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Background: Information about the long-term tolerability of tafasitamab is still limited. Methods: 5 of 92 patients treated within a phase IIa study of single-agent tafasitamab in relapsed or refractory B NHL were followed for up to five years or longer for long-term tolerability. Results: Treatment was very well tolerated in an outpatient setting with no hospitalizations needed and mild and tolerable adverse events that occurred mostly within the first two years of treatment. Conclusions: Given the excellent tolerability and efficacy of tafasitamab this agent can be used to induce remission in relapsed or refractory lymphoma either alone or in combination with chemotherapy.

The treatment and evolution of B-cell non-Hodgkin lymphoma (B-NHL) has undergone important changes in the last years with the emergence of targeted therapies, such as monoclonal antibodies, small molecules, antibody-drug conjugates, and bispecific antibodies. Nevertheless, a significant portion of patients remains refractory or relapsed (R/R) to the new therapeutic modalities, representing thus an unmet medical need. The use of CAR-T cells for the treatment of B-NHL patients has shown to be a promising therapy with impressive results in patients with R/R disease. The expectations are as high as the imminent approval of CAR-T cell therapy in Brazil, which it is expected to impact the prognosis of R/R B-NHL. The aim of this manuscript is to offer a consensus of specialists in the field of onco-hematology and cellular therapy, working in Brazil and United States, in order to discuss and offer recommendations in the present setting of the use of CAR-T cells for patients with B-NHL.

Acute lymphoblastic leukemia (ALL) continues to be the most frequent neoplasm in childhood, with a 5-year survival rate ranging from 78 to 91%. The increase in the survival rate in the last 40 years has been 30 to 80%, with no comparable improvement in the case of relapsed or refractory ALL. It is for this very reason that there is currently research into innovative treatments, such as CAR-T cell therapy. This treatment involves the ex vivo genetic modification of the patient’s own T cells, enhancing their specificity and cytotoxicity against antigens present in the majority of blasts, such as CD19. In clinical trials carried out worldwide, positive results have been obtained in patients with refractory or relapsed ALL treated with CAR-T 19 therapy, with disease-free survival at one year in up to 50% of patients, and overall survival at one year of 76%. The first published report in Spain with respect to this treatment reproduces the results obtained in clinical trials. The results were reported in HNJS in 2020 involving 8 patients treated with CAR-T 19. Complete remission was observed in 87.5% of patients one month after infusion followed by an overall survival of 75% at the time of analysis (7.6 months mean follow-up duration across all the patients). To date, the most frequent side effects described with the use of this therapy in the short term are cytokine release syndrome and neurotoxicity. This innovative therapy, therefore, represents a paradigm shift in the survival of pediatric patients with relapsed or refractory ALL. Further studies and evidence of its effectiveness and the long-term follow-up of patients treated with this therapy are still needed, but the results to date are encouraging.

Chimeric antigen receptor (CAR) T cell therapy, especially anti-CD19 CAR T cell therapy, has shown remarkable anticancer activity in patients with relapsed/refractory acute lymphoblastic leukemia, demonstrating an inspiring complete remission rate. However, with extension of the follow-up period, the limitations of this therapy have gradually emerged. Patients are at a high risk of early relapse after achieving complete remission. Although there are many studies with a primary focus on the mechanisms underlying CD19- relapse related to immune escape, early CD19+ relapse owing to poor in vivo persistence and impaired efficacy accounts for a larger proportion of the high relapse rate. However, the mechanisms underlying CD19+ relapse are still poorly understood. Herein, we discuss factors that could become obstacles to improved persistence and efficacy of CAR T cells during production, preinfusion processing, and in vivo interactions in detail. Furthermore, we propose potential strategies to overcome these barriers to achieve a reduced CD19+ relapse rate and produce prolonged survival in patients after CAR T cell therapy.

This review examines CAR T CD19 immunotherapy, a newly FDA approved targeted therapy for B-Cell Acute Lymphoblastic Leukemia treatment. This therapy utilizes modified T cells from the patient's immune system, engineered to possess an anti-CD19 receptor that can recognize the specific CD19 antigen expressed on the surface of malignant B-lymphocytes. Using this highly individualized treatment, cancer types with a high rate of metastasis or relapse can be treated by the targeted nature of this therapy. The review aims to summarize the process through which CAR T was developed, from its inception to FDA approval. The material examined is current until March 2019 and explores the mechanisms and management of CAR T cell toxicity experienced by patients undergoing treatment. Clinical trials from respective stages of development are also detailed and summarized. The viable treatment options for patients suffering from B-cell acute lymphoblastic leukemia (B-ALL) are outlined. Despite the promising remission rates of CAR T therapy, its accessibility is limited due to current cost of treatment. With advancements in technology and improved understanding of immune-based therapies, it is possible that this method can become a more viable and affordable treatment option for patients in the future.

Chimeric antigen receptor T-cells (CAR-T cells) have the potential to be a major innovation as a new type of cancer treatment, but are associated with extremely high prices and a high level of uncertainty. This study aims to assess the cost of the hospital stay for the administration of anti-CD19 CAR-T cells in France. Data were collected from the French Medical Information Systems Program (PMSI) and all hospital stays associated with an administrated drug encoded 9439938 (tisagenlecleucel, Kymriah®) or 9440456 (axicabtagene ciloleucel, Yescarta®) between January 2019 and December 2020 were included. 485 hospital stays associated with an injection of anti-CD19 CAR-T cells were identified, of which 44 (9%), 139 (28.7%), and 302 (62.3%) were for tisagenlecleucel in acute lymphoblastic leukaemia (ALL), tisagenlecleucel in diffuse large B-cell lymphoma (DLBCL), and axicabtagene ciloleucel respectively. The lengths of the stays were 37.9, 23.8, and 25.9 days for tisagenlecleucel in ALL, tisagenlecleucel in DLBCL, and axicabtagene ciloleucel, respectively. The mean costs per hospital stay were € 372,400 for a tisagenlecleucel in ALL, € 342,903 for tisagenlecleucel in DLBCL, and € 366,562 for axicabtagene ciloleucel. CAR T-cells represented more than 80% of these costs. n=13 hospitals performed CAR-T cell injections, with two hospitals accounting for more than 50% of the total number of injections. This study provides original data in a context of limited information regarding the costs of hospitalization for patients undergoing CAR-T cell treatments. In addition to the financial burden, distance may also be an important barrier for accessing CAR T-cell treatment.

Aims: To review recent data and relevant of the role of anti-CD19 chimeric antigen receptor (CAR) T-cell therapy for B-cell non-Hodgkin lymphoma (NHL). Methods: Review and compilation of the most recent and relevant data published in full text and abstract forms of anti-CD19 CAR T-cell therapy for B-cell NHL. Results: Different anti-CD19 CAR T-cell therapy products have been tested and shown significant clinical activity across B-cell NHL patients. The objective responses in relapsed DLBCL, FL and MCL were 50–83%, 83–93% and 93%, respectively. Conclusions: Anti-CD19 CAR T-cell therapy is a viable option for poor risk refractory B-cell NHLs.

Background Patients (pts) with aggressive B-cell non-Hodgkin lymphoma (NHL) progressing after anti-CD19 chimeric antigen receptor T (CART) cell therapy have poor prognosis and may benefit from new therapy options through clinical trials. However, in a single center report, only 12% of such pts were treated in trials (Chow et al. Am J Hematol, 2019). Identifying the reasons for this low enrollment is needed to design future studies for this population. Here, we evaluated the eligibility criteria for recent landmark trials for relapsed/refractory aggressive B-cell NHL to learn what eligibility barriers are present. Methods Pts with aggressive B-cell NHL who received FDA-approved CART cell therapy at Mayo Clinic (Rochester, Arizona, Florida) since 2018 and progressed after CART cell therapy were identified. The potential eligibility for the following key trials was evaluated: a) polatuzumab + bendamustine + rituximab, b) tafasitamab + lenalidomide, c) selinexor and d) loncastuximab. The eligibility for each trial was retrospectively assessed at the time of disease progression after CART cell therapy based on hemoglobin (Hb), absolute neutrophils count (ANC), platelet count (Plt), renal and liver function tests, ECOG performance status (PS), and central nervous system (CNS) involvement. Results Seventy-five pts had disease progression to axicabtagene ciloleucel (N=73, 97%) or tisagenlecleucel (N=2, 3%) and are included in this analysis. Median time to progression after CART was 2.1 months (IQR: 1.0 - 3.1). Thirteen (17%) pts were treated in clinical trials after progression following CART cell therapy, while 46 (61%) were treated off trials, and 16 (22%) pts never received any treatment after progression. At a median follow-up of 13.6 months (IQR: 9.1 - 26.7) from CART progression, the median overall survival (mOS) from CART progression was 5.8 months (95% CI 3.5 - 10.1) and 53 (71%) pts died. Thirty-eight pts (51%) did not meet eligibility criteria for any of the 4 recent landmark trials. Hematologic impairment was the most common barrier to inclusion of these patients in clinical trials: Hb < 9 g/dL n=23 (31%) or Hb < 10 g/dL n=36 (48%), ANC < 1.0 x 10 9/L n=19 (25%) or ANC < 1.5 x 10 9/L n=32 (43%), and Plt < 75 x 10 9/L n=30 (40%) or Plt < 90 x 10 9/L n=34 (45%). Renal (n=11, 15%) or liver dysfunction (n=5, 7%), CNS involvement (n=8, 11%) and ECOG PS > 2 (n=3, 4%) were less common reasons leading to exclusion from trials. Post CART trial ineligible pts had significantly shorter time to progression (median 1.7 months, IQR: 1.0 - 2.6 vs. 3.0 months IQR: 1.9 - 3.4, p < 0.01) and inferior overall response to CART (45% vs 67%, p = 0.06) compared to pts who met trial eligibility post CART. Baseline Hb (median Hb 9.5 g/dL, IQR: 8.5 - 10.5 vs. 10.9 g/dL, IQR: 9.7 - 12.2, p < 0.01) and Plt (median Plt 106 x 10 9/L IQR: 54 - 165 vs. 201 x 10 9/L IQR: 141 - 243, p < 0.01) were also significantly lower in pts ineligible for trials post CART. There were no significant differences between pts eligible or ineligible for trials with regards to age (median 59 vs. 60 years), number of prior therapies (median 3 vs. 3), prior autologous stem cell transplant (41% vs. 37%), bridging therapy (65% vs. 63%), baseline ANC (median 4,1 vs. 3,0 x10 9/L), or high-grade (grade ≥ 2) cytokine release syndrome (19% vs. 21%) or neurotoxicity (32%, vs. 42%), respectively. Survival after CART progression was significantly shorter (mOS 2.5 months, 95% CI: 1.6 - 5.1) for the 38 pts ineligible for trials compared to pts eligible for trials (mOS 10.6 months, 95% CI: 8.9 - NA), (p < 0.01). In the 59 pts who received therapy post CART progression, the mOS of pts treated on (n = 13) or off (n = 46) trials was 13.8 months (95% CI: 9.2 - NA) vs. 6.6 months (4.9 - 10.7), respectively (p = 0.047). Conclusion Approximately half of the pts (51%) with aggressive B-cell NHL progressing after CART cell therapy would have be excluded from landmark clinical trials. The current hematologic exclusion criteria are a major barrier to enrollment in clinical trials, which would exclude many pts who have disease progression within 3 months of CART cell therapy (ie, primary refractory disease), in whom cytopenia as a toxicity from therapy is prevalent. Given the known delayed hematologic recovery after CART cell therapy and the unmet need of pts progressing to CART cell therapy, the hematologic exclusion criteria should be adjusted to increase trial participation of this population, especially of those with primary refractory disease. Figure 1 Figure 1. Disclosures Munoz: Gilead/Kite Pharma, Kyowa, Bayer, Pharmacyclics/Janssen, Seattle Genetics, Acrotech/Aurobindo, Beigene, Verastem, AstraZeneca, Celgene/BMS, Genentech/Roche.: Speakers Bureau; Janssen: Research Funding; Pharmacyclics/Abbvie, Bayer, Gilead/Kite Pharma, Pfizer, Janssen, Juno/Celgene, BMS, Kyowa, Alexion, Beigene, Fosunkite, Innovent, Seattle Genetics, Debiopharm, Karyopharm, Genmab, ADC Therapeutics, Epizyme, Beigene, Servier: Consultancy; Seattle Genetics: Research Funding; Millennium: Research Funding; Pharmacyclics: Research Funding; Genentech: Research Funding; Incyte: Research Funding; Portola: Research Funding; Merck: Research Funding; Celgene: Research Funding; Gilead/Kite Pharma: Research Funding; Bayer: Research Funding; Seattle Genetics: Honoraria; Physicians' Education Resource: Honoraria; Targeted Oncology: Honoraria; OncView: Honoraria; Kyowa: Honoraria. Murthy: CRISPR Therapeutics: Research Funding. Maurer: Morphosys: Membership on an entity's Board of Directors or advisory committees, Research Funding; Nanostring: Research Funding; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Genentech: Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees. Bennani: Purdue Pharma: Other: Advisory Board; Daichii Sankyo Inc: Other: Advisory Board; Kyowa Kirin: Other: Advisory Board; Vividion: Other: Advisory Board; Kymera: Other: Advisory Board; Verastem: Other: Advisory Board. Paludo: Karyopharm: Research Funding. Wang: Genentech: Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; MorphoSys: Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees; Eli Lilly: Membership on an entity's Board of Directors or advisory committees; LOXO Oncology: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; InnoCare: Research Funding. Ansell: Bristol Myers Squibb, ADC Therapeutics, Seattle Genetics, Regeneron, Affimed, AI Therapeutics, Pfizer, Trillium and Takeda: Research Funding. Witzig: Karyopharm Therapeutics, Celgene/BMS, Incyte, Epizyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene/BMS, Acerta Pharma, Kura Oncology, Acrotech Biopharma, Karyopharm Therapeutics: Research Funding. Nowakowski: Celgene, NanoString Technologies, MorphoSys: Research Funding; Celgene, MorphoSys, Genentech, Selvita, Debiopharm Group, Kite/Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees. Lin: Vineti: Consultancy; Takeda: Research Funding; Sorrento: Consultancy; Novartis: Consultancy; Juno: Consultancy; Legend: Consultancy; Janssen: Consultancy, Research Funding; Bluebird Bio: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Merck: Research Funding; Gamida Cell: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding.

