What it is
Cagrilintide is a synthetic 37-amino-acid analog of human amylin, the pancreatic islet hormone co-secreted with insulin. The molecule was engineered at Novo Nordisk (development codes AM833 / NN1213) to address the two limitations of native amylin: a plasma half-life of minutes and a strong propensity to form amyloid fibrils. Kruse 2021 (J Med Chem) describes the structure-activity work: N14E and V17R form a stabilizing salt bridge in the central alpha-helix; P25/P28/P29 proline substitutions (borrowed from rat amylin) abolish beta-sheet fibril formation; P37Y tunes calcitonin-receptor activity; and a C20 fatty diacid is conjugated to a lysine side chain to enable reversible albumin binding. The lipidation raises the plasma half-life to 159–195 hours, supporting once-weekly dosing. Cagrilintide retains the Cys2–Cys7 disulfide of native amylin and behaves as a dual amylin / calcitonin-receptor agonist (DACRA), engaging AMY1R, AMY2R, AMY3R, and CTR (Cao 2025, Nature Communications, cryo-EM). It is an investigational compound — not approved in any jurisdiction — currently in Novo Nordisk's Phase 3 REDEFINE program, most visibly as the amylin component of the fixed-combination CagriSema (co-administered with semaglutide 2.4 mg).
In plain English
Cagrilintide is a lab-made, longer-lasting copy of amylin — a hormone your pancreas releases with insulin after you eat. Amylin itself doesn't work as a drug: it breaks down in minutes, and it tends to clump into sticky fibers. Novo Nordisk engineered cagrilintide (lab codes AM833 and NN1213) to fix both problems. They swapped in six amino acids — three of them borrowed from rat amylin — that stop the clumping. They added a piece of fatty acid that sticks to a blood protein called albumin, which slows how fast the body clears it (its half-life goes from minutes to 6–8 days). That's what lets it be injected just once a week. The finished molecule still hits all the amylin receptors in the body, plus the related calcitonin receptor. It's not approved anywhere. It's currently in late-stage human trials, mostly paired with semaglutide in the combo called CagriSema.
How it works
- 01
Amylin receptor pharmacology (AMY1R, AMY2R, AMY3R)
Amylin receptors are heterodimers of the calcitonin receptor (CALCR / CTR) with a receptor activity-modifying protein (RAMP1, RAMP2, or RAMP3), yielding AMY1R, AMY2R, and AMY3R respectively. Cagrilintide is a DACRA: it binds all three AMY subtypes and the naked CTR. Cao 2025 (Nature Communications) reported cryo-EM structures of cagrilintide in complex with Gs-coupled active states of AMY1R, AMY2R, AMY3R, and CTR, showing an amylin-like binding mode with distinct conformational dynamics compared with the endogenous ligands calcitonin and amylin. This structural promiscuity is the rationale for a long duration of action that still recruits the full amylin-receptor repertoire.
In plain English
It activates all three amylin receptor types
Your cells have three different "amylin receivers" (called AMY1R, AMY2R, and AMY3R), plus a related "calcitonin receiver." Each one is built from two proteins locked together. Cagrilintide turns on all four. A 2025 study used cryo-electron microscopy (a way to photograph proteins at super-cold temperatures) to show exactly how cagrilintide fits into each one. Hitting all four means it can cover the same jobs as natural amylin — but for much longer.
- 02
AMY1R / AMY3R dependence for weight loss (Coester 2025)
Coester 2025 (eBioMedicine) used RAMP1 and RAMP3 knockout mice to dissect which subtypes carry the weight-loss signal. RAMP1/3 double knockouts blunted cagrilintide-induced weight loss and attenuated c-Fos activation in hindbrain feeding circuits (area postrema, NTS, lateral parabrachial nucleus). Bulk mRNA sequencing pointed at synaptic-function and receptor-trafficking gene sets as the downstream correlates. The study is the cleanest in-vivo identification of AMY1R and AMY3R as the functionally relevant cagrilintide targets for appetite suppression.
In plain English
Two specific brain receivers drive the weight loss
Researchers bred mice missing two specific receiver parts (called RAMP1 and RAMP3). Those mice barely lost any weight on cagrilintide, and the normal brain-stem "I'm full" response was mostly gone. That's strong evidence that two of the three amylin receivers — AMY1R and AMY3R — are the ones that actually do the appetite-suppressing work. This was only shown in mice, not people.
