CD19 Chimeric Antigen Receptor Research Articles

Salvage radiotherapy for relapsed/refractory non‐Hodgkin lymphoma following CD19 chimeric antigen receptor T-cell (CART) therapy

CD19-targeting chimeric antigen receptor T-cell (CART) therapy is a promising treatment for relapsed/refractory non-Hodgkin lymphoma, but most patients experience post-CART progression. We describe our institutional experience of salvage radiotherapy (SRT) in this setting. Of 94 patients who received CART therapy from 2018 to 2020, 21 received SRT for post-CART progression. Patients were divided into two groups: locoregional disease (n=9 [43%], all disease encompassable within an RT field) and advanced disease (n=12 [57%]). Patterns of failure, progression-free survival (PFS), overall survival (OS), and toxicity were assessed. Median time from CART infusion to SRT was 4.0months (range, 0.6-11.5months). In the locoregional disease group, 8/9 patients (89%) were treated with comprehensive SRT to a median dose of 37.5Gy in a median of 15 fractions. In the advanced disease group, all patients (n=12) were treated with focal SRT to a median dose of 20.8Gy in a median of 5 fractions. Median follow-up post-SRT was 15.2months. In-field response was observed in 8/9 (89%) in the locoregional disease and 8/9 (89%) evaluable patients in the advanced disease groups. 17/18 evaluable patients (94%) patients experienced post-SRT progression, all with a distant component. Median OS was 7.4months; 21months for locoregional disease versus 2.4months for advanced disease (p=0.0002). Median PFS was 1.1month, and similarly poor regardless of group. No grade≥3 toxicities occurred. SRT post-CART therapy appears safe with encouraging in-field response but high rates of out-of-field progression, even for those presenting with locoregional disease, highlighting the need for integration of novel systemic agents.

Preinfusion factors impacting relapse immunophenotype following CD19 CAR T cells.

Relapse following chimeric antigen receptor (CAR) T-cell therapy directed against CD19 forrelapsed/refractory B-acute lymphoblastic leukemia (r/r B-ALL) remains a significant challenge. Three main patterns of relapse predominate: CD19 positive (CD19pos) relapse, CD19 negative (CD19neg) relapse, and lineage switch (LS). Development and validation of risk factors that predict relapse phenotype could help define potential pre- or post-CAR T-cell infusion interventions aimed at decreasing relapse. Our group sought to extensively characterize preinfusion risk factors associated with the development of each relapse pattern via a multicenter, retrospective review of children and young adults with r/r B-ALL treated with a murine-based CD19-CAR construct. Of 420 patients treated with CAR, 166 (39.5%) relapsed, including 83 (50%) CD19pos, 68 (41%) CD19neg, and 12 (7.2%) LS relapses. Agreater cumulative number of prior complete remissions was associated with CD19pos relapses, whereas high preinfusion disease burden, prior blinatumomab nonresponse, older age, and 4-1BB CAR construct were associated with CD19neg relapses. The presence of a KMT2A rearrangement was the only preinfusion risk factor associated with LS. The median overall survival following a post-CAR relapse was 11.9 months (95% CI, 9-17) and was particularly dismal in patients experiencing an LS, with no long-term survivors following this pattern of relapse. Given the poor outcomes for those with post-CAR relapse,study of relapse prevention strategies, such as consolidative hematopoietic stemcell transplantation, is critical and warrants further investigation on prospective clinical trials.

Comparison of the efficacy of second and third generation lentiviral vector transduced CAR CD19 T cells for use in the treatment of acute lymphoblastic leukemia both in vitro and in vivo models.

