In recent years, the field of hematologic malignancies has witnessed numerous groundbreaking advancements, with Chinese researchers making increasingly significant contributions, particularly in the area of cellular therapy. Their work has greatly accelerated both academic development and clinical practice in this domain. As we step into the new year, Hematology Frontier has invited Dr. Wenbin Qian from The Second Affiliated Hospital of Zhejiang University School of Medicine to provide an in-depth review of CAR-T cell therapy for B-cell lymphoma, summarizing approved CAR-T products, clinical trial data, real-world outcomes, and ongoing challenges. Additionally, this discussion explores strategies for enhancing CAR-T therapy, including novel targets, dual-target CAR-T designs, and gene-editing improvements, aiming to offer valuable insights for clinical practice and future research directions.

Current Landscape of CAR-T Cell Therapy for B-Cell Lymphoma

B-cell lymphoma, as a common type of hematologic malignancy, has remained a focal point of therapeutic innovation. CAR-T cell therapy, which utilizes genetic engineering to equip T cells with chimeric antigen receptors (CARs) that enable specific tumor recognition and destruction, has emerged as a transformative approach in treating relapsed/refractory (R/R) B-cell lymphomas. This article provides a comprehensive overview of CAR-T therapy in B-cell lymphoma, offering valuable references for clinical applications.

CAR-T Products: Clinical Trials and Real-World Data in 2024

Approved CAR-T Products for B-Cell Lymphoma

To date, several CD19-targeted CAR-T products have been approved worldwide for the treatment of B-cell lymphomas, reflecting rapid global progress and the continuous optimization of treatment strategies. These approvals highlight the remarkable strides made in CAR-T therapy and the expanding treatment options for patients with relapsed/refractory B-cell lymphoma (R/R BCL).

In October 2017, the United States approved Yescarta (axicabtagene ciloleucel, Axi-cel) for R/R large B-cell lymphoma (R/R LBCL) and R/R follicular lymphoma (R/R FL). This milestone marked the beginning of CAR-T’s clinical impact in hematologic malignancies.

Subsequently, in July 2020, the FDA approved Tecartus (brexucabtagene autoleucel, Brexu-cel) for patients with R/R mantle cell lymphoma (R/R MCL), further expanding the application of CAR-T therapy in aggressive lymphomas.

In February 2021, Breyanzi (lisocabtagene maraleucel, Liso-cel) was approved for R/R LBCL, providing an alternative CAR-T option with distinct pharmacokinetic and safety profiles compared to earlier products.

China’s Progress in CAR-T Therapy

China has quickly emerged as a key player in the CAR-T landscape, with notable approvals that enhance treatment accessibility for domestic patients.

In June 2021, the National Medical Products Administration (NMPA) approved Equecabtagene Autoleucel as China’s first commercial CAR-T therapy for R/R LBCL. Shortly thereafter, in September 2021, Relmacabtagene Autoleucel was also approved, marking a significant advancement in China’s cell therapy sector. These approvals have provided diversified treatment options for Chinese patients with relapsed/refractory B-cell lymphoma, demonstrating China’s increasing capabilities in CAR-T research, manufacturing, and clinical application.

As research continues to evolve, the next sections will explore clinical trial outcomes, real-world data, and emerging strategies that are shaping the future of CAR-T therapy for B-cell lymphoma.

Clinical Trials and Real-World Outcomes

To date, multiple clinical trials have demonstrated the efficacy of CD19 CAR-T therapies. Specifically, Axi-cel has shown remarkable objective response rates (ORR) in the treatment of relapsed/refractory (R/R) large B-cell lymphoma (LBCL) and R/R follicular lymphoma (FL), reaching 82% and 94%, respectively. Meanwhile, its complete response (CR) rates were 54% and 79%. For R/R mantle cell lymphoma (MCL), Brexu-cel achieved an ORR of 91% and a CR rate of 73%. Additionally, Liso-cel demonstrated an ORR of 73% and a CR rate of 53% in R/R LBCL. The domestically developed Relmacabtagene Autoleucel injection also exhibited promising efficacy in R/R LBCL, with an ORR of 77.6% and a CR rate of 53.5%.

