Clinical-stage biopharmaceutical company Accent Therapeutics announced on Thursday that it will present its Phase 1/2 study of the first-in-class oral DHX9 inhibitor, ATX-559, at the 2025 American Society of Clinical Oncology Annual Meeting, held from 30 May to 3 June 2025 in Chicago, Illinois.

This Phase 1/2, open-label, dose-escalation and expansion study is designed to evaluate multiple doses of ATX-559 in solid tumour patients, with expansion cohorts of patients with advanced or metastatic BRCA-1 and/or BRCA-2-deficient breast cancer and microsatellite instability-high (MSI-H) and/or deficient mismatch repair (dMMR) solid tumours.

Primary endpoints include identification of the recommended Phase 2 dose (RP2D) and assessment of the safety and tolerability of ATX-559.

ATX-559 is a first-in-class potent and selective inhibitor of DHX9, a novel and previously undrugged RNA and DNA/RNA helicase, shown to have a significant role in tumours with high levels of replication stress.