T cells genetically engineered to express a chimeric antigen receptor (CAR) specifically binding to a CD19 antigen has become the frontline of hematological malignancies immunotherapy. Their remarkable antitumor effect has exerted complete remission in treating B-cell malignancies. Although successful patient treatment has been shown, improvement to the structure of CAR to enhance its safety and efficacy profile is warranted. Transduction with a lentiviral vector (LVV) leading to the expression of CARs is also a critical step in redirecting T cells to target specific tumor antigens. To improve the efficacy of CD19 CARs in this study, the transduction ability of second and third generations LVV were compared. Ex vivo expansion of CD19 CARs T cells from healthy donors' peripheral blood mononuclear cells was performed after transduction of T cells with second and third generations LVV. Transduction efficacy of transduced T cells was determined to show a higher percentage in the third generations LVV transduced cells, with no changes in viability and identity of cells characterized by immunophenotyping. Testing the cytotoxic capacity of third generations LVV-transduced T cells against target cells showed higher reactivity against control cells. Cytokine expression was detected on the CD19 CARs T cells, suggesting that these cells limit in vitro growth of B-cell leukemia via secretion of the pro-inflammatory cytokine IFN γ. To investigate whether the third generation LVV transduced T cells can limit CD19 lymphoma growth in vivo, an analysis of tumor burden in a mouse model assessed by bioluminescence imaging was performed. We found that, in the presence of CD19 CARs T cells, the level of tumor burden was markedly reduced. In addition, an increase in the length of survival in mice receiving CAR-CD19 T cells was also observed. This suggests that transduction with third generations LVV generate a functional CAR-CD19 T cells, which may provide a safer and effective therapy for B-cell malignancies.

Novel extragenic genomic safe harbors for precise therapeutic T-cell engineering

AbstractCell therapies that rely on engineered immune cells can be enhanced by achieving uniform and controlled transgene expression in order to maximize T-cell function and achieve predictable patient responses. Although they are effective, current genetic engineering strategies that use γ-retroviral, lentiviral, and transposon-based vectors to integrate transgenes, unavoidably produce variegated transgene expression in addition to posing a risk of insertional mutagenesis. In the setting of chimeric antigen receptor (CAR) therapy, inconsistent and random CAR expression may result in tonic signaling, T-cell exhaustion, and variable T-cell persistence. Here, we report and validate an algorithm for the identification of extragenic genomic safe harbors (GSH) that can be efficiently targeted for DNA integration and can support sustained and predictable CAR expression in human peripheral blood T cells. The algorithm is based on 7 criteria established to minimize genotoxicity by directing transgene integration away from functionally important genomic elements, maximize efficient CRISPR/Cas9–mediated targeting, and avert transgene silencing over time. T cells engineered to express a CD19 CAR at GSH6, which meets all 7 criteria, are curative at low cell dose in a mouse model of acute lymphoblastic leukemia, matching the potency of CAR T cells engineered at the TRAC locus and effectively resisting tumor rechallenge 100 days after their infusion. The identification of functional extragenic GSHs thus expands the human genome available for therapeutic precision engineering.

Single-Cell Transcriptomics Reveals Immune Reconstitution in Patients with R/R T-ALL/LBL Treated with Donor-Derived CD7 CAR-T Therapy.

CD7 chimeric antigen receptor T (CAR-T) therapy has potent antitumor activity against relapsed/refractory (R/R) T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/LBL), however, immune reconstitution after CAR-T remains largely unknown. An open-label phase I clinical trial (ChiCTR2200058969) was initiated to evaluate safety and efficacy of donor-derived CD7 CAR-T cells in 7 R/R T-ALL/LBL patients. CAR-T cells were detected by flow cytometry and PCR. Cytokine levels were quantified by cytometric bead arrays. Single-cell RNA sequencing (scRNA-seq) was adopted to profile immune reconstitution. Optimal complete remission (CR) was 100% on day 28, and median followed-up time was 4 months. Leukopenia, thrombocytopenia, and neutropenia were observed in 6 patients, and infections occurred in 5 patients. Two patients died of serious infection and one died of a brain hemorrhage. CAR-T cells expanded efficiently in all patients. CD7+ T cells were eliminated in peripheral blood on day 11 after infusion, and CD7- T cells dramatically expanded in all patients. scRNA-seq suggested that immunologic activities of CD7- T cells were stronger than those of T cells before infusion due to higher expression levels of T-cell function-related pathways, and major characters of such CD7- T cells were activation of autoimmune-related pathways. Monocyte loss was found in 2 patients who died of serious infections, indicating the main cause of the infections after infusion. S100A8 and S100A9 were identified as potential relapse markers due to their notable upregulation in leukocyte lineage in relapsed patients versus non-relapse controls. Our data revealed cellular level dynamics of immune homeostasis of CD7 CAR-T therapy, which is valuable for optimizing the treatment of R/R T-ALL/LBL.

