196. Antibodies to Vaccine-preventable Infections After CAR-T Cell Immunotherapy for B Cell Malignancies

Abstract Background Chimeric antigen receptor-modified T (CAR-T) cell immunotherapy for B cell hematologic malignancies results in prolonged B cell depletion. Little is known about the effects of CAR-T cell therapy on pre-existing pathogen-specific humoral immunity. Methods We conducted a prospective, cross-sectional study of children and adults treated with CD19- or BCMA-CAR-T cell therapy. Eligible patients were ≥ 6 months post-CAR-T cell infusion and in remission without subsequent chemoimmunotherapy. We measured total immunoglobulin G (IgG), pathogen-specific IgG levels for 12 vaccine-preventable infections, and B cell subsets from blood. Seroprotective antibody titers were based on standard thresholds. We described the proportion of patients with seroprotective titers and tested for associations between clinical factors and seroprotection using generalized estimating equations. Results We enrolled 65 patients who received CD19- (n=54) or BCMA- (n=11) CAR-T cell therapy. Seven patients were &lt; 18 years old. Samples were collected a median of 20 months (range, 7–68) after CAR T cell infusion. Seroprotection to vaccine-preventable pathogens was generally comparable to the U.S. population (Fig 1) even though blood CD19+ B cell counts were low (&lt; 20 cells/mm3) in 60% of patients. Among 30 patients without IgG replacement in the prior 16 weeks (4 half-lives of IgG), 27 (90%) had hypogammaglobulinemia. Despite this, these individuals had seroprotection to a median of 67% (IQR, 59%-73%) of tested pathogens (Fig 2A). The proportion of patients with seroprotection was lowest for mumps, hepatitis A and B, H. influenzae type B (Hib), S. pneumoniae, and B. pertussis. Patients receiving BCMA-CAR-T cells had seroprotection to fewer pathogens than those receiving CD19-CAR-T cells (Fig 2B), but the difference did not reach statistical significance (Fig 3). There were no significant differences by other variables. Figure 1. Proportion of CAR-T cell recipients with seroprotection to vaccine-preventable infections compared to the U.S. population, stratified by receipt of IgG replacement in the previous 16 weeks. Figure 2 A-B. Percentage of pathogens with seroprotective antibody titers among patients without IgG replacement in the previous 16 weeks. Figure 3. Association of clinical factors with seroprotection to vaccine-preventable infections among patients without IgG replacement in the previous 16 weeks (n=30) Conclusion Seroprotection for vaccine-preventable infections after CD19-CAR-T cell therapy was comparable to the general population. BCMA-CAR-T cell recipients may benefit most from replacement IgG. Vaccinations after CAR-T cell therapy should be considered and prioritized for S. pneumoniae, Hib, hepatitis viruses, and B. pertussis. Disclosures Justin J. Taylor, PhD, Vir Biotechnology (Grant/Research Support) Damian J. Green, MD, Cellectar Biosciences (Grant/Research Support)GSK (Advisor or Review Panel member)Juno Therapeutics (Grant/Research Support, Advisor or Review Panel member, Other Financial or Material Support, Royalities)Seattle Genetics (Grant/Research Support, Advisor or Review Panel member) Michael Boeckh, MD PhD, AlloVir (Consultant)EvrysBio (Advisor or Review Panel member, Other Financial or Material Support, share options)Gilead (Consultant, Grant/Research Support)GSK (Consultant)Helocyte (Advisor or Review Panel member, Shareholder)Lophius (Grant/Research Support)Merck (Consultant, Grant/Research Support)SymBio (Consultant)VirBio (Consultant, Grant/Research Support) David G. Maloney, MD, PhD, A2 Biotherapeutics (Consultant, Other Financial or Material Support, Stock Options)Bioline Rx (Consultant)Celgene (Consultant, Grant/Research Support)Gilead (Consultant)Juno Therapeutics (Consultant, Research Grant or Support, Other Financial or Material Support, four pending patents, not issued, licensed, no royalities, no licensees)Kite Pharma (Consultant, Grant/Research Support)Novartis (Consultant)Pharmacyclics (Consultant) Cameron J. Turtle, MBBS, PhD, Allogene (Other Financial or Material Support, Ad hoc advisory board (last 12 months))ArsenalBio (Advisor or Review Panel member, Other Financial or Material Support, Stock/options)AstraZeneca (Grant/Research Support, Other Financial or Material Support, Ad hoc advisory board (last 12 months))Caribou Biosciences (Advisor or Review Panel member, Other Financial or Material Support, Stock/options)Century Therapeutics (Advisor or Review Panel member)Eureka Therapeutics (Advisor or Review Panel member, Other Financial or Material Support, Stock/options)Juno Therapeutics (Grant/Research Support, Other Financial or Material Support, Patent: Licensed to Juno Therapeutics)Myeloid Therapeutics (Advisor or Review Panel member, Other Financial or Material Support, Stock/options)Nektar Therapeutics (Grant/Research Support, Other Financial or Material Support, Ad hoc advisory board (last 12 months))PACT Pharma (Other Financial or Material Support, Ad hoc advisory board (last 12 months))Precision Biosciences (Advisor or Review Panel member, Other Financial or Material Support, Stock/options)TCR2 Therapeutics (Grant/Research Support)T-CURX (Advisor or Review Panel member) Joshua A. Hill, MD, Allogene (Consultant)Allovir (Consultant)Gilead (Consultant)Karius (Grant/Research Support, Scientific Research Study Investigator)Takeda (Grant/Research Support, Scientific Research Study Investigator) </jats:sec

