CD19-directed Chimeric Antigen Receptor T-cell Research Articles

INNV-30. TOXICITIES AND OUTCOME AFTER CD19-DIRECTED CHIMERIC ANTIGEN RECEPTOR T-CELL THERAPY FOR NEUROLYMPHOMATOSIS

Abstract BACKGROUND Lymphomatous infiltration of the peripheral nervous system (PNS), termed neurolymphomatosis, represents a distinct extranodal non-Hodgkin lymphoma variant with dismal outcome. CD19-directed chimeric antigen receptor (CD19-CAR) T-cell therapy has emerged as a safe and effective treatment for B-cell lymphomas. We aimed to assess toxicity and efficacy of CD19-CAR T-cells in neurolymphomatosis. METHODS Neurolymphomatosis treated with CD19-CAR T-cells were retrospectively identified at Massachusetts General Hospital over a six-year period. Toxicities were graded according to the ASTCT classification. Management, and response rates were recorded. RESULTS Eleven neurolymphomatosis cases, who had received a median 2 prior PNS-directed treatments (range: 1-3) before CD19-CAR T-cell exposure, were identified. Neurolymphomatosis localized to the nerve roots (8/11, 73%), plexus (5/11, 45%), peripheral (4/11, 36%) and cranial nerves (5/11, 45%). Low grade cytokine release syndrome was detected in 8/11 (73%; grade 1: N = 7; grade 2: N =1) cases. Low- and high-grade immune cell-associated neurotoxicity syndrome were recorded in 5/11 (45%; grade 1: N = 4; grade 2: N = 1) and 1/11 (9%; grade 4) patients, respectively. Seven of eleven neurolymphomatosis patients (64%) responded to CD19-CAR T-cells. Complete remissions were achieved in three cases (27%), of which two are still sustained now 9 and 46 months after CD19-CAR T-cell infusion. All radiographic responses were associated with remission of neurological symptoms. CONCLUSIONS CD19-CAR T-cell treatment was well tolerated and yielded promising efficacy in recurrent neurolymphomatosis, a difficult to treat condition with unmet medical need. Findings suggest that CD19-CAR may sufficiently penetrate the blood-nerve barrier, and toxicity and outcomes were overall similar to CAR-T cell therapy in CNS lymphoma.

Outcomes After Brexucabtagene Autoleucel Administered as a Standard Therapy for Adults With Relapsed/Refractory B-Cell ALL.

On the basis of the results of the ZUMA-3 trial, brexucabtagene autoleucel (brexu-cel), a CD19-directed chimeric antigen receptor T-cell therapy, gained US Food and Drug Administration approval in October 2021 for adults with relapsed/refractory (R/R) B-cell ALL (B-ALL). We report outcomes of patients treated with brexu-cel as a standard therapy. We developed a collaboration across 31 US centers to study adults with B-ALL who received brexu-cel outside the context of a clinical trial. Data were collected retrospectively from October 2021 to October 2023. Toxicities were graded per American Society for Transplantation and Cellular Therapy guidelines for cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). At the time of data lock, 204 patients had undergone apheresis and 189 were infused. Median follow-up time was 11.4 months. Forty-two percent of patients received brexu-cel in morphologic remission and would have been ineligible for participation in ZUMA-3. After brexu-cel, 151 achieved complete remission (CR), of which 79% were measurable residual disease (MRD) negative remissions. Median progression-free survival (PFS) was 9.5 months and median overall survival was not reached. Grade 3-4 CRS or ICANS occurred in 11% and 31%, respectively. In multivariable analysis, patients receiving consolidative hematopoietic cell transplantation (HCT; hazard ratio, 0.34 [95% CI, 0.14 to 0.85]) after brexu-cel had superior PFS compared with those who did not receive any consolidation or maintenance therapy. Similar to ZUMA-3, high rates of MRD-negative CR were observed after brexu-cel treatment for R/R B-ALL. The use of HCT as consolidation after brexu-cel resulted in improved PFS.

Eleven cases of laryngeal edema after tisagenlecleucel infusion: a 3-year single center retrospective study of CD19-directed chimeric antigen receptor T-cell therapy for relapsed and refractory B-cell lymphomas.

