Inclusion Criteria:

          -  Signed informed consent

          -  Subjects must be ≥ 18 years of age

          -  Subject with advanced or metastatic solid tumors that is not amenable to surgical
             resection and is not eligible or has refused other approved therapeutic options that
             have demonstrated clinical benefit.

          -  Histologically confirmed HER2 expression.

          -  Eastern Cooperative Oncology Group (ECOG) Performance Status ≤ 1

          -  Measurable or non-measurable evaluable disease according to RECIST 1.1

          -  Adequate hematologic and end-organ function at baseline

          -  Oxygen saturation via pulse oxygenation ≥ 90% at rest on room air

        Exclusion Criteria:

          -  Untreated central nervous system (CNS) metastases

          -  Multiple primary malignancies

          -  Clinically significant cardiovascular disease such as New York Heart Association
             (NYHA) cardiac disease (class III or greater)

          -  Pregnant or lactating female

          -  Serious, uncontrolled medical disorder that, in the opinion of the Investigator, would
             impair the ability of the subject to receive study treatment

          -  History of autoimmune or immune mediated symptomatic disease

          -  Any anti-cancer chemotherapy or targeted small molecule therapy, or experimental
             therapy/device within 4 weeks or 5 half-lives of the drug prior to planned start of
             the study