- 03
Central satiety and hindbrain activation
Cagrilintide acts on circumventricular organs whose amylin receptors are accessible from the periphery — principally the area postrema — and on second-order nuclei in the nucleus tractus solitarius and the lateral parabrachial nucleus (Lutz 2010 reviewed the broader amylin system; Coester 2025 localized the cagrilintide signal specifically). Amylin-receptor-expressing neurons co-localize with GLP-1R and GFRAL neurons, giving a partial anatomical rationale for why amylin and GLP-1 agonism are additive rather than redundant.
In plain English
It tells your brain stem you're full
Most parts of your brain are protected from drugs by a barrier. But a few small spots at the base of the brain stem don't have that barrier — they're designed to sense what's in the blood. Cagrilintide targets those spots to trigger the "I've eaten enough" signal. Those same brain cells are neighbors to the cells that respond to semaglutide-style GLP-1 drugs. That's part of why combining the two works better than either alone — they hit nearby but different systems.
- 04
Gastric emptying and postprandial glucose
Like native amylin and pramlintide, cagrilintide delays gastric emptying and suppresses postprandial glucagon. The gastric-emptying effect contributes to satiety and slows carbohydrate absorption; the glucagon suppression blunts hepatic glucose output. These effects are mechanistically additive to incretin action and are the pharmacological argument for CagriSema — amylin handles the postprandial glucagon / gastric-emptying axis while GLP-1 drives insulinotropic and appetite-center effects.
In plain English
It slows your stomach and keeps blood sugar steady
After you eat, cagrilintide slows down how fast food leaves your stomach. That keeps you feeling full and slows the sugar rush. It also turns down glucagon, a hormone that tells your liver to dump more sugar into the blood. Less stomach dumping and less liver sugar release means steadier blood sugar and longer fullness. This is different from what semaglutide does, which is part of why they stack well together.
- 05
Engineering that made once-weekly dosing possible
Kruse 2021 (J Med Chem) describes six amino acid substitutions plus C20 diacid lipidation. The prolines at 25/28/29 eliminate amyloid fibril formation (the failure mode of native amylin), the N14E/V17R salt bridge stabilizes the central helix, P37Y improves CTR affinity, and the C20 fatty acid enables reversible albumin binding that extends plasma half-life from minutes to 159–195 hours. This is the same albumin-anchoring lipidation strategy used in semaglutide, applied to a structurally unrelated peptide.
In plain English
Why it only needs to be injected once a week
Natural amylin disappears from your blood in a few minutes, and it tends to clump into sticky fibers (the same kind of clumping seen in some brain diseases). Cagrilintide changes six of the building-block amino acids to stop the clumping, then adds a fatty-acid tail that hooks onto a blood protein called albumin. Albumin is abundant, sticky, and hangs around for days — so the drug hitches a ride and slowly releases. The half-life goes from minutes to about 6–8 days. This is the same trick semaglutide uses.
- 06
What is NOT settled about the mechanism
The relative contribution of AMY1R versus AMY3R to cagrilintide's clinical effect is not yet quantified in humans — the Coester 2025 dissection is in mice. Whether the additive CagriSema effect reflects cooperative central circuitry, independent peripheral actions (gastric emptying + insulinotropy), or both is an open question. No human pharmacodynamic imaging studies distinguishing amylin versus GLP-1 CNS signatures have been published. Anti-drug antibody development with chronic dosing has been observed in amylin-class agents historically (pramlintide) and is a watch-item for long-term use, though REDEFINE 1 safety did not flag a clinically relevant immunogenicity problem in the headline release.
In plain English
What we still don't know about how it works
We've only mapped out which receivers matter in mice — not people. We also don't know exactly why the CagriSema combo adds up: is it because the two drugs team up in the same brain circuit, or because they each handle a separate part of digestion and appetite? Both? No one has run the brain imaging studies in humans to tell the difference. One thing to watch: older amylin drugs (like pramlintide) sometimes caused the body to build up antibodies against the drug over time. The REDEFINE 1 press release didn't flag this as a problem, but the full long-term data isn't out yet.