acid side chains that extend its duration to roughly one week, making once-weekly subcutaneous injection feasible in a clinical setting.

The compound is structurally distinct from GLP-1 receptor agonists such as semaglutide or tirzepatide. It acts primarily at amylin receptors (CALCR/RAMP complexes) rather than the GLP-1 receptor. Novo Nordisk's rationale for combining cagrilintide with semaglutide is that the two mechanisms are complementary: GLP-1 receptor activation reduces appetite through gut-brain signaling, while amylin receptor activation adds a separate satiety pathway and further slows gastric emptying. Preclinical rodent studies published in the early 2020s showed additive weight loss when both pathways were engaged simultaneously.

Cagrilintide as a standalone compound reached Phase 2 in a dose-finding trial (NCT03804827) published in The Lancet in 2021. That 26-week trial enrolled 706 adults with overweight or obesity and tested five doses against placebo. Participants receiving the 4.5 mg weekly dose achieved a mean body-weight reduction of 10.8% versus 3.0% for placebo. That result established the dose carried forward into combination studies.

Phase 3 Trial Readouts: The REDEFINE Program

The pivotal program for the fixed-dose combination of cagrilintide 2.4 mg plus semaglutide 2.4 mg, studied internally as CagriSema, is called REDEFINE. REDEFINE 1 (NCT05567796) is the flagship obesity trial. It enrolled approximately 3,400 adults with obesity or overweight plus at least one weight-related comorbidity, excluding type 2 diabetes. The 68-week trial read out in late 2024.

Top-line results from REDEFINE 1, announced by Novo Nordisk in December 2024, showed a mean body-weight reduction of approximately 22.7% in the CagriSema arm versus roughly 7.2% for placebo. The result was statistically significant. Novo Nordisk noted the outcome came in below their internal projection of around 25%, which the company attributed partly to a higher-than-expected proportion of participants not reaching the full maintenance dose by week 68. The trial is registered and ongoing for secondary endpoint analysis.

REDEFINE 2 (NCT05394519) targets adults with type 2 diabetes and obesity. Interim data presented at the European Association for the Study of Diabetes annual meeting in September 2023 showed meaningful HbA1c reductions alongside weight loss at 32 weeks, though full 68-week data were still pending as of early 2025. REDEFINE 3 and REDEFINE 4 are examining cardiovascular outcomes and other populations; both remain in active enrollment as of mid-2025.

A separate Phase 2 combination trial (NCT04982575) published in Nature Medicine in 2023 enrolled 92 adults with overweight or obesity and compared CagriSema head-to-head against cagrilintide alone and semaglutide alone over 32 weeks. The combination arm produced roughly 15.6% body-weight reduction, outperforming either monotherapy arm, which provided early human evidence supporting the mechanistic rationale.

Regulatory Status: Where Does Cagrilintide Stand Today?

As of mid-2025, cagrilintide has no regulatory approval anywhere in the world, either as a standalone compound or as part of the CagriSema combination. It is an investigational compound. Any version of cagrilintide sold outside a licensed clinical trial is not an approved drug and has not been evaluated for safety or efficacy by the FDA or equivalent agencies.

Novo Nordisk has not yet filed a New Drug Application or Biologics License Application with the FDA for CagriSema. Following the REDEFINE 1 readout in December 2024, the company indicated it was reviewing the full dataset before deciding on a regulatory submission timeline. Analysts widely expect a filing in 2025 or 2026, but no official submission date has been announced.

It is worth distinguishing the regulatory situation clearly. Semaglutide is FDA-approved as Ozempic (type 2 diabetes, Novo Nordisk, approved 2017) and Wegovy (chronic weight management, Novo Nordisk, approved 2021). Those approvals apply to those specific branded products at their specific approved formulations. A research-chemical version of semaglutide is not covered by those approvals. Cagrilintide has no equivalent approved product at all.

What Changed in 2024 and Early 2025

The biggest single development was the REDEFINE 1 top-line readout in December 2024. The 22.7% weight-reduction figure placed CagriSema above the efficacy seen with approved semaglutide 2.4 mg (Wegovy), which showed roughly 14.9% mean body-weight reduction in its own Phase 3 STEP 1 trial. The comparison is indirect and the trial designs differ, but the gap is large enough that analysts treated the result as meaningful even though it missed Novo Nordisk's internal target.

Earlier in 2024, Novo Nordisk reported additional safety data from ongoing REDEFINE substudies. The most commonly reported adverse events in the CagriSema arm were gastrointestinal in nature, consistent with the profile seen in GLP-1 receptor agonist trials. No new safety signals were identified that altered the program's trajectory.

On the competitive front, 2024 also saw Eli Lilly advance retatrutide (a GLP-1, GIP, and glucagon triple agonist) through Phase 2 with weight-loss figures exceeding 24% at 48 weeks in a 338-participant trial published in The New England Journal of Medicine in June 2023. That result increased investor and analyst scrutiny of whether CagriSema's 22.7% outcome at 68 weeks would be differentiated enough in a crowded market. Novo Nordisk has not publicly revised its development plans in response.

In early 2025, Novo Nordisk confirmed REDEFINE 1 full data would be submitted for presentation at a major medical conference, with peer-reviewed publication expected to follow. The company also confirmed REDEFINE 2 remained on track for a full readout in 2025.

Evidence Tiers and Research Context

The evidence base for cagrilintide spans multiple tiers. The strongest human data come from the REDEFINE 1 Phase 3 randomized controlled trial with approximately 3,400 participants, which provides the highest level of clinical evidence currently available for this compound. The Phase 2 Nature Medicine combination study (92 participants, 32 weeks) offers supportive but smaller-scale human RCT data.

The standalone Phase 2 Lancet trial (706 participants, 26 weeks) provides human RCT evidence for cagrilintide monotherapy, though that formulation is not the one being advanced toward approval. Earlier mechanistic work relied on animal models and in-vitro receptor-binding studies; those findings informed the clinical program but carry less weight than the human trial data now available.

Readers should note that even large Phase 3 trials do not guarantee regulatory approval, and approval does not guarantee a compound will reach the market in any particular form or timeline. The REDEFINE 1 result is a significant data point, but the full peer-reviewed publication, FDA review, and any advisory committee process have not yet occurred as of mid-2025.