Donor-derived CAR-T Cells Serve as a Reduced-intensity Conditioning Regimen for Haploidentical Stem Cell Transplantation in Treatment of Relapsed/Refractory Acute Lymphoblastic Leukemia: Case Report and Review of the Literature

The role of MSCs and CAR-MSCs in cellular immunotherapy

Chimeric antigen receptors (CARs) are widely used by T cells (CAR-T cells), natural killer cells dendritic cells and macrophages, and they are of great importance in cellular immunotherapy. However, the use of CAR-related products faces several challenges, including the poor persistence of cells carrying CARs, cell dysfunction or exhaustion, relapse of disease, immune effector cell-associated neurotoxicity syndrome, cytokine release syndrome, low efficacy against solid tumors and immunosuppression by the tumor microenvironment. Another important cell therapy regimen involves mesenchymal stem cells (MSCs). Recent studies have shown that MSCs can improve the anticancer functions of CAR-related products. CAR-MSCs can overcome the flaws of cellular immunotherapy. Thus, MSCs can be used as a biological vehicle for CARs. In this review, we first discuss the characteristics and immunomodulatory functions of MSCs. Then, the role of MSCs as a source of exosomes, including the characteristics of MSC-derived exosomes and their immunomodulatory functions, is discussed. The role of MSCs in CAR-related products, CAR-related product-derived exosomes and the effect of MSCs on CAR-related products are reviewed. Finally, the use of MSCs as CAR vehicles is discussed. Video Abstract.

Donor-derived CD19 CAR-T Cells versus Chemotherapy Plus Donor Lymphocyte Infusion for Treatment of Recurrent CD19-positive B-ALL After Allogeneic Hematopoietic Stem Cell Transplantation

OBJECTIVE

This study aimed to compare the efficacy of anti-CD19 chimeric antigen receptor T cells (CAR-T cells) versus chemotherapy plus donor lymphocyte infusion (chemo-DLI) for treating relapsed CD19-positive B-cell acute lymphoblastic leukemia (B-ALL) after allogeneic hematopoietic stem cell transplantation (allo-HSCT).

METHODS

Clinical data of 43 patients with B-ALL who relapsed after allo-HSCT were retrospectively analyzed. Twenty-two patients were treated with CAR-T cells (CAR-T group), and 21 with chemotherapy plus DLI (chemo-DLI group). The complete remission (CR) and minimal residual disease (MRD)-negative CR rates, leukemia-free survival (LFS) rate, overall survival (OS) rate, and incidence of acute graft-versus-host disease (aGVHD), cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) were compared between the two groups.

RESULTS

The CR and MRD-negative CR rates in the CAR-T group (77.3% and 61.5%) were significantly higher than those in the chemo-DLI group (38.1% and 23.8%) (P=0.008 and P=0.003). The 1- and 2-year LFS rates in the CAR-T group were superior to those in the chemo-DLI group: 54.5% and 50.0% vs. 9.5% and 4.8% (P=0.0001 and P=0.00004). The 1- and 2-year OS rates in the CAR-T versus chemo-DLI group were 59.1% and 54.5% vs. 19% and 9.5% (P=0.011 and P=0.003). Six patients (28.6%) with grade 2-4 aGVHD were identified in the chemo-DLI group. Two patients (9.1%) in the CAR-T group developed grade 1-2 aGVHD. Nineteen patients (86.4%) developed CRS in the CAR-T group, comprising grade 1-2 CRS in 13 patients (59.1%) and grade 3 CRS in 6 patients (27.3%). Two patients (9.1%) developed grade 1-2 ICANS.

CONCLUSION

Donor-derived anti-CD19 CAR-T-cell therapy may be better, safer, and more effective than chemo-DLI for B-ALL patients who relapse after allo-HSCT.

Combination strategies to optimize the efficacy of chimeric antigen receptor T cell therapy in haematological malignancies

Chimeric antigen receptor (CAR) T cell therapy has revolutionized the therapeutic landscape of haematological malignancies. However, resistance and relapse remain prominent limitations, and they are related to the limited persistence and efficacy of CAR T cells, downregulation or loss of tumour antigens, intrinsic resistance of tumours to death signalling, and immune suppressive microenvironment. Rational combined modality treatments are regarded as a promising strategy to further unlock the antitumor potential of CAR T cell therapy, which can be applied before CAR T cell infusion as a conditioning regimen or in ex vivo culture settings as well as concomitant with or after CAR T cell infusion. In this review, we summarize the combinatorial strategies, including chemotherapy, radiotherapy, haematopoietic stem cell transplantation, targeted therapies and other immunotherapies, in an effort to further enhance the effectiveness of this impressive therapy and benefit more patients.

