Ribupatide: experimental weight-loss injection (KAI-9531/HRS9531)
An injectable peptide that activates two gut hormones at once to reduce appetite and body weight; 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
Ribupatide (originator code HRS9531; Kailera code KAI-9531) is an investigational once-weekly injectable that activates two gut-hormone receptors at once — GLP-1R and GIPR — to reduce appetite and body weight. It was discovered and developed by Jiangsu Hengrui Pharmaceuticals in China, with ex-Greater China rights licensed in 2024 to Kailera Therapeutics, a US-based obesity-focused company. Ribupatide shares its receptor profile with tirzepatide (/card/pep-00018) but is a distinct peptide molecule engineered from a different scaffold; Kailera has described it preclinically as more potent and longer-acting than tirzepatide, though no head-to-head human trial has been completed to validate that claim.
The stored sequence on this card (GIRILLLKV, 9 aa) is a placeholder — the authentic ribupatide primary structure has not been disclosed in the published literature available at the time of authoring. The drug as administered is a long-acting modified peptide formulated for once-weekly subcutaneous dosing.
A Phase 3 trial in China (HRS9531-301) demonstrated substantial weight loss in adults with obesity or overweight, and Hengrui has submitted a marketing authorization application to China's National Medical Products Administration that has been accepted for review but not yet approved. The global KaiNETIC Phase 3 program began randomizing participants in January 2026, with readouts anticipated in 2028.
History
Hengrui developed HRS9531 as part of a strategic expansion into incretin biology, designing a balanced dual GLP-1/GIP agonist on a different peptide scaffold from tirzepatide with the stated goal of higher potency and longer duration of action. A Phase 1 single- and multiple-ascending-dose study in healthy volunteers established initial safety and pharmacokinetics (He and colleagues, Diabetes 2023, abstract 763-P). Phase 2 obesity data were presented at the American Diabetes Association annual meeting in 2024: 249 Chinese adults with BMI 28–40 kg/m² received 1.0, 3.0, 4.5, or 6.0 mg weekly versus placebo for 24 weeks, reaching a maximum placebo-adjusted mean weight loss of 16.7% at the 6 mg dose (Zhao and colleagues, Diabetes 2024, abstract 1861-LB).
A separate Phase 2 cohort at a higher 8 mg weekly dose was later reported to reach ~23% mean weight loss at 36 weeks with no observed plateau, a result that motivated dosing out to 10 mg weekly in subsequent programs. In 2024, Hengrui licensed ex-Greater China rights to Kailera Therapeutics; Kailera went public on Nasdaq in April 2026, raising ~$625 million, with ribupatide as the lead asset (Kailera Therapeutics Form 424B4, US Securities and Exchange Commission, April 2026). Hengrui's pivotal Phase 3 trial in China (HRS9531-301) reported topline results in July 2025 and additional data at ObesityWeek 2025; Hengrui subsequently submitted an NMPA marketing authorization application for chronic weight management, which has been accepted for review. A Phase 2 trial in Chinese adults with type 2 diabetes was reported the following year (Zhao and colleagues, Diabetes 2025, abstract 126-OR), and a Phase 1 study of the separate oral tablet formulation in healthy participants was reported in the same volume (Diabetes 2025, abstract 797-P).
What it does
Ribupatide activates two gut-hormone receptors simultaneously. The GLP-1 receptor component suppresses appetite, slows gastric emptying, and promotes a sense of fullness. The GIP receptor component complements those effects and is believed to improve adipose tissue handling of postprandial lipids and to offset some of the gastrointestinal discomfort associated with GLP-1-only agents. Together, dual activation produces appetite suppression, improved blood-sugar regulation, and weight loss sustained over months of weekly subcutaneous dosing (Zhao and colleagues, Diabetes 2024, abstract 1861-LB).
In Hengrui's completed China Phase 3 trial, ribupatide produced dose-dependent weight loss over 48 weeks. The global KaiNETIC program is testing doses up to 10 mg weekly across a broader population, with an active-comparator arm against semaglutide 2.4 mg in one of the three KaiNETIC trials.
A separate oral formulation (HRS9531-T / KAI-9531-T) is being developed in parallel as a once-daily tablet, using permeation-enhancing technology analogous to oral semaglutide to achieve sufficient systemic exposure.
