Testing ATX-559, a new oral drug, in patients with advanced solid tumors

A Phase 1/2, Open-Label, Dose-Escalation and Expansion First-In-Human Study of ATX-559, an Oral Inhibitor of the Helicase DHX9, in Patients With Locally Advanced or Metastatic Solid Tumors and Molecularly Defined Cancers

Phase 1 Interventional Accent Therapeutics · NCT06625515

This study is testing a new oral drug called ATX-559 to see if it is safe and helps people with advanced solid tumors, especially those with certain genetic markers, who have run out of other treatment options.

Quick facts

PhasePhase 1
Study typeInterventional
Enrollment100 (estimated)
Ages18 Years and up
SexAll
SponsorAccent Therapeutics Industry-sponsored
Locations4 sites (Oklahoma City, Oklahoma and 3 other locations)
Trial IDNCT06625515 on ClinicalTrials.gov

What this trial studies

This clinical trial aims to evaluate the safety and tolerability of ATX-559, an oral inhibitor of the DHX9 protein, in patients with advanced solid tumors and molecularly defined cancers. The study will assess the pharmacokinetics, pharmacodynamics, and preliminary anti-tumor activity of ATX-559 through a first-in-human, Phase 1, open-label, single-arm, dose-escalation design. Patients with specific tumor types, such as BRCA-deficient breast cancer and those with microsatellite instability-high (MSI-H) or deficient mismatch repair (dMMR), will be enrolled to determine the recommended phase 2 dose and explore biomarker responses. The trial will also include patients who have exhausted standard treatment options.

Who should consider this trial

Good fit: Ideal candidates include patients with advanced solid tumors, particularly those with BRCA1 or BRCA2 mutations or MSI-H/dMMR tumors, who have not responded to standard therapies.

Not a fit: Patients with clinically unstable central nervous system tumors or brain metastasis may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could provide a new treatment option for patients with advanced solid tumors that are currently difficult to treat.

How similar studies have performed: Other studies targeting similar molecular pathways have shown promise, suggesting potential for success with this approach.

Eligibility criteria

Show full inclusion / exclusion criteria
Key Inclusion Criteria:

* Patients with histologically confirmed solid tumors who have locally recurrent or metastatic disease
* Refractory to or relapsed after all standard therapies with proven clinical benefit, unless as deemed by the Investigator, the subject is not a candidate for standard treatment, there is no standard treatment, or the subject refuses standard treatment after expressing an understanding of all available therapies with proven clinical benefit
* For the expansion cohorts, participants must have histological confirmation of the specified tumor types:
* BRCA1 or BRCA2 deficient, HER2 negative metastatic breast cancer
* dMMR or MSI-H with unresectable or metastatic solid tumors
* There is no limit to the number of prior treatment regimens
* Have measurable or evaluable disease
* Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1

Key Exclusion Criteria:

* Clinically unstable central nervous system (CNS) tumors or brain metastasis
* Any other concurrent anti-cancer treatment
* Has undergone a major surgery within 3 weeks of starting study treatment
* Medical issue that limits oral ingestion or impairment of gastrointestinal function that is expected to significantly reduce the absorption of ATX-559
* Clinically significant (ie, active) or uncontrolled cardiovascular disease
* Unable to transition off strong or moderate CYP2C8 inhibitors or inducers
* Pregnancy or intent to breastfeed or conceive a child within the projected duration of treatment

Other inclusion and exclusion criteria as defined in the study protocol

Where this trial is running

Oklahoma City, Oklahoma and 3 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Advanced Solid TumorsBreast Cancer RecurrentColorectal Cancer MetastaticColon CancerRectal AdenocarcinomaEndometrial CancerMSI-high/dMMR tumorsBRCA1 mutation
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.