GSK acquires IDRx in $1.15bn GIST therapy deal
GlaxoSmithKline (GSK) has entered into an agreement to acquire Boston-based IDRx for up to $1.15 billion, securing rights to IDRX-42, a highly selective KIT tyrosine kinase inhibitor (TKI) designed to treat gastrointestinal stromal tumours (GIST). The deal comprises an upfront payment of $1 billion and a potential $150 million regulatory milestone payment.
Recent data from the phase I/Ib StrateGIST 1 trial presented at CTOS 2024 showed promising anti-tumour activity. Among patients with second-line or greater GIST, the objective response rate by modified RECIST v1.1 was 29% (n=87), including one complete response and 24 partial responses. Notably, in patients who received only one prior line of therapy, the response rate increased to 53% (n=15).
Mechanism targets treatment resistance
GIST predominantly manifests in the gastrointestinal tract, with 80% of cases driven by mutations in the KIT gene leading to tumour cell proliferation and survival. A significant clinical challenge arises as approximately 90% of patients treated in the first-line setting develop secondary KIT mutations, typically resulting in relapse. Currently available TKIs do not inhibit the complete spectrum of clinically relevant primary and secondary mutations in KIT.
IDRX-42 has demonstrated activity against all key primary and secondary KIT mutations, potentially addressing this therapeutic gap. The compound’s high selectivity may also confer improved tolerability compared to existing treatments.
Strategic portfolio expansion
Luke Miels, Chief Commercial Officer at GSK, said: “IDRX-42 complements our growing portfolio in gastrointestinal cancers. This acquisition is consistent with our approach of acquiring assets that address validated targets and where there is clear unmet medical need, despite existing approved products.”
The acquisition aligns with GSK’s expanding oncology portfolio, which includes ongoing trials with dostarlimab and GSK5764227, a B7-H3-targeted antibody-drug conjugate. The transaction supports GSK’s growth ambitions through 2031 and beyond.
Regulatory status and development plans
IDRX-42 has received Fast Track designation from the US Food and Drug Administration for treating patients with GIST after disease progression on or intolerance to imatinib, along with Orphan Drug designations. GSK will be responsible for success-based milestone payments and tiered royalties owed to Merck KGaA, Darmstadt, Germany.
The transaction remains subject to customary conditions, including regulatory clearances under the Hart-Scott-Rodino Act in the United States. Approximately 80,000 to 120,000 patients are diagnosed with GIST annually worldwide, highlighting the significant potential market for this therapeutic advancement.