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EASIX and m-EASIX predict CRS and ICANS in pediatric and AYA patients after CD19-CAR T-cell therapy

AbstractCytokine release syndrome (CRS) and immune effector cell–associated neurotoxicity syndrome (ICANS) are complications of CD19-directed chimeric antigen receptor (CD19-CAR) T-cell therapy. The Endothelial Activation and Stress Index (EASIX) and modified EASIX (m-EASIX) scores have been retrospectively proven to be predictive of CRS and ICANS in adult CAR T-cell recipients. However, these scores have not been evaluated in pediatric cohorts. We retrospectively report on 76 pediatric and adolescent and young adult (AYA) patients with relapsed/refractory B-cell acute lymphoblastic leukemia treated with CD19-CAR T cells at St. Jude Children’s Research Hospital or John’s Hopkins Hospital. Data included patient, disease, and treatment characteristics. EASIX and m-EASIX scores were calculated at days –5 before, 0, and +3 after CAR T-cell infusion. CRS and ICANS occurred in 47 and 17 patients, respectively. At all evaluated time points, the median EASIX scores were higher for patients who developed severe CRS and any grade ICANS, and the median m-EASIX scores were higher in patients who developed severe CRS and severe ICANS than those with no/mild CRS/ICANS. Receiver operating characteristic curve analysis showed that both scores were strong predictors of CRS, especially severe CRS, at all time points. Any grade and severe ICANS were best predicted by both scores at day +3. m-EASIX uniformly outperformed EASIX, except for predicting any grade ICANS. Our results validate the potential utility of EASIX and m-EASIX scores for predicting CAR T-cell–related complications for pediatric and AYA patients.

CD19-directed CART therapy for T-cell/histiocyte–rich large B-cell lymphoma

AbstractT-cell/histiocyte–rich large B-cell lymphoma (THRLBCL) is a rare histologic variant of LBCL. Limited data regarding CD19–directed chimeric antigen receptor T-cell (CART) therapy in relapsed/refractory (R/R) THRLBCL suggest poor efficacy. We investigated CART outcomes for R/R THRLBCL through the Center for International Blood and Marrow Transplant Research registry. A total of 58 adult patients with R/R THRLBCL who received commercial CD19-CART therapy between 2018 and 2022 were identified. Most patients (67%) had early relapse of disease (45% primary refractory) with a median of 3 (range, 1-7) prior therapies and were treated with axicabtagene ciloleucel (69%). At median follow-up of 23 months after CART therapy, 2-year overall and progression-free survival were 42% (95% confidence interval [CI], 27-57) and 29% (95% CI, 17-43), respectively. In univariable analysis, poor performance status before CART therapy was associated with higher mortality (hazard ratio, 2.35; 95%CI, 1.02-5.5). The 2-year cumulative incidences of relapse/progression and nonrelapse mortality were 69% and 2%, respectively. Grade ≥3 cytokine release syndrome and immune effector cell–associated neurologic syndrome occurred in 7% and 15% of patients, respectively. In this largest analysis of CD19-CART therapy for R/R THRLBCL, ∼30% of patients were alive and progression free 2 years after CART therapy. Despite a high incidence of progression (69% at 2 years), these results suggest a subset of patients with R/R THRLBCL may have durable responses with CARTs.

CD22-directed CAR T-cell therapy for large B-cell lymphomas progressing after CD19-directed CAR T-cell therapy: a dose-finding phase 1 study

Outcomes are poor for patients with large B-cell lymphoma who relapse after CD19-directed chimeric antigen receptor (CAR) T-cell therapy (CAR19). CD22 is a nearly universally expressed B-cell surface antigen and the efficacy of a CD22-directed CAR T-cell therapy (CAR22) in large B-cell lymphoma is unknown, which was what we aimed to examine in this study. In this single centre, open-label, dose-escalation phase 1 trial, we intravenously administered CAR22 at two dose levels (1 million and 3 million CAR22-positive T cells per kg of bodyweight) to adult patients (aged ≥18 years) who relapsed after CAR19 or had CD19-negative large B-cell lymphoma. The primary endpoints were manufacturing feasibility, safety measured by the incidence and severity of adverse events and dose-limiting toxicities, and identification of the maximum tolerated dose (ie, the recommended phase 2 dose). This study is registered with ClinicalTrials.gov (NCT04088890) and is active, but closed for enrolment. From Oct 17, 2019, to Oct 19, 2022, a total of 41 patients were assessed for eligibility; however, one patient withdrew. 40 patients underwent leukapheresis and 38 (95%) had CAR T-cell products manufactured successfully. The median age was 65 years (range 25-84), 17 (45%) were women, 32 (84%) had elevated pretreatment lactate dehydrogenase, 11 (29%) had refractory disease to all previous therapies, and patients had received a median of four lines of previous therapy (range 3-8). Of the 38 patients treated, 37 (97%) had relapsed after previous CAR19. The identified maximum tolerated dose was 1 million CAR T cells per kg. Of 29 patients who received the maximum tolerated dose, no patients developed a dose-limiting toxicity or grade 3 or higher cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, or immune effector cell-associated haemophagocytic lymphohistiocytosis-like syndrome. This trial identifies CD22 as an immunotherapeutic target in large B-cell lymphoma and demonstrates the durable clinical activity of CAR22 in patients with disease progression after CAR19 therapy. Although these findings are promising, it is essential to recognise that this is a phase 1 dose-finding study. Further investigations are warranted to establish the long-term efficacy and to delineate the patient subgroups that will derive the most benefit from this therapeutic approach. National Cancer Institute, National Institutes of Health, Stanford Cancer Institute, Leukemia & Lymphoma Society, Parker Institute for Cancer Immunotherapy, Lymph & Co, and the European Hematology Association.

