Inclusion Criteria:

          -  Male or female and ≥18 years-of-age at the time of signature of the informed consent

          -  Confirmed advanced solid tumors resistant or refractory to standard treatment

          -  Eastern Cooperative Oncology Group (ECOG) Performance Status score of 0 or 1.

          -  Measurable disease as per RECIST v1.1

          -  Next generation sequencing (NGS) report obtained in CLIA-certified or equivalent
             laboratory demonstrating eligible tumor biomarkers.

          -  Submission of available tumor tissue or willingness to have a biopsy performed if safe
             and feasible

          -  Acceptable hematologic and organ function at screening

          -  Negative pregnancy test for women of childbearing potential at Screening and prior to
             first study drug.

          -  Ability to swallow and retain oral medications.

        Exclusion Criteria:

          -  Prior therapy with an ATR or DNA-dependent protein kinase (DNA-PK) inhibitor.

          -  Chemotherapy, small molecule anticancer or biologic anticancer therapy given within 10
             days or 5 half-lives (whichever is longer), prior to first dose of study drug.

          -  Use of radiotherapy (except for palliative reasons) within 7 days prior to first dose
             of study drug.

          -  History or current condition, therapy, or laboratory abnormality that might confound
             the study results, or interfere with the patient's participation for the full duration
             of the study treatment.

          -  No other anticancer therapy is to be permitted while the patient is receiving study
             treatment.

          -  Major surgery ≤28 days or minor surgical procedures ≤7 days prior to first study
             treatment dose.

          -  Uncontrolled, symptomatic brain metastases.

          -  Uncontrolled high blood pressure

          -  History of myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) diagnosis

          -  Presence of other known active invasive cancers.

          -  Pregnant or breastfeeding women.

          -  Psychological, familial, sociological, or geographical conditions that do not permit
             compliance with the study protocol and/or follow-up procedures outlined in the
             protocol.