Inclusion Criteria:  Parts A and B:  Participants must have one of the following histologically- or cytologically-confirmed metastatic or unresectable solid tumor types  Non-small cell lung cancer (NSCLC) Head and neck squamous cell carcinoma (HNSCC) Esophageal squamous cell carcinoma (SCC) Participants must have disease that is relapsed or refractory, that has progressed on approved therapies, be intolerant to or refused such therapies, or such and therapies are contraindicated and in the judgement of the investigator, should have no appropriate SoC therapeutic option  Part C:  Participants must have disease that is relapsed or refractory or be intolerant to SoC therapies and must have one of the following tumor types  HNSCC  Participants with HNSCC must have histologically or cytologically-confirmed SCC of the head and neck  NSCLC Esophageal SCC Ovarian cancer Melanoma Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1 Measurable disease per RECIST v1.1 at baseline  Exclusion Criteria:  History of another malignancy within 3 years of first dose of study treatment or any evidence of residual disease from a previously diagnosed malignancy.  Known active central nervous system metastases. Participants with previously-treated brain metastases may participate provided they:  Are clinically stable for at least 4 weeks prior to study entry after brain metastasis treatment Have no new or enlarging brain metastases And are off of corticosteroids prescribed for symptoms associate with brain metastases for at least 7 days prior to first dose of study treatment Lepto-meningeal disease Prior treatment with an anti-PD-L1 agent within the last 6 months. Previous receipt of an monomethylauristatin E (MMAE)-containing agent. Pre-existing neuropathy ≥Grade 2 per National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) v5.0.  There are additional inclusion criteria. The study center will determine if criteria for participations are met.