In real-world studies, further validation of Axi-cel’s clinical efficacy was observed in a cohort of 1,297 patients with R/R LBCL, where it achieved an ORR of 70.9% and a CR rate of 52.4%, closely mirroring the results from clinical trials. Moreover, even among patients who did not fully meet the eligibility criteria of the ZUMA-1 trial, Axi-cel treatment still demonstrated clinical benefits. After adjusting for confounding factors using propensity score matching (PSM), a comparison with Tisa-cel revealed that while Axi-cel exhibited superior efficacy, it was also associated with a higher incidence of adverse effects.

These findings reinforce the clinical value of CD19 CAR-T therapies and provide robust evidence for shaping treatment strategies in the modern era.

Challenges in the Field: Resistance and Relapse

Although CAR-T cell therapy has demonstrated remarkable efficacy in the treatment of B-cell lymphomas, the field continues to face significant challenges, particularly CAR-T resistance and tumor relapse. The mechanisms underlying CAR-T resistance are complex and primarily involve three key aspects: CAR-T cell dysfunction, intrinsic tumor resistance, and the immunosuppressive tumor microenvironment.

CAR-T cell exhaustion is closely associated with several factors, including persistent antigen stimulation, the influence of immunosuppressive cells and factors, upregulated expression of inhibitory receptors (IRs), and metabolic disruptions. Meanwhile, intrinsic tumor resistance encompasses mechanisms such as antigen escape (through antigen loss, mutation, or conversion), upregulation of inhibitory ligands, impaired apoptotic pathways, lineage switching, and the lack of co-accessory molecules.

At the level of the immunosuppressive tumor microenvironment, factors such as poor vascular permeability and extracellular matrix (ECM) deposition hinder CAR-T cell infiltration. Additionally, immunosuppressive cells and cytokines, along with metabolic influences, may further contribute to resistance. A deeper understanding of these challenges is essential for enhancing the efficacy of CAR-T cell therapy and improving patient outcomes.

Exploration of New Targets

To address antigen escape observed in CD19 CAR-T cell therapy, researchers have developed various novel single-target and dual-target approaches. In the realm of single-target therapies, CAR-T cell products targeting CD20, CD22, CD70, ROR1, CD79, BAFF, and κ light chain (κLC) are currently undergoing active clinical trials.

Some of these trials have already yielded promising preliminary results. For instance, in a Phase 1 trial for patients with relapsed large B-cell lymphoma (LBCL) following CD19 CAR-T therapy, CD20 CAR-T (C-CAR066) induced complete remission (CR) in 8 out of 14 patients. Similarly, CD22 CAR-T therapy has demonstrated significant efficacy in CD19 CAR-T–refractory LBCL, achieving an objective response rate (ORR) of 68%, with a CR rate of 53% and a median survival of 14.1 months. Furthermore, CD70 CAR-T therapy has exhibited anti-lymphoma activity in patients with CD19-negative lymphoma.

These findings highlight the potential of novel CAR-T targets in overcoming resistance and improving treatment outcomes for patients with relapsed or refractory B-cell malignancies.

Dual-Target CAR-T Cell Therapy

Dual-target CAR-T cell therapy enhances therapeutic efficacy by simultaneously targeting two distinct antigens, effectively reducing the risk of resistance associated with single-target approaches. Common dual-target combinations include CD19/CD20, CD19/CD22, CD19/CD70, and CD20/CD22, with each structural design offering unique advantages and limitations.

Clinical research has demonstrated promising results for various dual-target CAR-T strategies. For instance, tandem CD19/CD20 CAR-T therapy in relapsed/refractory (R/R) B-cell lymphoma showed a 14% incidence of grade ≥3 cytokine release syndrome (CRS), with no cases of grade ≥3 immune effector cell-associated neurotoxicity syndrome (ICANS). Meanwhile, loop CD19/CD22 CAR-T therapy achieved an objective response rate (ORR) of 62% and a complete response (CR) rate of 29% in large B-cell lymphoma (LBCL). In B-cell acute lymphoblastic leukemia (B-ALL), the same therapy demonstrated an ORR of 100% and a CR rate of 88%, with a low incidence of grade ≥3 CRS and ICANS.

