Outcomes of Second Anti-CD19 CAR T-Cell Therapy (CART2) in Acute B Lymphoblastic Leukemia and the Impact of Allo-HSCT on Efficacy

For patients exhibiting a suboptimal response to the first chimeric antigen receptor (CAR) T-cell therapy (CART1) or relapse after remission, secondary CAR T-cell therapy (CART2) for the same target may be an option. We retrospectively analyzed patients with acute B-cell lymphoblastic leukemia (B-ALL) receiving CD19 CART1 at our center (n = 84) to report the clinical outcomes of CART2 and to identify the factors that may influence the outcomes. Twenty-six patients received CART2 for suboptimal response or relapse post-CART1. The incidence of cytokine release syndrome (CRS) after CART2 was 65.4% (17/26), with 11 cases classified as grade 1 (42.3%), four cases as grade 2 (15.4%), and two cases as grade 3 (7.7%). Neurotoxicity was observed in one patient (3.8%) after CART2 infusion. Fourteen patients (53.8%) achieved complete remission (CR) after CART2. CART2 exhibited an inferior response rate (CART2: 53.8%, 14/26; CART1: 81.0%, 64/79; P = 0.006) and a lower incidence of severe CRS (CART2: 7.7%, 2/26; CART1: 30.4%, 24/79; P = 0.020) compared with CART1, with a median progression-free survival (PFS) and a median overall survival (OS) of 6.2 months and 11.2 months, respectively. In particular, patients who progressed after consolidative allogeneic hematopoietic stem cell transplantation (allo-HSCT) following CART1 and then received CART2 demonstrated promising outcomes with a response rate of 80.0% (8/10), a median PFS of 7.9 months, and a median OS of 25.1 months. After adjusting for the confounding factors, the response rate (85.7%, 6/7) of CART2 administered to this cohort was better than those who did not bridge to allo-HSCT receiving CART2 (28.6%, 2/7) or non-CART2 treatments (13.3%, 2/15). The median OS after CART2, which was not reached, was significantly better than the median OS after CART2 (3.9 months, P = 0.014) and non-CART2 treatments (6.0 months, P = 0.012) administered in patients who did not undergo consolidative allo-HSCT post-CART1. Our results indicated that, although less effective than CART1, a subset of patients can still benefit from CART2 with mild adverse effects. For patients who relapsed after consolidative allo-HSCT post-CART1, treatment with CART2 is a viable option.