GSK confirms plan to buy cancer firm IDRx for $1bn

Last week's rumour that GSK was poised to make a bid to acquire IDRx and its experimental targeted therapy for a rare form of rare gastrointestinal cancer was on the money.

This morning, the UK pharma group confirmed it had signed an agreement to buy privately-held IDRx for $1 billion upfront, with another $150 million in payments to the biotech's shareholders if its pipeline delivered as expected.

The deal coincides with the start of the JP Morgan healthcare conference in San Francisco, which has become a popular venue for announcing M&A and other deals at the beginning of each year.

That pipeline is led by IDRX-42, a highly selective KIT tyrosine kinase inhibitor (TKI) that is being developed as a first- and second-line therapy for gastrointestinal stromal tumour (GIST), which is classed as rare, but is still the most common subtype of soft tissue sarcoma occurring in the gastrointestinal tract.

In a statement, GSK chief commercial officer Luke Miels said that the drug "complements [the company's] growing portfolio in gastrointestinal cancers," which also includes anti-PD-1 antibody Jemperli (dostarlimab), which is in mid-to late-stage clinical development for colorectal cancer, as well as B7-H3-dorected antibody-drug conjugate GSK5764227.

GSK said that IDRX-42 addresses all the key KIT mutations that drive tumour growth and progression in GIST, which is estimated to affect between 4,000 and 6,000 people in the US each year.

Approximately 80% of all GIST cases are driven by mutations in the KIT gene, and 90% of patients treated in the first-line develop new KIT mutations that typically lead to relapse with limited therapeutic options.

IDRX-42 is currently in the phase 1/1b StrateGIST 1 trial in patients with KIT-mutant GIST who have failed prior treatment with Novartis Gleevec/Glivec (imatinib mesylate) and other approved targeted drugs. The drug showed an objective response rate (ORR) of 29% overall, rising to 53% among those who had only received one previous line of treatment.

"We are excited by the early data from IDRX-42 and its unique ability to target all clinically relevant KIT mutations present in GIST, a major gap in the current standard of care," said GSK's chief scientific officer, Tony Wood.

"We look forward to accelerating its development in 2025 to redefine treatment," he added.

For GSK, the deal continues its strategy of building up its oncology pipeline through a series of bolt-on deals after all-but exiting the category a decade ago through a sale of its cancer assets to Novartis.

Recent examples include its $1.9 billion takeover of Sierra Oncology in 2022, adding myelofibrosis candidate Omjjara (momelotinib), as well as a pair of ADCs from China's Hansoh Pharma, in two transactions valued at $1.7 billion and $1.58 billion, respectively, alongside smaller deals involving Rgenta Therapeutics and Duality Biologics.

GSK has been working on extending its pipeline as it prepares to face patent expiry in 2027 for HIV drug dolutegravir, one of its biggest sellers, as well as competition to shingles vaccine Shingrix, currently its top product, from the likes of Pfizer/BioNTech and Moderna.