Evidence
- Human: Hengrui's Phase 3 HRS9531-301 in 567 adults with obesity or overweight in China reported mean weight loss of 11.2%, 17.4%, and 19.2% at 2, 4, and 6 mg weekly versus 1.4% on placebo at 48 weeks, with 88.0% of treated participants at the highest dose achieving ≥5% weight loss and 44.4% achieving ≥20% (Kailera and Hengrui, ObesityWeek 2025 presentation, November 2025). The Phase 2 program in 249 Chinese adults with obesity (1.0/3.0/4.5/6.0 mg weekly for 24 weeks) reached up to 16.7% placebo-adjusted mean weight loss at 6 mg (Zhao and colleagues, Diabetes 2024, abstract 1861-LB). A Phase 2 8 mg weekly cohort reported ~23% mean weight loss at 36 weeks with no observed plateau (Kailera and Hengrui press release, January 2025). The oral formulation Phase 2 (HRS9531-T-201, n=166) showed 6.9%, 12.1%, and 12.1% mean weight loss at 10, 25, and 50 mg daily over 26 weeks (Kailera and Hengrui press release, February 2026). A separate Phase 2 in Chinese adults with type 2 diabetes has been reported (Zhao and colleagues, Diabetes 2025, abstract 126-OR). The KaiNETIC global Phase 3 program — three placebo-controlled trials with a combined target enrollment of ~4,700 adults across obesity (KaiNETIC-1), type 2 diabetes with overweight or obesity (KaiNETIC-2), and higher-BMI obesity with an open-label semaglutide 2.4 mg comparator (KaiNETIC-3) — began randomizing in January 2026, with readouts anticipated in 2028 (Kailera press release, January 2026).
- Animal: Kailera has publicly described preclinical characterization suggesting higher potency and longer-lasting receptor-level effects than tirzepatide; peer-reviewed primary preclinical publications remain limited in the available literature, and the potency comparison has not been independently validated in published studies.
- In vitro / pharmacology: Phase 1 single- and multiple-ascending-dose studies in healthy volunteers characterized pharmacokinetics and pharmacodynamics of the injectable formulation (He and colleagues, Diabetes 2023, abstract 763-P) and the oral tablet (Diabetes 2025, abstract 797-P). Dual GLP-1R/GIPR agonism as a mechanism class is otherwise validated by tirzepatide's global Phase 3 program and post-marketing experience.
Evidence concentration caveat: every completed efficacy trial of ribupatide enrolled exclusively Chinese participants. Whether the weight-loss magnitudes observed translate to non-Chinese populations is the central question the KaiNETIC global program is designed to answer.
Known effects
- Weight loss (subcutaneous injectable) — Phase 3 human data (Chinese adults; 48 weeks)
- Weight loss (oral formulation) — Phase 2 human data (Chinese adults; 26 weeks; lower magnitude than injectable)
- Glycemic control in type 2 diabetes — Phase 2 (Chinese adults with T2DM)
- Appetite suppression, delayed gastric emptying — pharmacodynamic effects of GLP-1R agonism; observed across completed trials
- Reductions in blood pressure, fasting glucose, triglycerides — Phase 2 (Zhao and colleagues, Diabetes 2024, abstract 1861-LB)
- Superior potency vs tirzepatide at the receptor level — preclinical / sponsor-reported only; not validated by published head-to-head data
Myths and misconceptions
"Ribupatide is just a Chinese copy of tirzepatide." Ribupatide and tirzepatide share a receptor profile — both are dual GLP-1/GIP agonists — but they are distinct peptide molecules developed independently from different scaffolds. Framing ribupatide as a copy understates both the independent design work and the Phase 3 evidence base the program has generated.
"Because ribupatide produces more weight loss than tirzepatide in cross-trial comparisons, it must be better." Cross-trial comparisons between products tested in different populations with different protocols are methodologically unreliable. Ribupatide's reported weight-loss figures enrolled exclusively Chinese participants with a lower average baseline body weight than the SURMOUNT trial populations used for tirzepatide, which can inflate percentage-based weight-loss figures. Until KaiNETIC reads out in diverse global populations — and ideally until a head-to-head trial against tirzepatide is completed — relative ranking cannot be confidently established.
