SARS-CoV-2-reactive antibody waning, booster effect and breakthrough SARS-CoV-2 infection in hematopoietic stem cell transplant and cell therapy recipients at one year after vaccination.

The kinetics of SARS-CoV-2 reactive IgG antibodies after full vaccination and booster in allogeneic and autologous stem cell transplantation (allo-HSCT, ASCT) and chimeric antigen receptor T-cell therapy (CAR-T) are of utmost importance for estimating risk of infection. A prospective multicenter registry-based cohort study, conducted from December 2020 to July 2022 was used to analyze antibody waning over time, booster effect and the relationship of antibody response and breakthrough infection in 572 recipients (429 allo-HSCT, 121 ASCT and 22 CAR-T cell therapy). A significant decline in antibody titers was observed at 3 and 6 months after full vaccination in recipients without pre-vaccine SARS-CoV-2 infection, whereas recipients infected prior to vaccination showed higher and stable antibody titers over time. In poor responders, a booster dose was able to increase antibody titers in 83% of allo-HSCT and 58% of ASCT recipients but not in CART-T cell recipients [0%] (p < 0.01). One-year cumulative incidence of breakthrough infection was 15%, similar among cell therapy procedures. Immunosuppressive drugs at the time of vaccination [hazard ratio (HR) 1.81, p = 0.0028] and reduced intensity conditioning (HR 0.49, p = 0.011) were identified as the only conditions associated with different risk of breakthrough infection in allo-HSCT recipients. Antibody titers were associated with breakthrough infection and disease severity. No death was observed among the 72 breakthrough infections. Antibody level decay after the first two vaccine doses was common except in recipients with pre-vaccination SARS-CoV-2 infection. Poorly responding allo-HSCT recipients showed a response advantage with the booster as compared to ASCT and, especially, the null response found in CAR-T cell recipients. Antibody titers were positively correlated with the risk of breakthrough SARS-CoV-2 infection which was mainly driven by the immunosuppression status.

MM-198 Anti-BCMA Therapy in Multiple Myeloma: A Single-Center Experience

Context: Triple class exposed/refractory multiple myeloma (MM) represents an unmet medical need because there is no standard of care and overall survival (OS) does not exceed 9 months. B-cell maturation antigen (BCMA) has appeared as an interesting target to treat MM. Objective: To indirectly compare the time to access therapy and hospitalization as well as the toxicity and efficacy of BCMA bispecific monoclonal antibodies (BiAbs) and CAR-T. Design: An observational retrospective study was designed including MM patients treated with BCMA CAR-T or BiAbs in clinical trials at the Hospital of Salamanca (October 2018–April 2022). Patients or Other Participants: Forty-nine patients were treated with BCMA therapy. Intervention: N/A. Main Outcome Measures: The time to access the treatment and hospitalization, global responses, cytokine release syndrome (CRS), neurotoxicity, infections, progression-free survival (PFS), and OS. Results: Twenty-seven patients (55.1%) received CAR-T and 22 (44.9%) received BiAbs. Thirty-nine (79.6%) patients were triple exposed and 28 (57.1%) were triple refractory. Patients who received BiAbs were treated earlier (12 vs. 56 days;P<0.001) and were hospitalized for less time (13 vs. 21 days;P=0.018). Overall response rate was superior in CAR-T patients (100% vs. 52.4%;P<0.001) as was percentage of CR (70.4% vs. 47.6%;P=0.110). Incidence of CRS was higher in the CAR-T group than the BiAbs group (92.6% vs. 68.2%;P=0.028) as were the percentages of grade 4 neutropenia (92.6% vs. 22.7%;P<0.001) and thrombocytopenia (70.4% vs. 9.1%;P<0.001). Infections were more frequent in the BiAbs group (especially between the first and third month of treatment initiation, 55.6% vs. 14.8%;P=0.004), including COVID-19 infection (50.0% vs. 29.6%;P=0.002). With a median follow-up of 14.3 months (1.1–41.8), PFS was superior in patients treated with CAR-T (18.9 vs. 6.1 months;P=0.045) as was OS (not reached vs. 25.5 months;P=0.016). Conclusions: The times to access therapy and hospitalization were shorter in patients treated with BiAbs. The incidences of CRS and cytopenia were higher in the CAR-T group, but mid-term and COVID-19 infections were more frequent in the BiAbs group. Response, PFS, and OS were superior in patients treated with CAR-T than those treated with BiAbs.