CD34+-selected stem cell boost can safely improve cytopenias following CAR T-cell therapy

2] For example, in the ELIANA study, 41% and 53% of patients demonstrated grade 3 to 4 thrombocytopenia and neutropenia, respectively, persisting beyond day 30. Impaired hematological recovery after CAR T-cell therapy can lead to susceptibility to opportunistic infections, bleeding, and/or transfusion dependence, causing significant morbidity and mortality. Pre-CAR T-cell therapy lymphodepletion causes cytopenia that generally recovers in most patients within a month after CAR T-cell therapy. However, a proportion of patients develop persistent cytopenia, particularly neutropenia, associated with bone marrow (BM) hypoplasia that can persist for several months after CAR T-cell therpay. We hypothesized that for those patients who have undergone allogeneic SCT before CAR T-cell therapy and develop persistent cytopenia after CAR-T cell therapy, an unconditioned CD34 1 -selected stem-cell boost (SCB) from the SCT donor could be used to improve the cytopenia, similar to its use in those who have poor graft function after SCT. A cohort of 101 pediatric and young adults from 2 centers in the United Kingdom with r/r B-ALL were treated with CAR T-cell therapy from May 2016 through December 2021. Of those patients, 2 were not evaluable for assessment of cytopenias after day 128 of CAR infusion (1 died on post-infusion day 4, and 1 had a morphological relapse on day 28). Of the 99 evaluable patients, 52 had undergone SCT before CAR therapy and 23 (44.2%) of them developed grade 3 to 4 cytopenia. Of the 47 patients who did not undergo an SCT, 23 (48.9%) developed grade 3 to 4 cytopenia. The difference in the rate of cytopenia between the 2 groups was not significant (P 5 .5999).