The treatment of follicular lymphoma with CD19-directed chimeric antigen receptor T-cell therapy.

Follicular lymphoma (FL) is the most common indolent non-Hodgkin lymphoma. Significant unmet need remains for patients with relapsed/refractory FL after ≥3 lines of prior therapy. While recent advancements have likely improved the survival of patients with FL, most patients will eventually relapse. The treatment of patients with FL after multiple relapses or those with refractory disease has historically led to lower overall response rates (ORR) and shorter progression-free survival (PFS) with each subsequent line of therapy. New treatments with high ORR and durable PFS are needed in this setting, particularly in patients that progress within 2 years of first line chemoimmunotherapy (POD24) and/or those refractory chemoimmunotherapy. Chimeric antigen receptor T-cell therapies targeting the B-cell antigen CD-19 have shown to be an efficacious treatment option for both heavily pretreated patients and/or patients with refractory FL, resulting in a high ORR and durable remissions.

Optimization of older adults by a geriatric assessment–guided multidisciplinary clinic before CAR T-cell therapy

AbstractThe optimal means of assessing candidacy of older adults (≥65 years) for chimeric antigen receptor T-cell (CAR-T) therapy are unknown. We explored the role of a geriatric assessment (GA)–guided multidisciplinary clinic (GA-MDC) in selecting and optimizing older adults for CAR-T. Sixty-one patients were evaluated in a GA-MDC (median age, 73 years; range, 58-83). A nonbinding recommendation (“proceed” or “decline”) regarding suitability for CAR-T was provided for each patient based on GA results. Fifty-three patients ultimately received CAR-T (proceed, n = 47; decline, n = 6). Among patients who received B-cell maturation antigen (BCMA)–directed (n = 11) and CD19-directed CAR-T (n = 42), the median overall survival (OS) was 14.2 months and 16.6 months, respectively. GA uncovered high rates of geriatric impairment among patients proceeding to CAR-T therapy, with fewer impairments in those recommended “proceed.” Patients recommended “proceed” had shorter median length of stay (17 vs 31 days; P = .05) and lower rates of intensive care unit admission (6% vs 50%; P = .01) than those recommended “decline.” In patients receiving CD19- and BCMA–directed CAR-T therapy, a “proceed” recommendation was associated with superior OS compared with “decline” (median, 16.6 vs 11.4 months [P = .02]; and median, 16.4 vs 4.2 months [P = .03], respectively). When controlling for Karnofsky performance status, C-reactive protein, and lactate dehydrogenase at time of lymphodepletion, the GA-MDC treatment recommendation remained prognostic for OS (hazard ratio, 3.26; P = .04). Patients optimized via the GA-MDC without serious vulnerabilities achieved promising outcomes, whereas patients with high vulnerability experienced high toxicity and poor outcomes after CAR-T therapy.

Relapsed/Refractory Diffuse Large B-Cell Lymphoma: Is There Still a Role for Autologous Stem Cell Transplantation in the CAR T-Cell Era?

Recently, CD19-directed chimeric antigen receptor (CAR) T-cell therapies have revolutionized treatment strategies for diffuse large B-cell lymphoma (DLBCL). CAR T-cell therapy is increasingly used as a second-line therapy for patients with DLBCL with early relapse or refractoriness to initial chemoimmunotherapy and displaced high-dose chemotherapy, followed by autologous stem cell transplantation (ASCT) as the standard of care for these patients. However, patients with late relapse or chemosensitive disease still benefit from autologous stem cell transplantation. We will review practice-changing studies in early relapse (ZUMA-7 and TRANSFORM) under consideration of the negative BELINDA trial, with a focus on register data, comparing CAR T-cell therapy and ASCT for patients responding to salvage therapy.

Circulating Tumor DNA as a Complementary Prognostic Biomarker during CAR-T Therapy in B-Cell Non-Hodgkin Lymphomas.