Anti-HLA antibodies in recipients of CD19 versus BCMA-targeted CAR T-cell therapy

Antibodies against foreign human leukocyte antigen (HLA) molecules are barriers to successful organ transplantation. B cell-depleting treatments are used to reduce anti-HLA antibodies but have limited efficacy. We hypothesized that the primary source for anti-HLA antibodies is long- lived plasma cells, which are ineffectively targeted by B cell depletion. To study this, we screened for anti-HLA antibodies in a prospectively enrolled cohort of 49 patients who received chimeric antigen receptor T-cell therapy (CARTx), targeting naive and memory B cells (CD19-targeted, n = 21) or plasma cells (BCMA-targeted, n = 28) for hematologic malignancies. Longitudinal samples were collected before and up to 1 year after CARTx. All individuals were in sustained remission. We identified 4 participants with anti-HLA antibodies before CD19-CARTx. Despite B cell depletion, anti-HLA antibodies and calculated panel reactive antibody scores were stable for 1 year after CD19-CARTx. Only 1 BCMA-CARTx recipient had pre-CARTx low-level anti-HLA antibodies, with no follow-up samples available. These data implicate CD19(neg) long-lived plasma cells as an important source for anti-HLA antibodies, a model supported by infrequent HLA sensitization in BCMA-CARTx subjects receiving previous plasma cell-targeted therapies. Thus, plasma cell- targeted therapies may be more effective against HLA antibodies, thereby enabling improved access to organ transplantation and rejection management

Pathogen-Specific Humoral Immunity and Infections in B Cell Maturation Antigen-Directed Chimeric Antigen Receptor T Cell Therapy Recipients with Multiple Myeloma

Chimeric antigen receptor (CAR) T cell therapy targeting B cell maturation antigen (BCMA-CARTx) is an emerging treatment for relapsed or refractory multiple myeloma (R/R MM). Here we characterize the epidemiology of infections, risk factors for infection, and pathogen- specific humoral immunity in patients receiving BCMA-CARTx for R/R MM. We performed a retrospective cohort study in 32 adults with R/R MM enrolled in 2 single-institution phase 1 clinical trials of BCMA-CARTx administered after lymphodepleting chemotherapy alone (n = 22) or with a gamma secretase inhibitor (GSI). We tested serum before and up to approximately 180 days after BCMA-CARTx for measles-specific IgG and for any viral-specific IgG using a systematic viral epitope scanning assay to describe the kinetics of total and pathogen-specific IgG levels pre- and post-BCMA-CARTx. We identified microbiologically documented infections to determine infection incidence and used Poisson regression to explore risk factors for infections within 180 days after BCMA-CARTx. Most individuals developed severe neutropenia, lymphopenia, and hypogammaglobulinemia after BCMA-CARTx. Grade >/=3 cytokine release syndrome (CRS; Lee criteria) occurred in 16% of the participants; 50% of the participants received corticosteroids and/or tocilizumab. Before BCMA-CARTx, 28 of 32 participants (88%) had an IgG <400 mg/dL, and only 5 of 27 (19%) had seropositive measles antibody titers. After BCMA-CARTx, all participants had an IgG <400 mg/dL and declining measles antibody titers; of the 5 individuals with baseline seropositive levels, 2 remained above the seroprotective threshold post-treatment. Participants with IgG MM (n = 13) had significantly fewer antibodies to a panel of viral antigens compared with participants with non-IgG MM (n = 6), both before and after BCMA-CARTx. In the first 180 days after BCMA-CARTx, 17 participants (53%) developed a total of 23 infections, of which 13 (57%) were mild-to- moderate viral infections. Serious infections were more frequent in the first 28 days post-treatment. Infections appeared to be more common in individuals with higher-grade CRS. Individuals with R/R MM have substantial deficits in humoral immunity. These data demonstrate the importance of plasma cells in maintaining long-lived pathogen-specific antibodies and suggest that BCMA-CARTx recipients need ongoing surveillance for late-onset infections. Most infections were mild- moderate severity viral infections. The incidence of early infection appears to be lower than has been reported after CD19-directed CARTx for B cell neoplasms, possibly due to differences in patient and disease characteristics and regimen-related toxicities

