Real-world infectious complications and IVIG utilization after teclistamab in relapsed/refractory multiple myeloma.

Abstract

e19516 Background: Teclistamab, a BCMA×CD3 bispecific antibody, demonstrates significant efficacy in relapsed/refractory multiple myeloma (RRMM). However, infectious complications are common in clinical practice, and optimal supportive care strategies, including intravenous immunoglobulin (IVIG), remain poorly characterized. Methods: We performed a retrospective single-center review of RRMM patients treated with teclistamab between April 2024 and May 2025. Data collected included prior therapy exposure, IVIG utilization, documented infections, hospitalizations, ICU admissions, immunoglobulin levels, and bone marrow assessment of normal plasma cells before and 3–6 months after therapy. Results: 57 patients were included. Patients were heavily pretreated, among which 22.8% had prior BCMA-directed therapy. 36/57 patients (63.2%) received IVIG with Teclistamab. Mean infection rates were ~2 per patient. Hospitalizations occurred in about 58% and ICU admissions in 14% patients. Patients without IVIG support had higher hospitalization (66.7% vs 52.8%) and ICU admissions (19.0% vs 11.1%). Paired bone marrow assessments were available in 26 patients using initial and 3–6 month evaluations of normal plasma cells. Teclistamab was associated with marked depletion of the normal plasma cell compartment (median 5.35% before vs 0.1% at 3–6 months). 21 of 26 patients (80.8%) demonstrated < 1% normal plasma cells after treatment. Patients who had < 1% normal plasma cells had risk of infection, with ~80% of patients experiencing ≥1 infection irrespective of IVIG support. Among patients with preserved normal plasma cells (≥1%), IVIG support was associated with elimination of hospitalization (0% vs 33%). Conclusions: Teclistamab results in profound depletion of the normal plasma cell compartment in most patients, providing a biologic explanation for the high infectious burden observed in practice. While IVIG does not prevent infections in the setting of normal plasma cell depletion in the marrow, it appears to reduce the severity of infectious complications when plasma cell reconstitution is preserved, and these findings warrant confirmation in a larger prospective study. Infection burden and severity in patients receiving Teclistamab and change in normal plasma cell compartment. IVIG support Normal plasma cells at 3–6 mo (%) Δ Normal PCs N=26 Mean number of infections Hospitalization ICU Prior BCMA therapy Median prior lines of therapy No Preserved (≥1) +20.9% 3 1.33 33.3% 0% 0% 8 No Severe depletion (<1) NA * 5 2.20 40.0% 0% 0% 9 Yes Preserved (≥1) 0.0% 2 1.50 0% 0% 50.0% 11 Yes Severe depletion (<1) −8.55% 16 2.50 56.2% 0% 25.0% 10 Δ normal PCs denotes the difference in normal plasma cells before Teclistamab and 3-6 months after Teclistamab treatment. *NA = no paired marrow available in that subgroup.