Editor's Note： At the 5th Annual Meeting of Chinese Alliance for Societies of Hematology (2025 CASH), Professor Ying Wang from the Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences, presented a detailed summary of the latest research on CAR-T therapy for ALL. Her presentation covered the efficacy and safety of CAR-T therapies targeting various antigens, including CD19, CD22, and dual-target CAR-T approaches, as well as their application in specific patient populations. She also explored the factors influencing CAR-T therapy outcomes and discussed future directions to optimize this treatment for clinical use. Hematology Frontier has compiled the key insights from her presentation.

Current Landscape and Directions for CAR-T Therapy in B-ALL

Approved CD19 CAR-T therapies have significantly transformed the treatment landscape for relapsed or refractory B-ALL (R/R B-ALL). However, challenges remain, including relapse after CD19 CAR-T treatment, which highlights the need for alternative CAR-T designs and new target antigens. Beyond CD19, CD22 has emerged as a key target. CAR-T cells targeting CD22 are particularly beneficial for patients with low or absent CD19 expression or those who relapse after CD19-targeted therapy. Dual-target CAR-T approaches, including dual transgene, bispecific tandem, co-transduction, and co-administration strategies, are under active development. These therapies have demonstrated the potential to achieve complete remission in cases where CD19 CAR-T therapy has failed, although further optimization of infusion timing and binding domains is required to enhance their efficacy.

Another promising strategy is the reinfusion of CD19 CAR-T cells, which offers a viable option for patients who lose CAR-T cell engraftment. In addition, allogeneic CAR-T therapy, which is currently under investigation, presents advantages such as reduced delays and lower production costs compared to autologous CAR-T. To improve accessibility and treatment readiness, next-day CAR-T manufacturing protocols have also been developed and have entered Phase I clinical trials.

Latest Advances in CD19 CAR-T Therapy for B-ALL

Recent updates from the pivotal Phase II clinical trial for naxitamab in B-ALL demonstrate its transformative potential. Within three months, the objective response rate (ORR) was 85.4%, with 70.8% of patients maintaining a response at the three-month mark. After a median follow-up of 23.7 months, the median duration of response (DOR) among patients with and without subsequent hematopoietic stem cell transplantation (HSCT) was 20.7 months. At three months, the median relapse-free survival (RFS) was 21.6 months, and the median overall survival (OS) had not been reached. The two-year overall survival rate was 55.2%, indicating promising long-term outcomes.

Regarding safety, the rate of grade 3 or higher cytokine release syndrome (CRS) was 12.5%, while immune effector cell-associated neurotoxicity syndrome (ICANS) of the same grade occurred in 6.2% of patients. All cases of CRS and ICANS were resolved after treatment, with no treatment-related fatalities reported.

Pharmacokinetic data showed that the median time to peak CAR-T concentration was 11 days post-infusion, with a median peak concentration of 1.75×10⁵ copies/μg gDNA. CAR-T cells demonstrated sustained in vivo persistence, with a median duration of 92 days (ranging from 14.0 to 733.7 days). At the data cutoff, the longest detectable CAR-T presence was 24 months post-infusion.

These findings highlight the remarkable efficacy, durable response, and manageable safety profile of naxitamab, positioning it as a highly promising therapy for R/R B-ALL. The demonstrated ability of CAR-T cells to persist in vivo over an extended period underscores their potential to provide lasting therapeutic benefits in this challenging patient population.

Real-world data from the Center for International Blood and Marrow Transplant Research (CIBMTR) (ASH P5092) reported on 242 patients, the majority of whom had previously received at least one targeted therapy. Among them, 62% had been treated with blinatumomab, 44% with inotuzumab ozogamicin, and 32% had undergone prior allogeneic stem cell transplantation (alloSCT). The overall response rate (ORR) was 80%, with estimated 6-month rates for duration of response (DOR, n=192), relapse-free survival (RFS, n=242), and overall survival (OS, n=242) being 67%, 55%, and 80%, respectively.

