History

Cagrilintide (AM833 / NN9838) was developed by Novo Nordisk and described in the medicinal-chemistry literature by Kruse and colleagues in the Journal of Medicinal Chemistry in 2021. The same year brought a phase 1b combination trial and a 706-person phase 2 monotherapy trial, both in The Lancet. A phase 2 CagriSema trial in type 2 diabetes followed in 2023. The pivotal phase 3 REDEFINE 1 topline arrived in December 2024 at 22.7% weight loss, below company expectations, and the stock fell roughly 20%. REDEFINE 1 and 2 were published in NEJM in June 2025, and Novo filed a CagriSema NDA in December 2025.

Cagrilintide is one of the more genuinely promising compounds you will find circulating on gray-market peptide menus, and also one where the gap between the headline science and what a person can actually buy is widest. It is an investigational, once-weekly synthetic analog of amylin, a hormone your pancreas releases alongside insulin to signal fullness. Novo Nordisk has run it through large, well-designed randomized trials published in top journals. But almost all of that strong evidence is for cagrilintide combined with semaglutide in a fixed-dose product called CagriSema, not for cagrilintide on its own. The standalone drug, which is what is being sold informally, has only preliminary human support and no approved product anywhere in the world.

What it is

Cagrilintide is a 37-amino-acid lipidated peptide built on the human amylin (islet amyloid polypeptide) backbone. Native amylin is short-lived and prone to clumping into amyloid fibrils, so the molecule was re-engineered to fix both problems. According to the development paper by Kruse and colleagues, substitutions at positions 14 and 17 form a salt bridge that stabilizes the peptide’s central helix, while three proline substitutions (positions 25, 28 and 29) reduce its tendency to aggregate. A fatty-acid chain attached through a linker lets the peptide bind reversibly to albumin in the blood, the same half-life-extension trick used in semaglutide and insulin degludec. The result is a half-life of roughly 159 to 195 hours, long enough for once-weekly subcutaneous injection.

Mechanistically, cagrilintide is a non-selective agonist at the amylin receptors and the calcitonin receptor, a family of related signaling proteins. It acts on appetite-regulating regions of the brainstem and hypothalamus to reduce hunger, increase satiety and slow gastric emptying. Because that pathway is distinct from how GLP-1 drugs like semaglutide work, the two are thought to be complementary, which is the entire rationale for pairing them in CagriSema.

The claims

In legitimate clinical development, cagrilintide is being studied for chronic weight management in people with overweight or obesity, and as part of CagriSema for combined weight loss and blood-sugar control in type 2 diabetes.

On gray-market “research-use-only” peptide sites, it is marketed as a weight-loss and appetite-suppression peptide, frequently bundled with semaglutide or tirzepatide and accompanied by suggested dosing and “stacking” advice. None of those products are FDA-approved, pharmacy-dispensed or quality-assured, and none of the vendor guidance reflects regulatory review. Marketing pages are not evidence, and this profile does not cover dosing.

The evidence

The human dataset is unusually large for a compound in this category, but it has to be read carefully.

The first human combination data came from a phase 1b trial (Enebo and colleagues, The Lancet 2021), a placebo-controlled multiple-ascending-dose study in 96 randomized participants at a single US center. It established that cagrilintide and semaglutide could be co-escalated with no meaningful drug-drug interaction, confirmed the long half-life, and showed greater weight loss with the combination than placebo. Importantly, every active arm in that study also received semaglutide, so the weight-loss figures are combination results, not cagrilintide alone.

The main standalone human dataset is a phase 2 dose-finding trial (Lau and colleagues, The Lancet 2021): 706 adults with obesity but without diabetes, randomized across 57 sites in 10 countries, with both a placebo arm and an active liraglutide comparator, over 26 weeks. Cagrilintide monotherapy produced 6.0% to 10.8% weight loss across doses versus 3.0% for placebo, and the top 4.5 mg dose (10.8%) modestly beat liraglutide 3.0 mg (9.0%). That is meaningful, but it is a single dose-finding study, not a pivotal trial.

A phase 2 CagriSema trial in type 2 diabetes (Frias and colleagues, The Lancet 2023) ran 32 weeks across 17 US sites and showed the combination outperformed either drug alone on both weight and glucose.