These findings highlight the potential of dual-target CAR-T strategies in improving treatment outcomes while mitigating resistance in B-cell malignancies.

Advances in Gene-Edited CAR-T Therapy

Gene editing has been leveraged to enhance CD19 CAR-T therapy, aiming to improve efficacy while reducing toxicity. Innovations such as fourth-generation armored CAR-T cells (Truck CAR-T) and PD-1 blockade CAR-T have been designed to boost therapeutic potency. Additionally, strategies like IL-6 knockout to mitigate cytokine release syndrome (CRS) and Toll-like receptor (TLR) insertion to reduce immune effector cell-associated neurotoxicity syndrome (ICANS) are being explored.

A notable example is the 7×19 armored CAR-T therapy developed by Wenbin Qian’s team, which has demonstrated promising results in a Phase I/II trial for relapsed/refractory large B-cell lymphoma (R/R LBCL). The study reported an objective response rate (ORR) of 79.5%, a complete response (CR) rate of 56.4%, and a partial response (PR) rate of 23.1%. The median progression-free survival (mPFS) reached 13 months, while the incidence of grade ≥3 CRS was 12.8%, and grade ≥3 ICANS was 10.3%. The estimated five-year overall survival (OS) and progression-free survival (PFS) were 43.6% and 30.8%, respectively. These results highlight the potential of gene-edited CAR-T therapies in optimizing treatment outcomes while minimizing severe adverse effects.

Emerging Next-Generation CAR-T Technologies

Next-generation CAR-T technologies, including allogeneic CAR-T (Allo CAR-T), FAST CAR-T, and in vivo CAR-T, are rapidly evolving, offering innovative approaches to overcome current limitations.

Allogeneic CAR-T therapy has gained attention due to its multiple advantages. It improves accessibility by eliminating the need for patient-specific manufacturing, reduces the risk of production failure, broadens applicability, and enables immediate off-the-shelf treatment. This approach also facilitates optimized cell selection and scalable manufacturing. However, Allo CAR-T therapy presents challenges, including an increased risk of graft-versus-host disease (GVHD), potential autoimmune reactions, risks associated with gene editing such as off-target toxicity and mutations, reduced persistence of CAR-T cells in vivo, and in certain cases, the possible need for hematopoietic stem cell transplantation.

FAST CAR-T technology has demonstrated exceptional efficacy and tolerability in clinical trials. The objective response rate has reached 80%, with a complete response rate of 80%. Cytokine release syndrome is primarily mild, with grade 1–2 cases occurring in 30% of patients, while the incidence of grade 3 ICANS remains at 10%. These advancements underscore the growing potential of next-generation CAR-T therapies in refining treatment strategies, improving patient outcomes, and addressing key limitations in current CAR-T approaches.

In addition, numerous in vivo CAR-T technologies are currently in the preparatory stages for clinical trials, signaling further advancements and expansion in this field. At the same time, researchers are actively exploring the potential of various alternative cell types, including but not limited to double-negative T cells (DNT), γδ T cells, umbilical cord blood-derived T cells, NK cells, macrophages, invariant natural killer T cells (iNKT cells), cytokine-induced killer (CIK) cells, and induced pluripotent stem cell (iPSC)-derived cells. Each of these cell types offers unique advantages, yet they also come with their own potential limitations and challenges.

Currently, the manufacturing process for CAR-T cells remains highly complex, resulting in approximately 7% of patients being unable to tolerate the wait until the treatment product is ready. Additionally, high tumor burden is a critical factor limiting the effectiveness of CAR-T therapy. Compared to patients with a maximum lesion diameter of less than 5 cm, those with lesions of 5 cm or larger have demonstrated lower response rates, shorter progression-free survival (PFS), and reduced overall survival (OS) following CAR-T treatment. As a result, implementing bridging therapy strategies to reduce tumor burden has become increasingly important.