The safety profile was manageable, with grade 3 or higher cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) observed in 13% and 24% of patients, respectively.

Multivariate analysis revealed that prior alloSCT was associated with improved DOR (hazard ratio [HR], 0.22) and RFS (HR, 0.62) compared to those who had not undergone alloSCT. However, a bone marrow blast percentage greater than 50% before lymphodepletion, primary refractory disease, and a history of cardiac comorbidities were associated with an increased risk of grade 3 or higher CRS. Additionally, factors such as prior alloSCT, high-risk cytogenetic scores, and moderate-to-severe pulmonary comorbidities at the time of infusion were linked to a higher risk of grade 3 or higher ICANS.

These findings underline the importance of prior treatment history and patient-specific factors in shaping outcomes and safety profiles in the real-world use of CAR-T therapies, emphasizing the need for personalized treatment approaches.

A study on Meta10-19 CAR-T cells expressing IL-10 demonstrated the induction of complete remission and improved long-term persistence in relapsed or refractory B-cell hematologic malignancies (ASH Oral 92). The overall response rate (ORR) reached 100%, with a median time to best response of 0.9 months. The median duration of response (mDOR) and median progression-free survival (mPFS) had not yet been reached. No cases of grade 2 or higher immune effector cell-associated neurotoxicity syndrome (ICANS) were observed, and the incidence of grade 3 or higher cytokine release syndrome (CRS) in the R/R B-ALL cohort was 10%.

These findings highlight the remarkable efficacy and manageable safety profile of Meta10-19 CAR-T cells in this patient population.

A study conducted by Sant Joan de Déu Children’s Hospital on the use of CAR-T cell reinfusion (CART2) for R/R B-ALL patients, analyzed as part of the GoCART consortium (ASH Oral 965), showed promising results. Over 80% of patients received a second infusion due to relapse, with 92% of reinfusions involving autologous CAR-T cells.

The reasons for CART2 included early loss of B-cell aplasia (17%), relapse (83%), molecular relapse (14.6%), and morphologic relapse (68.3%). The second infusion was found to be safe and effective, with no cases of grade 3 or higher cytokine release syndrome (CRS) or immune effector cell-associated neurotoxicity syndrome (ICANS). The MRD negativity rate reached 50%, and the 2-year overall survival (OS) rate was 54.3%.

Importantly, lower tumor burden prior to CART2 was associated with better outcomes, including improved OS and leukemia-free survival (LFS). These findings underscore the potential of CART2 as an effective therapeutic strategy for R/R B-ALL patients, particularly when tumor burden is minimized before reinfusion.

(2) Latest Advances in Dual-Target CD19/CD22 CAR-T Therapy for B-ALL

Experience with CD19/CD22 bicistronic CAR-T cells in children and young adults (ASH Oral 680) demonstrated remarkable efficacy. At the DL-1 dose level, BiCis19/22 CAR-T cells achieved a 100% MRD negativity rate, significantly improving persistence.

Furthermore, early intervention for cytokine release syndrome (CRS) and immune effector cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS) enhanced the safety profile for patients with high tumor burden. These findings highlight the potential of dual-target CAR-T therapy to provide deep remissions while ensuring better safety outcomes in this challenging patient population.

(3) Advances in CD19 CAR-T Therapy for Special Populations with B-ALL

Data from ASH Oral 523 highlighted the efficacy of CD19 CAR-T therapy in relapsed or refractory B-ALL (R/R B-ALL) patients aged 60 and older. The complete remission (CR) or CR with incomplete hematologic recovery (CRi) rate was consistent across age groups, reaching approximately 90%.

The overall response rate (ORR) remained around 90% across age stratifications, but patients aged 70 and older exhibited relatively lower median progression-free survival (PFS) and 12-month PFS rates, while overall survival (OS) showed no significant differences between groups.

The incidence of grade 3–4 cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) was comparable across groups. However, patients aged 70 and older experienced a relatively higher rate of grade 1–2 ICANS.