Anti-CD19 chimeric antigen receptor (CAR) T-cells represent a novel immunotherapy that has shown remarkable success in the treatment of adult relapsed or refractory (R/R) B-cell non-Hodgkin's lymphoma, adult R/R mantle cell lymphoma, and R/R acute paediatric lymphoblastic leukaemia. One barrier to the widespread use of CAR T-cell therapy is toxicity, primarily cytokine release syndrome (CRS) with a variable grade of severity. The main manifestations of CRS are fever, hypotension, cytopenia, organ dysfunction among others. Neurological toxicities vary widely and range from headaches to encephalopathy. In addition, anti-CD19 CAR T-cell therapy provokes an array of less frequent events, such as coagulopathies, delayed cytopenia, and cardiovascular toxicities. In general, toxicities are usually reversible and resolve on their own in most cases, though severe cases may require intensive care and immunosuppressive therapy. Deaths due to CRS, neurologic toxicity and infectious complications have been reported, which highlights the gravity of these syndromes and the critical nature of appropriate intervention. In this paper, we look at all available FDA- and EMA-approved information about the pathophysiology, clinical manifestations, risk factor reviews of existing toxicity grading systems, current management strategies, and guidelines for anti-CD19 CAR T-cell toxicities. We also present new approaches, which are under investigation, to mitigate these adverse events.

BackgroundChimeric antigen receptor modified (CAR) T cells have revolutionized the treatment of blood cancers, though some patients still show a poor response in either CAR expansion, effector response, or persistence.1 In this study, we determined the features of pre-infusion CAR-transduced T cells that generated optimally functional responses after infusion.MethodsUsing both the pre-infusion product and PBMCs isolated at weeks 1–4, 8, and 3-months post-infusion from 15 patients undergoing experimental anti-CD19 CAR T cell treatment for refractory or relapsed B-ALL, we generated a comprehensive single cell gene expression and T cell receptor (TCR) sequencing dataset on over 180,000 CAR T cells (figure 1).ResultsAs expected, pre-infusion CAR T cells tend to highly express genes associated with proliferation, while post-infusion CARs show signs of either cytotoxic effector differentiation or dysfunctional terminal differentiation. Sequencing of the endogenous TCR, at the single cell level, allows us to track the trajectories of clonally and transcriptionally related cells (figure 2). Post-infusion cells with significant cytotoxic effector function share TCRs with a statistically defined subset of CARs in the pre-infusion sample (figure 3). Using a machine learning approach, we found that potent effector precursor CAR T cells have a specific transcriptional profile distinct from the other pre-infusion CAR T cells, including markers of early effector function such as increased EOMES, GNLY, GZMH, GZMK, KLRD1, and IFNγ. Formalizing this signature, we have developed a robust classifier that can predict with 82.8% accuracy whether a CAR T is likely to become a favorable effector based on its pre-infusion profile (figure 4). This prediction model can be used to evaluate the extent to which a patient‘s generated CAR product will be able to mount a robust response after encountering its target. Additionally, there are a number of genes, as a part of this signature, that are expressed on the cell surface and can be utilized as a method to differentiate the effector precursor pre-infusion CAR T cells from other pre-infusion CARs, including CD52, CD74, CD86, and LAG3, among others.Abstract 152 Figure 1Clustering of 184, 791 CAR-transduced T cells based on gene expressionAbstract 152 Figure 2Alluvial plot depicting CAR T cell lineage tracing using the endogenous T cell receptorAbstract 152 Figure 3Visualization of CAR T cell clusters with arrows indicating the shared TCRs between pre-infusion and post-infusion cellsAbstract 152 Figure 4Machine learning classifier of pre-infusion, early effector CAR T cell phenotypeConclusionsOur findings suggest a therapeutic approach that enriches these cells prior to infusion resulting in superior per cell CAR effector activity.ReferenceXu X, Huang S, Xiao X, Sun Q, Liang X, Chen S, et al. Challenges and Clinical Strategies of CAR T-cell Therapy for Acute Lymphoblastic Leukemia: Overview and Developments. Front Immunol 2020;11:569117.Ethics ApprovalThis study was approved by St. Jude Children’s Research Hospital’s Institutional Review Board (IRB); IRB number Pro00007661. All patients consented to the use of materials for the research study.

Background Treatment of relapsed/refractory diffuse large B cell lymphoma (DLBCL) eligible for transplantation is limited by the efficacy of salvage therapy. Chimeric antigen receptor modified T cell (CAR-T) therapy has achieved the highest response rate of salvage therapy for relapsed/refractory aggressive B cell lymphoma. Cytokine release syndrome (CRS) and cytopenia are main side effects of CAR-T therapy. Case presentation A 61 years old Chinese male diagnosed as DLBCL was treated with rituximab combined with chemotherapy, unfortunately, he was resistant to first-line chemotherapy and other regimens. Due to high expression of BCL2 protein and amplification of BCL2 by next sequence generation, BCL2 inhibitor combined with low intensity chemotherapy was given to him as a bridge to anti-19 CAR-T therapy. Although escalation of dose from 100mg per day to 400mg in one week, he had no tumor lysis syndrome and achieved partial response. He suffered persist pancytopenia after CAR T-cells infusion, moreover, a severely secondary CRS on 54th day was observed and responded well to steroid.Discussion and conclusions BCL2 inhibitor may have a role in frontline or salvage therapy of DLBCL, especially for those with high BCL2 protein expression, mechanism of which should be still investigated. CAR-T therapy revolutionized the salvage of primary refractory DLBCL, but we should focus on persist cytopenia and severe CRS, and we reported the latest secondary CRS till now.

Relapse or refractory B-cell malignancies have been reported in multiple clinical trials after treatment of Anti-CD19 Chimeric Antigen Receptor (CAR) T-cells. Many clinical studies have demonstrated the potential immune escape mechanism for B-cell malignancies like genetic mutation, transcriptional deregulation, lineage switch, loss of CAR T-cells, and trogocytosis. The study of these mechanisms can provide us insights in designs of future immunotherapies regarding both B-cell malignancies and even other solid tumors. The potential solution for the immune escape mechanisms regarding CAR T-cell treatment is engineering multispecific CARs. In this article, I review most of the upto- date immune escape mechanism studies and some multispecific CAR T-cell treatment clinical studies and trials that may prevent the escape route and have to potential to cure B-cell malignancies.

Neurotoxicity is a common occurrence and a major form of morbidity in adult patients with relapsed or refractory (R/R) diffuse large B cell lymphoma (DLBCL) patients treated with anti-CD19 directed chimeric antigen receptor (CAR) T-cell therapy. Variables related to the incidence and severity of neurotoxicity have been relatively well delineated, but the association between neurotoxicity and the efficacy of CAR T-cell therapy has not been well studied. We performed a retrospective analysis of the outcomes of DLBCL patients who developed neurotoxicity following anti-CD19 CAR T-cell treatment. The analysis included 26 patients with R/R DLBCL who received commercial anti-CD19 CAR T-cell therapy. All patients received a lymphodepleting chemotherapy regimen consisting of fludarabine and cyclophosphamide. Twenty-five patients received axicabtagene ciloleucel, and 1 received tisagenlecleucel. The overall incidence of neurotoxicity was 88%; 31% developed severe neurotoxicity (Grade III-IV by CTCAE). Higher neurotoxicity was associated with better PFS by both CTCAE (CR 2.4 ± 1.1 vs. PD 1.4 ± 1.3, p = 0.051) and CARTOX-10 (CR 3.78 ± 4.6 vs. PD 7.7 ± 3.8, p = 0.044) grading systems. Higher neurotoxicity continued to show a trend at 6, 9, and 12 months by the CTCAE grading system (CR 2.4 ± 1.0 vs. PD 1.7 ± 1.3, p = 0.085), and no patients had disease recurrence after 6 months. In this limited cohort, neurotoxicity severity was paradoxically positively correlated with progression-free survival with commercial CAR T-cell therapy and may therefore indicate an effective therapeutic response.

Chimeric antigen receptor T cells (CARTs) against CD19 antigen represent an effective therapy for relapsed/refractory diffuse large B-cell lymphoma (rrDLBCL). There is no diagnostic test able to predict which patients with residual disease will relapse from those that will reach a delayed complete response. Positron emission tomography/computed tomography scan (PET-CT) is characterized by a significant number of false positive results after immunotherapy. Circulating tumor DNA (ctDNA) may be a good-useful tool to quantify minimal residual disease and for monitoring disease response.We present a patient with DLBCL treated with CART cells in which we tested the combined use of ctDNA and PET-CT scan.Disease reassessment with PET-CT scan showed a partial remission (3 weeks) and a very good partial remission (2 months). A clinical progression at 3 months was confirmed with PET-CT scan. Levels of ctDNA progressively decreased and became undetectable. An initial increase in KMT2D p.E4385G variant allele frequency confirmed disease progression.Our case shows how the complementary use of ctDNA and PET-CT scan could be a helpful tool in the clinical management of these patients.

