Accent Therapeutics Announces First Patient Dosed in Phase 1/2 Trial of Novel KIF18A Inhibitor ATX-295 and Receives FDA Fast Track Designation for Lead Assets ATX-295 and DHX9 Inhibitor ATX-559

First-in-human Phase 1/2 study initiated for ATX-295, a potential best-in-class oral inhibitor of KIF18A, focused on patients with advanced solid tumors including ovarian cancer 

FDA grants Fast Track designation to Accent's two lead clinical-stage programs – ATX-295 and ATX-559 – for the treatment of adult patients with advanced/metastatic platinum-resistant or refractory ovarian cancer, and unresectable/metastatic dMMR/MSI-H colorectal cancer post checkpoint inhibitor treatment, respectively

LEXINGTON, Mass., April 15, 2025 /PRNewswire/ -- Accent Therapeutics, a clinical-stage biopharmaceutical company focused on novel, targeted, small molecule cancer therapeutics, today announced that the first patient has been dosed in a first-in-human Phase 1/2 clinical trial evaluating the safety and tolerability of ATX-295, a potential best-in-class oral KIF18A inhibitor. In addition, the company has received Fast Track designation from the U.S. Food and Drug Administration (FDA) for ATX-295 for the treatment of adult patients with advanced/metastatic platinum-resistant or refractory ovarian cancer, and for ATX-559, a first-in-class potent and selective inhibitor of DHX9, for the treatment of adult patients with unresectable/metastatic dMMR/MSI-H colorectal cancer post checkpoint inhibitor treatment.

"Cancers with high chromosomal instability, such as in certain ovarian, breast, and lung cancers, collectively affect a large patient population but have limited treatment options. With ATX-295 entering the clinic, we are excited to translate multiple years of KIF18A research into the development of a potentially best-in-class program," said Jason Sager, M.D., Chief Medical Officer of Accent Therapeutics. "With the launch of our Phase 1/2 clinical trial of ATX-295, we now have two investigational drugs in the clinic, bringing us closer to achieving our mission of transforming cancer care. Additionally, receiving FDA Fast Track designation for both of our lead assets underscores the power of our approach and the potential for these investigational drugs to urgently address high unmet medical needs."

ATX-295 is a selective inhibitor of KIF18A, a mitotic kinesin motor protein critical for cell division in select tumors with chromosomal instability, but not in healthy cells. Accent has demonstrated that its novel, potent, and selective small molecule KIF18A inhibitor displays selective dose-dependent tumor growth inhibition in preclinical models, including in high grade serous ovarian cancer and triple negative breast cancer, supporting its advancement to the clinic.

The ATX-295 Phase 1/2 open-label, dose-escalation and expansion study (NCT06799065) is designed to evaluate the molecule's safety profile at multiple dose levels, assessing the tolerability, pharmacokinetics, pharmacodynamics, and preliminary efficacy of orally administered ATX-295. The trial is enrolling patients with locally advanced or metastatic solid tumors, including high-grade serious ovarian cancer.

The initiation of the Phase 1/2 ATX-295 study follows closely after Accent's initial clinical asset, ATX-559, a first-in-class oral inhibitor of DHX9, entered clinical evaluation in late 2024. Both clinical assets have been granted Fast Track status by the FDA. Fast Track designation is designed to facilitate the development and expedite the review of novel drug candidates that address serious conditions marked by unmet medical need, with the aim of accelerating patient access to novel treatment options.

Accent will present new preclinical data supporting the continued clinical assessment of ATX-295 and ATX-559 at the 2025 AACR Annual Meeting taking place April 25-30 in Chicago, Illinois. Accent will also present a trial-in-progress update on the ATX-559 Phase 1/2 clinical trial at the 2025 ASCO Annual Meeting taking place May 30 – June 3 in Chicago, Illinois.

About 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 play a critical role in tumors with high levels of replication stress (including breast, ovarian, colorectal, endometrial, gastric, and others), representing large patient populations with significant unmet medical need. DHX9 has been reported to play important roles in replication, transcription, translation, RNA splicing, RNA processing, and maintenance of genomic stability, making it a compelling novel oncology target. In addition to exploiting key tumor vulnerabilities in DNA repair deficient backgrounds (e.g., BRCA) and hyper-mutated states (e.g., MSI-H/dMMR), Accent is exploring the sensitivity of other tumor types to DHX9 inhibition, and the potential to combine DHX9 inhibitors with other cancer treatments to maximize its full potential for helping patients. Accent retains full worldwide rights to ATX-559, currently being evaluated in a Phase 1/2 clinical trial (NCT06625515), and the DHX9 program.

About ATX-295
Accent's second lead program, ATX-295, is a potential best-in-class inhibitor for KIF18A which may address a large patient population across several cancer indications, including ovarian and triple negative breast cancer (TNBC). KIF18A is a mitotic kinesin motor protein critical for cell division in select tumors with chromosomal instability, but not in healthy cells. KIF18A inhibitor treatment results in rapid cell death for cancers with an abnormal number of chromosomes (aneuploid) in vitro and in vivo, while cells with normal numbers of chromosomes (euploid) are unaffected. Accent retains full worldwide rights to the KIF18A program, currently being evaluated in a Phase 1/2 clinical trial enrolling solid tumor patients (NCT06799065).

About Accent Therapeutics
Accent Therapeutics is pioneering a new class of small molecule precision cancer therapies targeting critical intracellular dependencies that span multiple types of cancer. Building upon industry-leading expertise in RNA-modifying proteins (RMPs) and the systematic mapping of both the RMP space and adjacent high-value areas for drug discovery, the company employs a flexible model that allows for a diversity of approaches to developing potentially transformative biomarker-driven cancer medicines. Accent's therapies are designed for both novel and known, but suboptimally addressed, high-impact oncology targets with the potential to benefit large patient populations with significant unmet need. For more information on Accent's mission to translate extraordinary science into life-changing therapeutics for patients living with cancer, visit www.accenttx.com or follow us on LinkedIn.

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SOURCE Accent Therapeutics