CLINICAL TRIAL / NCT06385080

Inclusion Criteria: - Have histologically or cytologically confirmed recurrent/metastatic head and neck squamous cell carcinoma (R/M HNSCC) that is considered incurable by local therapies. Acceptable prior lines of therapy will be determined according to specific cohort 1, 2, 3A and 3B: (a) The eligible primary tumor locations are the oropharynx, oral cavity, hypopharynx, or larynx; (b) Any known p16 status of tumor must be negative (Note: All participants with an oropharyngeal tumor must have results of p16 status, per local testing); (c) Participants must provide local testing results of programmed cell death ligand 1 (PD-L1) status, if available; Cohort 4: (a) Patients must have primary tumor location in oropharynx. Unknown primary tumors are not included (b) Primary tumor must be HPV-positive, confirmed by positive p16 test or high-risk human papillomavirus (HPV) in-situ hybridization (ISH) in tissue (current or archival) (c) Participants must provide local testing results of PD-L1 status, if available - Participants in Cohorts 1, 2, and 3B and 4 must have measurable disease according to RECIST version 1.1. Participants in Cohort 3A must have evaluable disease (defined as having at least 1 non-target lesion according to RECIST version 1.1 - Toxicities from previous anticancer therapies should have resolved to baseline levels or to Grade 1 or less prior to the first dose of study treatment (except for alopecia or post-radiation skin changes [any grade], Grade less than or equal to [<=]2 peripheral neuropathy and Grade <=2 hypothyroidism stable on hormone replacement) - Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1 - Participant must have adequate organ and bone marrow function as follows, without history of red blood cell transfusion, platelet transfusion, or use of granulocyte colony-stimulating factor within 7 days prior to the date of the laboratory test. Participants should have: a) Hemoglobin >=9 grams per deciliter (g/dL); b) Neutrophils >=1.5 x 10^3/mcg; c) Platelets >=100 x 10^3/mcg Exclusion Criteria: - Uncontrolled illness including any medical history or current (non-infectious) interstitial lung disease (ILD)/ pneumonitis/ pulmonary fibrosis, or where suspected ILD/pneumonitis/pulmonary fibrosis cannot be ruled out by imaging at screening - Participant with untreated brain metastases leptomeningeal disease, or spinal cord compression not definitively treated with surgery or radiation - Participant with a history of clinically significant cardiovascular disease - Received prior chemotherapy, targeted cancer therapy, immunotherapy, or treatment with an investigational anticancer agent within 2 weeks or 4 half-lives, whichever is longer, before the first administration of study treatment. The maximum required washout is 28 days - Received radiotherapy for palliative purposes within 7 days of the first administration of study treatment