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Abstract Introduction: B cell maturation antigen (BCMA) is a novel target for T cell immunotherapy in MM including bispecific antibody (bsAb) and chimeric antigen receptor therapy (CAR-T). BCMA is critical for survival of the long-lived plasma cell, responsible for generation of protective antibodies. Impaired immune reconstitution, cytopenias, B cell aplasia and hypogammaglobinemia can compound preexisting MM-induced immunosuppression. In the case of bsAb, potential redirection/activation of T regulatory cells can create an immunosuppressive milieu. Herein, we describe the clinically relevant infectious complications observed across different BCMA-directed therapies used across multiple clinical trials at our center. Methods: Infections confirmed by microbiologic or histopathologic evidence were captured from the D1 C1 of bsAb and D 1 of lymphodepleting chemotherapy of autologous BCMA CAR-T therapies. The NCI CTCAE v5 was used to describe the site and grade of infections. Hypogammaglobinemia and severe hypogammaglobinemia were defined as ≤700 mg/dl and ≤400 mg /dl, respectively. Standard antimicrobial prophylaxis included herpes zoster prophylaxis for all MM patients with antibacterial (levofloxacin) / antifungal (fluconazole) during periods of neutropenia and IVIG supplementation as per the treating physician's discretion. PCP prophylaxis was prescribed to CAR T recipient per institutional guidelines. Descriptive statistics and comparisons were performed using two-sample t-test for continuous variables and chi-square goodness of fit test for categorical variables. Results: We identified 62 patients who received BCMA-directed bsAb (n=36) or CAR-T (n=26) between 2019-2021(table 1). The median age was 66 (range 48-84) years with % females and 14.8% of patients belonging to Black race. The median time to bsAb and CAR-T use from diagnosis were 6.6 (range 0.83-15.5) and 2.6 (range 0.35-14.4) years, respectively. The median lines of prior therapy were 6 (range 1-11) with BCMA CAR-T recipients receiving fewer prior lines of therapy (4 vs 6, p=0.001). The baseline lymphocyte count was higher in the CAR-T (14.71 vs 0.84; p=0.001). Baseline severe hypogammaglobulinemia and lymphopenia were present in 30% and 26.7% of all patients, respectively. Tocilizumab was used in 40.9% (bsAb -30.8% versus CAR-T 55.6%) patients for CRS. IVIG was used in 25% of patients. The median study duration for bsAb was 4 (range 0.03- 24) months across multiple dose levels. Median follow up among CAR-T recipients was 3.9 (range 0.3 - 22.3) months. Among recipients of bsAb, 41.2% of patients experienced at least one episode of infection vs. 23.1% with CAR-T (p=0.141). The cumulative incidence of infection with bsAb and CAR-T were 22 and 8, respectively. The spectrum of infections with bsAb was predominantly bacterial (64.3% While gram negative infection (Escherichia coli and Klebsiella pneumoniae bacteremia, Proteus mirabilus and Psuedomonas aeroginosa urinary tract infections) were seen in 6 patients, skin infection including cellulitis occurred in 4 patients, with 1 case of necrotizing cellulitis. Bacteremia with rare opportunistic pathogens - Rhizobium radiobacter and recurrent Ochrobacterium anthropi were also observed . Viral infections included rhinovirus, cytomegalovirus, and parvovirus B19 reactivation, and COVID-19. About 50% of infections were ≥ grade 3 with 2 grade 5 events (Pseudomonas aeruginosa bacteremia and COVID-19). In the CAR-T group, we observed more viral infections (66.7% vs 35.7%; p=0.028) and fewer bacterial infections (33.3% vs 64.3%; p=0.028) . Common viral infections included rhinovirus, RSV, and herpes simplex virus reactivation. In this group 25% of infections were ≥grade 3. Conclusion: BCMA-targeted therapies seem to be associated with clinically significant bacterial and viral infections. Repetitive dosing with bsAb therapies could be the reason for the propensity to serious bacterial infections compared to CAR-T recipients and may need novel prophylaxis strategies. Figure 1 Figure 1. Disclosures Mohan: Medical College of Wisconsin: Current Employment. Dhakal: Fate: Research Funding; Carsgen: Research Funding; Natera: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Speakers Bureau; Sanofi: Research Funding, Speakers Bureau; BMS: Honoraria, Speakers Bureau; GSK: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Chhabra: GSK: Honoraria. D'Souza: Imbrium, Pfizer, BMS: Membership on an entity's Board of Directors or advisory committees; Janssen, Prothena: Consultancy; Sanofi, Takeda, Teneobio, CAELUM, Prothena: Research Funding. Hari: GSK: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Karyopharm: Consultancy; Oncopeptides: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene-BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other, Research Funding, Speakers Bureau; Adaptive Biotech: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millenium: Membership on an entity's Board of Directors or advisory committees, Research Funding.
Mohan et al. (Fri,) studied this question.