Inclusion Criteria

        All Patients:

          -  Documentation of confirmed HPV 16+ cancer via genotype testing.

          -  ≥ 1 measurable lesion by imaging for tumor response following RECIST

          -  ECOG performance status of 0 to 1.

          -  Prior curative radiation therapy and prior focal palliative completed per
             protocol-specified wash-out windows.

          -  Screening laboratory values must meet protocol-specified criteria.

          -  Able to provide tumor tissue following last treatment, unless otherwise agreed.

        Treatment Group 1, Group 3, Group 5, Group 6, Group A, or Group D:

          -  Documentation of confirmed head and neck squamous cell carcinoma.

          -  Tumor progression or recurrence on standard of care therapy, including ≥ 1 systemic
             therapy.

        Treatment Group 2, Group 4, Group C, or Group F:

        • Tumor progression or recurrence on standard of care therapy, including ≥ 1 systemic
        therapy.

        Treatment Group B or Group E:

          -  Documentation of confirmed head and neck squamous cell carcinoma.

          -  Eligible, per standard of care, to receive immune checkpoint inhibitor.

        Anal Cancer Cohort:

          -  Documentation of confirmed HPV 16+ locally advanced or metastatic SCC of anal canal.

          -  Tumor progression or recurrence on standard of care therapy, including ≥1 systemic
             therapy.

        Imaging Sub-Study (for specific participants at Memorial Sloan Kettering Cancer Center
        only):

          -  Meeting requirements of inclusion criteria for Treatment Group 1 or Group 3.

          -  At least 1 non-irradiated measurable lesion documented through imaging.

        Exclusion Criteria:

        All patients:

          -  Untreated and/or symptomatic metastatic central nervous system disease, unless
             protocol-defined criteria is met.

          -  Any serious or uncontrolled medical disorder that, in the opinion of the Investigator,
             may increase the risk associated with study participation / treatment administration.

          -  Concurrent malignancy that is clinically significant or requires active intervention,
             unless protocol-defined criteria is met.

          -  Active, known or suspected, autoimmune or inflammatory disorders requiring
             immunosuppressive therapy.

          -  Any toxicities attributed to systemic prior anticancer therapy o that have not
             resolved to Grade 1 or baseline prior to the first administration of study drug,
             unless protocol-defined criteria is met.

          -  Not meeting the protocol-specified washout periods for prohibited medications.

          -  Prior anaphylactic or other severe reaction to human immunoglobulin or antibody
             formulation administration.

          -  Positive hepatitis B surface antigen (HBsAg) or hepatitis C virus (HCV) antibody,
             indicating acute or chronic infection.

          -  Known history of acquired immunodeficiency syndrome.

        For patients in Groups B or E and certain backfill cohorts:

          -  History of severe hypersensitivity reaction to or other contraindication to receiving
             immune checkpoint inhibitor.

          -  Allogenic tissue/solid organ transplant.

          -  History of/Presently having non-infectious pneumonitis requiring treatment.

        Imaging Sub-Study (for specific participants at Memorial Sloan Kettering Cancer Center
        only):

          -  Having splenic disorders or prior splenectomy, and can compromise protocol objectives
             per Investigator and/or Sponsor.

          -  Meeting requirements of exclusion criteria for Treatment Group 1 or Group 3