"Ribupatide is approved in China." Hengrui has submitted a marketing authorization application to China's NMPA and that submission has been accepted for procedural review, but approval has not been granted as of April 2026. Acceptance of a filing is an administrative milestone, not a regulatory endorsement of efficacy or safety.
"The oral formulation matches the injectable on weight loss." Oral ribupatide produced roughly 12% weight loss at 26 weeks at the two higher doses in a China Phase 2 trial — a meaningful result for an oral peptide, but shorter in duration and lower in magnitude than the 17–19% seen with the injectable at 48 weeks. The two formulations should be understood as separate products with different pharmacokinetic profiles and dose requirements rather than interchangeable forms of the same drug.
Safety signals
The safety profile from completed Phase 2 and Phase 3 trials is consistent with the GLP-1 receptor agonist class. Gastrointestinal adverse events — nausea, vomiting, diarrhea, constipation, and decreased appetite — are dose-dependent and concentrate at titration steps, with available trial reports describing them as mostly mild-to-moderate and indicating low discontinuation rates (Zhao and colleagues, Diabetes 2024, abstract 1861-LB; Kailera and Hengrui, ObesityWeek 2025 presentation). In the oral Phase 2, nausea was reported in 11.9%, 22.7%, and 20.0% of participants at 10, 25, and 50 mg, with vomiting in 2.4%, 11.4%, and 7.5% respectively (Kailera and Hengrui press release, February 2026).
Class-based signals that trial protocols address by exclusion include the rodent medullary thyroid carcinoma signal (C-cell tumors observed across incretin therapies in rodents; clinical relevance to humans not established) and acute pancreatitis (trial protocols excluded participants with prior pancreatitis). No ribupatide-specific carcinogenicity or pancreatitis incidence data have been reported in the available literature. Modest dose-dependent heart-rate elevation has been observed across incretin therapies; ribupatide's specific cardiovascular pharmacodynamic profile will be further characterized in the KaiNETIC program.
Long-term safety beyond approximately 48–76 weeks is not yet characterized. All reported trials ran 36–48 weeks; KaiNETIC extends to 76 weeks but has not read out.
Regulatory status
- US (FDA): Not approved. Investigational under Kailera's KaiNETIC program; available only through enrollment in sponsor-run clinical trials. No legal compounding pathway exists — ribupatide has no approved reference product and is not on the validated bulk drug substance list.
- China (NMPA): Marketing authorization application accepted for review based on HRS9531-301; not approved as of April 2026.
- EU (EMA), UK (MHRA), Canada (Health Canada), Australia (TGA): Not authorized.
- WADA: Not listed by name, but ribupatide falls under WADA S0 ("any substance not currently approved by any governmental regulatory health authority for human therapeutic use") outside of any eventual China approval. Athletes subject to the WADA code should treat ribupatide as prohibited in and out of competition.
Mechanism
Ribupatide is a long-acting peptide dual agonist of the glucagon-like peptide-1 receptor (GLP-1R) and the glucose-dependent insulinotropic polypeptide receptor (GIPR), both class B G-protein-coupled receptors that signal primarily through the Gαs–cAMP pathway (Drucker, Cell Metabolism 2023 review of GIPR/GLP-1R dual agonist pharmacology). GLP-1R activation stimulates glucose-dependent insulin secretion from pancreatic β-cells, suppresses glucagon release, delays gastric emptying, and engages hypothalamic and brainstem satiety circuits. GIPR activation enhances insulin secretion under hyperglycemic conditions, modulates adipose tissue handling of postprandial lipids, and contributes to satiety through distinct central pathways from GLP-1, while also mitigating some of the gastrointestinal tolerability burden of pure GLP-1 agonism.
Ribupatide is formulated for once-weekly subcutaneous administration. A separate oral formulation (HRS9531-T / KAI-9531-T) uses permeation-enhancing technology to achieve sufficient systemic exposure from daily oral dosing — an approach analogous to oral semaglutide.
Kailera has publicly described preclinical characterization suggesting a more potent and longer-acting receptor-level profile than tirzepatide; that claim has not been tested in a completed head-to-head human trial. Mechanistic confidence in ribupatide reflects the broader dual-agonist class validation by tirzepatide rather than molecule-specific evidence of equivalent depth.
