GSK Bolsters Gastrointestinal Cancer Portfolio with $1.15B Acquisition of IDRx
In a strategic move to expand its oncology pipeline, GSK plc (LSE/NYSE: GSK) announced on Tuesday, it has entered into a definitive agreement to acquire IDRx, Inc., a Boston-based clinical-stage biopharmaceutical company focused on precision therapeutics for gastrointestinal stromal tumours (GIST). The transaction, valued at up to 1.15 billion, includes an upfront payment of $1 billion and an additional $150 million contingent upon regulatory milestones.
Key Asset: IDRX-42 – A Potential Best-in-Class KIT TKI for GIST
The acquisition centers on IDRX-42, a highly selective KIT tyrosine kinase inhibitor (TKI) designed to address critical gaps in GIST treatment. GIST, the most common subtype of soft tissue sarcoma, is primarily driven by KIT mutations, with approximately 80% of cases linked to primary (activating) mutations in exons 9 and 11. Despite existing therapies, 90% of first-line patients develop secondary (resistance) mutations in exons 13 and 17, leading to relapse and limited therapeutic options.
Current TKIs fail to comprehensively inhibit the full spectrum of KIT mutations, leaving a significant unmet medical need. IDRX-42 has demonstrated potent activity against all key primary and secondary KIT mutations, positioning it as a potential best-in-class therapy with improved tolerability and efficacy.
Clinical Data from StrateGIST 1 Trial Shows Promising Anti-Tumour Activity
Recent findings from the ongoing Phase I/Ib StrateGIST 1 trial were presented at the Connective Tissue Oncology Society (CTOS) 2024 Annual Meeting, reinforcing IDRX-42’s clinical potential. Among 87 efficacy-evaluable patients with advanced GIST (second-line or later), the objective response rate (ORR) by modified RECIST v1.1 was 29%, including 1 complete response (CR) and 24 partial responses (PRs). Notably, in patients with only one prior line of therapy, the ORR reached 53% (n=15), with 1 CR and 7 PRs. Durability data were also encouraging, with confirmed responses post-data cut. The safety profile was manageable, with treatment-related adverse events (TRAEs) primarily low-grade at the recommended Phase Ib dose.
Strategic Fit for GSK’s Expanding GI Cancer Portfolio
The acquisition aligns with GSK’s strategy to target validated pathways in high-need oncology indications.
Luke Miels, Chief Commercial Officer, GSK, emphasised:
“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.”
Tony Wood, Chief Scientific Officer, GSK, added:
“We are excited by 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. We look forward to accelerating its development in 2025 to redefine treatment.”
Tim Clackson, CEO, IDRx, underscored the significance of the partnership:
“We are looking forward to working with GSK to advance IDRX-42 for patients with GIST given there have been no major advances to the standard of care for almost 20 years. Combining our experience to date with GSK’s expertise in GI cancers, global clinical development capability, and strong commercial presence in oncology will help to accelerate the development of this novel medicine for patients.”
Financial and Transaction Details
Under the agreement, GSK will acquire 100% of IDRx’s equity, including options and incentive equity. The $1.15 billion total consideration includes an upfront payment of $1 billion with potential for an additional $150 million success-based regulatory approval milestone payment. Additionally, GSK will assume success-based milestone payments and tiered royalties owed to Merck KGaA, Darmstadt, Germany, related to IDRX-42.
The transaction is subject to customary closing conditions, including Hart-Scott-Rodino Act clearance in the U.S. Centerview Partners LLC acted as exclusive financial advisor to IDRx, with Goodwin Procter LLP providing legal counsel. GSK engaged Leerink Partners LLC as its exclusive financial advisor.
GSK’s Broader GI Cancer Strategy and Future Development
This acquisition strengthens GSK’s presence in gastrointestinal cancers, complementing ongoing programs such as dostarlimab, an investigational PD-1 inhibitor, and GSK5764227 (GSK’227), a B7-H3-targeted antibody-drug conjugate. The addition of IDRX-42 aligns with GSK’s portfolio approach of identifying best-in-class molecules with targeted mechanisms of action. IDRX-42 has received Fast Track designation from the U.S. FDA for the treatment of GIST post-imatinib progression, along with Orphan Drug designation for GIST treatment. GSK plans to accelerate development in 2025, with the potential to redefine GIST therapeutic standards and address a critical unmet need in oncology.
This acquisition underscores GSK’s commitment to advancing precision oncology, particularly in high-need GI cancers. With IDRX-42’s compelling early data and best-in-class potential, GSK is poised to address a critical gap in GIST treatment, reinforcing its 2031 growth ambitions and delivering innovative therapies to patients worldwide.
Lead Image Credits: “Gastrointestinal stromal tumour” Nephron, CC BY-SA 3.0, via Wikimedia Commons
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