Study of Ulevostinag (MK-1454) Alone or in Combination With Pembrolizumab (MK-3475) in Participants With Advanced/Metastatic Solid Tumors or Lymphomas (MK-1454-001)

The purpose of this study is to identify a maximum tolerated dose (MTD) or maximum administered dose (MAD) of ulevostinag alone and of ulevostinag in combination with pembrolizumab in participants with advanced/metastatic solid tumors or lymphomas in Part 1, and to evaluate the safety and efficacy of ulevostinag via intratumoral (IT) injection in combination with pembrolizumab in selected solid tumors in Part 2. Ulevostinag will be administered IT; pembrolizumab (pembro) will be administered via intravenous (IV) infusion. In Part 1, participants will be allocated to one of three treatment arms: ulevostinag monotherapy (cutaneous/subcutaneous \[cut/subcut\] lesions), ulevostinag +pembro (cut/subcut lesions), or ulevostinag +pembro (visceral lesions). In Part 2, participants with head and neck squamous cell carcinoma (HNSCC) who are anti-programmed cell death-protein 1 or anti-programmed cell death-ligand 1 (anti-PD-1/PD-L1) refractory or with anti-PD-1/PD-L1 treatment (TrT)-naïve triple-negative breast cancer (TNBC) or with anti-PD-1/PD-L1 TrT-naïve solid tumors with liver metastases/lesions will receive ulevostinag via IT injection at the preliminary Recommended Phase 2 Dose (RP2D) determined in Part 1 PLUS pembrolizumab via IV infusion for up 35 cycles (up approximately 2 years).

Participants will receive either ulevostinag monotherapy or ulevostinag in combination with pembrolizumab for up to 35 cycles (approximately 2 years). Participants will undergo at least a 24-hour inpatient observation period following the first dose administration of ulevostinag on Cycle 1 Day 1 in Part 1. For Part 2, the length of the observation period following administration of the first dose of ulevostinag on Cycle 1 Day 1 is at least 8 hours.