Inclusion Criteria:

          -  Has a histopathologically documented locally advanced or metastatic head and neck,
             gastric, or esophageal cancer, or the other types of solid tumors.

          -  Has a relapsed or refractory disease that is not amenable to curative standard
             therapy.

          -  Is 18 years of age or older (or complies with country-specific regulatory
             requirements, at least 20 years of age in Japan).

          -  Has an Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0-1, with no
             deterioration for two weeks.

          -  Has a measurable disease based on Response Evaluation Criteria in Solid Tumors
             (RECIST) version 1.1.

          -  Has adequate organ function within 7 days before enrollment.

          -  Is able to provide written informed consent and is willing and able to comply with the
             protocol.

        Exclusion Criteria:

          -  Has a concurrently active second malignancy, other than adequately treated
             non-melanoma skin cancers, in situ melanoma or in situ cervical cancer. Participants
             with history of the second malignancy have been disease-free for <3 years.

          -  Has a history of (non-infectious) interstitial lung disease (ILD) that required
             steroids, currently has ILD, or when suspected ILD cannot be ruled out by imaging at
             screening.

          -  Has a history of severe pulmonary compromise or requirement of supplemental oxygen
             within 6 months before enrollment.

          -  Has active hepatitis B or hepatitis C virus infection.

          -  Has received prior immunotherapy with a Grade 3 or higher, or any unresolved ≥Grade 2
             immune-related adverse event.