The emergence of CD19-directed chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment paradigm for R/R B-cell NHLs. However, challenges persist in accurately evaluating treatment response and detecting early relapse, necessitating the exploration of novel biomarkers. Circulating tumor DNA (ctDNA) via liquid biopsy is a non-invasive tool for monitoring therapy efficacy and predicting treatment outcomes in B-NHL following CAR-T therapy. By overcoming the limitations of conventional imaging modalities, ctDNA assessments offer valuable insights into response dynamics, molecular mechanisms of resistance, and early detection of molecular relapse. Integration of ctDNA monitoring into clinical practice holds promise for personalized therapeutic strategies, guiding the development of novel targeted therapies, and enhancing patient outcomes. However, standardization of assay methodologies and consensus on clinical response metrics are imperative to unlock the full potential of ctDNA in the management of B-NHL. Prospective validation of ctDNA in clinical trials is necessary to establish its role as a complementary decision aid.

Sequencing of Anti-CD19 Therapies in the Management of Diffuse Large B-Cell Lymphoma.

Several second- and third-line immunotherapeutic options for patients with relapsed or refractory diffuse large B-cell lymphoma ineligible for autologous stem cell transplant are directed against the B-cell antigen cluster of differentiation 19 (CD19). The anti-CD19 monoclonal antibody tafasitamab, paired with the immunomodulator lenalidomide, mediates antibody-dependent cellular toxicity and phagocytosis; the antibody-drug conjugate loncastuximab tesirine delivers the DNA cross-linking agent tesirine via CD19 binding and internalization; and CD19-directed chimeric antigen receptor T-cell therapy (CAR-T) products are engineered from autologous T cells. Although CD19 expression is assessed at diagnosis, clinically relevant thresholds of CD19 expression-which may not be detectable using current routine methodologies-have not been defined and may vary between CD19-directed treatment modalities. Determining optimal treatment sequencing strategies for CD19-directed therapy is hampered by the exclusion of patients who have received prior CD19-directed therapies from major clinical trials. Antigen escape, which is attributed to mechanisms including epitope loss and defective cell surface trafficking of CD19, is an important cause of CAR-T failure. Limited data suggest that CD19 expression may be maintained after non-CAR-T CD19-directed therapy, and retrospective analyses indicate that some patients with disease relapse after CAR-T may benefit from subsequent CD19-directed therapy. To date, clinical evidence on the effect of anti-CD19 therapy prior to CAR-T has been limited to small case series. Prospective studies and detailed analyses are needed to understand how pretreatment and posttreatment CD19 expression correlates with clinical responses to subsequent CD19-directed therapy to fully maximize treatment strategies.

Bendamustine as Lymphodepletion for Brexucabtagene Autoleucel Therapy of Mantle Cell Lymphoma

Brexucabtagene autoleucel (brexu-cel) is an autologous CD19-directed chimeric antigen receptor (CAR) T-cell therapy approved for treatment of relapsed/refractory mantle cell lymphoma (MCL). During a fludarabine shortage, we used bendamustine as an alternative to standard cyclophosphamide/fludarabine (cy/flu) lymphodepletion (LD) prior to brexu-cel. We assessed MCL patient outcomes as well as CAR T-cell expansion and persistence after brexu-cel following bendamustine or cy/flu LD at our center. This was a retrospective single institution study that utilized prospectively banked blood and tissue samples. Clinical efficacy was assessed by 2014 Lugano guidelines. CAR T-cell expansion and persistence in peripheral blood were assessed on day 7 and at ≥month 6 for patients with available samples. Seventeen patients received bendamustine and 5 received cy/flu. For the bendamustine cohort, 14 (82%) received bridging therapy and 4 (24%) had CNS involvement. Fifteen patients (88%) developed CRS with 4 (24%) ≥grade 3 events. Six (35%) patients developed ICANS with 4 (24%) events ≥grade 3. No patient had ≥grade 3 cytopenias at day 90. Best objective (BOR) and complete response (CRR) rates were 82% and 65%, respectively. At 24.5 months median follow-up, 12-month progression-free survival (PFS) was 45%, 24-month PFS was 25%, and median duration of response was 19 months. Median OS was not reached. BOR was 25% (1/4) for patients with CNS involvement. CAR transgene expansion after bendamustine LD was observed on day 7 in all (4/4) patients tested and persisted at ≥6 months (2/2), regardless of response. Bendamustine LD before brexu-cel for MCL is feasible and safe with a lower frequency and shorter duration of cytopenias than reported for cy/flu. Both CAR T-cell expansion and persistence were observed after bendamustine LD. Outcomes appear comparable to the real world outcomes reported with cy/flu LD.

