Inclusion Criteria:

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

          -  Has at least 1 measurable lesion according to Response Evaluation Criteria in Solid
             Tumors (RECIST) Version 1.1.

          -  Has adequate cardiac, hematopoietic, renal and hepatic functions

          -  Has an adequate treatment washout period prior to start of study treatment

        Additional Inclusion Criteria for Part 1 (Dose Escalation)

          -  Has a pathologically documented advanced/unresectable or metastatic head and neck
             squamous cell carcinoma, esophageal squamous cell carcinoma, squamous and
             adenocarcinoma non-small cell lung cancer (NSCLC), bladder cancer, sarcoma,
             endometrial cancer, melanoma, prostate cancer, breast cancer that is refractory to or
             intolerable with standard treatment, or for which no standard treatment is available.

        Additional Inclusion Criteria for Part 2 (Dose Expansion)

          -  Has a pathologically documented advanced/unresectable or metastatic head and neck
             squamous cell carcinoma, esophageal squamous cell carcinoma, squamous-NSCLC that is
             refractory to or intolerable with standard treatment, or for which no standard
             treatment is available. Additional or alternative indications may be added to
             expansion cohorts based on preliminary signals of activity in dose escalation via a
             protocol amendment.

        Exclusion Criteria:

          -  Has prior treatment with B7-H3 targeted agent.

          -  Has prior treatment with an antibody drug conjugate that consists of an exatecan
             derivative that is a topoisomerase I inhibitor (e.g., trastuzumab deruxtecan).

          -  Has multiple primary malignancies, except adequately resected non-melanoma skin
             cancer, curatively treated in situ disease, or other solid tumors curatively treated,
             with no evidence of disease for ≥3 years.

          -  Has a medical history of myocardial infarction, symptomatic congestive heart failure
             (CHF) (New York Heart Association classes II-IV), unstable angina or serious cardiac
             arrhythmia.

          -  Has an uncontrolled infection requiring systemic therapy.

          -  Has clinically significant pulmonary compromise or requirement for supplemental
             oxygen.

          -  Has substance abuse or any other medical conditions that would increase the safety
             risk to the subject or interfere with participation of the subject or evaluation of
             the clinical study in the opinion of the Investigator.