Existing bridging therapy approaches primarily include bridging chemotherapy, bridging immunotherapy, and bridging radiotherapy. These strategies aim to optimize the timing and conditions for CAR-T therapy, potentially improving treatment response and enhancing long-term survival outcomes for patients.

Bridging Chemotherapy

Bridging chemotherapy, while widely used in clinical practice, has notable limitations. Despite being a common approach, its effectiveness in reducing tumor burden before CAR-T therapy remains suboptimal, as most patients do not experience significant tumor shrinkage. Comparative studies between patients who received bridging chemotherapy and those who did not indicate that the former group often exhibits poorer progression-free survival (PFS) and overall survival (OS). Although dose reduction in chemotherapy can improve safety and minimize adverse effects, there is currently no conclusive clinical evidence demonstrating that low-dose bridging chemotherapy effectively prolongs OS in CAR-T-treated patients.

Bridging Immunotherapy

Bridging immunotherapy encompasses a variety of therapeutic agents, including monoclonal antibodies such as CD20 and PD-1 inhibitors, antibody-drug conjugates (ADCs) targeting CD30, CD79, CD19, and CD22, as well as bispecific antibodies like CD20/CD3 and CD19/CD3.

One critical consideration in bridging immunotherapy is the potential interference between the selected therapeutic target and the subsequent CAR-T treatment. Some studies suggest that the use of the CD19/CD3 bispecific antibody blinatumomab before CAR-T therapy in B-cell acute lymphoblastic leukemia (B-ALL) patients may lead to reduced response rates, likely due to antigen escape mechanisms. However, other studies indicate that in relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL), patients who previously received CD19-targeted ADCs could still achieve an objective response rate (ORR) of 50% following CD19 CAR-T therapy.

Further insights from Brinkmann’s research suggest that CD20/CD3 bispecific antibodies may enhance CD19 CAR-T responses in in vitro lymphoma models and in vivo chronic lymphocytic leukemia (CLL) models. Additionally, in R/R LBCL patients, prior treatment with bispecific antibodies such as CD20/CD3 or CD22/CD3 did not appear to compromise the efficacy of subsequent CAR-T therapy, except for cases where patients had previously received CD19/CD3 bispecific antibodies. Currently, there is no definitive evidence supporting the existence of cross-resistance between CAR-T therapy and bispecific antibodies when they do not target the same antigen.

Bridging Radiotherapy

Radiotherapy, a well-established treatment modality, has demonstrated multiple therapeutic benefits when used as a bridging strategy before CAR-T therapy. It not only helps activate the immune system and effectively reduce tumor burden but also plays a role in improving the tumor immune microenvironment. Additionally, radiotherapy has been shown to alleviate CAR-T-related toxicities, which helps ensure that patients remain eligible for CAR-T cell infusion while also addressing resistance mechanisms associated with CAR-T therapy.

In a cohort of 169 patients with large B-cell lymphoma (LBCL) who received bridging radiotherapy, one-year progression-free survival (PFS) showed a significant advantage compared to those who did not undergo any bridging treatment. Furthermore, patients in the radiotherapy group exhibited better outcomes than those who received chemotherapy, systemic therapy, or hormonal therapy alone. Although no statistically significant difference was observed in one-year overall survival (OS) between the radiotherapy group and patients who did not receive bridging therapy, radiotherapy still provided superior benefits compared to chemotherapy, systemic therapy, or hormonal therapy alone.

The mechanisms underlying CAR-T resistance primarily involve CAR-T cell dysfunction, intrinsic tumor resistance, and the immunosuppressive tumor microenvironment. To enhance the therapeutic efficacy of CAR-T therapy while reducing toxicity, researchers have explored various combination strategies that target these resistance mechanisms.

Small-molecule drugs such as Bruton’s tyrosine kinase inhibitors (BTKi) enhance CAR-T cell function by targeting inhibitory receptors, thereby promoting cytokine production, Th1 polarization, and immune synapse formation. Lenalidomide further amplifies these effects by increasing cytokine release, strengthening immune synapses, and enhancing CAR-T cell activation.