Reducing and controlling metabolic active tumor volume prior to CAR T-cell infusion can improve survival outcomes in patients with large B-cell lymphoma

Bridging therapy before CD19-directed chimeric antigen receptor (CAR) T-cell infusion is frequently applied in patients with relapsed or refractory Large B-cell lymphoma (r/r LBCL). This study aimed to assess the influence of quantified MATV and MATV-dynamics, between pre-apheresis (baseline) and pre-lymphodepleting chemotherapy (pre-LD) MATV, on CAR T-cell outcomes and toxicities in patients with r/r LBCL. MATVs were calculated semi-automatically at baseline (n = 74) and pre-LD (n = 68) in patients with r/r LBCL who received axicabtagene ciloleucel. At baseline, patients with a low MATV (< 190 cc) had a better time to progression (TTP) and overall survival (OS) compared to high MATV patients (p < 0.001). High MATV patients who remained stable or reduced upon bridging therapy showed a significant improvement in TTP (p = 0.041) and OS (p = 0.015), compared to patients with a high pre-LD MATV (> 480 cc). Furthermore, high MATV baseline was associated with severe cytokine release syndrome (CRS, p = 0.001). In conclusion, patients with low baseline MATV had the best TTP/OS and effective reduction or controlling MATV during bridging improved survival outcomes in patients with a high baseline MATV, providing rationale for the use of more aggressive bridging regimens.

Reinfusion of CD19 CAR T cells for relapse prevention and treatment in children with acute lymphoblastic leukemia

AbstractRelapse after CD19-directed chimeric antigen receptor (CAR)–modified T cells remains a substantial challenge. Short CAR T-cell persistence contributes to relapse risk, necessitating novel approaches to prolong durability. CAR T-cell reinfusion (CARTr) represents a potential strategy to reduce the risk of or treat relapsed disease after initial CAR T-cell infusion (CARTi). We conducted a retrospective review of reinfusion of murine (CTL019) or humanized (huCART19) anti–CD19/4-1BB CAR T cells across 3 clinical trials or commercial tisagenlecleucel for relapse prevention (peripheral B-cell recovery [BCR] or marrow hematogones ≤6 months after CARTi), minimal residual disease (MRD) or relapse, or nonresponse to CARTi. The primary endpoint was complete response (CR) at day 28 after CARTr, defined as complete remission with B-cell aplasia. Of 262 primary treatments, 81 were followed by ≥1 reinfusion (investigational CTL019, n = 44; huCART19, n = 26; tisagenlecleucel, n = 11), representing 79 patients. Of 63 reinfusions for relapse prevention, 52% achieved CR (BCR, 15/40 [38%]; hematogones, 18/23 [78%]). Lymphodepletion was associated with response to CARTr for BCR (odds ratio [OR], 33.57; P = .015) but not hematogones (OR, 0.30; P = .291). The cumulative incidence of relapse was 29% at 24 months for CR vs 61% for nonresponse to CARTr (P = .259). For MRD/relapse, CR rate to CARTr was 50% (5/10), but 0/8 for nonresponse to CARTi. Toxicity was generally mild, with the only grade ≥3 cytokine release syndrome (n = 6) or neurotoxicity (n = 1) observed in MRD/relapse treatment. Reinfusion of CTL019/tisagenlecleucel or huCART19 is safe, may reduce relapse risk in a subset of patients, and can reinduce remission in CD19+ relapse.

Monocytes in leukapheresis products affect the outcome of CD19–targeted CAR T-cell therapy in patients with lymphoma

AbstractCD19–directed chimeric antigen receptor (CAR) T cells can induce durable remissions in relapsed/refractory large B-cell lymphomas (R/R LBCLs), but 60% of patients do not respond or relapse. Biological mechanisms explaining lack of response are emerging, but they are largely unsuccessful in predicting disease response at the patient level. Additionally, to maximize the cost-effectiveness of CAR T-cell therapy, biomarkers able to predict response and survival before CAR T-cell manufacturing would be desirable. We performed transcriptomic and functional evaluations of leukapheresis products in 95 patients with R/R LBCL enrolled in a prospective observational study, to identify correlates of response and survival to tisagenlecleucel and axicabtagene ciloleucel. A signature composed of 4 myeloid genes expressed by T cells isolated from leukapheresis products is able to identify patients with a very short progression-free survival (PFS), highlighting the impact of monocytes in CAR T-cell therapy response. Accordingly, response and PFS were also negatively influenced by high circulating absolute monocyte counts at the time of leukapheresis. The combined evaluation of peripheral blood monocytes at the time of leukapheresis and the 4-gene signature represents a novel tool to identify patients with R/R LBCL at very high risk of progression after CAR T-cell therapy and could be used to plan trials evaluating CAR T cells vs other novel treatments or allogeneic CAR T cells. However, it also highlights the need to incorporate monocyte depletion strategies for better CAR T production.

