Ideaya Biosciences (Nasdaq: IDYA) announced on April 6 that the first patient has been dosed in a Phase I dose-escalation trial of IDE574, an oral small molecule designed to inhibit both KAT6 and KAT7 lysine acetyltransferases, in patients with solid tumors including breast, prostate, colorectal, and lung cancer. The announcement marks a clinical milestone only; no safety or efficacy data have been reported.
The company stated that the Phase I trial is designed to evaluate safety, preliminary efficacy, and pharmacokinetics of IDE574 as a monotherapy in a dose-escalation format across the named solid tumor indications. No NCT registration number was publicly available at the time of this report.
The available numerical data are drawn entirely from preclinical studies. Ideaya reported single-digit to low-teen nanomolar cellular potency in target engagement assays against both KAT6 and KAT7, with approximately 350-to-2,000-fold selectivity over the KAT5 and KAT8 paralogs, which the company noted are required for normal cell function. In cell-derived xenograft and patient-derived xenograft models, IDE574 showed anti-tumor activity in tumors carrying 8p11 amplifications and ESR1 mutations, which the company said was superior to KAT6-selective inhibition alone. The data remain preclinical and have not been peer-reviewed in published form; a presentation at AACR 2026 was announced separately. ESR1 mutations, cited by Ideaya as a rationale for its breast cancer focus, are a known mechanism of resistance to endocrine therapy, as per published literature cited by the company.
IDE574 inhibits the acetyltransferase activity of KAT6 and KAT7, epigenetic regulators of cell identity and lineage commitment programs that the company describes as corrupted by oncogenic transformation. The KAT6/7 target class sits within a broader competitive context that includes KAT6-selective agents that have entered clinical evaluation; Ideaya's stated rationale for dual inhibition is that KAT6-selective inhibition alone produced inferior preclinical activity compared with simultaneous KAT6 and KAT7 blockade.
Spot something wrong? Report an issue with this article