The efficacy and safety of donor-derived anti-CD19 CAR T cells vs DLI for the management of relapsed B-cell acute lymphoblastic leukemia (B-ALL) after allo-hematopoietic stem cell transplantation (HSCT) remain unclear. Thirteen B-ALL patients with relapsed after allo-HSCT and thus were treated with donor-derived anti-CD19 CAR T-cell (study group). Fifteen B-ALL patients relapsed after allo-HSCT and thus were treated with DLI (DLI group). The rates of MRD-negative complete remission (61.5%) in the study group were significantly higher than those in the DLI group (13.3%) (p = 0.02). The complete remission duration in study group and DLI group were median 8.0 months (range, 3–25 months) and 4.4 months (range, 1–25 months; p = 0.026), respectively. The overall survival of patients in the study group was superior to that of the DLI group: 9.5 months (range,3–25 months) versus 5.5 months (range, 1–25 months; p = 0.030). One patient with grade 1 acute graft-versus-host disease (aGVHD) was identified in the study group. While five (33.3%) patients in the DLI group developed grades III–IV aGVHD. Three patients (23.07%) developed grade 3 or 4 cytokine release syndrome in the study group. This study suggested that donor-derived anti-CD19 CAR T-cell therapy is promising, safe, and potentially effective for relapsed B-ALL after allo-HSCT and may be superior to DLI.

Anti-CD19 chimeric antigen receptor (CAR) T-cell therapies can be effective for diffuse large B-cell lymphoma (DLBCL), a cancer with limited treatment options and poor outcomes, particularly for patients with relapsed or refractory (r/r) disease. Axicabtagene ciloleucel (axi-cel) and tisagenlecleucel (tisa-cel) are CAR T-cell therapies approved by regulatory bodies for certain patients with r/r DLBCL on the basis of demonstrated treatment effects in their pivotal single-arm trials, ZUMA-1 and JULIET, respectively. In the absence of head-to-head trials, the question of whether a valid indirect treatment comparison (ITC) between axi-cel and tisa-cel could be performed using existing evidence is of interest to patients, physicians, payers, and other stakeholders. This article addresses that question by summarizing the current evidence from clinical trials and real-world studies and discussing the challenges and limitations of potential analytical approaches associated with an ITC. Two ITC approaches attempting to adjust for cross-trial heterogeneity between ZUMA-1 and JULIET, matching-adjusted indirect comparison and regression-prediction model analysis, were evaluated. After evaluating the current clinical trial data and real-world evidence, and present and prior ITC analyses of axi-cel and tisa-cel, the authors conclude that a valid comparative analysis is not currently feasible. The substantial differences (e.g., timing of leukapheresis and enrollment, use of bridging chemotherapy [90% in JULIET vs. 0% in ZUMA-1], lymphodepleting regimens) between the two trials' designs and patient populations preclude a robust and reliable ITC. No other approaches are able to account for such differences. The current real-world data are still too immature to be used for ITCs. Thus, drawing conclusions from such ITCs should be avoided to prevent misinforming treatment choices or limiting patient access to effective treatment options. Additional data from ongoing or future real-world studies with appropriate statistical analyses are needed to provide insights into the comparative effectiveness and safety of these two treatments.

This article will review the use of anti-CD19 CAR-T therapy used in relapsed/refractory diffuse large B cell lymphoma. The clinical outcomes, safety analysis, and other relevant considerations will be discussed with an emphasis on the most recently published data regarding the ZUMA-1, JULIET, and TRANSCEND NHL-001 trials. Anti-CD19 CAR-T therapy is an exciting new therapy now approved and available to patients with relapsed/refractory diffuse large B cell lymphoma. Secondary to the increasing success and availability of these products, caregivers should expect to become familiar with the indications, toxicity, and limitations of these treatment options and when patients should be considered for referral.

Introduction Clinical outcomes of anti-CD19 chimeric antigen receptor T-cell (CAR-T CD19) therapy for the treatment of relapsed/refractory Diffuse Large B Cell lymphoma (r/r DLBCL) must be improved, as patients undergoing CAR-T CD19 therapy can expect a cure rate of only 41% and a median survival of just 6.3 months if unresponsive. Of patients presenting with naïve DLBCL, 35% will advance to third-line treatment with CAR-T CD19 therapy. Poor clinical responses to CAR-T CD19 therapy and a small window of survival for unresponsive patients highlights the critical need for improvement of CAR-T CD19 therapy in the setting of r/r DLBCL. Overexpression of anti-apoptotic Bcl-2 protein has been characterized in r/r DLBCL, and contributes to the disease's aggressive phenotype. Aberrant expression of the Bcl-2 protein proves targetable by an FDA-approved small molecule inhibitor which mimics the role of pro-apoptotic BH3 proteins, known as Venetoclax. Here, we investigate the effect of Venetoclax on CAR-T CD19 cell immunophenotype, effector function, and cytotoxicity upon co-culture with a lab-generated model of immortalized rituximab/chemo-resistant B cell lymphomas (Raji4RH) which recapitulate the resistant phenotype of r/r DLBCL seen in patients. Methods PBMCs were isolated and activated from apheresis samples from consenting adults (healthy donors) using the Miltenyi Biotec TransACT human CD3/CD28 Kit. Cells were transduced with lentiviral vectors encoding for 2nd generation CAR constructs 24 hours post-activation. Transduced cells were cultured in RPMI media supplemented with hIL-2 (1ng/mL) and hIL-7 (10ng/mL). At day 14, cells were cultured with Raji4RH and Venetoclax in either combined or solitary cultures. Co-culture cytotoxicity assays were performed by pre-labeling target cells with permeant dye (Thermo Fisher Scientific CellTrace Blue Proliferation Kit), then incubating with CAR-T CD19 cells (GFP labeled) at various effector:target ratios and Venetoclax concentrations for 24 hours. Sample wells were stained with viability dye and acquired on BD LSR II Cytometer. CAR-T CD19 cell immunophenotype was identified following 24-hour exposure of Venetoclax to CAR T cell populations at various concentrations. Following exposure, samples were stained with viability dye, CD3, CD4, CD8, CD45RA, CD45RO, CD62L, CCR7, CD25, and CD95. Frequencies of T REG, T Central Memory, T naive, and T Stem Cell Memory populations were calculated. CAR-T CD19 cell effector function was elucidated by activating (24 hours), then exposing CAR-T CD19 cells to concentrations of Venetoclax for 24 hours. Brefeldin A was added to culture for the remaining 4 hours of incubation. Cells were collected and stained intracellularly for IFNγ, Perforin, and Granzyme B; and extracellularly for CD3, CD4, and CD8. Sample acquisition for effector function assay was performed on BD LSRII Cytometer. Results Concurrent in vitro CAR-T CD19 administration and Venetoclax exposure significantly increases Raji4RH cell death as opposed to single agent cohorts. CAR-T CD19 cell viability is unaffected by Venetoclax at concentrations which confer synergy, and a predominantly CD8+ population is favored. Finally, Venetoclax appears to significantly increase the frequency of T N/T SCM and T CM within exposed cultures, while affording a 21% decrease in T REG frequency. Additionally, the notable increase in T N/T SCM and T CM phenotypes following exposure to Venetoclax did not arise as a consequence of decreased cellular viability. Conclusion The combination of Venetoclax exposure and αCD19 CAR T cell administration demonstrates synergy when employed in the context of rituximab-resistant lymphoma cells, which may be explained by the effect of the BH3 mimetic's exposure on CAR-T CD19 cell immunophenotype. The ability to manipulate Bcl-2 protein expression within CAR-T CD19 cells affords insight into the role that the Bcl-2 family pathway plays within CAR-T CD19 cell biology. In addition to answering fundamental questions of CAR T cell biology, the combination of Venetoclax and CAR-T CD19 therapy may provide a solution to the observed clinical gap, in which CAR-T CD19 therapy alone cures less than half of all patients who advance to this third line treatment regimen. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

INTRODUCTION Chimeric antigen receptor (CAR) T cell therapy provides a potential cure for patients who don't respond to standard treatments. One of the major challenges for current mainstream CAR-T therapy is lack of in vivo persistence of transferred cells. Intriguingly, more differentiated effector T cells that acquire enhanced in vitro anti-tumor properties were found to be paradoxically less effective for in vivo tumor treatment. It has become clear that the persistence of adoptive transferred T cells is crucial for in vivo activities. A significant linear correlation was found between the differentiation status of infused T cells and the potency of tumor regression, in the order of Tscm > Tcm >Tem. While promising, CAR-Tscm cell therapy demands technical innovation for precision cell processing and production. Here, we show CAR-Tscm cells generated by microbubble-based technologies for precision T cell sorting and activation and viral transduction are more robust than those generated by the conventional method in in vitro assays and in vivo animal study using the NSG mouse model. METHODS Naïve T cells were isolated by sequential sorting with 3 targeted lipid shell microbubbles (conjugated with anti-CD8, anti-CD45RA, and anti-CD62L). Briefly, CD8+ T cells were floated by anti-CD8 conjugated microbubbles and separated from nontargeted cells in PBMC. The floated CD8+ cells returned to solution after the microbubbles had undergone dissolution by increasing ambient pressure. These cells were subsequently floated by anti-CD45RA and anti-CD62L microbubbles sequentially, as described earlier. To generate CD19-CAR-modified Tscm-enriched cells, isolated naïve T cells were activated by anti-CD3/CD28 conjugated microbubbles and transduced by CD19-CAR retrovirus via Retronectin conjugated microbubbles. Transduced naïve T cells were cultured in media with IL-7, IL-21, and TWS119. Control CD19-CAR T cells were produced from same donors' PBMCs using standard culture conditions (soluble IL-2 and anti-CD3/CD28 coated culture flasks). Raji cells were co-cultured with effector cells (Tscm-enriched and standard CD19 CAR T cells) at a gradient ET ratio for in vitro cytotoxicity assay. Tscm-enriched and standard CD19-CAR T cells were injected into Raji-luc-bearing NSG mice. Tumor burden was measured by the XenogenIVIS system. RESULTS Naïve CD8+ T lymphocytes were enriched by sequential isolation of CD8+, CD62L+, and CD45RA+ cells from healthy donor PBMCs using respective antibody conjugated microbubbles. The CD8, CD62L, and CD45RA triple positive population was enriched from initial 10.08%± 2.4% to 71.84%±1.9% (n=4). We discovered that Retronectin conjugated microbubbles are advantageous to replace spinoculation technique to simplify viral transduction procedures. The average transduction efficiency was 27.71%± 8.7% using unconcentrated retroviral vectors. The Tscm-like cells were significantly enriched after two-week culture, compared to the standard method (37.78± 14.5% vs. 4.38± 0.7%). Tscm-enriched CD19-CAR T cells exhibited a stronger in vitro cytotoxicity towards Raji cells in comparison with standard CD19-CAR T cells (Figure 1). Consistently, in the NSG mice engrafted with Raji-Luc cancer cells, the CD19-CAR-modified Tscm-enriched cells showed longer-lasting antitumor responses than the CD19-CAR-T cells generated by the standard manufacturing process (Figure 2). CONCLUSION We have developed a bead-free, multi-positive selection system for CAR-Tscm production, and demonstrated that these Tscm cells effectively cause tumor regression and prolong diseased animal lifespan. A closed, automated, microbubble-based CAR-T cell manufacturing system, combining T cell isolation, activation, and transduction will be developed to improve performance and reduce costs. Figure 1 Figure 1. Disclosures Fu: Diagnologix LLC: Current Employment. Shi: Diagnologix LLC: Current Employment. Liu: Diagnologix LLC: Current Employment.

