Inclusion Criteria:

   1. Signed informed consent

   2. ≥ 18 years of age

   3. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

   4. Adequate organ and bone marrow function

   5. Has measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) v1.1.

   6. Have advanced (metastatic/unresectable) cancers in one of the following:

      1. Histologically or cytologically confirmed urothelial cancer

      2. Histologically or cytologically confirmed poorly differentiated neuroendocrine
      carcinoma

      3. Histologically or cytologically confirmed homologous recombination
      deficient-positive malignancies agnostic, which may include endometrial, biliary
      tract, urothelial, breast (TNBC or HR+HER2- breast cancer), pancreas, gastric, or
      esophageal solid tumors with preidentified germline and/or somatic pathogenic
      mutation

   7. Adequate contraceptive precautions

Exclusion Criteria:

   1. Known symptomatic central nervous system (CNS) metastasis requiring steroids

   2. History of prior malignancy within 2 years of enrollment

   3. Clinically significant cardiovascular disease

   4. Active infection requiring systemic therapy

   5. Significant non-neoplastic liver disease

   6. Prior treatment with trabectedin or lurbinectedin

   7. Treatment with an investigational agent within 4 weeks of enrollment

   8. Received live vaccine with 4 weeks of first dose

   9. Prior allogeneic bone marrow or solid organ transplant

10. Positive hepatitis B virus (HBV) or hepatitis C virus (HCV) infection at screening

11. Positive human immunodeficiency virus (HIV) infection at screening