GSK plc has completed its previously announced acquisition of IDRx Inc., a Boston-based, clinical-stage biopharmaceutical company dedicated to developing precision therapeutics for the treatment of gastrointestinal stromal tumors (GIST).

The acquisition includes IDRX-42, an investigational, highly selective tyrosine kinase inhibitor (TKI) specifically designed to enhance outcomes for patients with gastrointestinal stromal tumors (GIST). IDRX-42 exhibits activity against all clinically relevant primary and secondary KIT mutations, which are crucial medical needs in current GIST treatment. GIST usually originates in the gastrointestinal tract, with 80% of cases driven by mutations in the KIT gene that promote tumor growth, proliferation, and survival (primary or activating mutations). Notably, 90% of patients treated in the initial line develop new KIT mutations (secondary or resistance mutations), which often lead to relapse with limited therapeutic options.

Hesham Abdullah, Senior Vice President, Global Head Oncology R&D, GSK, said, “This acquisition adds to GSK’s growing pipeline of targeted therapeutics for cancers originating in the gastrointestinal tract. We plan to advance IDRX-42 for second line treatment of gastrointestinal stromal tumors, where there are no approved treatments to effectively address all resistance mutations, and accelerate development in an earlier setting.”

The total cash consideration for this acquisition is up to $1.15 billion. This includes an upfront payment of $1 billion, with an additional $150 million milestone payment contingent upon regulatory approval. GSK will also be responsible for making success-based milestone payments and tiered royalties for IDRX-42 owed to Merck KGaA, Darmstadt, Germany.

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