Transforming CLL management with immunotherapy: Investigating the potential of CAR T-cells and bispecific antibodies

Immunotherapies, such as chimeric antigen receptor (CAR) T-cell therapy and bispecific antibodies or T-cell engagers, have revolutionized the treatment landscape for various B-cell malignancies, including B-acute lymphoblastic leukemia and many non-Hodgkin lymphomas. Despite their significant impact on these malignancies, their application in chronic lymphocytic leukemia (CLL) management is still largely under investigation. Although the initial success of CD19-directed CAR T-cell therapy was observed in 3 multiply relapsed CLL patients, with 2 of them surviving over 10 years without relapse, recent CAR T-cell therapy trials in CLL have shown reduced response rates compared to their efficacy in other B-cell malignancies. One of the challenges with using immunotherapy in CLL is the compromised T-cell fitness from persistent CLL-related antigenic stimulation, and an immunosuppressive tumor microenvironment (TME). These challenges underscore a critical gap in therapeutic options for CLL patients intolerant or resistant to current therapies, emphasizing the imperative role of effective immunotherapy. Encouragingly, innovative strategies are emerging to overcome these challenges. These include integrating synergistic agents like ibrutinib to enhance CAR T-cell function and persistence and engineering newer CAR T-cell constructs targeting diverse antigens or employing dual-targeting approaches. Bispecific antibodies are an exciting "off-the-shelf" prospect for these patients, with their investigation in CLL currently entering the realm of clinical trials. Additionally, the development of allogeneic CAR T-cells and natural killer (NK) cells from healthy donors presents a promising solution to address the diminished T-cell fitness observed in CLL patients. This comprehensive review delves into the latest insights regarding the role of immunotherapy in CLL, the complex landscape of resistance mechanisms, and a spectrum of innovative approaches to surmount therapeutic challenges.

Determinants of outcomes and advances in CD19-directed chimeric antigen receptor therapy for B-cell acute lymphoblastic leukemia.

Relapsed and refractory B-cell acute lymphoblastic leukemia (B-ALL) is an aggressive B-cell neoplasm associated with poor outcomes. Conventional multiagent chemotherapy and bispecific antibody therapy may induce remission; however, relapse rates remain high and overall survival is poor. Chimeric antigen receptor T-cell (CAR-T) therapy provides durable, deep complete remission, and long-term cures in relapsed and refractory B-ALL. However, with this new treatment modality, 10%-30% of patients do not achieve remission, and over 50% experience relapse after therapy. Currently, there are two approved CD19-specific CAR-T cell constructs in B-ALL, Tisagenlecleucel and Brexucabtagene Autoleucel by the United States Food and Drug Administration, and the European Medicines Agency (EMA). In this review, we discuss patients, disease, and CAR-T predictors of outcomes in B-ALL. We describe the two approved CD19-directed CAR-T cell products, review the current literature, and discuss factors associated with high risks of therapy failure and future direction in CAR-T cell therapy for B-ALL.

Infections in children following chimeric antigen receptor T-cell therapy for B-cell acute lymphoblastic leukemia.

CD19-directed chimeric antigen receptor T-cell (CAR-T) therapy is transforming care for pediatric patients with relapsed or refractory B-cell acute lymphoblastic leukemia (B-ALL). There are limited pediatric-specific data concerning the infection risks associated with CD19 CAR-T therapy and the adequacy of current antimicrobial prophylaxis guidelines for these patients. We describe the antimicrobial prophylaxis used and the types of infectious occurring in the first 100 days following CAR-T therapy for relapsed or refractory B-cell ALL in children and adolescents (≤18 years) at our centre. Twenty-seven patients received their first CAR-T infusion (CTI) during the study period. Almost all patients (96%) had a comprehensive Infectious Diseases review prior to CTI, which informed a personalised prophylaxis or fever/sepsis plan in six (22%). Overall, six (22%) patients had one or more infections during the study period including five (19%, 0.9 per 100 days-at-risk) from days 0-30 and three (n = 20, 15%, 0.6 per 100 days-at-risk) from days 31-100. Bacterial blood stream infections were the most common type of infection encountered during both time periods, and one patient had probable pulmonary aspergillosis. There were no infection-related deaths. Our study contributes important information on the spectrum of infections encountered in pediatric patients with B-ALL post CAR-T therapy. Overall, the burden of infectious complications post CAR-T therapy in our cohort is lower than previously reported in the literature. Results suggest that our prophylaxis recommendations are effective in this population.