Humoral immunogenicity of the seasonal influenza vaccine before and after CAR-T-cell therapy: a prospective observational study

Recipients of chimeric antigen receptor-modified T (CAR-T) cell therapies for B cell malignancies have profound and prolonged immunodeficiencies and are at risk for serious infections, including respiratory virus infections. Vaccination may be important for infection prevention, but there are limited data on vaccine immunogenicity in this population. We conducted a prospective observational study of the humoral immunogenicity of commercially available 2019-2020 inactivated influenza vaccines in adults immediately prior to or while in durable remission after CD19-, CD20-, or B cell maturation antigen-targeted CAR-T-cell therapy, as well as controls. We tested for antibodies to all four vaccine strains using neutralization and hemagglutination inhibition (HAI) assays. Antibody responses were defined as at least fourfold titer increases from baseline. Seroprotection was defined as a HAI titer >/=40. Enrolled CAR- T-cell recipients were vaccinated 14-29 days prior to (n=5) or 13-57 months following therapy (n=13), and the majority had hypogammaglobulinemia and cellular immunodeficiencies prevaccination. Eight non-immunocompromised adults served as controls. Antibody responses to >/=1 vaccine strain occurred in 2 (40%) individuals before CAR-T-cell therapy and in 4 (31%) individuals vaccinated after CAR-T-cell therapy. An additional 1 (20%) and 6 (46%) individuals had at least twofold increases, respectively. One individual vaccinated prior to CAR-T-cell therapy maintained a response for >3 months following therapy. Across all tested vaccine strains, seroprotection was less frequent in CAR-T-cell recipients than in controls. There was evidence of immunogenicity even among individuals with low immunoglobulin, CD19(+) B cell, and CD4(+) T-cell counts. These data support consideration for vaccination before and after CAR-T-cell therapy for influenza and other relevant pathogens such as SARS-CoV-2, irrespective of hypogammaglobulinemia or B cell aplasia. However, relatively impaired humoral vaccine immunogenicity indicates the need for additional infection-prevention strategies. Larger studies are needed to refine our understanding of potential correlates of vaccine immunogenicity, and durability of immune responses, in CAR-T-cell therapy recipients

Antibodies against vaccine-preventable infections after CAR-T cell therapy for B cell malignancies

BACKGROUNDLittle is known about pathogen-specific humoral immunity after chimeric antigen receptor-modified T (CAR-T) cell therapy for B cell malignancies.METHODSWe conducted a prospective cross-sectional study of CD19-targeted or B cell maturation antigen-targeted (BCMA-targeted) CAR-T cell therapy recipients at least 6 months posttreatment and in remission. We measured pathogen-specific IgG against 12 vaccine-preventable infections and the number of viral and bacterial epitopes to which IgG was detected ("epitope hits") using a serological profiling assay. The primary outcome was the proportion of participants with IgG levels above a threshold correlated with seroprotection for vaccine-preventable infections.RESULTSWe enrolled 65 children and adults a median of 20 months after CD19- (n = 54) or BCMA- (n = 11) CAR-T cell therapy. Among 30 adults without IgG replacement therapy (IGRT) in the prior 16 weeks, 27 (90%) had hypogammaglobulinemia. These individuals had seroprotection to a median of 67% (IQR, 59%-73%) of tested infections. Proportions of participants with seroprotection per pathogen were comparable to population-based studies, but most individuals lacked seroprotection to specific pathogens. Compared with CD19-CAR-T cell recipients, BCMA-CAR-T cell recipients were half as likely to have seroprotection (prevalence ratio, 0.47; 95% CI, 0.18-1.25) and had fewer pathogen-specific epitope hits (mean difference, -90 epitope hits; 95% CI, -157 to -22).CONCLUSIONSeroprotection for vaccine-preventable infections in adult CD19-CAR-T cell recipients was comparable to the general population. BCMA-CAR-T cell recipients had fewer pathogen-specific antibodies. Deficits in both groups support the need for vaccine and immunoglobulin replacement therapy studies.FUNDINGSwiss National Science Foundation (Early Postdoc Mobility grant P2BSP3_188162), NIH/National Cancer Institute (NIH/NCI) (U01CA247548 and P01CA018029), NIH/NCI Cancer Center Support Grants (P30CA0087-48 and P30CA015704-44), American Society for Transplantation and Cellular Therapy, and Juno Therapeutics/BMS