281 - Clinical Outcomes and Salvage Therapies of Pediatric Patients with Progressive B-ALL Following CD19 Chimeric Antigen Receptor (CAR) T Cell Therapy

281 - Clinical Outcomes and Salvage Therapies of Pediatric Patients with Progressive B-ALL Following CD19 Chimeric Antigen Receptor (CAR) T Cell Therapy

263 - Patterns of Leukocyte Recovery after CD19 Chimeric Antigen Receptor T-Cell Therapy in a Real-World Setting

263 - Patterns of Leukocyte Recovery after CD19 Chimeric Antigen Receptor T-Cell Therapy in a Real-World Setting

Enhancing CAR-T cell functionality in a patient-specific manner

Patient responses to autologous CD19 chimeric antigen receptor (CAR) T-cell therapies are limited by insufficient and inconsistent cellular functionality. Here, we show that controlling the precise level of stimulation during T-cell activation to accommodate individual differences in the donor cells will dictate the functional attributes of CAR-T cell products. The functionality of CAR-T cell products, consisting of a diverse set of blood samples derived from healthy donors, acute lymphoblastic leukemia (ALL), and chronic lymphocytic lymphoma (CLL) patient samples, representing a range of patient health status, is tested upon culturing on artificial antigen-presenting cell scaffolds to deliver T-cell stimulatory ligands (anti-CD3/anti-CD28) at highly defined densities. A clear relationship is observed between the dose of stimulation, the phenotype of the T-cell blood sample prior to T-cell activation, and the functionality of the resulting CAR-T cell products. We present a model, based on this dataset, that predicts the precise stimulation needed to manufacture a desired CAR-T cell product, given the input T-cell attributes in the initial blood sample. These findings demonstrate a simple approach to enhance CAR-T functionality by personalizing the level of stimulation during T-cell activation to enable flexible manufacturing of more consistent and potent CAR-T cells.

Chimeric Antigen Receptor T-Cell Therapy of Neurolymphomatosis Monitored by FDG PET/CT.

18 F-FDG PET/CT was performed to evaluate possible recurrent B-cell lymphoblastic lymphoma in a 34-year-old man. The images showed multiple foci of increased activity in the nerve root and peripheral nerve. A biopsy confirmed the diagnosis of neurolymphomatosis. After receiving chemotherapy, PET/CT showed progressive disease. The patient subsequently received the CD-19 chimeric antigen receptor T-cell therapy. A follow-up PET/CT acquired 30 days after chimeric antigen receptor T-cell therapy revealed no abnormal FDG activity.

Engineering CD20 CARs with a Twist.

CD20 is highly expressed in several types of B-cell lymphoma and is an intuitive target for chimeric antigen receptor (CAR) T-cell therapy. However, with conventional approaches, it has been challenging to provide CD20 CAR designs that confer efficacy in preclinical models and in clinical trials. In this issue, Chen and colleagues report several improved CD20 CARs, developed with minimal deviations from conventional design principles, that confer curative anti-lymphoma efficacy in preclinical models. These novel CD20 CARs enrich the pipeline for clinical development and provide an example of rational CAR design that is informed by insights into the structural biology of CAR domains. See related article by Chen et al., p. 150 (3).

Chimeric Antigen Receptor T Cell Therapy for Acute Leukemia.

