Petrelintide: weekly weight-loss injection (NN9213/ZP8396)
An experimental weekly injection for weight loss that works through the body's amylin system, a different pathway from Ozempic-type drugs; developed by Zealand Pharma and partnered with Roche in 2025. Experimental, not yet an approved drug.
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Petrelintide (also called ZP8396) is an investigational weekly injection for weight management that works through the body's amylin system — a pathway completely separate from the GLP-1 drugs (such as semaglutide and tirzepatide) that currently dominate the obesity market. It was developed by the Danish biotech Zealand Pharma and partnered with Roche in March 2025 in a deal valued at up to $5.3 billion, the largest single-asset pharma partnership of that year.
Unlike native amylin and earlier analogs such as pramlintide, petrelintide is heavily engineered — acylated and sequence-modified — to be chemically stable at neutral pH, which prevents the amyloid fibrillation that hampered earlier amylin drugs and allows co-formulation with other peptides. This stability, and a half-life of approximately 33.8 hours, is what makes once-weekly dosing possible. It is structurally distinct from cagrilintide, Zealand Pharma's earlier amylin analog being developed separately in combination with semaglutide under a Novo Nordisk partnership.
History
Petrelintide grew out of Zealand Pharma's amylin medicinal-chemistry program, which had previously produced cagrilintide. The key engineering challenge was reformulating an amylin analog to remain stable at neutral pH — avoiding the fibrillation that limited native amylin and required the acidic formulations of pramlintide — while extending half-life enough to support once-weekly dosing. The discovery and optimization chemistry is described in a 2025 Journal of Medicinal Chemistry publication (PMID 41217931).
Following Phase 1 single-ascending-dose (SAD) and Phase 1b multiple-ascending-dose (MAD) studies, Zealand reported topline data from the Phase 2b ZUPREME-1 trial (493 participants, 42 weeks) in March 2026, showing up to 10.7% mean weight loss versus 1.7% on placebo, with GI tolerability described as similar to placebo. The March 2025 Roche partnership reshaped the asset's development path: a Phase 3 monotherapy program is expected to begin in H2 2026, alongside a Phase 2 combination study pairing petrelintide with Roche's dual GLP-1/GIP agonist CT-388.
What it does
Petrelintide mimics amylin — a hormone the pancreas releases with insulin after meals — to tell the brain that enough food has been consumed. In clinical studies, this translated to meaningful weight loss over 42 weeks, with a side-effect profile that looked much closer to placebo than to GLP-1 receptor agonists. Withdrawal rates in the ZUPREME-1 trial were notably lower on the drug (8.4%) than on placebo (13.6%), suggesting that participants tolerated it well enough to stay on it.
In preclinical diet-induced obesity (DIO) rat studies, petrelintide produced preferential fat-mass loss while preserving relative lean mass compared with a liraglutide comparator — a potential differentiator from the GLP-1 class — though this has not yet been confirmed in published human body-composition data.
Evidence
- Human: Phase 2b ZUPREME-1 (493 adults with overweight or obesity, 42 weeks) reported topline results in March 2026: up to 10.7% mean weight loss at the 9 mg dose versus 1.7% on placebo, with all five dose arms meeting the primary endpoint versus placebo at week 28. Diarrhea and constipation rates were described as single-digit and similar to placebo; nausea was mostly mild and largely resolved after participants reached the maintenance dose; 98% of top-cohort participants reached that dose. Earlier Phase 1b MAD work in 48 adults over 16 weeks showed dose-dependent weight loss of 4.8–8.6%, and Phase 1 SAD studies in 56 adults showed an early weight signal of up to 4.2% at one week sustained to six weeks. A Phase 2b trial in adults with type 2 diabetes (ZUPREME-2) is ongoing with topline results expected H2 2026. The ZUPREME-1 full trial publication has not yet appeared in the available literature; the evidence base rests on topline reporting.
- Animal: In DIO rats, petrelintide produced preferential fat-mass loss with relative lean-mass preservation compared with liraglutide. The discovery and optimization chemistry, including preclinical receptor pharmacology, is described in the 2025 Journal of Medicinal Chemistry paper (PMID 41217931).