Notably, the use of growth factors, transfusion support, and infection rates among elderly patients were low, indicating the treatment’s manageable safety profile even in this age group.

A single-center, single-arm, non-randomized preliminary study evaluated the use of CD19 CAR-T cells as the final consolidation therapy for elderly B-ALL patients achieving their first complete remission (CR) (ASH Oral 966). The results showed that CD19 CAR-T cells effectively expanded in peripheral blood at low antigen burden levels (MRD-negative) and were detectable in cerebrospinal fluid. These cells remained detectable in peripheral blood for up to 9 months post-infusion.

Among the 14 patients who received the infusion, 2 maintained MRD-negative CR for over a year, and 9 maintained MRD-negative CR for more than 6 months. One patient with Ph+ ALL experienced molecular relapse via next-generation sequencing (NGS) at 6 months post-infusion but achieved remission and remained alive following hematopoietic stem cell transplantation.

No dose-limiting toxicity (DLT) events were observed among the 14 patients. Grade 1 cytokine release syndrome (CRS) occurred in 64% of patients, but no cases of grade 2 or higher CRS or ICANS of any grade were reported.

These findings suggest that CD19 CAR-T cells are a safe and effective consolidation therapy option for elderly B-ALL patients with low antigen burden, providing durable MRD-negative remission in a significant proportion of patients.

A multicenter study conducted by the Bone Marrow Transplant Center of the First Affiliated Hospital, Zhejiang University School of Medicine, evaluated the efficacy of CD19 CAR-T therapy in treating Ph-positive relapsed/refractory B-ALL (R/R B-ALL) (ASH P4201). The study demonstrated significant short-term efficacy, with an overall response rate (ORR) of 87.1% (81/93) and an MRD negativity rate of 96% (78/81). Molecular response was achieved in 78.5% of patients overall.

With a median follow-up of 25 months, the median overall survival (OS) was 20.8 months, and the 1-year OS rate was 66.3%. Among the 81 patients who achieved CR or CRi, the median OS was 25.5 months, with 6-month and 12-month OS rates of 88.9% and 69.1%, respectively. The median leukemia-free survival (LFS) was 8.1 months, with 6-month and 12-month LFS rates of 61.8% and 42.5%, respectively. Patients who achieved deep remission (MRD negativity or CMR/MMR) had longer OS durations.

Multivariate analysis indicated that patients with an ECOG performance status of 0–2 had better OS and LFS outcomes, while those with complex karyotypes and ABL1 kinase mutations showed poorer OS and LFS. The incidence rates of grade 3 or higher cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) were 16.3% and 2.2%, respectively.

These findings highlight the strong efficacy and manageable safety profile of CD19 CAR-T therapy in treating Ph-positive R/R B-ALL, with deep remission significantly contributing to improved survival outcomes.

A retrospective, single-center analysis conducted by the Hematology Department at Tongji Hospital, Tongji Medical College of Huazhong University of Science and Technology (ASH P1447) demonstrated that CAR-T therapy offers a longer duration of response (DOR) and better central nervous system (CNS) penetration compared to blinatumomab (BiTE) in relapsed/refractory B-ALL (R/R B-ALL) patients.

At 3 months, the CAR-T group achieved a higher overall response rate (ORR) compared to the BiTE group (87% vs. 65%). At 6 months, the CAR-T group also demonstrated a higher DOR (89% vs. 72.6%) compared to the BiTE group. In pre-specified subgroup analyses, prior transplant history was the only adverse prognostic factor for 6-month DOR in the BiTE group (hazard ratio [HR] 7.24).

Notably, CAR-T therapy achieved a 100% response rate in four cases of CNS leukemia (CNSL) that developed after BiTE treatment. However, CAR-T therapy was associated with higher rates of grade 3 or greater cytokine release syndrome (CRS) and neurotoxicity compared to BiTE.

