Study to Evaluate the Safety and Efficacy of a Combination of MK-4280 and Pembrolizumab (MK-3475) in Participants With Hematologic Malignancies (MK-4280-003)

Inclusion Criteria:

- Has measureable disease, defined as ≥1 lesion that can be accurately measured in 2
dimensions with diagnostic quality cross sectional anatomic imaging (computed
tomography or magnetic resonance imaging). Minimum measurement must be >15 mm in the
longest diameter or >10 mm in the short axis

- Is able to provide a core or excisional tumor biopsy for biomarker analysis from an
archival (within 3 months) or newly obtained biopsy at screening

- Has a performance status of 0 or 1 on the Eastern Cooperative Oncology Group (ECOG)

Exclusion Criteria:

- Has known clinically active central nervous system (CNS) involvement

- Has received prior therapy with an anti-lymphocyte activation gene-3 (LAG-3) antibody

- Has received chimeric antigen receptors (CAR)-T-cell therapy

- Has received prior anticancer therapy or thoracic radiation therapy within 14 days
before the first dose of study treatment

- Has ≥Grade 2 non-hematological toxicities from prior therapy

- Has had a prior anticancer monoclonal antibody within 4 weeks prior to study Day 1 or
who has not recovered (i.e., ≤Grade 1 or at baseline) from AEs due to agents
administered ≥4 weeks earlier

- Has received a live vaccine within 30 days prior to first dose of study treatment

- Is currently participating and receiving study therapy or has participated in a study
of an investigational agent and received study therapy or used an investigational
device within 28 days before study Day 1

- Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy
or any other form of immunosuppressive therapy within 7 days prior the first dose of
study drug

- Has a known additional malignancy that is progressing or requires active treatment
with the exception of basal cell carcinoma of the skin, squamous cell carcinoma of the
skin, or in situ cervical cancer that has undergone potentially curative therapy

- Has active autoimmune disease that has required systemic treatment in past 2 years
(i.e., with use of disease modifying agents, corticosteroids or immunosuppressive
drugs)

- Has a history of (non-infectious) pneumonitis that required steroids or current
pneumonitis

- Has an active infection requiring intravenous systemic therapy

- Has a known history of human immunodeficiency virus (HIV) infection

- Has known, active hepatitis B or hepatitis C infection

- Is pregnant or breastfeeding, or expecting to conceive or father children within the
projected duration of the study, starting with the screening visit through 120 days
after the last dose of study treatment

- Has had an allogeneic hematopoetic stem cell/solid organ transplantation within the
last 5 years