Introduction and Background
Cagrilintide (previously designated AM833 and NN9838) is a long-acting acylated amylin analogue developed by Novo Nordisk for the investigation of energy homeostasis and body weight regulation. Amylin, a 37-amino-acid peptide hormone co-secreted with insulin from pancreatic beta cells in response to nutrient ingestion, has long been recognised as a key neuroendocrine mediator of satiety and postprandial glucose metabolism (Lutz, 2010). Despite its well-characterised physiological role, the therapeutic exploitation of amylin signalling has historically been constrained by the peptide's extremely short circulating half-life of approximately 13 minutes, necessitating frequent dosing with the synthetic analogue pramlintide (Hay et al., 2015).
Cagrilintide was engineered to overcome these pharmacokinetic limitations through strategic acylation with a C18 fatty diacid moiety, enabling high-affinity binding to albumin and thereby extending the elimination half-life to approximately 160 hours. This modification permits once-weekly subcutaneous administration whilst preserving agonist activity at the amylin receptor complex (Enebo et al., 2021). The development of cagrilintide represents a renewed effort to harness the anorexigenic properties of amylin receptor signalling, building upon decades of preclinical and clinical research into the neurobiological regulation of appetite and energy expenditure (Williams, Nawaz and Evans, 2020).
Mechanism of Action
The pharmacological activity of cagrilintide is mediated through agonism at the amylin receptor, a heterodimeric complex formed by the calcitonin receptor (CTR) in association with receptor activity-modifying proteins (RAMPs), principally RAMP1, RAMP2, and RAMP3. These receptor subtypes — designated AMY1, AMY2, and AMY3 respectively — are expressed in several brain regions implicated in appetite regulation, most notably the area postrema and the nucleus of the solitary tract within the dorsal hindbrain (Lutz, 2010). The area postrema, a circumventricular organ situated outside the blood-brain barrier, serves as a critical integration centre for peripheral satiety signals, and its ablation in rodent models abolishes the anorexigenic effects of amylin administration.
Upon binding to amylin receptors in the area postrema, cagrilintide activates intracellular signalling cascades involving cyclic adenosine monophosphate (cAMP) and extracellular signal-regulated kinase (ERK) pathways, which in turn modulate neuronal firing patterns in ascending projections to the hypothalamus and the mesolimbic reward circuitry (Hay et al., 2015). These central nervous system effects culminate in reduced meal size, decreased eating rate, and enhanced post-meal satiation. Importantly, amylin receptor agonism appears to engage distinct neuronal populations from those activated by glucagon-like peptide-1 (GLP-1) receptor agonists, suggesting mechanistic complementarity between these two signalling axes (D'Ascanio, Mullally and Frishman, 2024).
A further well-characterised peripheral action of amylin receptor agonism is the deceleration of gastric emptying. Native amylin slows the rate of nutrient delivery from the stomach to the duodenum via vagal efferent signalling, thereby attenuating postprandial glycaemic excursions and contributing to prolonged satiety (Young, 2005). Cagrilintide retains this gastroparetic activity, and the resultant modulation of nutrient transit time is considered an important contributor to its overall effects on energy intake. Additionally, preclinical evidence has indicated that amylin agonism may restore leptin sensitivity in states of diet-induced leptin resistance, a phenomenon that could amplify the weight-reducing effects of amylin signalling through synergistic adiposity feedback (Roth et al., 2008).
Clinical Research
The clinical development of cagrilintide has progressed through several key trials that have established its pharmacological profile and efficacy as a research compound. A pivotal phase 2, randomised, double-blind, placebo-controlled and active-controlled trial evaluated multiple doses of cagrilintide (0.3 mg, 0.6 mg, 1.2 mg, 2.4 mg, and 4.5 mg once weekly) against placebo and liraglutide 3.0 mg daily in 706 adults with overweight or obesity without diabetes over a 26-week treatment period (Lau et al., 2021).
Results from this dose-finding study demonstrated dose-dependent reductions in body weight, with the highest dose of cagrilintide (4.5 mg) achieving a mean weight reduction of 10.8% from baseline at week 26, compared with 9.0% for liraglutide 3.0 mg and 3.0% for placebo. The 2.4 mg dose produced a mean reduction of 7.8%. The weight loss trajectory had not plateaued by the end of the 26-week treatment period, suggesting that longer treatment durations may yield additional reductions (Lau et al., 2021). The safety profile was broadly consistent with that of other injectable peptide therapies, with gastrointestinal adverse events — principally nausea, diarrhoea, and constipation — representing the most common treatment-emergent findings, typically mild to moderate in severity and tending to diminish over time.
