HRS9531 (KAI-9531)

What It Is

HRS9531 is an injectable peptide dual agonist of the glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptors, developed independently by Jiangsu Hengrui Pharmaceuticals, one of China's largest pharmaceutical companies. It works by the same validated mechanism as Eli Lilly's tirzepatide (marketed as Zepbound for obesity and Mounjaro for type 2 diabetes): activating both incretin receptors simultaneously to reduce appetite, slow gastric emptying, improve insulin secretion and sensitivity, and drive substantial weight loss. In 2024, Hengrui out-licensed HRS9531 and the rest of its GLP-1 obesity portfolio (ex-Greater China rights) to Kailera Therapeutics, a Waltham, Massachusetts- and San Diego-based biotech launched with roughly $400 million in financing specifically to bring these Chinese-developed incretin drugs to global markets; Kailera is developing the injectable as KAI-9531, its lead program. More than 2,000 patients have been dosed with HRS9531 across Phase 1, Phase 2, and Phase 3 studies in China. The pivotal GEMINI-1 study (also referred to as HRS9531-301; NCT06396429) was a multi-center, randomized, double-blind, placebo-controlled Phase 3 trial that enrolled 567 Chinese adults (531 completed) with obesity (BMI at or above 28 kg/m2) or overweight (BMI at or above 24 kg/m2) plus at least one weight-related comorbidity, and without type 2 diabetes. Participants were randomized 1:1:1:1 to once-weekly subcutaneous HRS9531 2 mg, 4 mg, 6 mg, or placebo for 48 weeks. Results, presented at ObesityWeek 2025 (The Obesity Society) after topline data in mid-2025, met both co-primary endpoints. Under the per-protocol (hypothetical) estimand, mean weight loss was about 11.2% (2 mg), 17.4% (4 mg), and 19.2% (6 mg) versus about 1.4% for placebo; under the more conservative treatment-policy estimand it was about 10.7%, 16.4%, and 17.7% (roughly 16.3% placebo-adjusted at 6 mg). Weight loss had not plateaued at 48 weeks. About 68-88% of treated participants lost at least 5% of body weight, and about 44.4% of those on 6 mg lost at least 20% - figures that put HRS9531 in the same competitive range as tirzepatide, which achieved about 20.9% weight loss at 36 weeks in its SURMOUNT program. Treatment also improved cardiometabolic risk factors, including blood pressure, lipids, measures of insulin resistance, and high-sensitivity C-reactive protein (hsCRP). Safety and tolerability were consistent with the GLP-1/incretin class: most treatment-emergent adverse events were mild to moderate and gastrointestinal (nausea, vomiting, diarrhea), and permanent discontinuations due to adverse events were very low (0.7% at 2 mg, 0.7% at 4 mg, 1.4% at 6 mg, and 0% for placebo). An earlier Phase 2 trial (NCT06054698) that tested a higher 8 mg dose reported about 23.6% mean weight loss (about 21.7% placebo-adjusted) at week 36, again with no plateau. On the strength of the Phase 3 data, Hengrui submitted a marketing authorization application to China's National Medical Products Administration (NMPA) for chronic weight management, which was accepted. Kailera's global Phase 3 program comprises three trials of KAI-9531 - one in adults with a BMI above 30 (or above 27 with a comorbidity) without type 2 diabetes, one in adults with a BMI above 27 and type 2 diabetes, and one in adults with a BMI above 35 without type 2 diabetes - evaluating higher maintenance doses (8 mg and 10 mg) and at least 52 weeks of maintenance dosing, with the program initiated around the end of 2025. The strategic significance is twofold: HRS9531 is one of the most advanced 'fast-follower' incretin dual agonists positioned to compete with tirzepatide on efficacy, and it is a flagship example of a broader trend in which Chinese-originated obesity drugs are licensed to Western companies for global development. Important caveats remain: the pivotal efficacy data come from a China-only population and have been reported via conferences and press releases rather than a full peer-reviewed publication; the global Phase 3 program is still early; long-term safety, durability, and outcomes beyond weight (such as cardiovascular events) are not yet established; and cross-trial comparisons with tirzepatide or semaglutide are not head-to-head. HRS9531/KAI-9531 has no marketing approval anywhere as of this writing (it is under regulatory review in China), is not a supplement or research chemical, and any product sold as 'HRS9531' or 'KAI-9531' outside a regulated clinical trial is unverified and unsafe.