Immune checkpoint inhibitors play a crucial role in boosting CAR-T cell activation. Anti-PD-1 antibodies, by blocking the interaction between PD-1 and PD-L1, significantly enhance CAR-T activation, leading to accelerated tumor cell death. Similarly, anti-CTLA-4 antibodies improve CAR-T cell function by increasing activation levels, thereby facilitating more efficient tumor eradication.

Radiotherapy, as a physical treatment modality, promotes the release of damage-associated molecular patterns (DAMPs), which accelerate the maturation and activation of dendritic cells (DCs). This process increases the production of pro-inflammatory cytokines, enhances CAR-T cell infiltration and activation, and ultimately leads to the destruction of cancer cells.

Oncolytic viruses leverage their tumor-specific lytic properties to replicate within cancer cells, inducing cell lysis and releasing DAMPs and tumor antigens. These molecules further stimulate DC maturation and activation, induce M1 macrophage polarization, and boost pro-inflammatory cytokine secretion, thereby significantly enhancing CAR-T cell infiltration and activation, leading to effective tumor destruction.

Additional strategies, including monoclonal antibodies, bispecific T-cell engagers (BiTEs), and cancer vaccines, offer new therapeutic avenues for CAR-T therapy. Anti-CD20 antibodies efficiently eliminate tumor cells through targeted action, while combining CD19 CAR-T with CD3×CD20 BiTEs enables more precise targeting. Vaccine-based approaches further augment CAR-T expansion by delivering tumor antigens to antigen-presenting cells (APCs), thereby enhancing the proliferation and efficacy of CAR-T cells.

Collectively, these combination treatment strategies offer a multidimensional approach to overcoming CAR-T resistance, providing novel insights and expanding therapeutic possibilities in the field of hematologic malignancies.

Clinical Research Progress

Extensive clinical research is underway to explore and optimize CAR-T combination therapies across various indications. In diffuse large B-cell lymphoma (DLBCL), the combination of lenalidomide with CD19 CAR-T therapy has demonstrated significantly improved clinical outcomes compared to CAR-T therapy alone. The one-year overall survival (OS) rate increased from 33.3% to 100%, while the objective response rate (ORR) rose from 77.8% to 85.7%, and the complete response (CR) rate improved from 33.3% to 42.9%, highlighting the potential benefits of combination strategies.

In the treatment of non-Hodgkin lymphoma (NHL), the combination of nivolumab and CD19 CAR-T therapy has also shown promising results. Clinical studies have reported an ORR of 81.81%, a CR rate of 45.45%, and a median progression-free survival (PFS) of six months, with an immune effector cell-associated neurotoxicity syndrome (ICANS) incidence of 9%.

For relapsed/refractory NHL (R/R NHL), the combination of CD19/CD22 dual-target CAR-T therapy with a PD-1 inhibitor has provided additional therapeutic advantages. Compared to CAR-T therapy alone, this combination has increased ORR from 60% to 82.9%, while the two-year PFS has significantly improved from 21.3% to 59.8%, offering renewed treatment prospects for patients with R/R NHL.

Beyond these approaches, numerous combination strategies are actively being investigated, and ongoing clinical trials are exploring the integration of CAR-T therapy with demethylating agents, histone deacetylase (HDAC) inhibitors, tyrosine kinase inhibitors (TKIs), Bruton’s tyrosine kinase inhibitors (BTKi), phosphoinositide 3-kinase (PI3K) inhibitors, Janus kinase (JAK) inhibitors, monoclonal antibodies, and immune checkpoint inhibitors. These studies are paving the way for expanded treatment possibilities, aiming to enhance therapeutic efficacy and provide patients with broader options for managing hematologic malignancies.

Adverse Effects and Management of CAR-T Therapy in 2024

The adverse effects of CAR-T therapy can be categorized into acute and chronic toxicities. Acute toxicities include cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), tumor lysis syndrome (TLS), and hemophagocytic lymphohistiocytosis/macrophage activation syndrome (HLH/MAS). Chronic toxicities primarily involve immune effector cell-associated hematologic toxicity (ICAHT), prolonged cytopenias, hypogammaglobulinemia, increased susceptibility to infections, and secondary malignancies. A comprehensive understanding of these toxicities and their appropriate management is crucial for ensuring patient safety and optimizing treatment efficacy.

