A Platform Study of Novel Immunotherapy Combinations as First-Line Treatment in Participants With PD-L1 Positive Recurrent/Metastatic Squamous Cell Carcinoma of the Head and Neck- GALAXIES H&N-202

Inclusion Criteria:

• Have histologically or cytologically-confirmed HNSCC that is R/M and is consideredincurable by local therapies. A) Subjects must not have had prior systemic therapyadministered in the R/M setting. Chemoradiation therapy which was completed morethan 4 months prior to signing consent if given as part of multimodal treatment forlocally advanced disease is allowed B) The eligible primary tumor locations areoropharynx, oral cavity, hypopharynx, and larynx C) Subjects may not have a primarytumor site of nasopharynx (any histology)

• Has measurable (target) disease based on RECIST 1.1 as determined by theinvestigator.

• Has an Eastern Cooperative Oncology Group performance status (ECOG PS) of 0 or 1

• Provides a tumor tissue sample obtained at the time of or after the initialdiagnosis of R/M HNSCC. A fresh tumor tissue sample obtained within 90 days ofscreening is highly preferred, If fresh biopsy is not possible, an archival tumorspecimen is acceptable unless it was obtained prior to administration ofchemoradiation for the treatment of a participant's tumor. Needle or excisionalbiopsies or resected tissue is required. Cytological specimens such as fine needleaspirates, bone marrow samples, or cell blocks are not acceptable. Bone specimen isnot acceptable.

• Has tumor Programmed death ligand 1 (PD-L1) expression

• If the primary tumor site is oropharyngeal carcinoma, the participant must haveHuman papillomavirus (HPV) results

Exclusion Criteria:

• Has received prior therapy with any immune checkpoint inhibitors, includingantibodies or drugs targeting Programmed death protein 1 (PD-1), PD-L1, CytotoxicT-lymphocyte-associated protein 4 (CTLA-4), T cell immunoreceptor withimmunoglobulin and immunoreceptor tyrosine based inhibitory motif domains (TIGIT),Cluster of differentiation (CD) 96, or other immune checkpoint pathways.

• Participants with previous malignancies (except non-melanoma skin cancers, and thefollowing in situ cancers: bladder, gastric, esophageal, colon, endometrial,cervical/dysplasia, melanoma, or breast) unless a complete remission was achieved atleast 2 years prior to study entry AND no additional therapy is required during thestudy period.

• Have active tumor bleeding or a high risk of bleeding (examples include but are notlimited to radiographic evidence of major blood vessel invasion/infiltration ortumor demonstrates >90 degree abutment or encasement of a major vessel [carotid,jugular, bronchial artery] and/or exhibits other high-risk features such asarteriovenous fistula).

• Has PD within 4 months of completion of curatively intended treatment forlocoregionally advanced HNSCC

• Participants with any carcinomatous meningitis or leptomeningeal spread and thosewith uncontrolled or symptomatic Central Nervous System (CNS) metastases

• Active autoimmune disease that has required systemic disease-modifying orimmunosuppressive treatment within the last 2 years. (Stable, medically managedautoimmune endocrinopathies are acceptable if participant otherwise meets entrycriteria.)