The worldwide use of CD19 chimeric antigen receptor (CAR)-T cells has increased the response rate in patients with refractory or relapsed B-cell acute lymphoblastic leukemia. Clinical practice has become much safer with the help of immunotherapy-related toxicity management guidelines, such as the ASTCT consensus grading system. Tocilizumab and steroids are the major interventions for controlling cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). New drugs and interventions for uncontrolled CRS and ICANS, including JAK1/2 inhibitors, have also been investigated. The combination of ruxolitinib and steroids effectively controlled severe CRS without impeding CAR-T cell expansion. Patients with refractory CNS3 status and CNS masses were excluded from the clinical trials because of the high risk of severe ICANS. Intracranial injections of steroids and Ommaya capsule implantation were effective. For some heavily treated patients, the difficulties in CAR-T cell manufacturing and expansion may be resolved by combination with blinatumumab. Relapse is a major concern after CAR-T therapy, and combination interventions, such as allogeneic stem cell transplantation, dual-target CAR-T cell therapies, and sequential CD19/22 CAR-T infusion, have been investigated in many centers. For T-lineage-targeted CAR-T therapies, the CAR T-cell fratricide can be overcome using many techniques. The efficacy and safety of CD7+ CAR-T cell therapy have been widely reported in recent years. A high response rate can be achieved when the immune reconstitution is prolonged. Infections, particularly viral reactivations, should be carefully monitored, as relapses are another potential issue. Switching targets and eliminating residual CD7+ CAR-T cells in the blood are key points for patients who relapse after CD7+ CAR-T cell therapy. CAR-T cell therapies for AML have not been investigated in a large-scale cohort, except for CD19-positive AML with the AML1-ETO fusion gene.

Development of a microfluidic cell transfection device into gene-edited CAR T cell manufacturing workflow.

Genetic reprogramming of immune cells to recognize and target tumor cells offers a possibility of long-term cure. Cell therapies, however, lack simple and affordable manufacturing workflows, especially to genetically edit immune cells to more effectively target cancer cells and avoid immune suppression mechanisms. Microfluidics is a pathway to improve the manufacturing precision of gene modified cells. However, to date, it remains to be demonstrated that microfluidic treatment preserves the functionality of T cell products in a complete workflow. In this study, we used microfluidics to perform CRISPR/Cas9 gene editing of CD5, a negative T-cell regulator, followed by the insertion of a chimeric antigen receptor (CAR) transgene via lentiviral vector transduction to generate CAR T cells targeted against the B cell antigen CD19. As part of the workflow, we have optimized a microfluidic device that relies on convective volume exchange between cells and surrounding fluid to deliver guide RNA and Cas9 ribonucleoprotein to primary T cells. We comprehensively tested critical design features of the device to improve the gene-edited product yield. By combining high-speed video and cell mechanics measurements using the atomic force microscope, we validate a model that relates the device design features to cell properties. Our findings showed enhanced performance was obtained by focusing the cells to counteract the flow resistance caused by the ridge constrictions, providing a ridge layout that allows sufficient cycles of compression and time for volume recovery, and including a gutter to clear aggregates that could reduce cell viability. The optimized device was used in a workflow to generate CD5-knockout CD19 CAR T cells. The microfluidics approach resulted in >60% CD5 editing efficiency, ≥80% cell viability, similar memory phenotype composition as unprocessed cells, and superior cell growth. The microfluidics workflow yielded 4-fold increase of edited T cells compared to an electroporation workflow post-expansion. The transduced CAR T cells showed similar transduction efficiency and cytotoxicity against CD19-positive leukemia cells. Moreover, patient-derived T cells showed the ability to be similarly edited, though their distinct biomechanics resulted in slightly lower outcomes. Microfluidics-based manufacturing is a promising path towards more productive clinical manufacturing of gene edited CAR T cells.

Allogeneic CD34+ selected hematopoietic stem cell boost following CAR T-cell therapy in a patient with prolonged cytopenia and active infection.