Hypogammaglobulinemia and Infection Risk in Relapsed Refractory B Cell Malignancy Patients Treated with Varnimcabtagene Autoleucel (IMN-003A), a CD19-Directed Chimeric Antigen Receptor T (CAR-T) Cell Therapy, in the Phase-2 Study (IMAGINE)

Background: Varnimcabtagene autoleucel (IMN-003A) is an anti-CD19 CAR-T cell immunotherapy for patients with relapsed refractory B cell malignancies (RR BCM) in the Phase 2 IMAGINE study. Hypogammaglobinemia can result from normal CD19+ B cell depletion (on-target, off-site effect) by CD19 directed CAR-T cells. RR BCM patients (pts) are already at risk for infections due to impaired immune function, lymphodepletion preparative regimen and prior immunosuppressive therapies. Intravenous immunoglobulin (IVIg) replacement is used to reduce the risk of infections due to hypogammaglobulinemia. We report the impact of var-cel on hypogammaglobinemia, infectious complications, risk factors, IVIg usage and clinical outcomes for RR BCM patients treated in first-in-India industry study (CTRI/2022/03/041162). Methods: RR BCM pts treated with var-cel in this study were reviewed. Hypogammaglobulinemia was defined as IgG &amp;lt;4 g/L. Infections reported during pre-apheresis (post screening), D0 to D+28 post CAR-T infusion and beyond D+29 for study duration were analyzed. IVIg usage for hypogammaglobulinemia was at investigator discretion. Patients were monitored for infection events. RR BCM response was assessed as per NCCN (B-ALL) and IWG (B-NHL) criteria. Appropriate statistical tools were used for data analysis. Results: At data cut-off, of 25 pts enrolled (median age 31 yrs, range 3 - 66) with RR BCM (n=13 B-ALL; n=12 B-NHL), 24 pts received var-cel (1 withdrawal). Median follow-up after IMN-003A administration was 205 days (range 12 - 434). Overall response rate (ORR) was 91.7% (22/24) at D+28 (B-ALL 91.7%; B-NHL 91.7%) and 80.9% (17/21) at D+90 (B-ALL 80%; B-NHL 81.8%). Treatment related mortality was 4.2% (n=1/24); 3 pts died of disease progression. Of the 24 pts, none had hypogammaglobulinemia (IgG &amp;lt;4g/L) at baseline. Eleven pts (45.8%) developed hypogammaglobulinemia post var-cel infusion. Of these, 10 pts (90.9%) received prophylactic intravenous immunoglobulin (IVIg). In total, 70.8% (n=17/24) pts received IVIg infusions (Table 1). The median time to initiation of IVIg after var-cel infusion was 58 days (range 15 to 189 days). Of evaluable pts, IVIg was used in 15 of 17 (88.2%) responders at D+90 (CR / PR) vs 0 of 4 (0%) in non-responders (SD / PD) (p=0.06). 52.9% (n=9/17) pts on prophylactic IVIg reported infections. Patients who received IVIg had more infections (30 events; p=0.76). The mean number of infections with and without IVIg was 1.8 and 1.6 respectively. The median overall survival was significantly higher in pts who received IVIg prophylaxis (p=0.02). There was no difference in survival observed based on presence or absence of hypogammaglobulinemia post var-cel infusion (p=0.46). A total of 41 infections were reported in 13 pts. Of these, the incidence from screening to D-1; D0 to D+28 and beyond D+29 were 9 events (4 pts); 12 (11) and 20 (7) respectively. Bacterial, viral and fungal infections reported were 28 events (11 pts); 12 (8) and 1 (1) respectively. Bacterial infections were sepsis (n=7); urinary tract infections (n=5), respiratory (n=14) and central line (n=2). There were 12 viral events, 11 of respiratory origin and one involving conjunctiva. There was one episode of probable fungal candidemia. Stool surveillance detected 27 positive events in 13 pts. Table 2 summarizes the reported infectious organisms. There were 23 infections documented in 13 patients who did not develop hypogammaglobulinemia (median 2 infections; mean 1.8; range 1 - 6). Of 11 pts with hypogammaglobulinemia, there were 18 infections (median 3.5; mean 1.6; range 1 - 9). Complete and partial responders had more infections compared to non-responders (p = 0.05). Conclusions: This is the first-in-India report evaluating hypogammaglobulinemia and infection risk post CAR-T cell infusion. The IVIg usage and documented infections was more in responders. The safety and efficacy outcomes of varnimcabtagene autoleucel (IMN-003A) are consistent with reported outcomes of approved CD19 directed CAR-T cell therapies. The use of prophylactic IVIg, often led by individual practice, to reduce the number of infections and its impact on efficacy outcomes remains uncertain. Potential strategies to reduce infection risk may help improve outcomes.