Novel CD19 chimeric antigen receptor T cells manufactured next-day for acute lymphoblastic leukemia

Chimeric antigen receptor-engineered T (CAR-T) cells have shown promising efficacy in patients with relapsed/refractory B cell acute lymphoblastic leukemia (R/R B-ALL). However, challenges remain including long manufacturing processes that need to be overcome. We presented the CD19-targeting CAR-T cell product GC007F manufactured next-day (FasTCAR-T cells) and administered to patients with R/R B-ALL. A total of 21 patients over 14 years of age with CD19⁺  R/R B-ALL were screened, enrolled and infused with a single infusion of GC007F CAR-T at three different dose levels. The primary objective of the study was to assess safety, secondary objectives included pharmacokinetics of GC007F cells in patients with R/R B-ALL and preliminary efficacy. We were able to demonstrate in preclinical studies that GC007F cells exhibited better proliferation and tumor killing than conventional CAR-T (C-CAR-T) cells. In this investigator-initiated study all 18 efficacy-evaluable patients achieved a complete remission (CR) (18/18, 100.00%) by day 28, with 17 of the patients (94.4%) achieving CR with minimal residual disease (MRD) negative. Fifteen (83.3%) remained disease free at the 3-month assessment, 14 patients (77.8%) maintaining MRD negative at month 3. Among all 21 enrolled patients, the median peak of CAR-T cell was on day 10, with a median peak copy number of 104899.5/µg DNA and a median persistence period of 56 days (range: 7–327 days). The incidence of cytokine release syndrome (CRS) was 95.2% (n = 20), with severe CRS occurring in 52.4% (n = 11) of the patients. Six patients (28.6%) developed neurotoxicity of any grade. GC007F demonstrated superior expansion capacity and a less exhausted phenotype as compared to (C-CAR-T) cells. Moreover, this first-in-human clinical study showed that the novel, next-day manufacturing FasTCAR-T cells was feasible with a manageable toxicity profile in patients with R/R B-ALL.

Optimizing the Clinical Impact of CAR-T Cell Therapy in B-Cell Acute Lymphoblastic Leukemia: Looking Back While Moving Forward

Chimeric antigen receptor T-cell (CAR-T) therapy has been successful in creating extraordinary clinical outcomes in the treatment of hematologic malignancies including relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL). With several FDA approvals, CAR-T therapy is recognized as an alternative treatment option for particular patients with certain conditions of B-ALL, diffuse large B-cell lymphoma, mantle cell lymphoma, follicular lymphoma, or multiple myeloma. However, CAR-T therapy for B-ALL can be surrounded by challenges such as various adverse events including the life-threatening cytokine release syndrome (CRS) and neurotoxicity, B-cell aplasia-associated hypogammaglobulinemia and agammaglobulinemia, and the alloreactivity of allogeneic CAR-Ts. Furthermore, recent advances such as improvements in media design, the reduction of ex vivo culturing duration, and other phenotype-determining factors can still create room for a more effective CAR-T therapy in R/R B-ALL. Herein, we review preclinical and clinical strategies with a focus on novel studies aiming to address the mentioned hurdles and stepping further towards a milestone in CAR-T therapy of B-ALL.

The consensus from The Chinese Society of Hematology on indications, conditioning regimens and donor selection for allogeneic hematopoietic stem cell transplantation: 2021 update

The consensus recommendations in 2018 from The Chinese Society of Hematology (CSH) on indications, conditioning regimens and donor selection for allogeneic hematopoietic stem cell transplantation (allo-HSCT) facilitated the standardization of clinical practices of allo-HSCT in China and progressive integration with the world. There have been new developments since the initial publication. To integrate recent developments and further improve the consensus, a panel of experts from the CSH recently updated the consensus recommendations, which are summarized as follows: (1) there is a new algorithm for selecting appropriate donors for allo-HSCT candidates. Haploidentical donors (HIDs) are the preferred donor choice over matched sibling donors (MSDs) for patients with high-risk leukemia or elderly patients with young offspring donors in experienced centers. This replaces the previous algorithm for donor selection, which favored MSDs over HIDs. (2) Patients with refractory/relapsed lymphoblastic malignancies are now encouraged to undergo salvage treatment with novel immunotherapies prior to HSCT. (3) The consensus has been updated to reflect additional evidence for the application of allo-HSCT in specific groups of patients with hematological malignancies (intermediate-risk acute myeloid leukemia (AML), favorable-risk AML with positive minimal residual disease, and standard-risk acute lymphoblastic leukemia). (4) The consensus has been updated to reflect additional evidence for the application of HSCT in patients with nonmalignant diseases, such as severe aplastic anemia and inherited diseases. (5) The consensus has been updated to reflect additional evidence for the administration of anti-thymocyte globulin, granulocyte colony-stimulating factors and post-transplantation cyclophosphamide in HID-HSCT.