Hematological toxicity (hematotoxicity) leading to peripheral cytopenias is a common long-term adverse effect following the use of CD19-chimeric antigen receptor (CD19-CAR) T-cell therapies. However, management remains unclear for patients whose cytopenias persist beyond 1month after CAR T-cell infusion. We present the case of a 21-year old who received CD19-CAR T-cell therapy for relapse following a haploidentical transplant. He developed hematotoxicity and consequently multiple life-threatening infections. We administered a CD34+ hematopoietic stem cell boost (HSCB) from his transplant donor, which led to hematopoietic recovery and resolution of his infections without any effect on the activity of CD19-CAR T cells. CD34+ HSCB can be a safe and effective option to treat hematotoxicity following CD19-CAR T-cell therapy.

Safety and Efficacy of Humanized Versus Murinized CD19 and CD22 CAR T-Cell Cocktail Therapy for Refractory/Relapsed B-Cell Lymphoma.

CD19 chimeric antigen receptor T-cell (CAR-T) therapy is efficacious for refractory/relapsed (R/R) B-cell hematological malignancies, yet relapse due to CD19 antigen escape remains a challenge. Our trial explored simultaneous targeting of multiple B-cell antigens as a therapeutic approach that may reduce the risk of relapse. We tested the safety and efficacy of CAR19/22 T-cell cocktail therapy including murinized and humanized products among patients with R/R aggressive B-cell lymphoma. In the group that received the humanized product, 11/12 (91.7%) patients achieved an objective response, including 9/12 (75%) complete responses (CRs) by day 28. The overall response rate and CR rate in the murinized group was 92.9% (13/14) and 42.9% (6/14), respectively. Nine of 12 (75%) patients in the humanized group maintained CR at month 3 following infusion, compared to 5/14 patients (35.7%) in the murinized group. Progression-free survival (PFS) was more favorable in the humanized compared to the murinized group. Most patients had mild cytokine release syndrome (CRS) (grade 1-2) in both groups. This study demonstrates that CAR19/22 T-cell cocktail therapy is safe and effective for R/R B-cell lymphoma and that patients treated with a humanized CAR-T exhibited better efficacy compared to patients treated with a murinized CAR-T therapy.

2097. Bacterial Infections in the Setting of Late Neutropenia Following CD19 Chimeric Antigen Receptor T-Cell (CAR-T) Therapy for Non-Hodgkin Lymphoma (NHL)

Abstract Background Cellular therapies such as CAR-T therapy have excellent clinical efficacy for treatment of relapsed and refractory hematologic malignancies. Late neutropenia, occurring more than 30 days after CAR-T cell infusion, is a frequent complication, though its impact on infection risk is not well understood. Methods We performed a retrospective study of 280 adults receiving CD19 CAR-T therapy for NHL between December 2017 and September 2021 (n=280). Levofloxacin prophylaxis was used after CAR-T infusion until initial count recovery (absolute neutrophil count (ANC) ≥ 1000). Patients were evaluated for late neutropenia with ANC < 1000 during three time periods following cell infusion: day 30 – 100; day 100 – 365; and after day 365. Infections were recorded if there was a microbiologic diagnosis with correlating symptoms and treatment. Infection severity was determined using Blood and Marrow Transplant Clinical Trials Network criteria. Patients were censored on the first day of any additional antineoplastic therapy after relapse, death or last follow up until 1/25/2022. Results Of 280 patients with NHL who received CAR-T therapy, 116 (41%) had late neutropenia. Baseline characteristics and early CAR-T toxicities are shown in Table 1. Amongst patients with late neutropenia, 11 (9%) developed a bacterial infection during late neutropenia and 3 (3%) developed Clostridioides difficile infection. The most frequent infection site was the bloodstream (n=5), followed by the urinary tract (UTI; n=4). Most infections were moderate in severity (n = 9, 64%), though several were serious (Severe=4; Life-threatening=1). Median time from CAR-T therapy to bacterial infection was 70 days (range 30 - 584); 10 occurred among 99 at risk during day 30-100 (10%), 3 among 39 at risk during day 101-365 (8%), and 1 among 12 at risk after day 365 (8%). All but one of the severe or life-threatening infections occurred prior to Day 100. Characteristics and timing of individual infections are outlined in Table 3. Table 3.Characteristics and Timing of Individual Bacterial Infections Conclusion Bacterial infections were relatively uncommon in patients with late neutropenia after CD19 CAR-T therapy for NHL in the absence of antibacterial prophylaxis and most severe infections in this population occurred between day 30 and 100. Further studies are needed to inform optimal prevention strategies. Disclosures Sarah P. Hammond, MD, F2G: Advisor/Consultant|F2G: Grant/Research Support|GSK: Grant/Research Support|Scynexis: Grant/Research Support Caron Jacobson, MD, MMSc, Abintus Bio: Advisor/Consultant|Bluebird Bio: Advisor/Consultant|BMS/Celgene: Advisor/Consultant|Daiichi-Sankyo: Advisor/Consultant|Epizyme: Advisor/Consultant|ImmPACT Bio: Advisor/Consultant|Instill Bio: Advisor/Consultant|Ipsen: Advisor/Consultant|Kite/Gilead: Advisor/Consultant|Kite/Gilead: Grant/Research Support|Lonza: Advisor/Consultant|Novartis: Advisor/Consultant|Pfizer: Grant/Research Support.

