Overview
Cagrilintide (code designations AM833, NN0174-0833; slug cagrilintide) is a rationally engineered, lipidated peptide agonist of amylin receptors, developed as a long-acting analogue of human islet amyloid polypeptide (IAPP), better known as amylin. The molecule belongs to the class of so-called dual amylin and calcitonin receptor agonists (a DACRA-like profile) and is studied in the research literature primarily as a tool for probing the neuroendocrine regulation of satiation and energy homeostasis. This material is strictly a research-use-only (RUO) reference and contains no guidance for human use.
Discovery and background
Amylin was identified in the mid-1980s as the principal protein component of amyloid deposits in pancreatic islets in type 2 diabetes and in insulinomas; the sequence of the 37-amino-acid peptide was determined from amyloid fibrils, and the same neuropeptide-like protein was shown to be present in normal β-cells as well [1]. Native amylin is co-secreted with insulin by β-cells in response to meals and acts as a satiation factor, a slower of gastric emptying, and a suppressor of postprandial glucagon secretion [2]. Practical use of amylin itself as a tool was limited by two physicochemical liabilities: a marked propensity to aggregate into amyloid fibrils and an extremely short half-life. The first clinically usable analogue, pramlintide, solved the aggregation problem with three proline substitutions but retained a short duration of action. Cagrilintide was the next step: a Novo Nordisk team engineered it to combine aggregation resistance with albumin-binding lipidation for a radical extension of duration [3].
Structure and physicochemistry
Cagrilintide is a 37-residue peptide analogue with a C-terminal amide and an intrachain Cys2-Cys7 disulfide bridge that closes the small N-terminal loop characteristic of the calcitonin/amylin family [3][4]. Relative to human amylin, the backbone carries a set of deliberate substitutions that lower amyloidogenicity (notably proline substitutions in the C-terminal region, analogous to pramlintide) and improve solubility and charge profile. The key distinction is the attachment of a lipid "anchor": a C20 dicarboxylic (eicosanedioic) fatty acid conjugated through a γ-glutamate linker to the N-terminal region of the molecule. This lipid moiety confers reversible binding to serum albumin, which slows renal filtration and proteolytic clearance and is the molecular basis of the weekly activity profile [3]. The empirical formula is C194H312N54O59S2, average molecular mass approximately 4409 g/mol; CAS (Chemical Abstracts Service number) number 1415456-99-3. In its research form the substance is usually supplied as a lyophilized acetate.
Molecular mechanism of action
Amylin receptors (AMY) are not distinct gene products: they are formed as heterodimers of the calcitonin receptor (CTR, a class B GPCR) with receptor activity-modifying proteins (RAMP1/2/3). CTR+RAMP1 yields AMY1, CTR+RAMP2 yields AMY2, and CTR+RAMP3 yields AMY3; it is the presence of a RAMP that remodels the CTR binding pocket to confer high affinity for amylin [2][4]. Cagrilintide, like native amylin, binds these complexes; its long lipidated N-terminal segment and disulfide-stabilized loop engage the extracellular domain and transmembrane bundle, while the C-terminal region inserts into the orthosteric pocket, triggering conformational activation of the receptor [4]. Cryo-electron microscopy studies of calcitonin-family receptor complexes bound to the Gs protein have shown how peptide agonists of this family insert into the transmembrane core and rearrange the extracellular loops, providing the structural basis of activation [5]. The role of the specific RAMP is not confined to affinity: work on AMY3 has shown that RAMP3 alters the very propagation of signal through the extracellular loops of CTR, i.e. it modulates efficacy and signalling bias, not only binding [6].
Signaling and downstream effects
The activated AMY complex, via the Gs protein, stimulates adenylyl cyclase, raises intracellular cAMP and activates protein kinase A; engagement of ERK1/2 pathways and intracellular calcium has also been described, depending on RAMP type and cellular context [2][4]. Systemically, the central target of amylin and its analogues is the area postrema, a circumventricular hindbrain region outside the blood-brain barrier, whose neurons express AMY receptor components and are directly activated by amylinemia [7]. The signal from the area postrema is relayed to the nucleus tractus solitarii, the lateral parabrachial nucleus, and onward to hypothalamic appetite-control centres, generating a sensation of satiation. In addition to central effects, amylin signalling slows gastric emptying and suppresses postprandial glucagon secretion by α-cells [2][7]. Cagrilintide reproduces this action profile but with prolonged exposure owing to albumin binding.
Preclinical research
In the paper describing the engineering of cagrilintide, the analogue was characterized by its affinity for AMY and CTR receptors, aggregation stability, albumin binding and pharmacokinetics in animal models; the key preclinical result was a prolonged in vivo half-life together with retained activity at amylin receptors, which justified the once-weekly regimen [3]. In rodent obesity models, amylin agonists consistently reduce food intake and body weight, and combination with GLP-1 receptor agonists shows additive or supra-additive effects on weight. This preclinical logic underpinned the pairing of cagrilintide with semaglutide [7]. Model systems used in this field include cell lines with recombinant co-expression of CTR and specific RAMPs (for affinity profiling and functional cAMP responses), as well as physiological studies of area postrema neuron activation [6][7].
