Study of ImmunoPet Imaging of PD-L1 in Tumors Using 89Zr-DFO-REGN3504 in Adult Participants With Advanced PD-L1 Positive Malignancies

Key Inclusion Criteria:

* Participants with at least 1 radiologically measurable (by RECIST 1.1) lesion (Note: Lesions 10 mm in diameter or larger at the high end Program Dealth-Ligand 1 (PD-L1) expression are expected to be detectable by 89Zr-DFO-REGN3504 PET imaging).
* Availability of an archival, formalin-fixed, paraffin-embedded (FFPE) tumor tissue sample (blocks or slides) from a primary/metastatic/recurrent site, which has not been previously irradiated, with presence of any PD-L1 expression by Immunohistochemistry (IHC) in tumor or immune cells, performed by a Clinical Laboratory Improvement Amendments of 1988 (CLIA), a certified laboratory, using either freshly cut or archived FFPE slides. If the analysis will be done using archived FFPE slides, the slides must be \<6 months old after being cut from the tissue block. The age of a tissue block is not limited. If the patient has a report of ≥1% PD-L1 expression, there is no need to repeat the assay; the report has no time limit.
* Eastern Cooperative Oncology Group (ECOG) performance status of ≤2 (Oken, 1982) and anticipated life expectancy of at least 3 months
* Adequate organ and bone marrow function

Key Exclusion Criteria:

* Participants receiving therapy with a monoclonal antibody against PD-L1 (eg. durvalumab, atezolizumab, avelumab) or have received treatment with anti-PD-L1 within 135 days prior to the 89Zr˗DFO˗REGN3504 infusion date
* For Part B only, participants in whom anti-PD-1 therapy was initiated 1 month or less, prior to the 89Zr˗DFO˗REGN3504 infusion date
* Active or untreated brain metastases or spinal cord compression. Participants are eligible if the central nervous system (CNS) metastases are adequately treated and participants' neurological symptoms have returned to baseline levels (except for residual signs or symptoms related to the CNS treatment) for at least 2 weeks prior to enrollment. Participants with brain metastases must be off doses of corticosteroid therapy that are considered by the investigator to be immunosuppressive
* Known history of human immunodeficiency virus or known acquired immunodeficiency syndrome indicating uncontrolled active infection. Participants on highly active antiretroviral therapy with undetectable RNA levels and CD4 counts above 350 are permitted
* Receipt of an investigational compound or device within 30 days of screening or within 5 half-lives of the investigational compound or therapy being studied (whichever is greater)
* Major surgery or significant traumatic injury within 4 weeks prior to first dose of 89Zr˗DFO˗REGN3504
* Known psychiatric or substance abuse disorder, including current use of any illicit drugs, that would interfere with the participant's participation in, or compliance with the requirements of, the study
* History of hypersensitivity response to any protein therapeutics (eg, recombinant proteins, vaccines, IV immune globulins, monoclonal antibodies, receptor traps). If a patient intends to receive a COVID-19 vaccine during Part A only, participation in the dose-escalation part of the study should be delayed at least 1 week after the final dose of COVID-19 vaccine before the start of study drug.
* Sexually active men and women of childbearing potential who are unwilling to practice highly effective contraception prior to the initial dose/start of the first treatment, during the study, and for at least 6 months after the last dose.
* Part B only: Has been enrolled in Part A

Note: Other Protocol Inclusion/Exclusion Criteria apply