Main Inclusion Criteria:

          -  Male or female patients aged ≥ 18 years.

          -  Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1.

          -  Patients must have measurable disease (at least one unidimensional measurable lesion
             by Computed tomography [CT] or Magnetic resonance imaging [MRI]) per Response
             evaluation criteria in solid tumors (RECIST) 1.1, and following histologically
             confirmed, advanced or metastatic solid tumors:

               -  Dose escalation: All solid tumor types with a likelihood of sensitivity to
                  immunotherapy, as judged by the investigator.

               -  Expansion of Bapotulimab in combination with pembrolizumab in Head and neck
                  squamous cell carcinoma (HNSCC): recurrent or metastatic head and neck squamous
                  cell carcinoma IO-naïve PDL1+/ CPS≥1(PD-L1: Programmed death ligand 1; CPS:
                  Combined positive score).

          -  Provision of archival tumor tissue at screening is mandatory for all patients in dose
             escalation.

          -  For dose escalation, patients: must have received standard therapy or have no standard
             therapy available or patients have actively refused any treatment which would be
             regarded standard. Or in the opinion of investigator have been considered ineligible
             for a particular form of standard therapy on medical grounds.

          -  Adequate bone marrow, liver and renal function.

          -  Adequate cardiac function, measured by echocardiography.

        Main Exclusion Criteria:

          -  History of severe immune related adverse effects from prior immunotherapy (CTCAE v.5.0
             Grade 4; CTCAE v.5.0 Grade 3 requiring treatment > 4 weeks), except hypothyroidism
             clinically stable on hormone replacement treatment and controlled type 1 diabetes.

          -  Severe (CTCAE v.5.0 Grade ≥ 3) infections within 4 weeks before the first study drug
             administration, including but not limited to hospitalization for complications of
             infection, bacteremia, or severe pneumonia. Clinically active infections (CTCAE v.5.0
             > Grade 1) within 2 weeks before the first study drug administration.

          -  Previous or active myocarditis/myositis in history (independent of cause)

          -  Active or history of autoimmune disease.

          -  Known human immunodeficiency virus (HIV) infection.

          -  Active hepatitis B virus (HBV) or hepatitis C virus (HCV) infection.

          -  Treatment with systemic immunosuppressant medications within 2 weeks before the first
             study drug administration.

          -  Ongoing or previous anti-cancer treatment or any immunostimulatory treatment including
             but not limited to interferons (IFNs), interleukin (IL)-2 and agonists for members of
             the tumor necrosis factor (TNF) receptor superfamily (e.g. 4-1BB) within 4 weeks
             before the first study drug administration.

          -  For dose expansion cohort of Bapotulimab in combination with pembrolizumab in HNSCC:
             has progressive disease (PD) within six (6) months of completion of curatively
             intended systemic treatment for locoregionally advanced HNSCC.