Evaluating the Safety of HCAR19 (Now Actalycabtagene Autoleucel- Actaly-Cel™), a Novel Humanized CD19-Directed Chimeric Antigen Receptor T-Cells in Pediatric, Adolescents, and Young Adults with Relapsed/ Refractory B- Acute Lymphoblastic Leukemia (ESHA) - Report of Phase-1B

Background and aims Chimeric Antigen Receptor (CAR) T-cell therapies for relapsed-refractory Pediatric B-cell Acute Lymphoblastic Leukemia (r/r-B-ALL) show remarkable success but remain prohibitively expensive. We developed and reported a Humanized CD19-directed novel CAR T-cell- HCAR19 (now -Actalycabtagene autoleucel- Actaly-cel™) with robust activity and low toxicity in pre-clinical studies. This led to regulatory approval for the first CART-cell trial in India as a Pilot Phase-1 study (CTRI/2021/05/033348), and it's encouraging safety profile and responses led to approval for a roll-on Phase 1b/2 Trial (CTRI/2023/03/050689) to monitor safety, identify Phase-2 Dose (P2D) and assess efficacy. Trial design permitted pooling of data of both trials for all objectives. We report here the Phase-1b analysis of Actaly-cel in r/r-B-ALL in Pediatric, Adolescents and Young Adults 3-25 years of age. Methods Patients with r/r B-ALL not in remission after 2 or more lines of therapy ineligible for Allogenic-Stem Cell Transplant (Allo-SCT) were included if no CD19-negative blasts population were detected on flow-cytometry records. Those with isolated extra-medullary disease, active neurological involvement/ sequelae, genetic syndromes/prior malignancy, or prior CD19-directed therapy were excluded. Bridging therapy was at physician discretion. Lymphodepletion was with Fludarabine (30mg/m 2) x 3-days and cyclophosphamide (500 mg/m 2) x 2-days. There were 3 Target Doses, TD-1, 2 &amp; 3 CART-cells at 1 x10 6, 3-5 x10 6 and 10-15 x10 6/kg recipient weight respectively. Escalation and de-escalation followed 3+3 design with Coherence-guided dose-decision for bivariates- efficacy and toxicity, allowing all patients to be evaluable. Primary end-point was Overall Response Rates (ORR) at Day-30 on bone-marrow flow-cytometry. Patients were monitored for toxicities, in-vivo dynamics of Actaly-cel, and cytokine profiles. Results Of 12 patients enrolled Actaly-cel was infused in 9 at time of analysis as 2 were withdrawn prior to apheresis (1-progression, 1-withdrawl of consent) while 1 is awaiting infusion. Three patients were assigned TD-1 and 6, TD-2. In TD-2 group, 1 received lower dose (2.13x10 6/kg) due to obesity and weight gain from severe-Covid19 prior to infusion. Median age was 16-yrs (range:8-24), M:F-3:2, median prior lines of therapy were 3 (range:2-5), 6 had high-risk cytogenetics, and median pre-infusion bone-marrow blasts were 19.5%(range:0-88%). Eight patients were evaluable for response and toxicities. All had Grade 3 leukopenia and thrombocytopenia. Peak cytokine release syndrome (CRS) was Grade-3 in 1(12.5%), Grade-2 in 2(25%), and Grade-1 in 5(62.5%). Those with ≥ Grade-2 CRS received tocilizumab with full recovery. Only 1 patient had Immune effector cell associated neurotoxicity syndrome (ICANS) peak-Grade 3, and was also the only one with Grade-3 CRS and had severe-Covid19 prior to infusion. ICANS resolved with steroids in 4 weeks, but recurred in the second month post-infusion, this time associated with leukemia-progression. Toxicities corroborated with IL-6 (median peak: 25pg/ml, range:2.8-3604), but not with Ifn-γ, which remained low (median peak:6.25pg/ml, range:0-68.1) (Fig-1). ORR was 87.5% (1 no-response-NR), 3 Morphological Remission with MRD-positive (Partial Response-PR), and 4 MRD-negative (Complete Response-CR). Responses correlated with Actaly-cel expansion dynamics (Fig-2) the only non-response being in a patient with poor expansion. At median follow-up of 3 months (range:1-15) 3 patients with no or partial Day-30 response expired from progression within few weeks. All 4 with CR had B-cell aplasia needing intravenous immunoglobulin. Two of them underwent subsequent Allo-SCT, 1 relapsed post-transplant and died from disease progression 15 months later, while the other is alive in remission at 15 months. Two patients remain in CR at 3 and 12 months without further therapy, while 1 with PR is on follow-up. Patients receiving TD-2 had ORR of 100% (CR-3, PR-1) with peak toxicity of Grade-2 CRS in only 1. Conclusion In a Phase-1/1b trial, Actaly-cel had good safety profile with low toxicity and robust activity resulting in high ORR that improved at higher doses. In-vivo dynamics and toxicity profile of Actaly-cel showed robust activity and low cytokines corroborating with pre-clinical studies. A median dose of 5x10 6/kg Actaly-cel is proposed as the P2D.