INTRODUCTION Diffuse large B-cell lymphoma (DLBCL) represents several distinct clinical pathologic entities recently identified by molecular profiling. Treatment with anti-CD19 chimeric antigen receptor (CAR) T-cell therapies is now standard for many patients with relapsed/refractory (R/R) disease. Although antigen loss of CD19 represents a known cause of late relapses, the majority of CAR-T cell treatment failure occurs very soon after treatment at which time the impact of molecular subtype and other somatic mutations of DLBCL is undefined. We sought to determine impact of molecular features of DLBCL tumors on clinical outcomes in a cohort of patients with R/R disease who were treated with axicabtagene ciloleucel (axi-cel) or tisagenlecleucel (tisa-cel) in order to provide insight into the mechanism of response or resistance to CAR-T cell therapy. METHODS We collected clinical data and formalin-fixed, paraffin embedded (FFPE) biopsy specimens from 121 DLBCL patients at the time of R/R disease after prior treatment with standard chemoimmunotherapy across 12 US academic medical centers who subsequently received commercial CAR-T cell treatment. Whole exome and transcriptome sequencing was performed on all cases to measure gene expression and gene copy number alterations. Genetic analysis was done on 96 patients with pre-treatment biopsies that passed sequencing quality filters, and expression analysis on 93 patients. Progression-free and overall survival (PFS, OS) measured from the day of CAR-T cell infusion were estimated using the Kaplan-Meier method and compared with the log-rank test. RESULTS Baseline demographics and treatment details of the patient population are shown in the Table (Panel A). Best overall response was CR in 43% of patients and PR in 10% patients. PFS and OS were significantly different based on best response to treatment (P CONCLUSIONS DLBCL patients whose tumors have molecular features that are predictive of inferior response to standard frontline treatment including the high-risk subgroups (C2/A53) and (C5/MCD) have favorable treatment outcomes with CAR-T cell therapy. In contrast, individual driver mutations including MYC and BCL2, CDKN2A, and KLHL6 are associated with inferior PFS with CAR-T cell therapy, while mutations in BTG2, MYD88, and CD79B are associated with a favorable PFS. In addition, gene expression analysis implicates a potential role for the microenvironment in modulating responses to CAR-T therapy. These findings suggest that predictive biomarkers for response to traditional chemoimmunotherapy and cellular immunotherapy are distinct. Our results provide insight into potentially targetable pathways for the development of rational treatment strategies that may augment response CAR-T cell therapy. Figure 1 Figure 1. Disclosures Hill: Celgene (BMS): Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Gentenech: Consultancy, Honoraria, Research Funding; Kite, a Gilead Company: Consultancy, Honoraria, Other: Travel Support, Research Funding; Beigene: Consultancy, Honoraria, Research Funding; AstraZenica: Consultancy, Honoraria; Epizyme: Consultancy, Honoraria; Incyte/Morphysis: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Karyopharm: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria, Research Funding. McKinney: Novartis: Research Funding; Nordic Nanovector: Research Funding; Molecular Templates: Consultancy, Research Funding; Kite/Gilead: Honoraria, Speakers Bureau; Incyte: Research Funding; Genetech: Consultancy, Honoraria, Research Funding; Epizyme: Consultancy; Celgene: Consultancy, Research Funding; BTG: Consultancy; Beigene: Research Funding; ADC Therapeutics: Consultancy, Speakers Bureau; Pharmacyclics: Consultancy; Verastem: Consultancy. Neff: Spring Discovery: Consultancy, Ended employment in the past 24 months; EUSA Pharma: Speakers Bureau; Enzyvant: Consultancy. Reshef: BMS, Regeneron, TScan, Synthekine, Atara, Jasper, Bayer: Consultancy; ilead, BMS, Precision, Immatics, Atara, Takeda, Shire, Pharmacyclics, Incyte: Research Funding; Bayer: Consultancy; Gilead and Novartis: Honoraria. Oluwole: Janssen: Consultancy; Pfizer: Consultancy; Curio Science: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding. Ghosh: Incyte: Consultancy, Honoraria; Pharmacyclics LLC, an AbbVie Company: Consultancy, Honoraria, Research Funding, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau; Seattle Genetics: Consultancy, Honoraria, Speakers Bureau; TG Therapeutics: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Honoraria, Research Funding, Speakers Bureau; Genmab: Consultancy, Honoraria; Epizyme: Honoraria, Speakers Bureau; Bristol Myers Squibb: Consultancy, Honoraria, Research Funding, Speakers Bureau; AstraZeneca: Consultancy, Honoraria, Speakers Bureau; ADC Therapeutics: Consultancy, Honoraria; Adaptive Biotech: Consultancy, Honoraria; AbbVie: Honoraria, Speakers Bureau; Karyopharma: Consultancy, Honoraria; Genentech: Research Funding. Chen: Actinium Pharmaceuticals: Other: Principal Investigator, SIERRA Trial, Actinium. Hernandez-Ilizaliturri: AbbVie: Other: Advisory Boards; Incyte: Other: Advisory Boards; Celgene: Other: Advisory Boards; BMS: Other: Advisory Boards; Pharmacyclics: Other: Advisory Boards; Amgen: Other: Advisory Boards; Kite: Other: Advisory Boards; Gilead: Other: Advisory Boards; Epyzime: Other: Advisory Boards. Shah: Lily: Consultancy, Honoraria, Research Funding; Miltenyi Biotec: Consultancy, Honoraria, Research Funding; Kite: Consultancy; Epizyme: Consultancy; Legend: Consultancy; Incyte: Consultancy; Umoja: Consultancy. Stephens: Epizyme: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding; Innate Pharma: Membership on an entity's Board of Directors or advisory committees; Beigene: Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees; Adaptive: Membership on an entity's Board of Directors or advisory committees; JUNO: Research Funding; Novartis: Research Funding; Abbvie: Consultancy; AstraZeneca: Consultancy; CSL Behring: Consultancy; Celgene: Consultancy; Mingsight: Research Funding; Arqule: Research Funding. Patel: Janssen: Consultancy; Kite Pharma: Consultancy, Speakers Bureau; TG Therapeutics: Consultancy, Speakers Bureau; MEI Pharma: Consultancy; Abbvie: Consultancy; Genentech: Consultancy; Bristol Myers Squibb: Consultancy, Speakers Bureau; BeiGene: Consultancy; Morphosys: Consultancy; Pharmacyclics: Consultancy; AstraZeneca: Consultancy, Research Funding, Speakers Bureau; ADC Therapeutics: Consultancy; Lilly: Consultancy. Pagel: Gilead: Consultancy; Actinium Pharmaceuticals: Consultancy; Kite, a Gilead Company: Consultancy; Incyte/MorphoSys: Consultancy; AstraZeneca: Consultancy; Pharmacyclics/AbbVie: Consultancy; Epizyme: Consultancy; BeiGene: Consultancy; MEI Pharma: Consultancy. Hsi: AbbVie Inc, Eli Lilly: Research Funding. Goy: Genentech/Hoffman la Roche: Research Funding; AbbVie/Pharmacyclics: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta: Consultancy, Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kite, a Gilead Company: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees; Medscape: Consultancy; AstraZeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Physicians' Education Resource: Consultancy, Other: Meeting/travel support; Xcenda: Consultancy, Honoraria; Genomic Testing Cooperative: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Other: Leadership role; LLC(Targeted Oncology): Consultancy; Hoffman la Roche: Consultancy; Vincerx: Honoraria, Membership on an entity's Board of Directors or advisory committees; Rosewell Park: Consultancy; Infinity/Verastem: Research Funding; MorphoSys: Honoraria, Other; Elsevier PracticeUpdate: Oncology: Consultancy, Honoraria; Xcenda: Consultancy; Bristol Meyers Squibb: Membership on an entity's Board of Directors or advisory committees; Vincerx pharma: Membership on an entity's Board of Directors or advisory committees; OncLive Peer Exchange: Honoraria; COTA (Cancer Outcome Tracking Analysis): Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees, Other: Leadership role; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Elsevier's Practice Update Oncology, Intellisphere, LLC(Targeted Oncology): Consultancy; Incyte: Honoraria; AbbVie/Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Michael J Hennessey Associates INC: Consultancy; Novartis: Consultancy, Honoraria; Janssen: Membership on an entity's Board of Directors or advisory committees; Janssen: Research Funding; Karyopharm: Research Funding; Bristol Meyers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Phamacyclics: Research Funding; Constellation: Research Funding; Hackensack Meridian Health, Regional Cancer Care Associates/OMI: Current Employment. Ohgami: Stemline Therapeutics: Research Funding. Andreadis: CRISPR Therapeutics: Research Funding; GenMAB: Research Funding; Novartis: Research Funding; Roche: Current equity holder in publicly-traded company, Ended employment in the past 24 months; Epizyme: Honoraria; Incyte: Honoraria; TG Therapeutics: Honoraria; Kite: Honoraria; Karyopharm: Honoraria; Atara: Consultancy, Honoraria; BMS: Research Funding; Merck: Research Funding. Thacker: Data Driven Bioscience: Current Employment. Rozzi: Data Driven Bioscience: Current Employment. Parker: Data Driven Bioscience: Current Employment. Happ: Data Driven Bioscience: Current Employment. Dave: Data Driven Bioscience: Current equity holder in publicly-traded company.

Introduction - Data regarding efficacy and toxicity of different bridging strategies prior to CAR-T therapy are scanty. Tisagenlecleucel (Kymriah TM, Novartis) and axictagene ciloleucel (Yescarta TM, Kite/Gilead) were commercially approved for relapsed/refractory (R/R) DLBCL since 2019. We analyzed real-life data of CAR-T therapy among all consecutive patients who were treated in 4 different CAR-T centers in Israel. Methods - From May 2019, 144 R/R DLBCL patients underwent apheresis and continued to receive bridging therapy that included chemo/immunotherapy (n=78, 54%), radiation (n=11, 7.6%), chemoradiation (n=22, 15%), steroids only (n=5, 3.5%) and none (n=28, 19.4%). All patients were evaluated after bridging therapy and prior to CAR-T infusion by PETCT (96%) or CT scan (4%). Results - Median age was 68 (20-88) years and Median follow-up was 13 (4-26) months. All 144 patients underwent successful apheresis. Reasoning for choosing specific bridging therapy was based on low tumor mass (n= 23, 16%), high tumor mass (n=73, 51%), frailty of the patient (n=27, 19%), ongoing significant prior regimen's toxicities (n=14, 10%) and local disease (n=7, 4%). In patients given radiation therapy median dose was 23 (range, 8-30) Gy. In patients given chemo/immunotherapy or chemoradiation, sepsis was the main complications (9% of all patients) during bridging therapy. However, none of the patients had a fatal event. 14 patients (9.7%) did not proceed to CAR-T infusion; 6 (4.2%) had disease progression and died; 8 (5.6%) had manufacture failure). Among the 130 patients that received CAR-T infusion, PET-CT prior to preparative regimen demonstrated CR/PR status in 38%, 50%, 40%, 17%, and 16% of patients given chemotherapy, radiation, chemoradiation, steroids only, or no bridging therapy, respectively (p=.15), Figure 1. Any bridging therapy was associated with a better disease control compared to either steroids only or no treatment (p=.012). There were no differences in the incidences of overall CRS (p=.692), grade 3-4 CRS (p=.196), overall ICANS (p=.941), grade 3-4 ICANS (p=.281), acute kidney disease (p=.244), and liver dysfunction (p=.45) between the 5 different bridging strategies. Cardiovascular complications were more common after chemoradiation (36%), chemotherapy (19%) and radiation (13%), compared with steroids (0%) or no bridging therapy (4%), p=.05. Non-relapse mortality was 0 in all subgroups. PETCT at 1-month post CAR-T infusion demonstrated an increase in CR status percentage across all subgroups with no statistically significant difference in the incidence between the subgroups (p=.27), Figure 1. There was no difference in both progression-free survival (Figure 2) and overall survival between the 5 subgroups (p=.7, and p=.23). Cox regression model identified preinfusion lower ECOG status (HR=0.8, p=.04), preinfusion CR/PR status (HR=.46, p=.037) and 1-month post infusion CR status as a time dependent co-variate (HR=.14, p Conclusions - Bridging to CAR-T should be tailored based on patient's and disease's characteristics with the aim to achieve the best disease control prior to CAR-T. However the chosen strategy per-se does not impact long-term outcomes. Intensive bridging therapy is associated with more cardiovascular events after CAR-T infusion. A prospective-controlled-trial allocating patients to different bridging strategies is needed to verify these results. Figure 1 Figure 1. Disclosures Ram: Gilead: Honoraria; Novartis: Honoraria. Yehudai-Ofir: Novartis: Membership on an entity's Board of Directors or advisory committees; Gilead Sciences: Membership on an entity's Board of Directors or advisory committees. Avivi: Novartis: Speakers Bureau; Kite, a Gilead Company: Speakers Bureau. Zuckerman: Cellect Biotechnology: Honoraria; Gilead Sciences: Honoraria, Speakers Bureau; Novartis: Honoraria; Janssen: Honoraria; BioSight Ltd: Honoraria; Orgenesis Inc.: Honoraria; AbbVie: Honoraria. Yeshurun: Astellas: Consultancy; Janssen: Consultancy. Gurion: Medison; Gilead Sciences; Takeda Pharmaceuticals: Consultancy; JC Health CARE; Roche: Honoraria. Levi: AbbVie: Consultancy, Research Funding.