Engineering stem cells for cancer immunotherapy

Engineering stem cells presents an attractive paradigm for cancer immunotherapy. Stem cells engineered to stably express various chimeric antigen receptors (CARs) or T-cell receptors (TCRs) against tumor-associated antigens are showing increasing promise in the treatment of solid tumors and hematologic malignancies. Stem cells engraft for long-term immune cell generation and serve as a sustained source of tumor-specific effector cells to maintain remissions. Furthermore, engineering stem cells provides 'off-the-shelf' cellular products, obviating the need for a personalized and patient-specific product that plagues current autologous cell therapies. Herein, we summarize recent progress of stem cell-engineered cancer therapies, and discuss the utility, impact, opportunities, and challenges of cellular engineering that may facilitate the translational and clinical research.

How to Combine the Two Landmark Treatment Methods-Allogeneic Hematopoietic Stem Cell Transplantation and Chimeric Antigen Receptor T Cell Therapy Together to Cure High-Risk B Cell Acute Lymphoblastic Leukemia?

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) has made tremendous progress in the last few decades and is increasingly being used worldwide. The success of haploidentical HSCT has made it possible to have "a donor for everyone". Patients who received transplantation in remission may have a favorable outcome, while those who were transplanted in advanced stages of disease have a poor prognosis. Although chimeric antigen receptor T (CAR-T) cell therapy is currently a milestone in the immunotherapy of relapsed or refractory (R/R) B cell acute lymphoblastic leukemia (B-ALL) and has demonstrated high remission rates in patients previously treated in multiple lines, the relatively high relapse rate remains a barrier to CAR-T cell therapy becoming an excellent cure option. Therefore, combining these two approaches (allo-HSCT and CAR-T cell therapy) is an attractive area of research to further improve the prognosis of R/R B-ALL. In this review, we will discuss the current clinical practices of combining allo-HSCT with CAR-T cell therapy based on available data, including CAR-T cells as a bridge to allo-HSCT for R/R B-ALL and CAR-T cell infusion for post-transplant relapse. We will further explore not only other possible ways to combine the two approaches, including CAR-T cell therapy to clear minimal residual disease peri-transplantation and incorporation of CAR technology to treat graft-versus-host disease, but also the potential of CAR-T cells as a part of allo-HSCT.

Donor-derived CD19 CAR-T cell therapy of relapse of CD19-positive B-ALL post allotransplant

Safety and efficacy of allogeneic anti-CD19 chimeric antigen receptor T cells (CAR-T cells) in persons with CD19-positive B-cell acute lymphoblastic leukemia (B-ALL) relapsing after an allotransplant remain unclear. Forty-three subjects with B-ALL relapsing post allotransplant received CAR-T cells were analyzed. 34 (79%; 95% confidence interval [CI]: 66, 92%) achieved complete histological remission (CR). Cytokine release syndrome (CRS) occurred in 38 (88%; 78, 98%) and was ≥grade-3 in 7. Two subjects died from multiorgan failure and CRS. Nine subjects (21%; 8, 34%) developed ≤grade-2 immune effector cell-associated neurotoxicity syndrome (ICANS). Two subjects developed ≤grade-2 acute graft-versus-host disease (GvHD). 1-year event-free survival (EFS) and survival was 43% (25, 62%). In 32 subjects with a complete histological remission without a second transplant, 1-year cumulative incidence of relapse was 41% (25, 62%) and 1-year EFS and survival, 59% (37, 81%). Therapy of B-ALL subjects relapsing post transplant with donor-derived CAR-T cells is safe and effective but associated with a high rate of CRS. Outcomes seem comparable to those achieved with alternative therapies but data from a randomized trial are lacking.

