Inclusion Criteria:

• Are aged 18 years and over.
• Recurrent or metastatic squamous cell carcinoma of the head and neck (SCCHN), (oral cavity, oropharynx, hypopharynx, or larynx) which has progressed on or after previous systemic cancer therapy and is not amenable to curative therapy
• Received prior treatment using a PD-(L)1 inhibitor.
• Prior platinum failure.
• Received 1 or 2 prior systemic regimens for recurrent or metastatic SCCHN.
• Has measurable disease per RECIST 1.1.
• A fresh or recently acquired tumor tissue for the purpose of biomarker testing.
• World Health Organization (WHO)/Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.

Exclusion Criteria:

• Head and neck cancer of any primary anatomic location in the head and neck not specified in the inclusion criteria, including participants with SCCHN of unknown primary or non-squamous histologies.
• Had prior cetuximab therapy (unless it was administered in curative locally advanced setting with radiotherapy and no disease progression for at least 6 months following the last cetuximab dose).
• Active or prior documented autoimmune or inflammatory disorders (including inflammatory bowel disease [e.g., colitis or Crohn's disease], diverticulitis.
• Any concurrent anticancer treatment, except for hormonal therapy for non-cancer-related conditions (e.g., hormone replacement therapy).