Anti-CD19 chimeric antigen receptor T (CART19) cell therapy has resulted in unprecedented outcomes in patients with relapsed/refractory B-cell malignancies, which led to the FDA approval for several indications. However, CART19 cell therapy is limited by the development of severe life-threatening toxicities, as well as by the limited rates of durable response. It has become apparent that myeloid cells contribute to the development of both CART cell toxicity and also to the inhibitory tumor microenvironment. We and others have identified that granulocyte-monocyte-colony-stimulating factor (GM-CSF) depletion results in decreased myeloid activation, reduced toxicities, and enhancement of CART19 cell therapy efficacy in pre-clinical models. Furthermore, we observed that GM-CSF knockout (GM-CSF k/o) in CART19 cells resulted in the improvement of their functions (in vitro and in vivo). These findings suggest that there is also a direct effect of GM-CSF on CART19 cells, which is independent of the GM-CSF impact on myeloid cell activation. To further evaluate this, we first examined GM-CSF receptor alpha (GM-CSFRα) expression by flow cytometry on resting and activated CART19 cells (using FMC63-41BBζ). When CART19 cells were stimulated with either anti-CD3/CD28 beads or lethally irradiated (120 Gy) CD19 + Nalm6 cells (B cell acute lymphoblastic leukemia cancer cell line), GM-CSFRα expression was upregulated upon both T cell receptor (TCR) (data not shown) and CAR stimulation (Figure 1A). Having demonstrated that GM-CSFRα is significantly upregulated on stimulated CART19 cells, we aimed to determine the impact of GM-CSF neutralization (clinical-grade anti-GM-CSF antibody, lenzilumab, 10 µg/mL) versus GM-CSFRα blockade (research-grade antibody, 10 µg/mL) on CART19 cell function and CART cell-monocyte interactions. An IgG isotype antibody was used as a control antibody. Neither the GM-CSF neutralizing antibody, nor GM-CSFRα blocking antibody, had any impact on CART19 cell antigen-specific killing against the CD19 + JeKo-1 cells (mantle cell lymphoma cancer cell line), in the presence or absence of CD14 + monocytes (ratio 1:1:1) isolated by magnetic beads from healthy donors (Figures 1B-C). Next, we compared the effects of GM-CSF neutralization versus GM-CSFRα blockade on CART19 cell antigen-specific proliferation. Here, CART19 cells were co-cultured with lethally irradiated CD19 + cell line JeKo-1 at 1:1 ratio in the presence of 10 µg/mL of the GM-CSF neutralizing antibody, increasing doses of the GM-CSFRα blocking antibody (10-100 µg/mL), or an IgG control. The absolute number of CART cells was measured by flow cytometry on day 5. GM-CSF neutralization did not affect CART19 cell proliferation, but GM-CSFRα blocking antibody significantly inhibited CART19 cell proliferation in a dose-dependent manner. Then, we assessed the effects of GM-CSF neutralizing antibody (20 µg/mL) versus GM-CSFRα blocking antibody (20 µg/mL) on CART19 cell antigen-specific proliferation in the presence of healthy donor monocytes (ratio 1:1:0.5) on day 3. Flow cytometric analysis revealed that GM-CSF neutralization, but not GM-CSFRα blockade, mitigated monocyte-suppression of CART19 antigen-specific proliferation (Figure 1E). In summary, our findings indicate significant differences on CART cell functions and CART cell-monocyte interactions when a specific cytokine, GM-CSF, is neutralized compared to blocking its receptor. Further mechanistic studies are ongoing to assess the functions of GM-CSFRα k/o and GM-CSF k/o CART cells. Figure 1 Figure 1. Disclosures Sakemura: Humanigen: Patents & Royalties. Parikh: Pharmacyclics, MorphoSys, Janssen, AstraZeneca, TG Therapeutics, Bristol Myers Squibb, Merck, AbbVie, and Ascentage Pharma: Research Funding; Pharmacyclics, AstraZeneca, Genentech, Gilead, GlaxoSmithKline, Verastem Oncology, and AbbVie: Membership on an entity's Board of Directors or advisory committees. Kay: Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Membership on an entity's Board of Directors or advisory committees; Tolero Pharmaceuticals: Research Funding; CytomX Therapeutics: Membership on an entity's Board of Directors or advisory committees; MEI Pharma: Research Funding; Dava Oncology: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Morpho-sys: Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Research Funding; Acerta Pharma: Research Funding; Genentech: Research Funding; Rigel: Membership on an entity's Board of Directors or advisory committees; Behring: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Sunesis: Research Funding; Targeted Oncology: Membership on an entity's Board of Directors or advisory committees; Juno Therapeutics: Membership on an entity's Board of Directors or advisory committees; Bristol Meyer Squib: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees; Oncotracker: Membership on an entity's Board of Directors or advisory committees; Agios Pharm: Membership on an entity's Board of Directors or advisory committees. Durrant: Humanigen Inc.: Current Employment. Ahmed: Humanigen Inc.: Current Employment, Current equity holder in publicly-traded company. Chappell: Humanigen Inc.: Current Employment, Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months. Cox: Humanigen: Patents & Royalties. Kenderian: Humanigen, Inc.: Consultancy, Honoraria, Research Funding.

Introduction: Although anti-CD19 autologous chimeric antigen receptor (CAR) T-cell therapy has transformed the management of relapsed/refractory non-Hodgkin lymphoma (NHL), the majority of patients will ultimately relapse. The prognostic implications of early (1-month) metabolic response on ultimate outcome are still poorly defined, yet would have significant implications on the development of consolidation strategies. Methods: We conducted a multi-center, retrospective study of patients with NHL who received commercial anti-CD19 CAR T-cell therapy at 5 academic medical centers between 7/2018-5/2021. All patients had a PET scan 30 (+/- 15) days following CAR T-cell infusion. Imaging responses were per investigator assessment using Lugano criteria. Cox proportional hazards models were used to identify predictors of progression free survival (PFS). Results: A total of 193 patients were identified who received axicabtagene ciloleucel (axi-cel, n=180) or tisagenlecleucel (tisa-cel, n=13). Histologies included diffuse large B-cell lymphoma (DLBCL), NOS, n= 134 (69%), DLBCL transformed from an indolent lymphoma, n=47 (24%), primary mediastinal B-cell lymphoma (PMBCL), n=8 (4%), and Richter's syndrome (RS), n=4 (2%). The median age was 62 (range 19-80) years; 66% of patients were male; IPI was low in 28%, intermediate in 27%, and high in 42%; median prior therapies was 3 (range 1-9); 44% had an elevated LDH prior to lymphodepletion; 30% had an elevated CRP prior to CAR T-cell infusion; 10% had bulky disease (≥10 cm) prior to lymphodepleting therapy; and 40% received bridging therapy. The median follow-up of the entire cohort was 22 months (m). Responses at 1m included complete response (CR), n= 101 (52%), partial response (PR), n=53 (27%), stable disease (SD), n=4 (2%), and progressive disease (PD), n=35 (18%). The median PFS of the entire cohort was 11m (95% CI: 6-not reached) (Figure 1B) and median overall survival (OS) was not reached. PFS for the entire cohort was 57% (95% CI: 50-65) at 6m and 49% (95% CI: 42-58) at 12m; and OS was 79% (95% CI: 73-85) at 6m and 67% (95% CI: 61-75) at 12m. The 12m PFS and OS for patients with CR at 1m was 70% (95% CI: 61-80) and 82% (95% CI: 74-91), respectively, and was 38% (95% CI: 26-55) and 69% (95% CI: 57-84) for patients with PR/SD (Figure 1C). The 12m PFS and OS based on 1m PET (Figure 1D) was 72% (95% CI: 61-85) and 82% (95% CI: 72-93), respectively, for Deauville 1/2, 68% (95% CI: 53-88%) and 82% (CI: 69-98) for Deauville 3, 55% (95% CI: 39-79) and 83 (95% CI: 69-100) for Deauville 4, and 12% (95% CI: 3-46) and 56% (95% CI: 27-56) for Deauville 5 with PR/SD. Indicators of shorter PFS across the entire cohort included elevated LDH at lymphodepletion (HR: 2.11 (95% CI: 1.41-3.16, p Discussion: We demonstrate that PFS is improved in patients with a CR at day +30 PET as compared to patients with a PR or SD. Furthermore, patients with Deauville 1/2 appear to have similar outcomes as those with a Deauville 3. No independent clinical variables were able to predict which patients with a PR/SD were likely to progress at the time of their next scan. Novel biomarkers such a minimal residual disease (MRD), may be necessary to further guide treatment modification in this setting. Figure 1 Figure 1. Disclosures Crombie: Karyopharm: Consultancy; Incyte: Consultancy; Merck: Research Funding; Abbvie: Research Funding; Bayer: Research Funding; Roche: Research Funding. Chow: AstraZeneca: Research Funding; ADC Therapeutics: Current holder of individual stocks in a privately-held company, Research Funding. Gauthier: Janssen: Membership on an entity's Board of Directors or advisory committees; Legend Biotech: Membership on an entity's Board of Directors or advisory committees; Multerra Bio: Consultancy; Larvol: Consultancy; JMP: Consultancy; Eusapharma: Consultancy. Shouse: Beigene: Honoraria; Kite Pharma: Speakers Bureau. Herrera: Kite, a Gilead Company: Research Funding; ADC Therapeutics: Consultancy, Research Funding; Tubulis: Consultancy; Takeda: Consultancy; Seagen: Consultancy, Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Merck: Consultancy, Research Funding; Gilead Sciences: Research Funding; AstraZeneca: Consultancy, Research Funding; Karyopharm: Consultancy. Cohen: Janssen, Adaptive, Aptitude Health, BeiGene, Cellectar, Adicet, Loxo/Lilly, AStra ZenecaKite/Gilead: Consultancy; Genentech, Takeda, BMS/Celgene, BioInvent, LAM, Astra Zeneca, Novartis, Loxo/Lilly: Research Funding. Jacobson: Lonza: Consultancy, Honoraria, Other: Travel support; Precision Biosciences: Consultancy, Honoraria, Other: Travel support; Pfizer: Consultancy, Honoraria, Other: Travel support, Research Funding; Axis: Speakers Bureau; Kite, a Gilead Company: Consultancy, Honoraria, Other: Travel support; Celgene: Consultancy, Honoraria, Other: Travel support; Humanigen: Consultancy, Honoraria, Other: Travel support; Novartis Pharmaceuticals Corporation: Consultancy, Honoraria, Other: Travel support; Nkarta: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria; Clinical Care Options: Speakers Bureau. Armand: Otsuka: Research Funding; Sigma Tau: Research Funding; Infinity: Consultancy; Kite: Research Funding; Pfizer: Consultancy; IGM: Research Funding; Tensha: Research Funding; Roche: Research Funding; Genentech: Consultancy, Research Funding; AstraZeneca: Consultancy; Epizyme: Consultancy; Regeneron: Consultancy; Enterome: Consultancy; C4: Consultancy; GenMab: Consultancy; Tessa Therapeutics: Consultancy; Miltenyi: Consultancy; Daiichi Sankyo: Consultancy; Morphosys: Consultancy; Celgene: Consultancy; ADC Therapeutics: Consultancy; Adaptive: Consultancy, Research Funding; Affimed: Consultancy, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Merck: Consultancy, Honoraria, Research Funding. Hess: BMS: Speakers Bureau; ADC Therapeutics: Consultancy.