[Impact of splenomegaly on outcomes of allogeneic hematopoietic stem cell transplantation in patients with chronic myelomonocytic leukemia]

目的

探讨脾肿大对慢性粒-单核细胞白血病（CMML）异基因造血干细胞移植（allo-HSCT）预后的影响。

方法

对2004年至2018年在北京大学血液病研究所接受allo-HSCT后的25例CMML患者进行回顾性分析，根据预处理前2周是否伴有脾脏肿大分为脾肿大组和非脾肿大组，比较两组患者在植入、移植物抗宿主病（GVHD）、复发以及生存方面的差异。

结果

①脾肿大组15例（男8例，女7例），中位年龄45（23~61）岁；非脾肿大组10例（男、女各5例），中位年龄39（12~56）岁。两组患者基线特征差异无统计学意义（P>0.05）。②脾肿大组、非脾肿大组粒细胞植入率分别为93.3%（14/15）、100.0%（10/10），中位植入时间分别为17（11~20）d、14（11~18）d（χ²=5.303，P=0.021）；脾肿大组、非脾肿大组血小板植入率分别为80.0%（12/15）、90.0%（9/10）（P=0.212），中位植入时间分别为17（12~33）d、15（12~19）d（χ²=0.470，P=0.493）。③脾肿大组5例发生急性GVHD（Ⅰ/Ⅱ度4例，Ⅲ/Ⅳ度1例），非脾肿大组6例发生急性GVHD（Ⅰ/Ⅱ度5例，Ⅲ/Ⅳ度1例）（χ²=0.204，P=0.652）。脾肿大组、非脾肿大组移植后100 d的急性GVHD累积发生率分别为33.3%（95%CI 14.9%~51.7%）、20.0%（95%CI 2.8%~37.2%）（P=0.635）。脾肿大组5例发生慢性GVHD（广泛型3例），非脾肿大组未发生慢性GVHD（P=0.041）。④脾肿大组、非脾肿大组3年累积复发率分别为（42.7±2.6）%、（11.1±1.2）%（χ²=1.824，P=0.122），3年总生存率分别为（61.5±13.5）%、（68.6±15.1）%（χ²=0.351，P=0.554），3年无白血病生存率分别为（56.3±14.8）%、（80.0±17.9）%（χ²=1.148，P=0.284）。

结论

脾肿大可致CMML患者allo-HSCT后粒细胞植入延迟，对生存及复发无影响。

CAR-T cells: the Chinese experience

INTRODUCTION

Chimeric antigen receptor T (CAR-T) cells are harnessed to identify and lyse malignant cells specifically, efficiently, and independently of the major histocompatibility complex (MHC). As a result, prognoses of relapsed or refractory (R/R) B cell hematological malignancies as well as limited types of solid tumors, have been ameliorated to a great extent. In China, a rising number of clinical trials that contribute to the development of novel CAR-T therapeutic strategies have been conducted on an extensive scale.

AREAS COVERED

We summarize registered clinical trials related to CAR-T therapy conducted in China by evaluating various parameters such as distribution, study phase, CAR structure, target antigen, and disease. The efficacy, toxicity, and, more importantly, the new strategies for optimization of CAR-T therapy of Chinese studies and clinical trials are elaborated in detail.

EXPERT OPINION

In terms of the number of CAR-T clinical trials, China is second to the USA, registering approximately 33% of trials worldwide. China's extensive explorations and breakthroughs in the search of novel target antigens, optimization of CAR structure, cocktail CAR-T therapy, combination therapy, and extension of CAR-T cell applications, imply that we are currently on the verge of a revolution in CAR-T therapy.

Allogeneic haematopoietic stem cell transplantation improves outcome of adults with relapsed/refractory Philadelphia chromosome-positive acute lymphoblastic leukemia entering remission following CD19 chimeric antigen receptor T cells

Relapsed/refractory Philadelphia chromosome-positive acute lymphoblastic leukemia (r/r Ph+ ALL) has an extremely poor prognosis. Chimeric antigen receptor T-cell (CART) therapy has acquired unprecedented efficacy in B-cell malignancies, but its role in the long-term survival of r/r Ph+ ALL patients is unclear. We analyzed the effect of CART on 56 adults with r/r Ph+ ALL who accepted split doses of humanized CD19-targeted CART after lymphodepleting chemotherapy. 51/56 (91.1%) achieved complete remission (CR) or CR with inadequate count recovery (CRi), including 38 patients with negative minimal residual disease (MRD) tested by bone marrow BCR-ABL1 copies. Subsequently, 30/51 CR/CRi patients accepted consolidative allogeneic haematopoietic stem cell transplantation (alloHSCT). Their outcomes were compared with those of 21/51 contemporaneous patients without alloHSCT. The 2-year overall survival (OS) and leukemia-free survival (LFS) of CR/CRi patients with alloHSCT were significantly superior to those without alloHSCT (58.9%, CI 49.8-68.0% vs. 22.7%, CI 12.7-32.7%, p = 0.005; 53.2%, CI 43.6-62.8% vs. 18.8%, CI 9.2-28.4%, p = 0.000, respectively). Multivariate analysis revealed that alloHSCT and MRD-negative post-CART were the independent prognostic factors for OS and LFS. CART therapy is highly effective for r/r Ph+ ALL patients, and consolidative alloHSCT could prolong their OS and LFS.

