GSK jilts Sosei, dropping bowel disease asset on cusp of clinic amid changes at immunology unit

GSK has jilted Sosei Heptares on the cusp of the clinic. With approval to start first-in-human studies in place, the Big Pharma has backed out of the program, reportedly because of changes at its immunology unit, and returned full rights to an inflammatory bowel disease asset Sosei sees as a potential blockbuster.

Three years ago, GSK struck a deal worth up to 34 million pounds ($43 million) across an upfront fee, potential near-term milestones and research funding for global rights to a portfolio of GPR35 agonists. The pact, which featured up to 336 million pounds ($423 million) in more distant milestones, established GSK at the vanguard of work to drug a G protein-coupled receptor that is expressed in the gastrointestinal tract.

The program has progressed since the partners formed the alliance, with GSK starting to pay a trickle of milestones, generating mechanistic, preclinical and safety data, and securing the green light to study a candidate, GSK4381406, in humans in the U.K. But that will be as far as GSK takes the program.

According to Sosei, GSK is returning full ownership of the asset after making the decision to “deprioritize and discontinue its development due to changes to both its immunology research strategy and immunology research leadership.” The decision wasn’t based on scientific, preclinical or safety data on GSK4381406, Sosei said. 

News of changes to GSK’s immunology team broke in September. John Lepore, M.D., GSK’s senior vice president and head of research, and a person involved in the Sosei deal, left the company. At the same, GSK split research into three teams that are “more closely aligned” with its core therapeutic groups: respiratory and immunology; vaccines and infectious diseases; and oncology. 

Work on GSK4381406 will continue without GSK. Sosei, which has had a strong presence in the U.K. since buying Heptares, plans to proceed with the authorized phase 1 trial while assessing how to advance the program, either internally or by striking another deal. 

The drug developer’s business model is to take candidates into early clinical development and then find a partner. Sosei acquired clinical development and commercialization capabilities in Japan and Asia Pacific, excluding China, earlier this year by buying Idorsia’s operations in the region for 400 million Swiss francs ($454 million).

Sosei has high hopes for the molecule, quoting an independent commercial analysis that “supports a worldwide peak sales opportunity of more than $3 billion for GSK4381406 with its unique target product profile.” Interest in the target, GPR35, has increased as researchers have overcome barriers to studying the receptor, such as differences between human and rodent biology, and linked it to multiple diseases.