Introduction: CD19-directed chimeric antigen receptor T (CART19) cell therapies have shown impressive clinical outcomes in CD19+ B-cell malignancies. All the FDA-approved CART19, including tisagenlecleucel, axicabtagene ciloleucel, brexucabtagene autoleucel, and lisocabtagene maraucel use an anti-CD19 single-chain variable fragments (scFv) derived from the FMC63 antibody that binds to a CD19 epitope that is located in the membrane-distal portion of CD19. While this CART19 products are very effective in the clinic, the majority of patients still fails treatment or eventually relapses due to several mechanisms of resistance, including CAR T cell dysfunction in the immunosuppressive microenvironment. Novel strategies to enhance the activity of CART cells are critically needed. We and others recently demonstrated that modifications of the binding region of the CAR (scFv) (Singh N., Nat Med, 2021) can drastically change the interaction between the CAR T cell and the cancer cells, potentially improving the anti-tumor effect. In this study, we aimed to develop a novel anti-CD19 CAR that binds to a membrane-proximal domain of CD19 with the goal of improving CART functions. Moreover, we hypothesized that such a CART product would be active against B-cell acute lymphoblastic leukemia (B-ALL) blasts that present aberrant expression of the CAR19(FMC63) on the surface as we described in two pediatric B-ALL patients relapsed after CART19 (CTL019) at our Institution (Ruella M., Nat Med, 2018). Methods and Results: To these goals, we screened a chicken immune scFv library against the CD19 extracellular domain. We selected an scFv clone (1218) that was not competing with FMC63 for CD19 binding in competition enzyme immunoassays and real-time interaction analysis. The chicken 1218 scFv was humanized by CDR-grafting to human germline genes and backmutations (h1218 scFv) and was confirmed to be specific for CD19 in cell microarray assays and flow cytometry analyses. In order to define the epitope that was recognized by the 1218 scFv, we performed mutagenesis assays replacing several residues of human CD19 with monkey CD19 residues showed that, as compared to FMC63, the epitope of the h1218 scFv is localized in a membrane-proximal location shown by three-dimensional modeling (Teplyakov A., Proteins, 2018) (Fig. 1A). Key residues needed for the binding of the h1218 scFv were identified as T51, S53, E55, K59 and K63, while the membrane-distal amino acid H218 is recognized as a key residue for FMC63 binding. Therefore, we designed a novel CAR construct using the h1218 scFv, a 4-1BB costimulatory and CD3z signaling domains, using a lentiviral backbone. This CAR(h1218) construct was very active in vitro in human T cells demonstrating cytotoxicity, cytokine release, and proliferation upon encounter with CD19+ leukemic and lymphoma cells (NALM6, RAJI, and OCI-Ly18) (data not shown). Moreover, CART19(h1218) showed enhanced long-term (12 days) tumor control as compared to CART19(FMC63) against wild type NALM6 (data not shown). In vivo, CART19(h1218) cells (1.5x10 6 CAR+ cells/mouse) demonstrated tumor clearance against both Raji (CD19+ B-cell lymphoma) and Nalm6 (CD19+ B-cell leukemia) xenografts (Fig. 1B). Remarkably, in a more challenging stress- test model with lower CART doses (0.75x10 6 CAR+ cells/mouse) CART19(h1218) demonstrated stronger tumor control against Nalm6 cells as compared to CART19(FMC63) (Fig. 1C). Furthermore, our group recently described the occurrence of a B-ALL relapse characterized by the expression of the CAR19 itself on the cell surface due to accidental transduction of leukemic cells during manufacturing. The CART19(h1218) product but not CART19(FMC63) was able to recognize and kill CAR19(FMC63)-expressing leukemic cells in vitro at varying E:T ratios. Of note, in a long-term (12 days) in vitro killing assay using a low, challenging E:T ratio of 0.125:1 we observed potent and prolonged tumor control (Fig. 1D). Conclusions: These results indicate that the development of a CAR binder able to recognize an alternative and membrane-proximal epitope of CD19 might lead to improved anti-leukemia and lymphoma activity and can recognize CAR19(FMC63)+ blasts that are not recognized by CART19(FMC63). This novel CART19(h1218) product will be tested in phase I-II clinical trials for patients with B-cell malignancies. Figure 1 Figure 1. Disclosures Patel: AbClon Inc.: Research Funding. Kim: Abclon Inc.: Current Employment. Lee: AbClon Inc.: Research Funding. Guruprasad: AbClon Inc.: Research Funding. Kim: AbClon Inc.: Current Employment. Choi: AbClon Inc.: Current Employment. Kim: AbClon Inc.: Current Employment. Kim: AbClon Inc.: Current Employment. Lee: AbClon Inc.: Current Employment. Lee: AbClon Inc.: Current Employment. Park: AbClon Inc.: Current Employment. Lee: AbClon Inc.: Current Employment. Cui: AbClon Inc.: Current Employment. Yoon: AbClon Inc.: Current Employment. Kim: AbClon Inc.: Research Funding. Kim: AbClon Inc.: Research Funding. Hwang: AbClon Inc.: Current Employment. Lee: AbClon Inc.: Current Employment. Lee: AbClon Inc.: Current Employment. Chung: AbClon Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding. Ruella: Novartis: Patents & Royalties; BMS, BAYER, GSK: Consultancy; AbClon: Consultancy, Research Funding; Tmunity: Patents & Royalties; viTToria biotherapeutics: Research Funding.

Introduction: Patients with diffuse large B-cell lymphoma (DLBCL) that is resistant to chimeric antigen receptor T-cell (CAR-T) therapy have poor outcomes (Chow VA, et al. Am J Hematol. 2019;94:E209-E13). The majority of patients with DLBCL who relapse after CAR-T therapy do so with disease that continues to express CD19 surface antigen (Shah NN, Fry TJ. Nat Rev Clin Oncol. 2019;16:372-85); however, it is unknown whether treatment with CD19-targeted agents is an effective strategy for patients with prior failure of anti-CD19 CAR-T therapy. Loncastuximab tesirine (loncastuximab tesirine-lpyl; Lonca) is an FDA-approved CD19-directed antibody-drug conjugate (ADC) which had encouraging phase 1 antitumor activity and acceptable safety in non-Hodgkin lymphoma (Hamadani M, et al. Blood. 2021;137:2634-2645). In the Phase 2 LOTIS-2 trial (NCT03589469) the efficacy and safety of Lonca was evaluated in patients with relapsed or refractory (R/R) DLBCL after ≥2 lines of systemic treatments (Caimi PF, et al. Lancet Oncol. 2021;22:790-800). The overall response rate (ORR) was 48.3%. The aim of this post-hoc analysis of the LOTIS-2 trial was to investigate the antitumor activity of Lonca in patients with DLBCL relapsed or refractory after CAR-T therapy. Methods: The methodology of the LOTIS-2 trial has been published. Briefly, patients were treated with Lonca (0.15 mg/kg for the first 2 cycles then 0.075 mg/kg for subsequent cycles) administered as a single 30-minute infusion, once every 3 weeks for up to 1 year, or until progressive disease or unacceptable toxicity. Patients with previous anti-CD19 CAR-T therapy were required to have persistent CD19 expression, evaluated by local review of immunohistochemistry of a post-CAR-T biopsy. The primary endpoint was ORR, defined as the proportion of patients with best overall response of complete response (CR) or partial response (PR), determined by independent review. Secondary endpoints included overall survival (OS), progression free survival (PFS), and duration of response (DOR). PET/CT imaging was performed 6 and 12 weeks after the first Lonca dose and every 9 weeks thereafter. Response was assessed using the Lugano 2014 criteria. Kaplan Meier survival analysis was performed from initiation of Lonca treatment. Results: The characteristics of 13 patients with DLBCL with disease relapse or progression after anti-CD19 CAR-T therapy are shown in table 1. The median time interval between CAR-T infusion and Lonca treatment was 7 months (range, 45-400 days). Ten (77%) patients received Lonca as the first therapy after CAR-T failure, 3 patients received other treatments prior to Lonca (chemoimmunotherapy [R-GemOx], n = 1; allogenic stem cell transplant, n = 1; chemoimmunotherapy [R-GemOx] followed by venetoclax + bromodomain inhibitor, n =1). The ORR to Lonca was 46.2% (n=6; CR, 15.4% [n = 2]; PR, 30.8% [n = 4]) after a median of 2 cycles (range, 1-9). Of the 6 patients who achieved a response to Lonca, 5 had a previous response to CAR-T and 1 had prolonged, stable disease for >1 year after CAR-T. With a median follow-up of 8 months, the median OS and PFS were 8.2 and 1.4 months, respectively (Figure 1); the 1-year OS estimate was 33.3%. The median DOR to Lonca was 8 months. Conclusions: Lonca achieved a response in 6 out of 13 patients who had failed prior CAR-T therapy. Five out of 6 responding patients had previously presented at least a partial response after CAR-T therapy. These data suggest that in patients without CD19 antigen loss, repeat therapy with another agent targeting this antigen can result in disease control. Prior response to anti-CD19 therapy may be associated with subsequent response to a second anti-CD19 treatment. Further studies are needed to confirm the feasibility and value of repeated anti-CD19 treatments in patients with B-cell non-Hodgkin lymphoma. Funding: This study was funded by ADC Therapeutics; medical writing support was provided by CiTRUS Health Group. Figure 1 Figure 1. Disclosures Caimi: Amgen Therapeutics.: Consultancy; XaTek: Patents & Royalties: Royalties from patents (wife); ADC Theraputics: Consultancy, Research Funding; Genentech: Research Funding; Kite Pharmaceuticals: Consultancy; Verastem: Consultancy; Seattle Genetics: Consultancy; TG Therapeutics: Honoraria. Ardeshna: Gilead, Beigene, Celegene, Novartis and Roche: Honoraria; Norvartis, BMS, Autolus, ADCT, Pharmocyclics and Jansen: Research Funding; Gilead, Beigene, Celegene, Novartis and Roche: Membership on an entity's Board of Directors or advisory committees. Reid: Aptose Biosciences: Other: Serves as Principle Investigator, Research Funding; ADC Therapeutics: Other: Serves as Principle Investigator, Research Funding; Millennium Pharmaceuticals: Other: Serves as Principle Investigator, Research Funding; Xencor: Other: Serves as Principle Investigator, Research Funding. Ai: Kymria, Kite, ADC Therapeutics, BeiGene: Consultancy. Lunning: Myeloid Therapeutics: Consultancy; Spectrum: Consultancy; Daiichi-Sankyo: Consultancy; Verastem: Consultancy; Janssen: Consultancy; AstraZeneca: Consultancy; Morphosys: Consultancy; Beigene: Consultancy; Legend: Consultancy; ADC Therapeutics: Consultancy; Acrotech: Consultancy; Celgene, a Bristol Myers Squibb Co.: Consultancy; AbbVie: Consultancy; Kite, a Gilead Company: Consultancy; TG Therapeutics: Consultancy; Novartis: Consultancy; Kyowa Kirin: Consultancy; Karyopharm: Consultancy. Zain: Secura Bio, DaichiSankyo, Abbvie: Research Funding; Kiyoaw Kirin, Secura Bio, Seattle Genetics: Honoraria; Secura Bio, Ono , Legend, Kiyowa Kirin, Myeloid Therapeutics Verastem Daichi Sankyo: Consultancy. Solh: ADCT Therapeutics: Consultancy, Research Funding; Jazz Pharmaceuticals: Consultancy; BMS: Consultancy; Partner Therapeutics: Research Funding. Kahl: AbbVie, Acerta, ADCT, AstraZeneca, BeiGene, Genentech: Research Funding; AbbVie, Adaptive, ADCT, AstraZeneca, Bayer, BeiGene, Bristol-Myers Squibb, Celgene, Genentech, Incyte, Janssen, Karyopharm, Kite, MEI, Pharmacyclics, Roche, TG Therapeutics, and Teva: Consultancy. Hamadani: Takeda, Spectrum Pharmaceuticals and Astellas Pharma: Research Funding; Janssen, Incyte, ADC Therapeutics, Omeros, Morphosys, Kite: Consultancy; Sanofi, Genzyme, AstraZeneca, BeiGene: Speakers Bureau.

