Patient description: The patient is a 60 year old man complaining of frequent headaches, generalized bone pain and difficulty chewing that started 6 years ago and is worsening. Examination shows bilateral swellings around the molars. The swellings have increased since his last examination. Several extraoral lesions are detected in the head and face. The swellings are non-tender and attached to the underlying bone. Further evaluation shows increased uptake of radioactive substance as well as an increase in urinary pyridinoline. His serum alkaline phosphatase is 300 IU/L (the normal range is 44- 147 IU/L). His family history is only significant for hypertension in his mother and DM type 2 in his father. The diagnosis of Paget's Disease of Bone was confirmed and Bisphosphonate will be started as first-line therapy.

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Neoplasms, Head and Neck Capable of giving signed informed consent Male or female, age >=18 years Histological or cytological documentation of Head and Neck Squamous Cell Carcinoma (HNSCC) that is considered incurable by local therapies Primary tumor location of the oral cavity, oropharynx, hypopharynx or larynx No prior systemic therapy administered in the recurrent or metastatic setting (except for systemic therapy given as part of multimodal treatment for locally advanced disease) Measurable disease per version 1.1 guidelines ECOG Performance PS score of 0 or 1 Adequate organ function Life expectancy of at least 12 weeks Female participants: must not be pregnant, not breastfeeding, and at least one of the following conditions apply: 1. Not a woman of childbearing potential (WOCBP) 2. A WOCBP who agrees to use a method of birth control from 30 days prior to randomization and for at least 120 days after the last dose of study treatment  Prior therapy with an anti-PD-1/L1/L2 and/or anti-ICOS directed agent Systemic approved or investigational anticancer therapy within 30 days or 5 half-lives of the drug, whichever is shorter Major surgery 28 days prior to randomization Toxicity from previous anticancer treatment that includes toxicity related to prior treatment that has not resolved to Grade 1 (except alopecia, hearing loss, endocrinopathy managed with replacement therapy, and peripheral neuropathy which must be Grade 2) Received transfusion of blood products or administration of colony stimulating factors within 14 days prior to randomization Central nervous system (CNS) metastases, with the following exception: Participants with asymptomatic CNS metastases who are clinically stable and have no requirement for steroids for at least 14 days prior to randomization Invasive malignancy or history of invasive malignancy other than disease under study within the last 3 years, except as noted below: a. Any other invasive malignancy for which the participant was definitively treated, has been disease-free for 3 years and in the opinion of the principal investigator and GSK Medical Monitor will not affect the evaluation of the effects of the study treatment on the currently targeted malignancy, may be included in this clinical study Autoimmune disease or syndrome that required systemic treatment within the past 2 years Has a diagnosis of immunodeficiency or is receiving systemic steroids (≥10 mg oral prednisone per day or equivalent) or other immunosuppressive agents within 7 days prior to randomization Receipt of any live vaccine within 30 days prior randomization