The purpose of this study is to assess the safety and effectiveness of ATRN-119 through the performance of a Phase 1/2a, open-label, safety, PK, and preliminary efficacy study of oral ATRN-119 in patients with advanced solid tumors.

Inclusion Criteria:

• DNA damage response (DDR) mutations documented in the past medical record or confirmed during the screening period.
• Measurable disease defined by RECIST 1.1.
• Life expectancy ≥ 3 months.
• Subject must be capable of oral administration of study medication.

Exclusion Criteria:

• Patient has had a cytotoxic chemotherapy, immunotherapy, radiotherapy or other targeted therapies within 4 weeks.
• Surgical procedure performed within 7 days prior to first scheduled dose of ATRN-119.
• Concomitant treatment with strong inhibitors or inducers of CYP3A4 and CYP2D6.
• Known human immunodeficiency virus infection (HIV).
• Subjects with active viral or bacterial infections and/or receiving systemic antibiotics or anti-viral medications.
• Current or past diagnosis of leukemia within the past 5 years.
• Prior radiotherapy at the target lesion unless there is evidence of disease progression.
• Known CNS metastases or clinical evidence of CNS involvement that is not stable for previous 1 month by radiology documentation (magnetic resonance imaging [MRI] brain).
• History of non-malignant gastronintestinal (GI) bleeding, gastric stress ulcerations, or peptic ulcer disease within the past 3-months.
• Patient has uncontrolled hypertension at time of enrollment.
• Complete left bundle branch block (LBBB), bifascicular block (right bundle branch block [RBBB] with either left anterior hemiblock or left posterior hemiblock).
• Any clinically significant ST segment and/or T-wave abnormalities.
• Myocardial infarction or unstable angina pectoris within 6 months prior to starting study medication.