IDEAYA Biosciences, Inc. announced that it has entered into a clinical trial collaboration and supply agreement with Merck (known as MSD outside the US and Canada) to evaluate IDE161, the company's investigational, potential first-in-class, small molecule poly (ADP-ribose) glycohydrolase, or PARG, inhibitor, in combination with KEYTRUDA® (pembrolizumab) Merck's anti-PD-1 therapy, in patients with microsatellite instability-, or MSI-, high and microsatellite stable, or MSS, endometrial cancer, in a Phase 1 clinical trial. IDE161 is a small molecule inhibitor targeting PARG, that is being evaluated in a Phase 1 clinical trial, which is currently in its monotherapy expansion stage. The trial is strategically focused on estrogen receptor positive (ER+), human epidermal growth factor receptor 2 negative (Her2-) breast cancer with HRD, as well as other solid tumors with HRD, such as endometrial cancer, colorectal cancer and prostate cancer.

In parallel, IDEAYA is continuing with a Phase 1 dose optimization. Of note, multiple partial responses by RECIST 1.1. and tumor shrinkage in priority solid tumor types were observed early in the Phase 1 dose escalation and dose expansion. IDE161 received the U.S. Food & Drug Administration Fast-Track designation for BRCA1/2 ovarian and breast cancers.

KEYTRUDA® is a registered trademark of Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, NJ, USA. Under the clinical trial collaboration and supply agreement, Merck will provide KEYTRUDA to IDEAYA, which will be the sponsor of the Phase 1 clinical combination trial. IDEAYA and Merck each retain all commercial rights to their respective compounds, including as monotherapy or as combination therapies.

The mechanistic rationale and preclinical data to support the IDE161 and PD-1 clinical combination will be provided as part of a future R&D update.