Accent Therapeutics, a clinical-stage biopharmaceutical company pioneering novel, targeted, small molecule cancer therapeutics, announced new preclinical data on its first-in-class oral DHX9 inhibitor, ATX-559, and its potentially best-in-class KIF18A inhibitor, ATX-295, in poster and oral presentations, respectively, at the AACR Annual Meeting 2025 taking place April 25-30 in Chicago, Illinois. ATX-559 and ATX-295 are currently under investigation in Phase 1/2 clinical trials.

"Our presentations at the AACR annual meeting showcase the outputs of Accent's precision oncology approach to drug development, with strong foundational data that inform our current and future clinical development plans for our lead programs, ATX-559 and ATX-295," said Serena Silver, Ph.D., Chief Scientific Officer of Accent Therapeutics. "These preclinical data reinforce our assets therapeutic potential across several cancer indications with high unmet need."

The company's poster presentation includes preclinical data supporting continued clinical evaluation of ATX-559, a first-in-class potent, selective, and orally bioavailable small-molecule inhibitor of DHX9. Results within characterize the compound's activity in cancer cell lines with genomic instability and elevated replication stress spanning several indications, including dMMR/MSI-H colorectal cancer and BRCA-altered triple negative breast cancer, and in subtypes of lung, gastric, ovarian, and prostate cancers. ATX-559 was shown to be well tolerated in vivo, leading to robust and dose dependent tumor growth inhibition and regression in BRCA deficient breast cancer and dMMR/MSI-H cell- and patient-derived xenograft models.

ATX-559 is currently under investigation in a first-in-human, Phase 1/2, open-label, dose-escalation and expansion study, with a focus on advanced or metastatic patients with BRCA-1 and/or BRCA-2-deficient breast cancer or MSI-H and/or dMMR solid tumors (NCT06625515). Additional undisclosed solid tumor indications undergoing replicative stress and representing significant patient populations may be explored either in parallel or in subsequent studies.

For Accent's second lead program, preclinical data included in the company's oral presentation demonstrates sensitivity to KIF18A inhibition across several solid tumor indications with high chromosomal instability, signaling significant opportunity for patient impact by leveraging KIF18A as a selective oncology target. Results further characterize ATX-295 as a potent and selective KIF18A inhibitor capable of inducing mitotic arrest, cell death, and anti-tumor activity in cancer models with high chromosomal instability. Studies in relevant cellular and xenograft models exhibiting whole genome doubling confirm selective anti-cancer activity, providing rationale for whole genome doubling as a predictive biomarker of ATX-295 sensitivity in ovarian and triple negative breast cancer.

Accent recently initiated clinical evaluation of ATX-295 in a first-in-human Phase 1/2 open-label, dose-escalation and expansion study designed to evaluate the molecule's safety, tolerability, and preliminary efficacy in patients with locally advanced or metastatic solid tumors, including high-grade serious ovarian cancer (NCT06799065).