Pharma Focus America

IDEAYA Biosciences Initiates Phase 1 Expansion and Reports Preliminary Clinical Proof-of-Concept for IDE161, a PARG Inhibitor in HRD Solid Tumors

Monday, September 11, 2023

IDEAYA Biosciences, Inc. (NASDAQ: IDYA), a precision oncology company specializing in the development of targeted therapeutics, has announced the commencement of a Phase 1 expansion in the first-in-human clinical trial for IDE161 (NCT 05787587).

Dr. Darrin M. Beaupre, M.D., Ph.D., Chief Medical Officer at IDEAYA Biosciences, expressed their satisfaction with the advancement of IDE161, a potential pioneering PARG inhibitor, into the Phase 1 clinical trial's expansion phase. The company is enthusiastic about investigating IDE161's potential in patients with homologous recombination deficiency (HRD) in various priority tumor types, including ER+, Her2(-) breast cancer, and ovarian cancer subjects with HRD.

Yujiro S. Hata, Chief Executive Officer of IDEAYA Biosciences, noted that the clinical update on IDE161 marks the initial reporting of preliminary clinical proof-of-concept for a PARG inhibitor in HRD solid tumors. The company eagerly anticipates further evaluation of IDE161 as a monotherapy for HRD solid tumors with significant unmet medical needs.

The Phase 1 clinical trial is designed to evaluate the safety, tolerability, pharmacokinetic, pharmacodynamic properties, and preliminary efficacy of IDE161 in patients with HRD tumors. Initial clinical data from dose escalation cohorts demonstrated dose-dependent pharmacodynamic modulation of poly-ADP ribose (PAR) proteins in peripheral blood, indicating successful engagement of IDE161 with its target. These clinical findings also showed IDE161 exposure levels in humans that align with preclinical efficacy, including tumor regressions in xenograft models.

The decision to expand the Phase 1 trial was based on preliminary evidence of tumor shrinkage in multiple HRD solid tumor patients. This included a patient with BRCA1/2 endometrial cancer who exhibited a partial response in the target lesion, a complete response in the non-target lesion, and an 87% reduction in the CA-125 tumor marker (from 2,638 units/ml at baseline to 360 units/ml at 6 weeks). The company is actively determining the optimal dose for Phase 2 expansion. The expanded Phase 1 trial will encompass patients with HRD-associated breast cancer and ovarian cancer, as well as a selection of other solid tumors. The breast cancer focus will be on estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (Her2-), HRD+ tumors, representing approximately 10% to 14% of breast cancer patients. The ovarian cancer focus will include approximately 50% of ovarian cancer cases where HRD is observed. IDEAYA aims to provide clinical program updates for IDE161 in the second half of 2023.

IDE161 is a potent, selective, small-molecule inhibitor of PARG, a novel target within the same clinically validated pathway as poly (ADP-ribose) polymerase (PARP). IDEAYA presented preclinical data profiling IDE161 in a poster at the 2023 Annual Meeting of the American Association for Cancer Research (AACR) in April 2023. The IDE161 poster is available online on the company's website at

IDEAYA retains ownership or control of all commercial rights for IDE161, subject to certain economic obligations outlined in its exclusive worldwide license agreement with Cancer Research UK and the University of Manchester.

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