Pembrolizumab in Treating Minimal Residual Disease in Patients With Acute Lymphoblastic Leukemia

PRIMARY OBJECTIVES: I. To evaluate the efficacy of pembrolizumab in minimal residual disease (MRD)-positive acute lymphoblastic leukemia (ALL). SECONDARY OBJECTIVES: I. To describe the toxicity profile of pembrolizumab in patients with previously-treated ALL. II. To gain a preliminary assessment of how MRD response translates into relapse-free and overall survival. EXPLORATORY OBJECTIVES: I. To compare disease assessments by multiparameter flow cytometry (MFC) and polymerase chain reaction (PCR) to a newly-developed and more sensitive next generation sequencing (NGS)-based platform. II. To correlate response to pembrolizumab to immunologic markers in peripheral blood and bone marrow specimens. III. To evaluate if treatment with pembrolizumab has a measurable impact on hematopoietic engraftment and graft-vs-host disease (GVHD) in patients who subsequently undergo allogeneic hematopoietic cell transplantation (HCT). OUTLINE: Patients receive pembrolizumab intravenously (IV) over 30 minutes on day 1. Cycles repeat every 21 days for 2 years in the absence of disease progression or unacceptable toxicity. Patients achieving complete MRD response may receive up to 1 additional year of treatment at the discretion of the investigator. After completion of study treatment, patients are followed up every 3 months for up to 2 years.