- In vitro / mechanistic: Amylin and calcitonin receptor biology is well-established through decades of pramlintide and amylin research (reviewed by Hay and colleagues and others; see Madsbad and colleagues, Expert Opinion on Investigational Drugs, 2025 for pipeline context). Petrelintide's specific receptor pharmacology and neutral-pH engineering are characterized in the J Med Chem 2025 development paper.
Known effects
- Weight loss — Phase 2b (topline): up to 10.7% at 42 weeks in adults with overweight or obesity
- GI tolerability advantage vs placebo comparison — Phase 2b: diarrhea/constipation similar to placebo; nausea mostly mild and resolving at maintenance dose
- Low trial discontinuation — Phase 2b: 8.4% withdrawal on drug vs 13.6% on placebo
- Lean-mass preservation (vs liraglutide) — Preclinical only (DIO rat model); not confirmed in human data
- Satiety / gastric emptying delay — Mechanistic (AMYR/CTR agonism); class-level evidence from pramlintide program
- Postprandial glucagon suppression — Mechanistic (class-level); not individually extracted from petrelintide-specific human data
- Leptin sensitivity restoration — Proposed preclinical mechanism; not established in human data
Safety signals
The safety profile reported in ZUPREME-1 (topline, 42 weeks) is notably favorable relative to GLP-1 receptor agonists: nausea was mostly mild and largely resolved after reaching the maintenance dose, and diarrhea and constipation rates were single-digit and similar to placebo. Injection-site reactions were described as mild and transient. The 98% maintenance-dose attainment rate in the top-dose cohort and the lower trial withdrawal rate on drug than on placebo (8.4% vs 13.6%) reflect this tolerability profile.
Important gaps remain. Long-term safety beyond 42 weeks has not been characterized; Phase 3 will be the first dataset for multi-year exposure. No cardiovascular outcomes trial has been conducted, so MACE effects are unestablished. Chronic calcitonin receptor agonism raises a theoretical question about bone metabolism that has not been studied in humans. No specific petrelintide pancreatitis signal was reported in available sources, but this has not been formally excluded in a long-term study.
Class-level considerations from pramlintide and the broader amylin literature include a potential for hypoglycemia risk when combined with insulin or insulin secretagogues, and slowed gastric emptying that can alter the absorption rate and peak concentration of orally co-administered medications with narrow therapeutic windows. These are class-level and precautionary inferences, not established petrelintide-specific label findings, given that petrelintide remains investigational.
Regulatory status
- US (FDA): Not approved. Investigational drug; legally administered only to participants in Zealand- or Roche-sponsored clinical trials. Not available through compounding pharmacies, telehealth platforms, or research-chemical suppliers.
- International: Not approved by any regulatory authority. No commercial access exists; trial sites operate under national investigational frameworks.
- WADA: Not individually listed by name on the current Prohibited List. The S0 category (substances not approved by any government regulatory health authority) and S2 (peptide hormones, growth factors, related substances and mimetics) categories are relevant. Athletes subject to WADA or equivalent anti-doping codes should treat petrelintide as prohibited.
FDA approval is not anticipated before approximately 2029–2030, pending Phase 3 completion and regulatory review.
Mechanism
Petrelintide is a 36-amino-acid acylated human amylin analog engineered for chemical stability at neutral pH. The acylation and sequence modifications are not represented in the stored raw sequence. Native amylin is a 37-residue peptide co-secreted by pancreatic beta cells with insulin in response to meals; its biological role is to reinforce satiety, slow gastric emptying, and suppress postprandial glucagon. Petrelintide reproduces this biology with extended duration by acting as a balanced potent agonist at both the amylin receptor (AMYR — a heterodimer of the calcitonin receptor, CTR, and receptor activity-modifying proteins, particularly RAMP1–3) and at the calcitonin receptor (CTR) directly.
Central signaling occurs primarily in hindbrain structures — the area postrema and nucleus tractus solitarius — producing satiety signals, delaying gastric emptying, suppressing postprandial glucagon, and in preclinical models restoring leptin sensitivity and increasing energy expenditure. Because these pathways are distinct from the GLP-1 receptor system, the tolerability profile differs substantially from GLP-1 receptor agonists.
The neutral-pH engineering solves the fibrillation problem that limited native amylin and pramlintide: early amylin analogs required acidic formulations incompatible with co-formulation. Petrelintide's neutral-pH stability is central to the Roche strategy, enabling potential fixed-dose co-formulation with CT-388. The half-life of approximately 33.8 hours supports once-weekly dosing at steady state. The receptor pharmacology and formulation chemistry are described in the J Med Chem 2025 development paper (PMID 41217931).