Regulatory Status

Why Researchers Study It

HRS9531 sits at the intersection of two of the most important stories in metabolic medicine: how far incretin-based weight loss can be pushed, and how quickly Chinese-developed drugs are entering the global obesity race. Mechanistically it is a dual GLP-1/GIP receptor agonist - the same class as tirzepatide, the most effective approved obesity medicine - so researchers study it as a test of whether a fast-following peptide can reproduce or exceed tirzepatide-level efficacy. The Phase 3 GEMINI-1 data are compelling on that score: roughly 17-19% mean weight loss at 48 weeks with no plateau, about 44% of high-dose patients losing at least a fifth of their body weight, and broad improvements in blood pressure, lipids, insulin resistance and inflammation, all with the familiar, mostly gastrointestinal tolerability profile of the class and very low discontinuation rates. Because the earlier Phase 2 study pushed to a higher 8 mg dose and produced about 23.6% weight loss by week 36 - still climbing - there is genuine interest in whether higher maintenance doses (8 mg and 10 mg, now in Kailera's global Phase 3 program) can move dual agonism closer to the weight loss once thought to require triple agonists or surgery. HRS9531 is equally interesting as a business and access story. Hengrui developed it independently in China, dosed more than 2,000 patients there, and licensed ex-Greater China rights to Kailera, a well-funded U.S. biotech built specifically to globalize Chinese incretin assets as KAI-9531; the program is a marker of how obesity innovation and manufacturing capacity are diversifying beyond the incumbents. Finally, researchers watch HRS9531 alongside its oral sibling KAI-7535 (HRS-7535) because the pair lets a single franchise test injectable versus oral, dual versus single incretin agonism, and different dose ceilings against the same competitive backdrop - even as the key open questions (durability, effects after stopping, lean-mass preservation, cardiovascular outcomes, and how China-only data generalize) remain to be answered in the global program.

Proposed Mechanisms

• Dual GLP-1/GIP receptor agonism: HRS9531 is an engineered peptide that simultaneously activates the glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptors - the same twin-incretin mechanism as tirzepatide - to amplify the body's natural incretin signaling.
• Appetite suppression and slowed gastric emptying: GLP-1 receptor activation in the brain and gut reduces hunger and food intake and slows stomach emptying, promoting sustained calorie deficit and weight loss (mean 17-19% at 48 weeks at 4-6 mg in Phase 3).
• Improved glucose control and insulin sensitivity: combined GLP-1 and GIP signaling enhances glucose-dependent insulin secretion and improves measures of insulin resistance, supporting development for type 2 diabetes as well as obesity.
• Broad cardiometabolic effects: in Phase 3, treatment improved blood pressure, lipids and high-sensitivity C-reactive protein (hsCRP), consistent with the weight-loss-linked cardiometabolic benefits seen across the incretin class.
• Once-weekly, long-acting design: HRS9531 is formulated for once-weekly subcutaneous injection, and the absence of a weight-loss plateau at 48 weeks (and at a higher 8 mg dose by week 36 in Phase 2) motivates testing of higher maintenance doses and longer durations in the global KAI-9531 program.

Evidence Snapshot

Commonly Discussed Benefits

Safety & Cautions

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Citations

1. [1] Hengrui Pharma and Kailera Therapeutics Report Positive Topline Data from Phase 3 Obesity Trial in China of Dual GLP-1/GIP Receptor Agonist HRS9531 - Kailera (July 15, 2025) PubMed
2. [2] Hengrui Pharma and Kailera Therapeutics Announce Additional Data from Phase 3 Obesity Trial in China of Dual GLP-1/GIP Receptor Agonist HRS9531 - BioSpace (November 4, 2025) PubMed
3. [3] Hengrui's GLP-1/GIP agonist reports 18% weight loss in phase 3 trial, readies China push - Fierce Biotech (July 15, 2025) PubMed
4. [4] GEMINI-1: A Study of HRS9531 Injection in Participants With Obesity or Overweight - ClinicalTrials.gov (NCT06396429) PubMed
5. [5] A Study of HRS9531 Injection in Adults With Overweight or Obesity (Phase 2) - ClinicalTrials.gov (NCT06054698) PubMed
6. [6] Hengrui and Kailera report positive data from Phase III obesity treatment trial - Clinical Trials Arena (2025) PubMed
7. [7] Kailera Therapeutics - Pipeline and KAI-9531 program overview PubMed

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