Kailera Therapeutics raises $600 million to push ribupatide into global Phase 3

Kailera Therapeutics, a US biotech, has raised $600 million in a Series B funding round to push its experimental obesity drug into global Phase 3 testing ^[1]. The drug, known as KAI-9531 or HRS9531, works on the same two gut hormones, GLP-1 and GIP, that Eli Lilly's Zepbound targets ^[1].

The funding round was led by Bain Capital Private Equity, with additional money from Adage Capital Management, the Canada Pension Plan Investment Board, a Qatari government investment fund, Royalty Pharma and other investors ^[1]. It ties with a March round from AI company Isomorphic Labs as the largest private biotech financing tracked this year by BioPharma Dive ^[1]. With this round, privately held obesity drug developers have raised more than $1 billion in 2025 alone ^[1].

Kailera holds rights to the drug outside Greater China through a partnership with Chinese firm Hengrui Pharma ^[1]. In July, the companies reported that people with obesity who took the drug lost an average of 18% of their body weight over 48 weeks in a Phase 3 trial conducted in China ^[1]. That trial enrolled 567 people ^[1]. By comparison, Zepbound's US approval trial enrolled more than 2,500 people and tracked weight loss over 72 weeks, finding that participants lost as much as 21% of body weight, or 18 percentage points more than those on placebo ^[1].

Kailera plans to start international Phase 3 studies of the drug by the end of 2026, using higher doses and a longer treatment period than the Chinese trial ^[1]. The company says the Food and Drug Administration will likely require this larger, longer, multi-country study before it would consider approving the drug for the US market ^[1]. The funding will also support development of a GLP-1 pill and further testing of a triple-acting therapy and an oral version of the injectable drug ^[1].

Why it matters for patients

This is not a new treatment option yet. The Chinese trial results are promising on paper, showing weight loss in the same range as some GLP-1 medicines already sold in the US, but the study was smaller and shorter than the one that led to Zepbound's approval ^[1]. US patients will not be able to access this specific drug until it clears a much larger multi-country trial that has not yet begun ^[1].

The deal is part of a broader pattern: several young companies are testing obesity drugs that were originally discovered in Chinese laboratories, and investors are betting heavily on this space ^[1]. For patients, more competition among drugmakers could eventually mean more choices and potentially different price points, but that outcome is still years away and not guaranteed.

It is not yet known from these sources how the side effect profile of this drug compares with Zepbound, Wegovy, or other approved GLP-1 medicines, since that data was not detailed in the available reporting.

What happens next

Kailera says it aims to begin global Phase 3 trials of the injectable drug by the end of 2026 ^[1]. Those trials will need to enroll more participants and run longer than the Chinese study before the company could seek FDA review ^[1]. No timeline for a possible US approval decision has been reported.