Background Approximately 60% of patients with aggressive large B-cell lymphoma (ALBCL) treated with anti-CD19 chimeric antigen receptor T-cell (CAR T) will ultimately progress or relapse. Allogeneic hematopoietic cell transplantation (Allo-HCT) is a potentially curative treatment for lymphoma patients who relapse after CAR T-cell therapy. However, the efficacy and toxicity profile of allo-HCT following CAR T in aggressive lymphoma patients are not well defined. Herein, we report our experience. Methods and patients A total of 29 adult patients (median age 45 years [IQR 40-55]) who received allo-HCT for ALBCL between 2017 to 2021 were included. All patients were previously treated with anti-CD19 CAR T-cell (academic CD28-costimulatory domain product [n=23, 79%]; tisagenlecleucel [n=6, 21%]). Twenty-five (86%) and 4 (14%) had a diagnosis of DLBCL and PMBCL, respectively. Median number of previous therapies before CAR T was 3 (IQR 2-4). Eight (28%) patients underwent a previous autologous HCT. No patient underwent a previous allo-HCT. Median hematopoietic cell transplantation-specific comorbidity index (HCT-CI) was 3 (IQR 2-3). Six (21%) patients had a Karnofsky performance status ≤ 80%. Allo-HCT was performed at a median of 4.1 months (IQR 2.2-5.4) post CAR T, with the majority of patients (48%) receiving transplant as first-line post CAR T. Reasons for allo-HCT were consolidation of complete response (CR) to CAR T in high-risk disease (n=4, 14 %), partial response (PR) to CAR T (n=7, 24%) and relapse /progression after CAR T (n=18, 62%). Disease response before allo-HCT was CR (n=11, 38%), PR (n=11, 38%) and progressive disease (n=7, 24%). Donors were matched siblings (n=13, 45%), matched unrelated (n=9, 31%) and mismatched unrelated /haploidentical donors (n=7, 24%). Myeloablative and reduced-intensity conditioning regimens were given in 13 (45%) and 16 (55%) patients, respectively. Methotrexate-based graft versus host disease (GVHD) prophylaxis was used in 20 (69%) patients. Antithymocyte globulin and post-transplantation cyclophosphamide were administered in 13 (45%) and 5 (14%), respectively. Results Median follow-up was 33 months (IQR 13-41). Neutrophil engraftment rate was 93% (two early deaths before engraftment due to infection and multi-organ failure). Two-year overall survival (OS) and progression-free survival were 44% (95% CI: 28-68) and 30% (95% CI: 17-55), respectively. Two-year cumulative relapse incidence and non-relapse mortality were 45% (95% CI: 25-63) and 25% (95% CI: 11-43), respectively (Figure). In a univariable Cox regression, factors significantly associated with a shorter OS were number of interim therapies between CAR T and allo-HCT (Hazard ratio [HR] 2.2 [95% CI: 1.3-3.9], p 0.006) and the length of time between CAR T and allo-HCT (HR 3.8 [95% CI: 1.2-12.1], p 0.02). Best response to CAR T and disease response before allo-HCT were not significant risk factors for a shorter OS. High rates of grade ≥ 3 hyperbilirubinemia (total bilirubin >3 ULN) and hepatic sinusoidal obstruction syndrome (SOS) were observed in 10 (35%) and 5 (17%) patients, respectively. These liver insults were not contributed to acute GVHD. All patients with SOS were treated with defibrotide and two patients died from related complications. Interestingly, 4/5 patients with SOS were conditioned with fludarabine and thiotepa. One-year cumulative incidence of grade II-IV acute GVHD was 34% (n=10; 95% CI: 18-52). Notably, 6 patients had grade IV acute GVHD, 4 of them were refractory to corticosteroids and 3 patients died due to acute GVHD. Two-year cumulative incidence of chronic GVHD was 23% (n=5; 95% CI: 7-46). Chronic GVHD was considered extensive in 4 of them. Bloodstream bacterial infection was documented in 11 (38%) patients. Invasive fungal infection occurred in 6 (21%) patients and included brain aspergillosis, cutaneous aspergillosis, 2 lung aspergillosis, hepatosplenic candidiasis and an ocular mucor mycosis. Conclusion Allogeneic hematopoietic cell transplantation is feasible after failure of CAR T-cell therapy in aggressive lymphoma, although with a relatively high rate of SOS and severe acute GVHD in these heavily pretreated patients. Overall survival is encouraging with approximately 30% of patients remaining alive and disease-free at two years. Larger scale studies are required to better define the role of allo-HCT in this setting. Figure 1 Figure 1. Disclosures Shouval: Medexus: Consultancy. Jacoby: NOVARTIS: Honoraria, Membership on an entity's Board of Directors or advisory committees. Avigdor: Takeda: Consultancy, Honoraria; Janssen: Research Funding; BMS: Research Funding; Gilead: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria.

Anti-CD19 chimeric antigen receptor (CAR) T cells can eliminate lymphoma, but CD19 loss from lymphoma can cause anti-CD19 CAR T-cell treatment failure. To address CD19 loss, we designed a bicistronic construct encoding 2 CARs. The first CAR in the bicistronic construct was the anti-CD19 CAR Hu19-CD828Z, which incorporated a human anti-CD19 single-chain variable fragment (scFv) along with CD28 and CD3ζ domains (Brudno et al. Nature Medicine 2020). The 2nd CAR in the construct was a novel anti-CD20 CAR incorporating a human anti-CD20 scFv, plus 4-1BB and CD3ζ domains. This bicistronic CAR construct, designated Hu1928-Hu20BB-original, was encoded by the mouse stem cell virus-based splice-gag (MSGV1) gamma-retroviral vector. Repeated segments of identical DNA sequence can lead to recombination events when retroviral vectors are utilized. Recombination events driven by repeated identical nucleotide segments can occur during retroviral vector production in packaging cells. Recombination events can also occur in transduced T cells during reverse transcription when repeated segments of identical nucleotides on the same nucleotide strand anneal, which leads to strand switching by the reverse transcriptase enzyme and deletion of part of the sequence. We assessed T cells transduced with Hu1928-Hu20BB-original for evidence of recombination. Southern blots of DNA from T cells transduced with Hu1928-Hu20BB-original showed a dominant band of the expected CAR transgene length and no aberrant bands after 21 hours of exposure; however, with extended exposure of 8 days, an unexpected band indicating shorter transgene length became visible. This aberrant band was consistent with deletion of part of the transgene sequence due to recombination. To investigate possible recombination by a more sensitive method, we assessed RNA from transduced T cells by single-molecule real-time RNA sequencing (SMRT-RNAseq, PacBio). Deletions of Hu1928-Hu20BB-original RNA sequence between segments of identical sequence were detected by SMRT-RNAseq. These findings were consistent with recombination. The most common recombination events were between the CD8α hinge and transmembrane (HT) domains of the 2 CARs of Hu1928-Hu20BB-original. These HT domains shared regions of identical nucleic acid sequence. Less commonly, recombination events occurred between segments of identical sequence shared by the heavy-chain domains and the light-chain domains of the two CARs in the construct. The attached table summarizes deletions consistent with recombination in Hu1928-Hu20BB-original RNA from transduced T cells of one patient. Similar results were obtained in T cells of 3 other patients. We confirmed deletions consistent with recombination in CAR RNA transcripts by short-read RNA sequencing (Illumina). Digital droplet PCR analysis of DNA from transduced T cells showed that recombination events between the HT domains of Hu1928-Hu20BB-original were present in DNA of transduced T cells. We modified the DNA sequence of Hu1928-Hu20BB-original to reduce repeated segments of identical DNA sequence to form a new CAR designated Hu1928-Hu20BB-standard. When T cells transduced with Hu1928-Hu20BB-standard were studied by SMRT RNAseq, deletions of RNA sequence consistent with recombination were substantially reduced (Table). We modified Hu1928-Hu20BB-standard by lengthening the linker in the anti-CD20 scFv to form a construct designated Hu1928-Hu20BB-long. We compared Hu1928-Hu20BB-standard to Hu1928-Hu20BB-long in vitro, and both specifically recognized CD19 and CD20 in assays of degranulation, cytokine release, and proliferation. In vitro assays showed higher interleukin-2 release by T cells transduced with Hu1928-Hu20BB-long versus Hu1928-Hu20BB-standard in response to 3 different CD20+ target cells (P value range 0.001 to 0.036). We tested Hu1928-Hu20BB-long against tumors established in nod-scid common gamma-chain knockout (NSG) mice. Human T cells expressing Hu1928-Hu20BB-long eliminated tumors of the following tumor cell lines: st486 (CD19+, CD20+), st486-CD19-negative (CD20+, CD19 low to negative expression), and NALM6 (CD19+, CD20 low expression). One million Hu1928-Hu20BB-long T cells per mouse eradicated st486 tumors. These optimized anti-CD19/CD20 bicistronic CAR constructs are promising for clinical treatment of B-cell malignancies. Figure 1 Figure 1. Disclosures Lam: Kite, a Gilead Company: Patents & Royalties. Kochenderfer: Bristol Myers Squibb: Research Funding; Kite, a Gilead Company: Patents & Royalties: on anti-CD19 CARs, Research Funding.

