Venetoclax for the Treatment of Patients With Relapsed Hairy Cell Leukemia

PRIMARY OBJECTIVE: I. To determine the objective response rate (ORR) of venetoclax. SECONDARY OBJECTIVES: I. To determine the complete remission (CR) and minimal residual disease (MRD)-negative CR rates of venetoclax in relapsed hairy cell leukemia/hairy cell leukemia variant (HCL/HCLv). II. To determine the rates of MRD-negative by blood flow cytometry with venetoclax. III. To determine the safety of venetoclax in relapsed HCL/HCLv. IV. To determine the response and CR duration and MRD-negative survival in relapsed HCL/HCLv receiving venetoclax. EXPLORATORY OBJECTIVES: I. To correlate response to TP53 mutations and other mutations, particularly for BRAF wild-type (WT) relapsed HCL/HCLv. II. To perform whole exome sequencing (WES) of relapsed HCL/HCLv samples to look for mutations, to correlate with response. OUTLINE: Patients receive venetoclax orally (PO) once daily (QD) on days 1-28 of each cycle. Treatment repeats every 28 days for up to 19 cycles in the absence of disease progression or unacceptable toxicity. Patients undergo computed tomography (CT) or magnetic resonance imaging (MRI) and blood sample collection throughout the study. Patients may undergo bone marrow biopsy and/or aspiration on study. Additionally, patients with known or suspected central nervous system (CNS) disease undergo lumbar puncture throughout the study. After completion of study treatment, patients are followed up at 30 days.