Novel xeno-free and serum-free culturing condition to improve piggyBac transposon-based CD19 chimeric antigen receptor T-cell production and characteristics

Background aimsChimeric antigen receptor (CAR) T cell is a novel therapy for relapse and refractory hematologic malignancy. Characteristics of CAR T cells are associated with clinical efficacy and toxicity. The type of serum supplements used during cultivation affects the immunophenotype and function of viral-based CAR T cells. This study explores the effect of serum supplements on nonviral piggyBac transposon CAR T-cell production. MethodsPiggyBac CD19 CAR T cells were expanded in cultured conditions containing fetal bovine serum, human AB serum or xeno-free serum replacement. We evaluated the effect of different serum supplements on cell expansion, transduction efficiency, immunophenotypes and antitumor activity. ResultsXeno-free serum replacement exhibited comparable CAR surface expression, cell expansion and short-term antitumor activity compared with conventional serum supplements. However, CAR T cells cultivated with xeno-free serum replacement exhibited an increased naïve/stem cell memory population and better T-cell expansion after long-term co-culture as well as during the tumor rechallenge assay. ConclusionsOur study supports the usage of xeno-free serum replacement as an alternative source of serum supplements for piggyBac-based CAR T-cell expansion.

Dasatinib is a potent enhancer for CAR T cell generation by CD3-targeted lentiviral vectors

CD3-targeted lentiviral vectors (CD3-LVs) mediate selective transduction of human T lymphocytes invitro and invivo while simultaneously activating the targeted cells. Previously, we have demonstrated that CD3-LV leads to downmodulation of the CD3:T cell receptor (TCR) complex. We therefore hypothesized that inhibition of CD3 phosphorylation by Src/Abl tyrosine kinase inhibitors such as dasatinib results in enhancement of gene delivery by Tcell-targeted LVs. Indeed, dasatinib treatment of Tcells prior to incubation with CD3-LV increased reporter gene delivery by 3- to 10-fold. Moreover, the presence of dasatinib enhanced selective transduction into non-activated target cells present in whole blood. When combined with delivery of the CD19-chimeric antigen receptor (CAR) gene, dasatinib increased CAR Tcell numbers by close to 10-fold. Importantly, the short-term exposure of Tcells to dasatinib during vector incubation did not interfere with tumor cell killing by the resulting CAR Tcells and rather came along with less upregulated exhaustion markers and a more naive phenotype. Our data suggest that dasatinib prevents CD3-LV-induced phosphorylation and CD3:TCR intake, thereby increasing the amount of CD3-LV bound to the cell surface. This is the first description of dasatinib as transduction enhancer, an activity particularly relevant for CAR Tcell generation with CD3-LV.

