Testing the Effect of Teclistamab on Recurrent Plasmablastic Lymphoma

PRIMARY OBJECTIVE: I. To determine the recommended phase 2 dose (RP2D) of teclistamab in relapsed/refractory (R/R) plasmablastic lymphoma (PBL). SECONDARY OBJECTIVES: I. To estimate the overall response rate (ORR), complete response (CR) rate, progression-free survival (PFS), and overall survival (OS) of teclistamab in R/R PBL. II. To observe and record anti-tumor activity. EXPLORATORY OBJECTIVES: I. To evaluate the utility of B-cell maturation antigen (BCMA) as a biomarker of response to teclistamab in PBL. II. To evaluate minimum residual disease (MRD) dynamics during treatment. OUTLINE: Patients receive teclistamab subcutaneously (SC) on days 1, 4, and 7 in the absence of disease progression or unacceptable toxicity (i.e., Cycle 1). Beginning 1 week later, patients receive teclistamab SC on day 1 (i.e., Cycle 2). Beginning 1 week later, 2 weeks later, or 4 weeks later (based on dose level), patients receive teclistamab SC on day 1 of remaining cycles. Based on dose level, cycles repeat weekly, every 2 weeks, or every 4 weeks in the absence of disease progression or unacceptable toxicity. Patients who have achieved a complete response (CR) by cycle 13 may discontinue study treatment. Patients achieving less than a CR but benefiting from treatment may continue to receive teclistamab beyond 13 cycles in the absence of disease progression, unacceptable toxicity, or achieving a CR. Additionally, patients undergo optional buccal swab collection at baseline and optional blood sample collection throughout the study. Patients also undergo positron emission tomography (PET)/computed tomography (CT) throughout the study. After completion of study treatment, patients are followed every 3 months for up to 2 years.