GSK's $1.15 Billion Acquisition of IDRx: A Strategic Move in the Battle Against Stomach Cancer

In a significant move to bolster its oncology portfolio, GlaxoSmithKline (GSK) has announced a definitive agreement to acquire IDRx, a US-based biotechnology company specializing in treatments for gastrointestinal cancers. The deal, valued at up to $1.15 billion, includes an upfront payment of $1 billion and an additional $150 million tied to regulatory milestones. This acquisition will give GSK full ownership of IDRx, including all outstanding equity interests and incentive equity, as well as responsibility for milestone payments and tiered royalties associated with IDRx's lead drug candidate, IDRX-42.

IDRX-42 is a highly selective KIT tyrosine kinase inhibitor (TKI) designed to treat gastrointestinal stromal tumours (GIST) by targeting all major KIT mutations, which are critical drivers of the disease. Unlike existing TKIs, IDRX-42 has the potential to inhibit the complete spectrum of clinically relevant primary and secondary KIT mutations, a gap in the current standard of care. This acquisition aligns with GSK's portfolio approach of identifying potentially best-in-class molecules with targeted mechanisms of action and supports the company's ambitions for growth through 2031 and beyond.



IDRx was founded in 2021 with a mission to address the limitations of today's precision cancer medicines with highly potent and selective targeted therapies to stop key tumor escape mechanisms and prolong patients' response to therapy. The company's investors include prominent venture capital firms such as Andreessen Horowitz (a16z), Casdin Capital, and Nextech Invest. IDRx's co-founders include renowned experts in the field, such as George Demetri, M.D., FACP, FASCO, FAACR, and Alexis Borisy.

GSK's acquisition of IDRx is a strategic move that complements its growing portfolio in gastrointestinal cancers, which already includes ongoing trials with dostarlimab and GSK5764227 (GSK'227), a B7-H3-targeted antibody-drug conjugate. This acquisition reflects GSK's commitment to addressing unmet medical needs and expanding its global clinical development capability and strong commercial presence in oncology.



IDRX-42 has demonstrated promising anti-tumour activity in patients with advanced GIST, with a manageable safety profile. In the ongoing phase I/Ib trial of IDRX-42 (StrateGIST 1), the objective response rate (ORR) by modified RECIST v1.1 in the total efficacy evaluable population was 29%, including one complete response (CR) and 24 partial responses (PRs). Among patients who had one prior line of therapy, the ORR was 53%. The emerging durability data from StrateGIST 1 was also favourable, with IDRX-42 generally well-tolerated and treatment-related adverse events (TRAEs) mainly low grade at the recommended phase Ib dose.

Luke Miels, Chief Commercial Officer of GSK, stated that IDRX-42 complements the company's growing portfolio in gastrointestinal cancers and is consistent with GSK's approach of acquiring assets that address validated targets and where there is clear unmet medical need, despite existing approved products. Tony Wood, Chief Scientific Officer of GSK, expressed excitement about 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. GSK plans to accelerate the development of IDRX-42 in 2025 to redefine treatment for this rare and challenging cancer.

In conclusion, GSK's acquisition of IDRx for up to $1.15 billion is a strategic move that aligns with the company's long-term oncology strategy. By gaining access to IDRX-42, a promising small molecule drug for gastrointestinal stromal tumors, GSK aims to address a significant unmet medical need and strengthen its position in the gastrointestinal cancers market. As the first major deal of the 2025 JP Morgan Healthcare Conference, this acquisition sets the stage for an active year in the biopharma M&A landscape.