Inclusion Criteria:

          1. Subjects ≥18 years of age for solid tumor; in the case of midline carcinoma with NUT
             rearrangement. subjects may be ≥16 years of age.

          2. Histopathologically confirmed diagnosis of an advanced solid tumor such as breast
             cancer or midline carcinoma with NUT rearrangement, that has progressed despite
             standard therapy, or for which no standard therapy exists. For enrollment in the
             expansion cohorts, histopathological confirmation of triple-negative breast cancer or
             high-grade serous ovarian cancer is required.

          3. Measurable or evaluable disease.

          4. Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2.

          5. Recovery to Grade 1 or baseline of any toxicity due to prior systemic treatments or
             radiotherapy (excluding alopecia).

        Exclusion Criteria:

          1. Systemic anticancer therapy within three weeks of study entry, except for nitrosoureas
             or mitomycin C within six weeks.

          2. Radiotherapy within one week prior to starting study treatment.

          3. Other investigational agent(s) within 21 days prior starting to study treatment.

          4. Symptomatic central nervous system (CNS) involvement or lymphangitic metastasis.
             Stable or improving CNS disease that is not under active treatment after receipt of
             adequate therapy is allowed.

          5. Uncontrolled or severe cardiovascular disease, including myocardial infarction or
             unstable angina within six months prior to study treatment, New York Heart Association
             (NYHA) Class II or greater congestive heart failure, serious arrhythmias requiring
             medication for treatment, clinically significant pericardial disease or cardiac
             amyloidosis.