A Phase 1 interventional study of ATX-559 in Advanced Solid Tumors, Breast Cancer Recurrent and Colorectal Cancer Metastatic, sponsored by Accent Therapeutics. Terminated at 5 sites in United States. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-02-24.
Sponsored by Accent Therapeutics · Phase 1, Interventional, and Treatment
The goal of this study is to identify a safe and tolerated dose of the orally administered DHX9 inhibitor ATX-559. In addition, this study will evaluate the pharmacokinetics, pharmacodynamics and preliminary antitumor activity of ATX-559 in patients with advanced solid tumors and molecularly defined cancers.
ATX-559 is an oral drug that inhibits a protein called DHX9, a multi-functional RNA helicase that is involved in the maintenance of genomic stability by resolving DNA/RNA secondary structures that may lead to DNA replication stress and DNA damage in certain molecularly defined cancers. ATX-559 has been shown preclinically to induce robust anti-tumor activity of a variety of different solid tumors, including models with BRCA deficiency and microsatellite instability-high (MSI-H) and/or deficient mismatch repair (dMMR).
This is a first-in-human, Phase 1, open-label, single-arm, dose-escalation and expansion study to:
Evaluate the safety profile of ATX-559 and determine the recommended phase 2 dose (RP2D). In addition, the study aims to characterize the PK, PD, and preliminary anti-tumor activity of orally administered ATX-559. Exploratory objectives include examination of biomarker responses in relationship to ATX-559 exposure.
Patients with molecularly selected locally advanced or metastatic solid tumors (for example, BRCA1- or BRCA2-deficient breast cancer and solid tumors with microsatellite instability (MSI-H) and/or deficient mismatch repair (dMMR) will be enrolled to preliminarily assess the anti-tumor effect, and further examine the safety and PK of ATX-559 at the RP2D.
2,457 studies on the registry are indexed under Colonic Neoplasms; 458 are open to participants now.
This study's enrollment of 17 is below the median of 75 across 1,711 interventional studies indexed under Colonic Neoplasms.
Browse Colonic Neoplasms studies →Accent Therapeutics is the lead sponsor of 2 studies on the registry; 1 is open to participants now.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria:
Key Exclusion Criteria:
Other inclusion and exclusion criteria as defined in the study protocol
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Relapsed: the illness came back after treatment had worked. Refractory: it did not respond to treatment, or stopped responding while still on it.
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Relapsed and refractory
Relapsed: the illness came back after treatment had worked. Refractory: it did not respond to treatment, or stopped responding while still on it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HER2
HER2 is a protein, made from the ERBB2 gene, that drives the growth of some cancers. A study may look for a level of the protein, extra copies of the gene, or a particular change in it.
In breast cancer, protein tests are read as HER2-positive, HER2-low or HER2-negative; other cancers use their own rules. Check which test result the study requires.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Brain metastases
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Subjects will be enrolled at various doses or schedules of ATX-559 to identify the RP2D
Drug: ATX-559
Drug: ATX-559
Drug: ATX-559
DHX9 tablets will be taken orally
Recommended phase 2 dose (RP2D) and/or maximum tolerated dose (MTD) of ATX-559
Identification of a tolerable and safe dose for expansion cohorts based on dose limiting toxicities
Time frame: 12 months
Safety and tolerability of ATX-559
Incidence of adverse events graded according to CTCAE v5.0
Time frame: 12 months
Preliminary evidence of antitumor activity
Objective response rate based on RECIST v1.1
Time frame: 12 months
Pharmacodynamic activity of ATX-559 in blood over time via measurement of circBRIP1 RNA levels
Time frame: 12 months
Maximum observed plasma concentration of ATX-559 (Cmax)
Time frame: 12 months
Calculated time to reach maximum observed plasma concentration (Tmax)
Time frame: 12 months
Calculated area under the plasma concentration-time curve of ATX-559 (AUC0-t)
Time frame: 12 months
Plan to share: No
No publications or documents are linked to this record.
Ran from Oct 2024 to primary completion in Jan 2026, 14 months.
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This study is terminated, as verified in Feb 2026. You cannot join it, but the record below documents what was studied.
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