Ideaya Biosciences initiates monotherapy expansion in IDE161 trial

Ideaya Biosciences announces initiation of a Phase 1 monotherapy expansion in the first-in-human clinical trial evaluating IDE161. The Phase 1 first-in-human clinical trial is evaluating the safety, tolerability, pharmacokinetic and pharmacodynamic properties and preliminary efficacy of IDE161 in patients having tumors with homologous recombination deficiency, or HRD. Early clinical data from the dose escalation cohorts showed dose-dependent pharmacodynamic modulation of poly-ADP ribose proteins in peripheral blood, demonstrating IDE161 target engagement. These clinical data also demonstrated IDE161 exposure levels in humans which correlate to preclinical exposures that were efficacious, achieving tumor regressions in xenograft models. The Phase 1 expansion is based on preliminary tumor shrinkage observed in multiple HRD solid tumor patients, including an BRCA1/2 endometrial cancer subject with a first imaging assessment of 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. The company is also continuing to evaluate the optimal move forward dose for Phase 2 expansion. The expansion portion of the Phase 1 trial will include patients having HRD-associated breast cancer and ovarian cancer, as well as a basket of other selected solid tumors. The breast cancer focus is on estrogen receptor positive, human epidermal growth factor receptor 2 negative, HRD+ tumors, which represent approximately 10% to 14% of breast cancer patients. The ovarian cancer focus represents approximately 50% of ovarian cancer where HRD is observed. Ideaya is targeting clinical program updates for IDE161 in the second half of 2023.