Clinical research (as literature data)
The published clinical observations below are given strictly as facts of the scientific literature. In a phase 2 dose-finding trial, once-weekly cagrilintide was studied in people with overweight and obesity; dose-dependent reductions in body weight relative to placebo and to a reference comparator were reported, with gastrointestinal disorders being the most common adverse events [8]. A key development strategy was a fixed co-agonist combination of cagrilintide with semaglutide (experimentally known as CagriSema): a phase 1b trial evaluated the safety, tolerability, pharmacokinetics and pharmacodynamics of concomitant administration and showed no clinically meaningful pharmacokinetic interaction between the two peptides [9]. In a phase 2 trial in people with type 2 diabetes, the combination of cagrilintide 2.4 mg plus semaglutide 2.4 mg was compared with monotherapy with each component, assessing glycaemic control and body weight [10]. The programme has been extended by large phase 3 trials (the REDEFINE series), in which co-administration of cagrilintide and semaglutide was compared with semaglutide alone in adults with overweight or obesity, including those with coexisting type 2 diabetes [11].
Pharmacokinetics and metabolism
The defining pharmacokinetic feature of cagrilintide is a prolonged elimination half-life: approximately 7–8 days (about 159 hours by early estimates), a direct consequence of albumin-binding lipidation: the peptide-albumin complex serves as a circulating depot from which the active molecule is slowly released while being protected from rapid renal filtration [3][9]. As a peptide, cagrilintide undergoes proteolytic degradation to shorter fragments and amino acids via general catabolic pathways, without dependence on cytochrome P450 isoenzymes, so the risk of classic drug metabolic interactions is low; in the co-administration study with semaglutide, no mutual effect on exposure was observed [9]. This profile provides stable concentrations at a weekly dosing interval and slow attainment of steady state.
Related compounds and analogues
Cagrilintide belongs to a historical lineage of amylin mimetics. Its direct clinical predecessor is pramlintide, a short-acting analogue stabilized by proline substitutions. Related pharmacology is shown by the endogenous peptides of the calcitonin family (calcitonin itself, CGRP and adrenomedullin), which share the CTR/CLR + RAMP receptor machinery [2][4]. A distinct subclass is formed by dual amylin and calcitonin receptor agonists (DACRAs), engineered to activate both receptor systems simultaneously. Within a combination-therapy strategy, the key partner of cagrilintide is the GLP-1 receptor agonist semaglutide, with which it is studied as a fixed co-formulation [9][10][11]. Comparative profiling of these molecules typically relies on radioligand or functional assays on recombinant AMY1/2/3 receptors [6].
Analytical characterization (HPLC/MS, purity)
The identity and purity of research batches of cagrilintide are confirmed by a set of methods standard for modified peptides. High-resolution mass spectrometry (ESI-MS) verifies the molecular mass accounting for the lipid moiety, the C-terminal amide and the disulfide bridge (expected average mass around 4409 Da for C194H312N54O59S2). Analytical reversed-phase HPLC (RP-HPLC, typically C18 columns with an acetonitrile/water gradient containing 0.1% TFA and detection at 210–220 nm) assesses chromatographic purity and the presence of related impurities. Peptide mapping after enzymatic digestion and confirmation of correct Cys2-Cys7 disulfide closure (e.g. by comparing the masses of the reduced and oxidized forms) verify the correctness of the structure described during molecule development [3]. For lipidated peptides, residual water, acetate and aggregate content are additionally controlled, because the propensity of native amylin toward amyloid formation makes assessment of the oligomeric state especially important [3][4].
Handling, reconstitution chemistry and storage
As a lyophilized peptide, cagrilintide in its research format behaves like other albumin-binding analogues of peptide hormones. The lyophilizate is stored frozen and protected from light and moisture; hygroscopicity and the tendency of amylin-like scaffolds to aggregate make control of freeze-thaw cycles critical. Reconstitution in research is usually performed in sterile water or an appropriate buffer followed by gentle mixing without vigorous vortexing, because mechanical stress and phase interfaces promote aggregate nucleation in peptides of this class [4]. The C20 diacyl lipid moiety makes the molecule amphiphilic, so surface adsorption and foaming are also considered when working with solutions. The foregoing pertains exclusively to laboratory handling of the reagent and is not guidance for human use.
Research applications and model systems
In a research context, cagrilintide is used primarily as a long-acting pharmacological probe of amylin signalling. Typical model systems include: recombinant cell lines co-expressing CTR and individual RAMPs for functional profiling (cAMP reporters, signalling-bias assays) [6]; electrophysiological and immunohistochemical studies of area postrema and hindbrain circuit neuron activation [7]; and in vivo energy-homeostasis models to study food-intake regulation and interaction with other incretin axes [3][7]. Owing to its weekly exposure, cagrilintide is convenient for experiments with a stable chronic receptor load, and its co-formulation with semaglutide serves as a model system for studying multi-receptor pharmacology of metabolic regulation [9][10][11]. All of the listed applications belong to basic and preclinical research.