GSK has completed its acquisition of IDRx, a Boston-based, clinical-stage bio/pharmaceutical company, in a deal worth up to $1.1 billion ($1 billion upfront and $150 million in milestone payments). The deal was announced in January 2025. 

The acquisition includes IDRx’s lead molecule, IDRX-42, being developed as a first- and second-line therapy for treating gastrointestinal stromal tumors (GIST). IDRX-42 is a investigational small-molecule tyrosine kinase inhibitor designed to target all key KIT mutations in GIST. The US Food and Drug Administration (FDA) has granted IDRX-42 fast-track designation for treating patients with GIST after disease progression or intolerance to imatinib. It was also granted orphan drug designations by FDA for the treatment of GIST.  

The acquisition adds to GSK’s portfolio in gastrointestinal cancers, including ongoing trials with dostarlimab and GSK5764227, a B7-H3-targeted antibody-drug conjugate.  

The total cash consideration for this acquisition amounts to up to $1.15 billion. This includes an upfront payment of $1 billion, with the possibility of an additional $150 million milestone payment contingent upon success-based regulatory approval. GSK will also be responsible for success-based milestone payments as well as tiered royalties for IDRX-42 owed to Merck KGaA.  IDRx, which was launched in 2022, acquired IDRX-42 and IDRX-73, small-molecule tyrosine kinase inhibitors for treating GIST through license agreements with Merck KGaA, and Blueprint Medicines, respectively, in 2022.   

Source: GSK