Inclusion Criteria:

- Age ≥18 years on the day the Informed Consent Form is signed.

- Histologically or cytologically confirmed R or M HNSCC. Eligible primary tumor
locations are oral cavity, hypopharynx, larynx or oropharynx (with documented
HPV-negative disease if presenting with OPSCC). Note: primary tumor location of
paranasal sinuses and nasopharynx, any histology are excluded.

- No prior systemic therapy administered in the R or M setting; and completed systemic
therapy >6 months prior if given as part of multimodal treatment for locoregionally
advanced disease in the adjuvant or definitive setting.

- Archival tumor tissue or willing to undergo pretreatment biopsy at Screening if
archival tissue is insufficient or unavailable.

- PD-L1 CPS ≥1 (by PD-L1 IHC 22C3 pharmDx assay).

- Measurable disease based on RECIST 1.1.

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

- Adequate organ function, as defined in the protocol.

Exclusion Criteria:

- Disease suitable for local therapy administered with curative intent.

- Prior treatment with anti-TGFβ therapy.

- Prior therapy with an anti-EGFR antibody (exception: radio sensitizing agents and
multimodal treatment for locoregionally advanced disease).

- Prior history of Grade ≥2 intolerance or hypersensitivity reaction to anti-EGFR
therapy or other murine proteins.

- Prior therapy with an immune checkpoint inhibitor completed within 6 months prior to
study treatment initiation.

- Progressive disease <6 months from completion of curative intent systemic therapy
for locoregionally advanced HNSCC.

- Life expectancy less than 3 months.

- Known active central nervous system metastases, history of spinal cord compression
from tumor involvement, a history of carcinomatous meningitis, or leptomeningeal
disease are excluded.

- Current active major bleeding, or a recent major bleeding episode within 4 weeks
prior to enrollment.

- Subject participated in another clinical study or received treatment with another
investigational drug must wait at least 5 half-lives of the treatment received or 4
weeks (whichever is shorter) following prior therapy.

- Active autoimmune disease requiring systemic treatment in the past 2 years.

- Subjects with chronic hepatitis B virus (HBV) infection with active disease who meet
the criteria for anti-HBV therapy and are not on a suppressive antiviral therapy
prior to initiation of study treatment.

- Subjects with a known history of hepatitis C virus (HCV) who have not completed
curative antiviral treatment or have an HCV viral load above the limit of
quantification at Screening.

- Known history of human immunodeficiency virus (HIV).

- Receipt of any organ transplantation, including autologous and allogeneic stem cell
transplantation, with the exception of transplants that do not require
immunosuppression.

- Known to be diagnosed and/or treated for any other additional malignancy within 2
years prior to randomization with the exception of the following: curatively treated
basal cell carcinoma or squamous cell carcinoma of the skin, and curatively resected
in situ cervical cancer, and curatively resected in situ breast cancer, and low-risk
early stage prostate cancer.

- Any condition requiring systemic treatment with either corticosteroids (>10 mg daily
of prednisone or equivalent) or other immunosuppressive medication within 7 days
prior to the first dose of study treatment, except for topical, intranasal,
intrabronchial, or ocular steroids.

- Use of a live or live attenuated vaccine within 4 weeks prior to Screening.

Other Inclusion/Exclusion criteria may apply as defined in the protocol.