This is a single-arm feasibility trial in which patients with histologically confirmed plasmablastic lymphoma (PBL) with or without HIV, who have achieved a Complete Response or Partial Response after definitive frontline chemotherapy, will receive Elranatamab (Elra) consolidation.

Patients will receive Elra subcutaneously for up to six 28-day cycles, beginning with a step-up dosing schedule (12 mg on day 1, 32 mg on day 4, followed by 76 mg weekly on days 8, 15, and 22 of Cycle 1). Patients will transition to 76 mg every 2 weeks (days 1 and 15) during Cycles 2 and 3, followed by an interim PET/CT assessment at the end of Cycle 3. During cycles 4 through 6, all patients will receive 76 mg every 4 weeks (on day 1 of each cycle).

Participants will undergo disease assessment with PET/CT at the end of Cycle 3, post-end of treatment (EOT) visit, and every 6 months thereafter (±2 weeks) for up to 2 years to assess recurrence and survival. Routine clinical follow-up will continue every 3 months, as per the standard of care (SOC).

Inclusion Criteria:

• Age ≥ 18 years at time of consent

• ECOG performance status (PS) 0 or 1

• Histologically and immunophenotypically confirmed PBL

• Ann Arbor stage at initial diagnosis: stage I with lactate dehydrogenase (LDH) > upper limit of normal (ULN) and/or bulky disease >7.5 cm or stage II-IV

• Received definitive front-line therapy for PBL with end-of-treatment PR or CR

• Adequate bone marrow function with recovery from prior therapy, defined as:

  • ANC ≥ 500 cells/mcL
  • Platelet count ≥ 50,000 cells/mcL

• Availability of archival tumor tissue (block or unstained slides) for mandatory central pathology review and correlative BCMA testing. Central pathology review and BCMA testing may be completed after enrollment.

• Able to provide written informed consent and HIPAA authorization for release of personal health information, via an approved UIC Institutional Review Board (IRB) informed consent form and HIPAA authorization. If a subject is unable to consent, a LAR may provide consent on their behalf.

• As determined at the discretion of the enrolling physician or protocol designee, the ability of the subject to understand and comply with study procedures for the entire length of the study

• If capable of becoming pregnant: Negative serum or urine pregnancy test

• If HIV-positive:

  • Receiving effective combined antiretroviral therapy
  • CD4+ T-cell count ≥ 50 cells/mcL within 4 weeks before enrollment

Exclusion Criteria:

Key inclusion criteria:

• Age ≥ 18 years at time of consent

• ECOG performance status (PS) 0 or 1

• Histologically and immunophenotypically confirmed PBL

• Ann Arbor stage at initial diagnosis: stage I with lactate dehydrogenase (LDH) > upper limit of normal (ULN) and/or bulky disease >7.5 cm or stage II-IV

• Received definitive front-line therapy for PBL with end-of-treatment PR or CR

• Adequate bone marrow function with recovery from prior therapy, defined as:

  • ANC ≥ 500 cells/mcL
  • Platelet count ≥ 50,000 cells/mcL

• Availability of archival tumor tissue (block or unstained slides) for mandatory central pathology review and correlative BCMA testing. Central pathology review and BCMA testing may be completed after enrollment.

• Able to provide written informed consent and HIPAA authorization for release of personal health information, via an approved UIC Institutional Review Board (IRB) informed consent form and HIPAA authorization. If a subject is unable to consent, a LAR may provide consent on their behalf.

• As determined at the discretion of the enrolling physician or protocol designee, the ability of the subject to understand and comply with study procedures for the entire length of the study

• If capable of becoming pregnant: Negative serum or urine pregnancy test

• If HIV-positive:

  • Receiving effective combined antiretroviral therapy
  • CD4+ T-cell count ≥ 50 cells/mcL within 4 weeks before enrollment

Key exclusion criteria:

• Prior BCMA bispecific therapy

• Stable or progressive disease following front-line therapy as determined by the investigator

• Receiving any other investigational agents

• Expected survival < 2 months

• Known or suspected PBL involvement of the parenchymal brain or spinal cord at diagnosis. Asymptomatic leptomeningeal disease only will be allowed.

• Uncontrolled intercurrent illness, including but not limited to uncontrolled infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements

• Concurrent malignancy requiring active therapy within the last 3 years, except for the following:

  • Basal cell carcinoma limited to the skin
  • Squamous cell carcinoma limited to the skin
  • Carcinoma in situ of the cervix or breast
  • Adequately treated lentigo malignant melanoma
  • Localized prostate cancer
  • Active therapy consists of adjuvant or maintenance therapy to reduce the risk of recurrence of a malignancy that was previously treated with curative intent and with no evidence of active disease within 2 years prior to screening

• Pregnant or nursing

• PWH with a history of AIDS-defining opportunistic infection within the past year

• Receipt of a live vaccine within 28 days prior to the first dose of study treatment