CagriSema Combination Research
Perhaps the most significant area of ongoing investigation involves the co-administration of cagrilintide with semaglutide 2.4 mg, a combination designated CagriSema. The scientific rationale for this approach rests on the complementary mechanisms of amylin and GLP-1 receptor agonism: whereas GLP-1 receptor agonists primarily engage hypothalamic and brainstem GLP-1 receptors to reduce appetite and enhance insulin secretion, amylin receptor agonists act predominantly through area postrema signalling and distinct hindbrain circuits (D'Ascanio, Mullally and Frishman, 2024). The hypothesis that these two pathways could produce additive or synergistic effects on energy balance was first examined in a phase 1b trial.
The phase 1b study evaluated the safety, tolerability, pharmacokinetics, and pharmacodynamics of concomitant cagrilintide and semaglutide 2.4 mg in 92 adults with overweight or obesity over 20 weeks (Enebo et al., 2021). The combination was well tolerated, with no pharmacokinetic interactions between the two agents. Notably, the co-administration group demonstrated a mean weight reduction of 17.1% at week 20, significantly exceeding that observed with semaglutide alone (9.8%) or cagrilintide alone (8.1%). These preliminary findings provided a strong signal of mechanistic synergy and stimulated further investigation.
A subsequent phase 2 trial assessed CagriSema in 92 participants with type 2 diabetes and overweight or obesity over 32 weeks (Frias et al., 2023). In this population, CagriSema (cagrilintide 2.4 mg plus semaglutide 2.4 mg) produced a mean body weight reduction of 15.6% from baseline, compared with 5.1% for semaglutide 2.4 mg alone. The combination also demonstrated superior glycated haemoglobin (HbA1c) reductions, with a mean decrease of 2.2 percentage points versus 1.8 percentage points for semaglutide monotherapy. These results suggest that the addition of cagrilintide to GLP-1 receptor agonist therapy may confer substantial incremental benefit in populations characterised by both adiposity and dysglycaemia.
Pharmacokinetics
The pharmacokinetic profile of cagrilintide has been characterised through multiple early-phase clinical studies. Following subcutaneous injection, cagrilintide exhibits slow absorption with a time to maximum plasma concentration (tmax) of approximately 24 to 72 hours. The C18 fatty diacid acylation moiety confers strong, reversible binding to serum albumin, which serves as a circulating depot and shields the peptide from enzymatic degradation. This albumin-binding strategy — analogous to that employed in semaglutide and liraglutide — yields an elimination half-life of approximately 160 hours (roughly seven days), supporting once-weekly dosing (Enebo et al., 2021).
Steady-state plasma concentrations are typically achieved after four to five weekly doses, consistent with the predicted accumulation kinetics for a compound with a seven-day half-life. Importantly, co-administration with semaglutide 2.4 mg does not appear to alter the pharmacokinetic parameters of either agent, indicating that the two peptides can be administered concomitantly without dose adjustment (Enebo et al., 2021). The primary route of elimination is through proteolytic degradation of the peptide backbone, with subsequent renal excretion of metabolic fragments. No intact cagrilintide has been detected in urine, confirming that renal clearance of the parent compound is negligible.
Current Research Directions
The clinical development programme for cagrilintide and CagriSema continues to expand, with several large-scale phase 3 trials underway or recently completed. The REDEFINE trial programme represents the pivotal phase 3 investigation of CagriSema, evaluating the combination in diverse populations including individuals with and without type 2 diabetes across multiple geographic regions. These trials are designed to assess long-term efficacy and safety over treatment periods of 68 weeks and beyond, addressing key questions regarding durability of effect and the clinical significance of the incremental weight reduction observed over semaglutide monotherapy.
Beyond weight management, the mechanistic profile of cagrilintide has prompted investigation into its potential effects on metabolic parameters associated with cardiometabolic risk. The modulation of gastric emptying, postprandial glycaemia, and central appetite circuits positions amylin agonism as a pathway of interest for research into conditions characterised by metabolic dysregulation. The broader landscape of obesity pharmacotherapy research has increasingly emphasised combination approaches targeting multiple anorexigenic pathways, and the CagriSema programme exemplifies this strategy (Aronne et al., 2024).
Ongoing preclinical research continues to elucidate the neurobiological substrates of amylin receptor agonism, with particular attention to the identification of specific neuronal populations in the area postrema and nucleus of the solitary tract that mediate the anorexigenic response. The interaction between amylin and leptin signalling pathways remains an active area of investigation, given early evidence suggesting that amylin agonism may potentiate leptin-mediated signalling in hypothalamic circuits (Roth et al., 2008). If confirmed in further studies, this mechanism could have significant implications for understanding the pathophysiology of weight regain following initial weight loss.
The development of cagrilintide represents an important chapter in the ongoing effort to translate neuroendocrine physiology into pharmacological tools for metabolic research. As the field continues to evolve, long-acting amylin analogues such as cagrilintide offer a distinct mechanistic avenue that complements existing GLP-1-based approaches, contributing to an increasingly nuanced understanding of the multi-factorial regulation of energy balance and body weight (Hay et al., 2015).