Open questions
- Global efficacy replication: KaiNETIC-1, -2, and -3 are the first multinational trials of ribupatide; whether the weight-loss magnitudes observed in Chinese Phase 3 participants translate to non-Chinese populations is the central unanswered question, with results anticipated in 2028.
- Head-to-head vs. tirzepatide: KaiNETIC-3 includes a semaglutide 2.4 mg open-label comparator but no tirzepatide arm; relative positioning against the other dual GLP-1/GIP agonist will require indirect comparison or a dedicated head-to-head trial that does not yet exist.
- Long-term safety beyond 76 weeks: all reported and planned trials end at or before that duration; multi-year safety data comparable to the semaglutide and tirzepatide post-marketing experience are not yet available.
- Weight-regain kinetics after discontinuation: no published withdrawal-arm data exist for ribupatide; the expectation of substantial regain after stopping is extrapolated from semaglutide and tirzepatide parallels rather than ribupatide-specific evidence.
- Cardiovascular outcomes: no dedicated cardiovascular outcomes trial has been completed or announced.
- Oral formulation in non-Chinese populations: global bioavailability, efficacy, and safety of the oral formulation in non-Chinese populations has not been characterized.
- Body composition at high doses: the balance of fat versus lean mass loss at 8–10 mg weekly across the full KaiNETIC dose range has not been reported in detail.
- Non-obesity indications: expansion into MASH/MASLD, cardiovascular disease, or obstructive sleep apnea — all pursued by tirzepatide — is speculative for ribupatide pending dedicated trial programs.
Related peptides
- Tirzepatide — FDA- and EMA-approved dual GLP-1/GIP receptor agonist (Mounjaro, Zepbound); the same receptor profile as ribupatide but a distinct molecule with extensive global Phase 3 and post-marketing data.
- Semaglutide — GLP-1 receptor agonist (Ozempic, Wegovy); the active comparator in KaiNETIC-3.
- Liraglutide — once-daily GLP-1 receptor agonist; earlier-generation incretin predecessor.
- Retatrutide, mazdutide, ecnoglutide — other incretin-class investigational agents in the same broader competitive landscape (platform cards not yet verified).
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 the way ribupatide is built make it hit one receptor harder than the other, and could that mean fewer stomach side effects?
Nausea and vomiting cause many people to stop taking current weight-loss injections. If ribupatide's design tips the balance toward the receptor linked to fat loss over the one that slows digestion, more patients might stay on treatment long enough to benefit.
Does activating two gut-hormone receptors at once help people lose fat without losing as much muscle?
If true, older adults or people at risk of muscle weakness could lose weight safely with ribupatide without the frailty risk that worries doctors about some current weight-loss drugs.
Is the only publicly available ribupatide sequence just a structural glue piece rather than the part that activates weight-loss receptors?
If true, it would explain why the sequence looks nothing like other weight-loss drugs and would help researchers understand what class of molecular engineering Hengrui used, which could guide development of next-generation obesity medicines.
Does ribupatide act directly on liver cells to slow scarring, separate from any weight it helps people lose?
Fatty liver disease that progresses to scarring can lead to liver failure or liver cancer. If ribupatide protects the liver directly, it could help millions of people with both obesity and liver disease, even those who do not lose much weight.
Is the small piece of ribupatide that is publicly known just the molecular hook used to keep the drug in the body for a week?
Knowing how long-acting obesity drugs are built helps scientists design better, cheaper versions in the future, and helps regulators assess biosimilar medicines when patents expire.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.813410758972168 | openfold3-mlx |
| ranking score | 0.8787189722061157 | openfold3-mlx |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.452 | global PDE — lower = better |
| disorder | 0.112 | fraction disordered |
| chain pair ipTM (A, B) | 0.813 | interface quality |
▸3-letter notation
▸recipeopenfold3-mlx 0.3.1
| parameter | value |
|---|---|
| model | openfold3-mlx 0.3.1 |
| weights | — |
| hardware | — |
| mlx version | — |
| python | — |
| random seed | — |
| msa strategy | — |
| diffusion samples | 1 |
| runtime | 80s |
| predicted by | mlx@peptide |
| predicted at | 2026-05-03 |
▸citationbibtex
@peptide{pep10921,
sequence = {GIRILLLKV},
target = {anticancer},
author = {peptidemodel},
year = {2026},
status = {computed}
}