Enrichment of T-cell proliferation and memory gene signatures of CD79A/CD40 costimulatory domain potentiates CD19CAR-T cell functions.

CD19 chimeric antigen receptor (CAR) T-cells have demonstrated remarkable outcomes in B-cell malignancies. Recently, the novel CD19CAR-T cells incorporated with B-cell costimulatory molecules of CD79A/CD40 demonstrated superior antitumor activity in the B-cell lymphoma model compared with CD28 or 4-1BB. Here, we investigated the intrinsic transcriptional gene underlying the functional advantage of CD19.79A.40z CAR-T cells following CD19 antigen exposure using transcriptome analysis compared to CD28 or 4-1BB. Notably, CD19.79A.40z CAR-T cells up-regulated genes involved in T-cell activation, T-cell proliferation, and NF-κB signaling, whereas down-regulated genes associated with T-cell exhaustion and apoptosis. Interestingly, CD19.79A.40z CAR- and CD19.BBz CAR-T cells were enriched in almost similar pathways. Furthermore, gene set enrichment analysis demonstrated the enrichment of genes, which were previously identified to correlate with T-cell proliferation, interferon signaling pathway, and naïve and memory T-cell signatures, and down-regulated T-cell exhaustion genes in CD79A/CD40, compared with the T-cell costimulatory domain. The CD19.79A.40z CAR-T cells also up-regulated genes related to glycolysis and fatty acid metabolism, which are necessary to drive T-cell proliferation and differentiation compared with conventional CD19CAR-T cells. Our study provides a comprehensive insight into the understanding of gene signatures that potentiates the superior antitumor functions by CD19CAR-T cells incorporated with the CD79A/CD40 costimulatory domain.

Donor CD7 Chimeric Antigen Receptor T Cell Bridging to Allogeneic Hematopoietic Stem Cell Transplantation for T Cell Hematologic Malignancy

It is crucial to quickly bridge to allogeneic hematopoietic stem cell transplantation (allo-HSCT) for hematopoietic reconstitution. Here we report on the efficacy and safety of donor CD7 chimeric antigen receptor (CAR) T cell therapy (CAR-T) bridging to allo-HSCT in treating 12 patients with relapsed/refractory (r/r) T-ALL or T-cell lymphoblastic lymphoma (T-LBL). The median time from CAR-T infusion to allo-HSCT was 33.5 days (range, 30 to 55 days). With reduced-intensity conditioning, all patients except 1 successfully engrafted. With a mean follow-up of 301 days (range, 238 to 351 days), the remaining 11 patients were alive and disease-free at their last follow-up. Acute graft-versus-host disease (GVHD) was observed in 3 patients, and chronic GVHD developed in 3 patients, all with a limited pattern. Under the current protocol, infection was the main complication post-transplantation, and all infections were well controlled except in 1 patient, who died of multiple organ failure caused by an infection-induced inflammatory cytokine storm at days 14 post-transplantation. One patient relapsed (CD7+), and 3 patients became minimal residual disease (MRD) positive (CD7+ in 1, CD7- in 1, fusion gene positive only in 1). Subsequently, all 3 of these patients achieved an MRD-negative complete remission with either CD7 CAR-T reinfusion or immunosuppressive agent withdrawal. Our study shows for the first time that a novel strategy of donor CD7 CAR-T bridging to allo-HSCT can be highly effective and feasible in improving disease-free survival for patients with r/r T-ALL or T-LBL. © 2022 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

Efficacy and Safety of Donor-Derived CD7 CAR T Cells for r/r T-Cell Acute Lymphoblastic Leukemia/Lymphoma: Interim Analysis from a Phase 2 Trial