These findings highlight the superior efficacy of CAR-T therapy over BiTE in achieving deeper and longer-lasting responses, particularly in CNS-involved cases, despite a higher risk of severe adverse events.

(4) Advances in Early Collection, Bridging Therapy, and Efficacy in CAR-T Cell Therapy

In a CD22 CAR-T trial (ASH P4853) involving children, adolescents, and young adults (CAYA) with relapsed/refractory B-ALL, researchers investigated early collection (EC) of T cells. EC patients were defined as those who relapsed after initial induction therapy or following reinduction therapy due to high-risk features. The T-cell phenotypes in the early collection group and healthy donor group were similar to those observed in the complete remission (CR) group following CD22 CAR-T therapy. Conversely, the non-responding (NR) group exhibited distinct T-cell phenotypes at the time of leukapheresis compared to the CR group. The CR group had a higher proportion of naïve and central memory T cells and a lower proportion of effector memory T cells compared to the NR group.

The study also revealed that specific T-cell markers in early collection samples could predict responses to CD22 CAR-T therapy. Key characteristics of the responding group included a lower degree of T-cell differentiation and increased expression of activation markers. Although early collection leukemia samples displayed some exhaustion features compared to healthy donor samples, they generally expressed favorable T-cell characteristics associated with CAR-T cell response. Preliminary data support the strategy of early T-cell collection in patients with relapsed or high-risk B-ALL to improve the likelihood of successful CAR-T therapy when needed in the future.

In the FELIX study (ASH P3458), 127 patients were divided into groups receiving bridging therapy (BT) with inotuzumab ozogamicin (InO), BT without InO, or no BT at all. CAR-T cell expansion was robust across all groups; however, peak expansion and the area under the curve (AUC0-28d) were significantly higher in the non-InO BT and no-BT groups compared to the InO group. In the non-InO BT and no-BT groups, higher expansion correlated with higher disease burden as well as the incidence of CRS and ICANS.

Compared to patients receiving non-InO BT or no BT, those who received InO bridging therapy had significantly reduced bone marrow tumor burden at the time of lymphodepletion. The InO group also achieved superior event-free survival (EFS) and overall survival (OS), with manageable safety profiles.

Conclusion and Outlook

CAR-T cell therapy has made significant progress in the treatment of ALL, demonstrating efficacy and safety advantages with different CAR-T targets and strategies across diverse patient populations and treatment settings. However, further optimization of CAR-T cell design, manufacturing, and treatment protocols is required to enhance efficacy, reduce adverse events, and expand its applicability, offering more ALL patients the potential for long-term survival.

Future research should focus on addressing the current challenges in CAR-T therapy, including relapse, adverse event management, and improving product accessibility. These efforts will drive the continued advancement of CAR-T technology in leukemia treatment.

---

Professor Ying Wang

Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences

Professor Ying Wang serves as the Director of the Immunocell Therapy Center at the Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences. She is a chief physician, holds a doctorate in medicine, and is a Ph.D. supervisor.

Professor Wang has been recognized as a Tianjin Medical Talent and holds prominent positions, including:

• Standing Committee Member of the 6th Hematological Oncology Professional Committee, Chinese Anti-Cancer Association
• Vice Chair of the Youth Working Group of the Hematological Rehabilitation Professional Committee, Chinese Rehabilitation Medicine Association (1st Session)
• Standing Committee Member of the Leukemia Branch, Chinese Medical Education Association
• Member of the Hematopoietic Stem Cell Transplantation and Cell Therapy Professional Committee, Chinese Medical Education Association
• Member of the Experimental Diagnostics Group, 11th Hematology Committee, Chinese Medical Association

In addition to her clinical and research roles, she is also an editorial board member for several esteemed journals, including:

• Corresponding Editorial Board Member for Chinese Journal of Hematology
• Editorial Board Member for Leukemia & Lymphoma

Professor Wang has also completed postdoctoral research at the Winship Cancer Institute, Emory University, USA, and her primary focus is on the clinical and basic research of leukemia