Donor-Derived CD123-Targeted CAR T Cell Serves as a RIC Regimen for Haploidentical Transplantation in a Patient With FUS-ERG+ AML

Background: Allogeneic hematopoietic stem cell transplantation (allo-HSCT) following chemotherapy is part of standard treatment protocol for patients with acute myeloid leukemia (AML). FUS-ERG+ AML is rare but has an extremely poor prognosis even with allo-HSCT in remission, possibly due to its a leukemia stem cell (LSC)-driven disease resulting in chemotherapy resistance and a novel therapy is urgently required. It has been reported that FUS-ERG-positive AML expresses CD123, a marker of LSC, in some cases. CD123-targeted CAR T cell (CART123) is promising immunotherapy, but how to improve the complete remission (CR) rate and rescue potential hematopoietic toxicity still need to explore.

Case Presentation: We used donor-derived CART123 as part of conditioning regimen for haploidentical HSCT (haplo-HSCT) in a patient with FUS-ERG+ AML who relapsed after allogeneic transplantation within 3 months, resists to multi-agent chemotherapy and donor lymphocyte infusion (DLI) and remained non-remission, aiming to reduce these chemotherapy-resistant blasts and rescue potential hematopoietic toxicity. The blasts in BM were reduced within 2 weeks and coincided with CAR copies expansion after CART123 infusion. The patient achieved full donor chimerism, CR with incomplete blood count recovery, and myeloid implantation.

Conclusion: Our results hints that CART123 reduces the chemotherapy-resistant AML blasts for FUS-ERG+ AML without affecting the full donor chimerism and myeloid implantation.

Use of chimeric antigen receptor T cells in allogeneic hematopoietic stem cell transplantation

The chimeric antigen receptor T (CAR-T) cells play an antileukemia role, and can be used to treat or prevent relapse by targeting minimal residual disease for patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the infusion of allogeneic CAR-T cells may also cause graft-versus-host disease, which limited their applications during and after allo-HSCT. In this review, we discuss the clinical trials that applying CAR-T cells before allo-HSCT and the use of donor-derived CAR-T cells as conditioning regimen during allo-HSCT. At last, we analyzed the effect of donor-derived CAR-T cells on preventive infusion after allo-HSCT.

Treatment Selection for Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia in the Era of Tyrosine Kinase Inhibitors

With the advent of tyrosine kinase inhibitors (TKIs), the treatment of Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia (ALL) has entered a new era. The efficacy of TKIs compared with other ALL treatment options is emphasized by a rapid increase in the number of TKI clinical trials. Subsequently, the use of traditional approaches, such as combined chemotherapy and even allogeneic hematopoietic stem cell transplantation (allo-HSCT), for the treatment of ALL is being challenged in the clinic. In light of the increased use of TKIs in the clinic, several questions have been raised. First, is it necessary to use intensive chemotherapy during the induction course of therapy to achieve a minimal residual disease (MRD)-negative status? Must a patient reach a complete molecular response/major molecular response before receiving allo-HSCT? Does MRD status affect long-term survival after allo-HSCT? Is auto-HSCT an appropriate alternative for allo-HSCT in those Ph+ ALL patients who lack suitable donors? Here, we review the recent literature in an attempt to summarize the current status of TKI usage in the clinic, including several new therapeutic approaches, provide answers for the above questions, and speculate on the future direction of TKI utilization for the treatment of Ph+ ALL patients.

Preventive infusion of donor-derived CAR-T cells after haploidentical transplantation: Two cases report

RATIONALE

Relapse is the main cause of death after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Unfortunately, there are no efficient methods to prevent relapse after allo-HSCT. Chimeric antigen receptor T (CAR-T) cells have achieved favorable outcomes in the treatment of refractory/relapsed acute lymphoblastic leukemia (ALL) because of their strong anti-leukemia activity. However, it is unclear whether the CAR-T cells constructed using viral systems can be used as preventive infusions to prevent relapse after haploidentical HSCT.

PATIENT CONCERNS

Two patients with ALL with high risk received haploidentical HSCT.

DIAGNOSES

Two patients were diagnosed with ALL with high risk.

INTERVENTIONS

Patients received preventive infusion of donor-derived CAR-T cells constructed using viral systems on day 60 after haploidentical HSCT.

OUTCOMES

The CAR-T cells were continually detected, and no graft versus host disease developed. The two patients survived with disease-free for 1 year and 6 months, respectively.

LESSONS

Preventive infusion of donor-derived CAR-T cells after haploidentical HSCT may be safe and that immunosuppressors may not affect the proliferation of CAR-T cells.