A 2-Part, Phase 3, Multicenter, Randomized, Open-Label, Active-Controlled Study to Assess Efficacy and Safety of REGN7508, a Monoclonal Antibody Against Factor XI, for the Treatment and Secondary Prevention of Venous Thromboembolism in Participants With Solid and Hematologic Cancers (ROXI-CAT-II)

Key Inclusion Criteria: 1. Has an Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 to 2 at the time of screening and day 1 prior to first dose of study intervention 2. In Part 1 participants with cancer and Part 2 participants: Histologically confirmed diagnosis of malignant solid or select hematologic tumor (other than basal-cell or squamous-cell carcinoma of the skin alone) as described in the protocol 3. Part 1 additional criteria: 1. Has newly diagnosed symptomatic lower extremity DVT or incidentally-detected proximal lower extremity DVT (eg, popliteal or femoral) within 5 days (120 hours) of randomization (with imaging confirmation) 2. Anticoagulation therapy with a therapeutic dose of a Direct Oral Anticoagulant (DOAC) for at least 3 months is indicated for the newly diagnosed proximal lower extremity DVT 4. Part 2 additional criteria: 1. Newly diagnosed VTE within 5 days (120 hours) of randomization (with imaging confirmation) as described in the protocol 2. Anticoagulation therapy with a therapeutic dose of a DOAC for at least 6 months is indicated for newly diagnosed VTE Key Exclusion Criteria: 1. Is at high risk of intracranial bleeding in the opinion of the investigator 2. Known bleeding conditions (eg, Hemophilia A or B, von Willebrand's disease), hemorrhagic tumor sites, or other conditions with a high risk for bleeding (eg, hepatic disease associated with coagulopathy) 3. Contraindication to anticoagulation in the opinion of the investigator 4. Life expectancy of \< 6 months 5. Part 1 participants with cancer and Part 2 additional exclusion criteria: 1. Has acute leukemia or myelodysplastic syndrome 2. Has primary brain tumor 3. Has brain metastases as described in the protocol 6. Part 1 additional exclusion criteria: 1. Has a symptomatic PE 2. Has an asymptomatic (incidentally-diagnosed) PE in a segmental or larger pulmonary artery 7. Part 2 additional exclusion criteria: PE leading to hemodynamic instability as described in the protocol Note: Other Protocol Defined Inclusion/ Exclusion Criteria Apply