A Study of ImmunoPet Imaging Using 89Zr-DFO-REGN5054 in Adult Participants With Solid Cancers Treated With Cemiplimab

Key Inclusion Criteria: * Advanced or metastatic solid tumors that may respond to anti-programmed cell death 1 (PD-1) immunotherapy * Measurable disease according to Response Evaluation Criteria in Solid Tumours (RECIST) 1.1 criteria * Eastern Cooperative Oncology Group (ECOG) performance status of ≤1 * Adequate organ and bone marrow function as defined in the protocol * Willing and able to comply with clinic visits and study-related procedures (including required tumor biopsy for Part B) Key Exclusion Criteria: * Currently receiving another cancer treatment or inadequate time since last therapy, as defined in the protocol * Has not yet recovered from acute toxicities from prior therapy; exceptions defined in the protocol * Prior treatment with a blocker of the PD-1/Programmed death ligand 1 (PD-L1) pathway * Currently receiving or has received chimeric antigen receptor (CAR-T) cell therapy * Symptomatic or untreated brain metastases, leptomeningeal disease, or spinal cord compression * Known history of or any evidence of interstitial lung disease, active, noninfectious pneumonitis (past 5 years) or active tuberculosis NOTE: Other protocol defined inclusion/exclusion criteria apply.