The primary objectives in the dose escalation phase are to evaluate safety and pharmacokinetics (PK) in order to determine the selected dose level(s) for expansion of REGN3767 as monotherapy and in combination with cemiplimab in patients with advanced malignancies, including lymphoma.

The primary objectives in the dose expansion phase are to assess preliminary anti-tumor activity of REGN3767 alone and in combination with cemiplimab (separately by cohort) as measured by objective response rate (ORR).

Key Inclusion Criteria:

• Dose escalation cohorts: Patients with histologically or cytologically confirmed diagnosis of malignancy (including lymphoma) with demonstrated progression of a tumor for whom there is no available therapy likely to convey clinical benefit AND who have not been previously treated with a PD-1/PD-L1 inhibitor. These patients do not require measurable disease
• Dose expansion cohorts: Patients with histologically or cytologically confirmed diagnosis of 1 of specified tumors with measurable disease per RECIST 1.1 or Lugano criteria. Some patients may have been previously treated with a PD-1 or PD-L1 inhibitor
• Eastern Cooperative Oncology Group performance status of 0 or 1
• Adequate organ and bone marrow function

Key Exclusion Criteria:

• Prior treatment with any LAG-3 targeting biologic or small molecule
• Radiation therapy within 2 weeks prior to randomization and not recovered to baseline from any AE due to radiation
• Untreated or active central nervous system metastases - Ongoing or recent (within 5 years) evidence of significant autoimmune disease
• Corticosteroid therapy (>10 mg prednisone/day or equivalent) within 1 week prior to the first dose of study drug
• Myocardial infarction within 6 months

Note: Other protocol defined Inclusion / Exclusion criteria apply