Kailera raises $600 million to move obesity drug KAI-9531 into global Phase 3
A $600 million funding round will push an experimental GLP-1/GIP obesity shot into global Phase 3 trials, but US approval is still several studies and years away.
Kailera Therapeutics has raised $600 million to fund global, late-stage testing of an injectable obesity drug that works like Eli Lilly's Zepbound, the company said Oct. 14, 2025 [1].
Bain Capital Private Equity led the Series B round, which also drew Adage Capital Management, the Canada Pension Plan Investment Board, an investment fund from the Qatari government, Royalty Pharma and several crossover investors that put money into both private and public drug companies [1]. BioPharma Dive reported the round matches the $600 million raised by Isomorphic Labs in March, and that the two are by far the largest private biotech financings it tracked this year [1]. Privately held obesity drug developers have now raised more than $1 billion in 2025, including Helicore Biopharma's $65 million in January and Verdiva Bio's $411 million launch [1].
The drug, called KAI-9531 or HRS9531, acts on two metabolism-altering gut hormones, GLP-1 and GIP — the same targets as tirzepatide, sold as Mounjaro and Zepbound [1]. Kailera and its partner Hengrui Pharma reported in July 2025 that the shot helped people with obesity lose 18% of their body weight on average over 48 weeks in a Phase 3 trial in China that enrolled 567 people [1].
That result lands roughly in the range of Zepbound, but it comes from a shorter and smaller study. Zepbound helped people with obesity lose as much as 21% of their body weight over 72 weeks in a Phase 3 trial of more than 2,500 people, 18 percentage points more than those who received a placebo [1]. The same report said the FDA will likely require a larger, longer, multi-country study before it would consider clearing KAI-9531 in the US [1].
Kailera plans to start international Phase 3 studies of KAI-9531 by the end of 2026 [1]. The company said the money will also move a GLP-1 pill into global trials, fund further testing of a triple-acting therapy, and support an oral version of KAI-9531 [1]. Kailera is led by Ron Renaud, who previously ran Idenix Pharmaceuticals, Translate Bio and Cerevel Therapeutics [1]. Chris Gordon, a partner and global co-head of Bain Capital Private Equity, said in a statement that KAI-9531 has the potential to "set the bar for the next generation of obesity treatments" [1].
Why it matters for patients
Another well-funded GLP-1/GIP candidate could eventually add competition among obesity treatments, and competition is one of the forces that can affect what insurers cover and what patients pay. But KAI-9531 is not approved in the US, and the China results are the basis for a possible filing there, not here [1].
The 18% weight-loss figure comes from 48 weeks of treatment in 567 people; the company has said the global trials will use higher doses and a longer treatment period [1]. Whether the drug matches or beats Zepbound, what it would cost, and whether insurers would cover it have not been reported [1].
For someone already taking semaglutide (Ozempic, Wegovy, Rybelsus) or tirzepatide (Mounjaro, Zepbound), a funding announcement changes nothing about access, supply or price of the drugs on the market now. No clinical data comparing KAI-9531 head-to-head with either drug has been reported.
What happens next
Kailera says it will begin international Phase 3 trials of KAI-9531 by the end of 2026 [1]. No timeline has been disclosed for a US regulatory filing or for a decision in China, where the company has said the Phase 3 data position it to seek approval [1].
Sources
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