Background: Results of a phase I trial of donor-derived CD7 chimeric antigen receptor (CAR) T cells for relapsed or refractory T-cell acute lymphoblastic leukemia (r/r T-ALL) (Pan et al. J ClinOncol 2021;39:3340-3351) have been reported previously. Herein, we report interim findings of the phase 2 trial on the efficacy and safety of donor-derived CD7 CAR T cells for relapsed or refractory T-cell acute lymphoblastic leukemia/lymphoma. Methods: The subjects in phase 2 were screened from the similar I/E criteria of phase 1 trial. Patients with prior stem cell transplantation (SCT) received CAR T cells from prior SCT donors, while patients without SCT history received CAR T cells from new donors who also provided stem cells for transplantation post CAR T therapy. The phase 2 trial was using Bayesian optimal phase 2 (BOP2) design to evaluate the efficacy and safety of the target dose of 1 × 106 (±20%) CD7 CAR T cells per kg of body weight in refractory/relapsed T-cell acute lymphoblastic leukemia/lymphoma (NCT04689659). The primary endpoint was efficacy with safety secondary. An interim analysis of phase 2 trial could be performed when the first 20 patients who receive CD7 CAR T cells have completed 3 months from infusion or discontinued earlier. Survival status were continuously followed up while severe adverse events (SAEs) were recorded until receiving other anti-leukemia therapy. Results: Eighteen (90%) of twenty enrolled patients responded in phase 2 trial and were followed up with a median time of 11.0 months (range 7.6-14.6) until May, 14th, 2022. Patients in phase 1 and 2 trial had similar baseline characteristics, whereas phase 2 trial included more patients with mediastinal malignancies.(Fig. A) The best overall response (BOR) rate was 90% at 3 months. The objective response rate (ORR) were 90% and 90% at 1 and 3 months post-infusion, which were similar to 95% and 95% at 1 and 3 months in phase 1 trial. The 3-months complete remission (CR) rate in patients with mediastinal tumors was lower than that in patients without mediastinal tumors, although there was no significant statistical difference (p=0.07, Fig. B) Of total 18 responders that were followed up, 12 (67%) patients who received no further therapy, all had continuously detectable CAR T cells until the last visit, three remained in remission, seven had a relapse (three CD7+, and three CD7-, one unknown), and two died of infection; 8 (44%) patients proceeded to SCT and no CAR T cells were detectable after SCT, and among them five remained in remission, two had a relapse (CD7-), and one died of infection. Patients relapsed at a median time of 4 (range 1.6-10.5) months. The one-year progressive-free survival (PFS) and overall survival (OS) rates were 62.3% (95% CI, 38.3-86.3) and 60.0% (95% CI, 38.5-81.5). Patients without mediastinal mass had longer OS than patients with mediastinal mass. (p<0.05, Fig. C) Updated phase 1 data at a median 1.5-year follow-up, shows PFS and OS rates of 60.0% (95%CI, 38.4-81.6) and 70.0% (95%CI, 50.0-90.0) Short-term adverse events included grade 3 or higher cytokine release syndrome (10%) and grade 1-2 graft-versus-host disease (GVHD, 40%), which were all reversible. Three late-onset (> 30 days post-infusion) SAEs occurred in 3 responders, including 1 grade 5 sepsis at month 2, 1 grade 5 fulminant hepatitis at month 2, and 1 grade 5 pneumonia at month 5. Severe infections occurred in 2/3 patients with no further therapy, and the total T cells in them reached a median count of 654.34/μL (range 41.87-1210.46), which were substantially lower than normal levels despite steadily increasing. The safety analysis was similar to the phase 1 trial of donor-derived CD7 CAR T cells. (Fig. D) Conclusions: Interim results from a phase 2 trial of donor-derived CD7 CAR T cell therapy showed similar encouraging activity in treating r/r T-ALL with phase 1 trial. Relapse emerges as major issues impeding long-term outcomes. CD7-negative relapse was commonly observed under CAR T cell surveillance. Late onset GVHD and infections may occur and should be carefully managed. Patients with mediastinal mass had poor overall survival and needed been further investigated. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal