• 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) (except nasopharyngeal cancer)

∙ Esophageal squamous cell carcinoma (SCC)

∙ Triple negative breast cancer (TNBC)

⁃ 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

⁃ Participants must have PD-L1 expression based on historical testing

• 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 HNSCC

∙ NSCLC

⁃ Participants must have histologically or cytologically-confirmed NSCLC. Participants with SCC and non--SCC histology are eligible. Note: Participants with a neuroendocrine component or histology are not eligible.

∙ Esophageal SCC

∙ Ovarian cancer

∙ Melanoma

∙ TNBC

∙ Gastric cancer

⁃ Participants must have been previously tested for PD-L1 expression and should have PD-L1 expression ≥1 or \<1 by CPS or TPS based on historical testing

• Part D and Part E:

‣ Participants must have histologically or cytologically-confirmed disease of the HNSCC or NSCLC

⁃ Participants must have PD-L1 expression based on historical testing

⁃ Participants with NSCLC; PD-L1 expression ≥ 1% by TPS

⁃ Participants with HNSCC; PD--L1 expression ≥1 by CPS

• Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1

• Measurable disease per RECIST v1.1 at baseline