Infectious Complications of BCMA-Targeted and CD19-Targeted Chimeric Antigen Receptor T-Cell Immunotherapy

Background: Chimeric antigen receptor T-cell (CAR T) immunotherapy is an evolving treatment for relapsed/ refractory non-Hodgkin lymphoma (NHL) and multiple myeloma (MM). There is a growing need to elucidate the infectious complications of BCMA- and CD19-directed CAR T therapy. We performed a single-center retrospective analysis of infection outcomes up to 1-year post BCMA and CD19-directed CAR T treatment. Methods: All patients treated at our institution with a BCMA-directed CAR T therapy for MM or with a CD19-directed CAR T for NHL from 2018-2020 were analyzed for risk factors for infection and infectious complications. Bacterial, viral and fungal infections were recorded if there was a microbiologic or histopathologic diagnosis or if clinical suspicion for infection required empiric treatment. Infection severity was classified as mild, moderate, severe, life-threatening, or fatal as previously described (Young et al. 2016, van Burnik et al. 2007). Infections were identified from the day of the first CAR T-cell infusion up to 1 year after infusion. Observation of infections was terminated at the time of disease progression, initiation of next therapy, or death, whichever occurred first. Fisher's exact test and Wilcoxon rank-sum test were used to compare between cohorts. Poisson mixed effects model with a subject-specific random intercept and an offset to account for the duration at risk was used to identify risk factors for infections. Results: Of the 104 subjects in this study, 55 patients (53%) had MM treated with BCMA CAR T and 49 patients (47%) had NHL treated with CD19 CAR T. Median number of prior therapies was 6 (4 - 9) in the BCMA cohort and 3 (2-4) in the CD19 cohort (Table 1). Prior to starting lymphodepleting (LD) chemotherapy, most patients did not have IgG 400, ALC 200, or ANC 500. Almost all the patients were on antibacterial (99%), antiviral (99%) and antifungal (92%) prophylaxis (ppx), with 18%, 90% and 9% of patients starting this before LD chemotherapy, respectively. Median follow-up time was 5.8 months (95% CI: 4.2-6.4). In total, there were 87 infection events (48 bacterial, 33 viral, and 6 fungal) observed in 56 patients (54%), with 47 infections in 29 (53%) patients in the BCMA CAR T cohort and 40 infections in 27 (55%) patients in the CD19 CAR T cohort (p =0.9). The BCMA cohort had 19 bacterial (40%) vs 29 bacterial (73%) in CD19 cohort (p=0.005), while BCMA cohort had 25 viral (53%) vs 8 viral (20%) in CD19 cohort (p=0.002). Fungal infection rates were comparable between BCMA and CD19 cohorts, 3 (6%) vs 3 (8%) respectively (p=1). Among the infections that occurred, 20 (23%) were high severity occurring in 16 patients (15%) of the overall cohort. Four high severity infections (5%) occurred in 3 patients (5%) in the BCMA cohort while 16 high severity infections (18%) occurred in 13 patients (27%) in the CD19 cohort (p 0.001) (Figure 1). The BCMA cohort had higher rates of respiratory infections (68% vs 50%, p=0.1), while the CD19 cohort had higher rates of bloodstream infections (15% vs 2%, p=0.05) and gastrointestinal infections (10% vs 0%, p=0.04). The rates of grade (Gr) 3-4 neutropenia and IgG 300 in both the cohorts at various time points post CAR T were comparable. At 9-12 months, Gr 3-4 neutropenia was 7% vs 8% (p=1) and IgG 300 was 7% vs 33% (p=0.1) for the BCMA and CD19 cohorts respectively. Adjusting for time periods, risk factors for development of infections were use of steroids (incidence rate ratio IRR 1.6, 95% CI: 1.1-2.5, p=0.03) and post CAR T hypogammaglobulinemia (IgG 600) (IRR =2.1, 95% CI: 1.2-3.9, p=0.02). Conclusions: This retrospective study is one of the largest studies to date comparing the post CAR T infections rates between BCMA and CD19 directed CAR T treated patients. While the incidence of infection, use of antimicrobial ppx, and rates of Gr 3-4 neutropenia and hypogammaglobulinemia were comparable between BCMA and CD19 CAR T cohorts, viral infections were more common post BCMA CAR T while bacterial infections were more frequent post CD19 CAR T. Use of steroids as well as post CAR T hypogammaglobulinemia are possible risk factors for development of infections. Further studies are needed to examine the infectious complications post-CAR T treatment, characterize the underlying risk factors, and to establish appropriate prophylactic approaches in patients undergoing CD19- and BCMA-directed CAR T therapy. Disclosures Fakhri: University of California San Francisco: Current Employment. Ai:Nurix Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; ADC Therapeutics, Kymera: Membership on an entity's Board of Directors or advisory committees. Martin:Seattle Genetics: Research Funding; GSK: Consultancy; Sanofi: Research Funding; AMGEN: Research Funding; Janssen: Research Funding. Wolf:Adaptive: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Shah:BMS, Janssen, Bluebird Bio, Sutro Biopharma, Teneobio, Poseida, Nektar: Research Funding; GSK, Amgen, Indapta Therapeutics, Sanofi, BMS, CareDx, Kite, Karyopharm: Consultancy. Andreadis:Genentech: Other: Spouse Employee (salary and stock); Novartis: Research Funding; Celgene/Juno: Research Funding; Amgen: Research Funding; Merck: Research Funding; Gilead/Kite: Other: Advisor; Jazz Pharmaceuticals: Other: Advisor; Astellas: Other: Advisor; Seattle Genetics: Other: Advisor; Karyopharm: Other: Advisor; Incyte: Other. Wong:GSK: Research Funding; Amgen: Consultancy; Sanofi: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Research Funding; Roche: Research Funding; Janssen: Research Funding; Fortis: Research Funding.