CRS management depends on the severity of symptoms, classified into grades I to IV, with an additional category for refractory CRS. Mild cases, classified as grade I or II, are managed with symptomatic and supportive care, including fever control with antipyretics, intravenous fluids for hydration, and close monitoring of vital signs. More severe cases, classified as grade III or IV, require intervention with systemic corticosteroids such as dexamethasone or methylprednisolone, as well as IL-6 receptor antagonists like tocilizumab. In critical cases, intensive care unit admission may be necessary for close monitoring and hemodynamic support. For patients with refractory CRS who do not respond to conventional therapies, cyclophosphamide may be considered as a potential rescue treatment.

As the clinical application of CAR-T therapy continues to expand, refining toxicity management strategies remains essential to improving patient outcomes and long-term treatment success.

ICANS management is classified based on severity, with diagnosis relying on neurological examinations, electroencephalography (EEG), and imaging techniques such as magnetic resonance imaging (MRI) or computed tomography (CT).

For mild cases, supportive treatment is the primary approach. Moderate to severe cases require corticosteroids, with seizure prevention measures implemented when necessary or transfer to the intensive care unit (ICU) for close monitoring. In cases of steroid-refractory ICANS, anakinra or cyclophosphamide may be considered as potential treatment options.

Before initiating treatment, it is essential to assess for glucose-6-phosphate dehydrogenase (G6PD) deficiency. High-risk patients may receive prophylactic treatment with allopurinol, rasburicase, or febuxostat to prevent tumor lysis syndrome (TLS). During treatment, TLS-related laboratory parameters should be closely monitored, and supportive care, including hydration and electrolyte management, should be provided as needed.

First-line treatment for hemophagocytic lymphohistiocytosis/macrophage activation syndrome (HLH/MAS) in international guidelines recommends anakinra with or without corticosteroids. However, the optimal first-line treatment strategy for Chinese patients requires further investigation.

Risk stratification for hematologic toxicity is recommended using the CAR-HEMATOTOX score, with routine monitoring of complete blood counts during treatment. For patients with severe cytopenias, supportive measures such as blood transfusions, growth factor therapy, or autologous stem cell reinfusion may be considered. Prophylactic use of antimicrobial agents is advised to reduce infection risk, and in certain cases, allogeneic hematopoietic stem cell transplantation may be necessary.

Strategies to reduce the risk of secondary malignancies include early treatment initiation, monitoring for clonal hematopoiesis, minimizing risk factors, and close disease surveillance. For secondary myeloid malignancies, treatment options include allogeneic hematopoietic stem cell transplantation, hypomethylating agents, pegfilgrastim, blood transfusions, and supportive care. The clonal hematopoiesis risk score (CHRS) can help predict the likelihood of therapy-related myeloid neoplasms, with patients classified as having moderate to high CHRS facing an increased risk of developing treatment-related myeloid malignancies within the first nine months following CAR-T therapy.

Biomarkers in CAR-T Therapy

Biomarkers play a critical role in assessing treatment prognosis, toxicity, and infection risk in CAR-T therapy. Among them, the CAR-HEMATOTOX score is a key indicator derived from a combination of platelet count, hemoglobin levels, absolute neutrophil count, C-reactive protein (CRP), and ferritin levels. This score is closely associated with treatment outcomes, potential toxicities, and the likelihood of infections following CAR-T therapy.

Additional Biomarkers in CAR-T Therapy

Beyond the CAR-HEMATOTOX score, 18F-FDG PET/CT is another crucial tool for evaluating prognosis in CAR-T therapy. In large B-cell lymphoma patients, a reduction in metabolic tumor volume (MTV) before CAR-T treatment has been associated with improved survival outcomes. Other biomarkers, including peripheral blood eosinophil count, circulating tumor DNA (ctDNA), and the prognostic nutritional index (PNI), also play significant roles in predicting treatment response, toxicity, and overall prognosis. These diverse biomarkers collectively establish a strong foundation for personalized CAR-T treatment strategies, offering a more comprehensive and precise reference for clinical decision-making.