Inclusion Criteria:

- Has histologically or cytologically confirmed diagnosis of metastatic, recurrent
head and neck squamous cell carcinoma (HNSCC) that is considered incurable by local
therapies.

- Has tumor PD-L1 expression of CPS ≥20. Tumor tissue must be provided for PD-L1
biomarker analysis.

- Has human papilloma virus (HPV) testing results for oropharyngeal cancer by p16
immunohistochemistry (IHC) testing.

- Has measurable disease per RECIST 1.1 guidelines.

- Has the primary tumor location of the oral cavity, oropharynx, hypopharynx, or
larynx.

- Has an Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.

- Female patients of childbearing potential must have a negative highly sensitive
pregnancy test within 72 hours prior to randomization and must not be breastfeeding.

- Male and female patients of childbearing potential must be willing to completely
abstain from heterosexual sex or agree to use a highly effective method of
contraception.

Exclusion Criteria:

- Has primary tumor site (any histology) of nasopharynx or salivary glands or occult
primary site.

- Has received prior systemic therapy (eg, prior chemo-, immune-, or biologic therapy)
for locally advanced unresectable or metastatic HNSCC.

- Prior systemic therapy completed >6 months prior to signing informed consent is
allowed if given as part of multimodal treatment for locoregionally advanced
disease with curative intent, and no PD/recurrence occurred within 6 months of
its completion. Prior systemic immunotherapy in the locoregionally advanced
disease with curative intent, including but not limited to anti-PD-(L)1 agents,
is allowed if PD/recurrence occurred ≥12 months after its completion.

- Has clinically active central nervous system metastases and/or carcinomatous
meningitis.

- Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any
other form of immunosuppressive therapy within 7 days prior to the first dose of
study treatment.

- Rapidly progressing disease or with features that may confer a high risk of
tumor-associated hemorrhage or uncontrolled tumor pain.

- Current or history of immune-related disease that required systemic treatment in
past 2 years, except for replacement therapy.