Front-line consolidation with CAR-t therapy in newly diagnosed adult ph-negative b-acute lymphoblastic leukemia: Results from a prospective, phase 2 study

Abstract Background: Achieving deep remission is crucial for durable responses in B-cell acute lymphoblastic leukemia (B-ALL). Our group has shown that CD19-directed CAR-T therapy induces deep remission in relapsed/refractory cases. However, its role as a front-line consolidation strategy to achieve longer-lasting remissions, reduce chemotherapy burden and toxicity, and potentially improve survival remains largely unexplored. Aims: Building upon this setting, we initiated a Phase 2 trial assessing whether front-line CAR-T consolidation further eradicates residual disease and improves long-term outcomes in newly diagnosed adult Ph-negative B-ALL. Methods: In this study, we prospectively enrolled untreated adult patients with Ph-negative B-ALL (≥18 years). These patients initially received pediatric-inspired induction therapy, which included a combination of vincristine, idarubicin, cyclophosphamide, asparaginase, prednisone, and venetoclax, followed by 1-2 consolidation cycles (for further details, see ClinicalTrials.gov Identifier: NCT06481241). Subsequently, they received a single infusion of murine-derived second-generation 4-1BB-CD19 CAR-T as consolidation therapy during the first remission period. Maintenance therapy consisted of alternating administrations of vincristine, methotrexate, mercaptopurine, prednisone, and oral venetoclax. Intrathecal methotrexate (MTX), cytarabine, and dexamethasone were administered for central nervous system (CNS) prophylaxis. Results: As of the cutoff date in February 2025, 44 patients were enrolled in the trial and received CD19 CAR-T therapy as consolidation. All patients were included in the efficacy and safety evaluation. The median age was 36 years (range, 18-70), with 28 patients (63.6%) being male, all patients were Asian. Among these, 8 (18.2%) had a Ph-like phenotype, 5 (11.4%) with a TP53 mutation, 4 (9.1%) had complex karyotypes and 1 with extramedullary involvement (2.2%). Other high-risk cytogenetic abnormalities included KMT2A rearrangement (4, 9.1%), ZNF384 rearrangement (4, 9.1%), IKZF1 alteration (5, 11.4%), and non-P80R PAX5 alteration or BCOR mutations (6, 13.6%). Prior to CAR-T therapy, 7 patients were MRD-positive tested by multiparametric flow cytometry, and 12/33 (51.5%) patients with detectable IgH MRD by NGS (>10-6). After CAR-T infusion, all patients achieved MRD negativity as confirmed by flow cytometry (below the lower limit of detection), and 96.9% (32/33) were free of NGS-detectable MRD within 3 months. Regarding CAR-T expansion, all patients exhibited CAR-T cell expansion, with a median peak expansion level of 1.1×10⁸ (4.31×106—4.89×10⁸) CAR-T cells/L. After a median follow-up of 10.6 months, the 1-year overall survival (OS) rate was 100%, and the 1-year leukemia-free survival (LFS) rate was 97.7%. One patient with morphological relapse underwent humanized CD19/CD22 dual-target CAR-T therapy followed by allogeneic hematopoietic stem cell transplantation (HSCT), while another patient with a positive flow cytometry result received CD19/CD22 dual-target CAR-T therapy as a salvage treatment. Both patients are now in sustained remission. Additionally, 4 patients with high-risk cytogenetic abnormalities who received allogeneic HSCT during complete remission (CR1) remain in sustained remission. In terms of toxicity, cytokine release syndrome (CRS) occurred in 26 patients (59.1%), all of whom experienced grade 1 severity, and no patient developed immune effector cell-associated neurotoxicity syndrome (ICANS). Furthermore, no patients experienced grade 3 or higher non-hematologic adverse events. Conclusion: First-line CAR-T therapy as consolidation treatment can effectively eradicate leukemia cells to a deep level and demonstrates a favorable safety profile, significantly shortening treatment duration while maintaining sustained remission.