Is GSK prepping a $1bn takeover bid for IDRx?

GSK is reportedly in late-stage negotiations about a $1 billion deal to acquire IDRx and its experimental targeted therapy for a form of rare gastrointestinal stromal tumour (GIST).

The rumoured deal – first reported in the Financial Times – comes just ahead of the annual JPMorgan healthcare conference, which starts next week, and generally sees a flurry of M&A activity involving biopharma companies.

Privately-held IDRx is backed by various venture capital and private equity firms, including Andreessen Horowitz, RA Capital, and Blackstone Group, and completed a $120 million Series B last August to fund clinical development of lead cancer drug candidate IDRX-42, which hiked its valuation to around $430 million. The company had also been considering a public listing, according to the FT.

The proceeds were earmarked for the ongoing phase 1/1b StrateGIST 1 trial of the selective KIT inhibitor in patients with KIT-mutant GIST who have failed prior treatment with Novartis Gleevec/Glivec (imatinib mesylate) and other approved targeted drugs, as well as a planned pivotal trial of the drug.

Results from the phase 1 portion of StrateGIST 1 reported at last year's ASCO cancer congress showed a 23% objective response rate (ORR) across all patients in the study – who had received a median of four prior lines of therapy – rising to 43% in those treated second-line with IDRX-42.

For GSK, the deal – if confirmed – will further 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 antibody-drug conjugates from China's Hansoh Pharma in tow deals 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.

Neither GSK nor IDRx has commented on the rumoured negotiations.

GIST is a rare cancer, but still the most common subtype of soft tissue sarcoma occurring in the gastrointestinal tract, affecting between 4,000 and 6,000 people in the US each year, according to Cambridge, Massachusetts-based IDRx. Approximately 80% of all GIST cases are driven by mutations in the KIT gene.