Study of Intratumoral (IT) Ulevostinag (MK-1454) in Combination With Intravenous (IV) Pembrolizumab (MK-3475) Compared to IV Pembrolizumab Alone as the First Line Treatment of Metastatic or Unresectable, Recurrent Head and Neck Squamous Cell Carcinoma (HNSCC) (MK-1454-002)

Exclusion Criteria

• •Has disease that is suitable for local therapy administered with curative intent
• •Has progressive disease (PD) within 6 months of completion of curatively intended systemic treatment for locoregionally advanced HNSCC
• •Has had chemotherapy or biological cancer therapy in the recurrent or metastatic setting for the treatment of HNSCC
• •Has had radiation therapy (or other non-systemic therapy) within 2 weeks prior to randomization or participant has not fully recovered from adverse events (AEs) due to a previously administered treatment
• •Is expected to require any other form of antineoplastic therapy while on study
• •Has a history of a second malignancy, unless potentially curative treatment has been completed, with no evidence of malignancy for at least 2 years
• •Has clinically active central nervous system (CNS) metastases and/or carcinomatous meningitis
• •Has an active autoimmune disease that has required systemic treatment in the past 2 years
• •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
• •Has had an allogenic tissue/solid organ transplant
• •Has a history of vasculitis
• •Has a history of interstitial lung disease
• •Has an active infection requiring systemic therapy
• •Has a known history of active tuberculosis (TB; Bacillus tuberculosis)
• •Has a history of (non-infectious) pneumonitis that required steroids or current pneumonitis
• •Has had a severe hypersensitivity reaction to treatment a monoclonal antibody/components of the study treatment
• •Has known Hepatitis B virus or Hepatitis C virus infections
• •Has received prior therapy with an anti-programmed cell death 1 (anti-PD-1), anti-programmed cell death-ligand 1 (anti-PD-L1), or anti-programmed cell death-ligand 2 (anti-PD-L2) agent or if the participant has previously participated in Merck Sharp \& Dohme (MSD) MK-3475 clinical trials
• •HIV infected participant who has had an HIV-related opportunistic infection within 6 months
• •HIV infected participants who have a history of Kaposi's sarcoma and/or Multicentric Castleman's Disease
• •Is pregnant, breastfeeding, or expecting to conceive or father children within the projected duration of the study, starting with the screening visit through 120 days after the last dose of study treatment
• •Has not fully recovered from any effects of major surgery without significant detectable infection
• •Has a history of re-irradiation for HNSCC at the projected injection site in the head and neck
• •Has received a live-virus vaccine within 30 days of planned study treatment start
• •Has been treated with a stimulator of interferon genes (STING) agonist (e.g. ulevostinag, ADU-S100)
• •Is currently participating and receiving study therapy or has participated in a study of an investigational agent and received study therapy, or used an investigational device, any of which occurred within 4 weeks of the first dose of study treatment