The pivotal evidence is REDEFINE 1 (NEJM 2025; ClinicalTrials.gov NCT04657458), a phase 3 trial of 3,417 adults with obesity and no diabetes, randomized to CagriSema, cagrilintide alone, semaglutide alone or placebo over 68 weeks. Weight reductions (trial-product estimand) were 22.7% for CagriSema, 16.1% for semaglutide, 11.8% for cagrilintide alone and 2.3% for placebo; more than 60% of CagriSema patients lost at least 20% of body weight. Two cautions matter. First, Novo had guided toward roughly 25%, so the 22.7% result was widely framed as disappointing and the stock dropped about 20% on the December 2024 topline. Second, only around 57% of CagriSema patients reached the maximum target dose, which complicates interpretation of the headline numbers. REDEFINE 2 (NEJM 2025), in 1,206 adults with type 2 diabetes, showed 15.7% weight loss with CagriSema versus about 3.1% placebo over 68 weeks.

The cagrilintide-monotherapy result (11.8% versus 2.3%) was presented as a REDEFINE 1 sub-analysis at the EASD meeting in September 2025 and billed as the first phase 3 data for a long-acting amylin used alone. On that basis Novo announced a dedicated standalone program, RENEW, beginning in late 2025. No standalone-monotherapy efficacy trial has reported results yet.

Animal work supports the mechanism: a 2025 eBioMedicine study (Carvas and colleagues) showed in mice that cagrilintide’s weight-lowering effect depends on specific amylin receptors, with a blunted response in knockout animals. A 2025 cryo-EM study in Nature Communications (Cao and colleagues) mapped how the drug binds the calcitonin and amylin receptors.

What is missing is significant: no completed standalone-efficacy trial, no long-term outcome data (cardiovascular events, mortality, durability beyond about 68 weeks), and essentially no large independent confirmation, since the pivotal and most mechanistic studies are Novo Nordisk-funded or Novo-authored.

Safety and side effects

The well-documented adverse effects are gastrointestinal. In REDEFINE 1, GI events occurred in 79.6% of CagriSema patients versus 39.9% on placebo, including nausea (55%), constipation (30.7%) and vomiting (26.1%), mostly mild-to-moderate and transient. Discontinuation due to adverse events was about 6% with CagriSema versus 3.7% with placebo. In the phase 2 monotherapy trial, GI adverse events ran 41% to 63% across cagrilintide doses versus 32% for placebo.

Several warnings that circulate online are class extrapolations rather than cagrilintide findings. Gallbladder problems are a known association of rapid weight loss generally, but no cagrilintide-specific incidence has been published. Pancreatitis is a theoretical class concern, not an established signal. Thyroid C-cell tumor concerns come from GLP-1 drug labeling based on rodent studies; because cagrilintide also engages the calcitonin receptor, the question is reasonable to raise, but there is no approved cagrilintide label and no human data establishing it. Most fundamentally, long-term human safety is genuinely unknown, since the longest trials run only about 68 weeks.

The honest summary: short-to-medium-term tolerability is dominated by manageable GI effects, serious-event rates in trials were low, and longer-term safety remains uncharacterized.

Legal and regulatory status

Cagrilintide is not approved anywhere as of June 2026. Novo Nordisk submitted a New Drug Application for CagriSema (the combination, for weight management) to the FDA on December 18, 2025, with review expected during 2026. Cagrilintide as a standalone drug has not been filed; its dedicated phase 3 program only recently began. The only previously approved amylin-class drug is pramlintide (Symlin), approved by the FDA in March 2005 and dosed at major meals as multiple daily injections; cagrilintide is positioned as the once-weekly next-generation successor.

For athletes, cagrilintide is not listed by name on the WADA Prohibited List, but as an investigational drug not approved by any government health authority for human use, it falls under Section S0 (non-approved substances), which is prohibited at all times, both in and out of competition. Treat it as banned in sport and verify through Global DRO.

The gray-market products sold as cagrilintide are unapproved, unregulated, and of unverified identity and purity. There is no legal pathway for human use of these products in the US.

Bottom line

Cagrilintide sits in a genuinely unusual spot. The combination it anchors, CagriSema, has some of the strongest randomized human data of any compound discussed on peptide forums, with multiple large phase 3 trials and NEJM publication. But that evidence is for the combination, not the standalone drug, and even the pivotal trial undershot the company’s own expectations and revealed a dose-titration problem. The cagrilintide-alone story rests on one dose-finding phase 2 trial and a single phase 3 sub-analysis, with the dedicated standalone program still in progress and no long-term safety data in hand. It is a serious drug with a serious development program, which is exactly why it deserves a finished, approved product and a real label rather than an unregulated vial. For now the grade is preliminary human: promising, well-studied as a combination, but unfinished as the thing being sold.

Cagrilintide: A Long-Acting Amylin Analog with Strong Combination Data and Thin Standalone Evidence