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Ideaya, GSK Cleared to Begin Phase I Trial of Werner Helicase Inhibitor in MSI-High Tumors

NEW YORK – Ideaya Biosciences on Monday said it has been cleared by the US Food and Drug Administration to begin a Phase I trial of its Werner helicase inhibitor IDE275 in patients with microsatellite instability-high (MSI-high) solid tumors.

The investigational new drug application is sponsored by GSK, which is codeveloping the drug with Ideaya. The companies plan to evaluate IDE275, also called GSK959, as both a monotherapy agent and in combination with a PD-1 inhibitor in a Phase I clinical trial for patients with MSI-high tumors. The Phase I trial is expected to begin in Q4 2024.

IDE275 is being developed by Ideaya and GSK under a 2020 collaboration focused on developing treatments that interrogate synthetic lethality including Ideaya's MAT2A, pol theta, and Werner helicase programs. GSK has an exclusive global license to develop and commercialize the Werner helicase program and is responsible for leading clinical development as well as contributing 80 percent of global R&D costs, with the remaining costs covered by Ideaya.

Acceptance of the IND by the FDA will trigger a $7 million milestone payment to Ideaya, and the firm may receive an additional $10 million milestone payment upon initiation of a Phase I clinical dose expansion. South San Francisco, California-based Ideaya also is eligible to potentially receive up to $465 million in further later-stage development and regulatory milestones from GSK. Upon commercialization, it would also be eligible to receive up to $475 million of commercial milestones, 50 percent of US net profits, and tiered royalties on global non-US net sales of IDE275, the firm noted.

Ideaya and GSK found in preclinical studies that IDE275 demonstrated robust and selective synthetic lethality in the MSI-high biomarker setting in mouse models and patient-derived xenografts.

"The robust preclinical efficacy observed by IDE275 selectively in the MSH-high biomarker setting, including monotherapy regressions, provides a double-digit percent prevalence target patient population across several major solid tumor types, including endometrial, colorectal and gastric cancer," Ideaya CEO Yujiro Hata said in a statement.

Ideaya's pipeline also includes PKC inhibitor darovasertib, MAT2A inhibitor IDE397, PARG inhibitor IDE161, and pol theta inhibitor IDE705.