Open questions
- Full Phase 2b publication: ZUPREME-1 topline results were reported in March 2026; the full peer-reviewed trial publication with detailed safety tables, body-composition subgroup analyses, and dose-response characterization has not yet appeared in the available literature.
- Human body-composition data: Preclinical DIO rat data showed preferential fat-mass loss with relative lean-mass preservation versus liraglutide, but whether this advantage translates to humans has not been confirmed in published data.
- Cardiovascular outcomes: No cardiovascular outcomes trial has been conducted. Whether petrelintide reduces MACE events as demonstrated with approved GLP-1 receptor agonists is not established.
- Long-term safety: Phase 3 will be the first characterization of multi-year exposure, including potential signals related to chronic CTR agonism on bone metabolism and pancreatic function.
- Type 2 diabetes: ZUPREME-2 is ongoing; dedicated T2DM efficacy and safety data are not yet available.
- Combination with CT-388: The Phase 2 combination study is expected to begin in H1 2026 and will be the first test of whether petrelintide plus a GLP-1/GIP incretin can match or exceed CagriSema-class outcomes with improved tolerability.
- Real-world adherence: Trial adherence was notably favorable, but performance outside controlled trial conditions has not been characterized.
Related peptides
- Cagrilintide — Zealand Pharma's earlier long-acting amylin analog, licensed to Novo Nordisk; being developed primarily in the CagriSema combination with semaglutide rather than as a monotherapy
- Pramlintide — the first approved amylin analog (Symlin, FDA 2005), used as an adjunct to insulin in T1D and T2D; short-acting (multiple daily injections), acidic formulation, the clinical predecessor to the long-acting amylin class
- Semaglutide — GLP-1 receptor agonist (Ozempic/Wegovy); the leading comparator and prospective combination partner context via CT-388
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Does petrelintide mainly suppress appetite by signaling through a specific brain region that is directly accessible from the bloodstream?
If true, it would explain variation in how well the drug works across individuals and could help doctors predict who will benefit most, while also guiding the design of drug combinations that target complementary appetite-suppression pathways.
When petrelintide and a GLP-1 drug are combined, do they produce more hunger suppression together than you would predict by simply adding their separate effects?
If true, it would scientifically justify the billions invested in developing this combination and could mean that patients who plateau on GLP-1 drugs alone could achieve substantially greater weight loss by adding petrelintide, addressing one of obesity medicine's most pressing clinical unmet needs.
Is the proline substitution in petrelintide's core sequence the key change that stops the peptide from forming the toxic protein clumps seen with older amylin drugs?
If true, it would mean future amylin-based drugs could be stabilized with minimal sequence changes, making them easier to manufacture and less likely to trigger immune reactions than drugs requiring extensive modification throughout their structure.
Does petrelintide's N-terminal loop structure prevent it from activating the receptor responsible for blood vessel dilation and flushing side effects?
If true, it would provide structural reassurance that petrelintide can be safely dosed weekly for years without the vascular side effects that derailed some earlier amylin analogs, strengthening the case for its long-term use in obesity treatment.
Could petrelintide also slow bone thinning in older women, addressing two major postmenopausal health problems with one weekly injection?
If true, it would distinguish petrelintide from GLP-1 drugs, which may actually worsen bone density through rapid weight loss, and could offer postmenopausal women a weight-loss drug that simultaneously guards against fractures, a combination not currently available.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.8308536410331726 | boltz-2 |
| ranking score | 0.8210369944572449 | boltz-2 |
▸3-letter notation
▸recipeboltz-2 2.2.1
| parameter | value |
|---|---|
| model | boltz-2 2.2.1 |
| weights | — |
| hardware | vast_v100_32gb |
| mlx version | — |
| python | — |
| random seed | 1 |
| msa strategy | colabfold_local |
| runtime | — |
| predicted by | — |
| predicted at | 2026-05-22 |
▸citationbibtex
@peptide{pep10905,
sequence = {KCNTATCATQRLANFLVHSSNNFGPILSSTNVGSNTYX},
target = {calcr},
author = {peptidemodel},
year = {2026},
status = {computed}
}