Background: Anti-CD19 chimeric antigen receptor T-cell therapy (CART) is a highly active therapy for relapsed/refractory (R/R) aggressive B-cell lymphoma. Nonetheless, most patients (pts) ultimately develop progressive disease (PD). There is little guidance on the optimal treatment approach(es) for these pts. We performed a multicenter retrospective analysis with a primary objective to assess treatment patterns and outcomes in pts with R/R aggressive B-cell lymphoma who develop PD after anti-CD19 CARTs. Methods: Pts with aggressive B-cell lymphoma treated with anti-CD19 CART between 2015 and 2020 across 12 US academic medical centers were included. Demographic and clinical characteristics were collected along with CART toxicities and response. Regimens administered as salvage post CART were assessed. Univariate analyses (UVA) were performed to determine impact of demographic and clinical variables on survival outcomes. All p-values were two-tailed. Survival curves were calculated using the Kaplan-Meier method. Results: A total of 400 pts received anti-CD19 CARTs and were included for analysis. For the entire cohort: median PFS and OS from time of CART infusion were 11 months [mo] and 27 mo respectively. On log-rank testing, pts who received ≥3 lines of pre-CART therapy and those with refractory disease pre-CART had significantly worse PFS (p=0.004 & 0.001) and OS (both p With median follow-up 22.4 mo, 190 pts (48%) had PD after CART; demographic and clinical variables of pts with and without PD are detailed in Table 1. Biopsy to confirm PD and assess CD19 status was done in 69 pts (36%) with CD19 negative relapse seen in 11 (16%). Of pts with PD, median PFS and OS from time of PD was 83 days (in pts who received salvage) and 174 days (for all PD pts) respectively. Pts with PD were more likely to have elevated LDH (p=0.001) and extranodal disease (p=0.003) at apheresis. For pts with PD after CART: 125 (65.5%) received further therapies. Pts were more likely to receive salvage therapies if their best response to CART was CR (p=0.026) or PR (p=0.015). Response rates of select first- and second-line therapies and PFS of first line therapies received after CART failure are detailed in figure 1. ORR and CRs were highest for polatuzumab, bendamustine, & rituximab (pola-BR; 73% & 40%), followed by BTK inhibitors (BTKi; 50% & 38%), and bispecific antibodies (bsAb) (50% & 25%). Five of 7 pts who received a BTKi had non-germinal center (GC) cell of origin (COO; 1 unknown COO). On log-rank testing, pts with elevated LDH (p=0.003) at time of apheresis and those with intermediate/high IPI (p=0.013) had inferior PFS with first salvage regimens. Median PFS was highest for pola-BR (4.5 mo, n=14), followed by bsAb (2.5 mo, n=8), lenalidomide +/- anti-CD20 antibody (1.8 mo, n=13), checkpoint inhibitors (CPI; 1.6 mo, n=10), BTKi (1.2 mo, n=8), radiation alone (1.2 mo; n=17), chemotherapy (1.1 mo, n=12), and tafasitamab + lenalidomide (0.9 mo, n=5). Median PFS for all treated pts was 1.8 mo. OS from start of first salvage regimen was highest for CPI (OS 12.4 mo, n=10), followed by pola-BR (8.9 mo, n=14), BTKi (8.8 mo, n=8), lenalidomide +/- anti-CD20 (8.7 mo, n=13), radiation alone (7.1 mo, n =17), bsAb (5.9 mo, n=8), chemotherapy (5.4 mo, n=12), and tafasitamab + lenalidomide (1.2 mo, n=5). 12 pts (6.3%) later received an allogeneic hematopoietic cell transplant (alloHCT). In alloHCT pts at last follow-up, 10 were evaluable for response: 7 had CR and 5 remain in CR. Clinical characteristics of pts who received alloHCT are detailed in table 2. Notably, median age was 59 years (41-68), 1 (8.3%) had a prior alloHCT, and 6 (50%) had prior autologous HCT. The majority had CR or PR as best response to CART (CR n=6, 50%; PR n=3, 25%), and only 1 pt (8.3%) with PD as best response to CART was salvaged with alloHCT. Conclusions: This is the largest reported analysis to date of pts with aggressive B-cell lymphoma who develop PD post-CART. The highest ORRs were with pola-BR, bsAb, and BTKi as first line of salvage. High response rates with BTKi may be attributed to non-GC COO in the majority of treated pts and perhaps a beneficial immunomodulatory effect on previously administered CARTs. AlloHCT remains a potential curative therapy for select pts with over half with durable remission; however, few ultimately received alloHCT. Despite increased use of novel therapies, survival in pts who progress after CART is still dismal warranting more effective therapies. Figure 1 Figure 1. Disclosures Epperla: Genzyme: Honoraria; Karyopharm: Other: Ad Board; Beigene: Speakers Bureau; Verastem: Speakers Bureau. Torka: TG Therapeutics: Membership on an entity's Board of Directors or advisory committees. Hess: ADC Therapeutics: Consultancy; BMS: Speakers Bureau. Cohen: Janssen, Adicet, Astra Zeneca, Genentech, Aptitude Health, Cellectar, Kite/Gilead, Loxo, BeiGene, Adaptive: Consultancy; Genentech, BMS/Celgene, LAM, BioINvent, LOXO, Astra Zeneca, Novartis, M2Gen, Takeda: Research Funding. Ma: Abbvie: Honoraria, Research Funding; Beigene: Research Funding, Speakers Bureau; Loxo: Research Funding; Juno: Research Funding; AstraZeneca: Honoraria, Research Funding, Speakers Bureau; Janssen: Research Funding, Speakers Bureau; TG Therapeutics: Research Funding; Pharmacyclics: Research Funding, Speakers Bureau. Winter: Gilead: Other: Husband: Consultancy; Janssen: Other: Husband: Consultancy; Ariad/Takeda: Other: Husband: Data and Safety Monitoring Board; Epizyme: Other: Husband: Data and Safety Monitoring Board; Agios: Other: Husband: Consultancy; Actinium Pharma: Consultancy; BMS: Other: Husband: Data and Safety Monitoring Board; Merck: Consultancy, Honoraria, Research Funding; Novartis: Other: Husband: Consultancy, Data and Safety Monitoring Board; Karyopharm (Curio Science): Honoraria. Gordon: Zylem Biosciences: Patents & Royalties: Patents, No royalties; Bristol Myers Squibb: Honoraria, Research Funding. Danilov: Bayer Oncology: Consultancy, Honoraria, Research Funding; Genentech: Consultancy, Honoraria, Research Funding; Rigel Pharm: Honoraria; Takeda Oncology: Research Funding; TG Therapeutics: Consultancy, Research Funding; Abbvie: Consultancy, Honoraria; Beigene: Consultancy, Honoraria; Pharmacyclics: Consultancy, Honoraria; SecuraBio: Research Funding; Astra Zeneca: Consultancy, Honoraria, Research Funding; Bristol-Meyers-Squibb: Honoraria, Research Funding; Gilead Sciences: Research Funding. Stephens: Adaptive: Membership on an entity's Board of Directors or advisory committees; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees; Beigene: Membership on an entity's Board of Directors or advisory committees; Epizyme: Membership on an entity's Board of Directors or advisory committees; JUNO: Research Funding; Mingsight: Research Funding; CSL Behring: Consultancy; Novartis: Research Funding; Abbvie: Consultancy; AstraZeneca: Consultancy; Arqule: Research Funding; Celgene: Consultancy; Innate Pharma: Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees, Research Funding. Shah: Miltenyi Biotec: Consultancy, Honoraria, Research Funding; Umoja: Consultancy; Incyte: Consultancy; Kite: Consultancy; Legend: Consultancy; Epizyme: Consultancy; Lily: Consultancy, Honoraria, Research Funding. Shouse: Beigene Pharmaceuticals: Honoraria; Kite Pharmaceuticals: Speakers Bureau. Barta: Acrotech: Honoraria; Daiichi Sankyo: Honoraria; Seagen: Honoraria; Kyowa Kirin: Honoraria. Karmali: Karyopharm: Consultancy; EUSA: Consultancy; Roche: Consultancy; Janssen/Pharmacyclics: Consultancy; Genentech: Consultancy; Morphosys: Consultancy, Speakers Bureau; Epizyme: Consultancy; Kite, a Gilead Company: Consultancy, Research Funding, Speakers Bureau; BMS/Celgene/Juno: Consultancy, Research Funding; AstraZeneca: Speakers Bureau; Takeda: Research Funding; BeiGene: Consultancy, Speakers Bureau.

Background . Anti-CD19 Chimeric Antigen Receptor (CAR) T-cells are a major therapeutic advance in the management of patients (pts) with relapsed/refractory aggressive B-cell lymphoma (R/R aggressive BCL) with reported overall response rates between 40% and 83% in the pivotal trials (ZUMA1, JULIET, TRANSCEND) as well as in the real-life cohorts with either axicabtagene ciloleucel (axi-cel, Yescarta) or tisagenlecleucel (tisa-cel, Kymriah). However, a significant number of pts will experience progression or relapse after infusion with an estimated 24-month progression-free survival (PFS) of between 33% and 42%. DESCAR-T is a nationwide registry that aims to collect real-life data for all pts treated with commercialized CAR T-cells in France. It represents a unique opportunity to investigate the outcome of pts who relapse after CAR T-cell therapy. Patients and Methods . In all, 680 pts with R/R aggressive BCL were registered in DESCAR-T from August 2018 and 550 were infused at the time of the present analysis (April 12, 2021) with either axi-cel (n=350) or tisa-cel, n=200). All pts gave informed informed consent before DESCAR-T registration. Progression and relapse after CAR T-cells were defined based on the Cheson 2014 response assessment criteria. Results . With a median follow-up (F-up) of 7.9 months, 238 pts (43.3%) out of 550 treated pts relapsed, after axi-cel in 136 pts (F-up = 9.0 months [5.1 - 9.7]) and after tisa-cel in 102 pts (F-up = 7.8 months [5.9 - 10.4]). Histological subtypes were DLBCL (n 178, 74.8%), PMBL (n=11, 4.6%), HGBCL (n= 3, 1.3%), transformed follicular lymphoma (tr FL) (n=31, 13%), or other histologies (FL n=2, PCNSL n=1, tr MZL n=3, unclassifiable hodgkin/DLBCL n=9). At time of registration, median age was 62 years (range 18;77), 43.6% were aged >65 yrs, and 67.2% were male; 184 (79.7%) presented with advanced disease (stage III or IV), and 13 (5.9%) with low age-adjusted International Prognostic Index (aaIPI), 82 (37.1%) with low-intermediate aaIPI, 110 (49.8%) with high-intermediate aaIPI, and 16 (7.2%) with high aaIPI. At time of CAR T-cell infusion, 36 (18.9%) pts presented with ECOG PS >=2 and 72 (38.9%) with an elevated LDH level. The median number of lines prior to CAR T-cell infusion was 3 (range 2-9), including 48 (20.1%) transplant (46 auto-HSCT and 2 allo-HSCT). Median time between order and infusion was 50 days (IQR 43; 59). Bridging therapy was administered to 87.8% of the pts, with a high-dose regimen including combined immunochemotherapy for 84.5% of the pts. Failure after CAR T-cells occurred after a median time of 2.71 months (range 0.2; 21.5), 54 (22.7%) being during the first month after infusion (< M1) and 156 (65.5%) during the first-three months after infusion ( Conclusion . This study is the first analysis reporting the outcome of patients with R/R aggressive BCL relapsing after anti-CD19 CAR T-cells. These results demonstrate the poor outcome of these pts and identifies the need for further innovative treatment strategies. Figure1. Overall survival from the CAR T-cell infusion in patients with R/R LBCL relapsing after CAR T-cells. (A) overall population. (B) according to the interval between CAR T-infusion and relapse (< 1 month and > 1 month) Figure 1 Figure 1. Disclosures Di Blasi: Novartis: Consultancy, Honoraria; Kite, a Gilead Company: Consultancy, Honoraria; Janssen: Consultancy, Honoraria. Bachy: Kite, a Gilead Company: Honoraria; Novartis: Honoraria; Daiishi: Research Funding; Roche: Consultancy; Takeda: Consultancy; Incyte: Consultancy. Cartron: Roche, Celgene-BMS: Consultancy; Danofi, Gilead, Novartis, Jansen, Roche, Celgene-BMS, Abbvie, Takeda: Honoraria. Le Bras: Takeda: Honoraria, Research Funding; Kite Gilead: Honoraria; Novartis: Honoraria; Celgene BMS: Research Funding. Feugier: Janssen: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria; Amgen: Honoraria; Astrazeneca: Consultancy, Honoraria. Casasnovas: Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead Kite: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; MSD: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Abbvie: Consultancy, Honoraria. Mohty: Amgen: Honoraria; Jazz: Honoraria, Research Funding; Sanofi: Honoraria, Research Funding; Pfizer: Honoraria; Novartis: Honoraria; Takeda: Honoraria; Janssen: Honoraria, Research Funding; Gilead: Honoraria; Celgene: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria; Astellas: Honoraria; Adaptive Biotechnologies: Honoraria. Sesques: Kite, a Gilead Company: Honoraria; Novartis: Honoraria; Chugai: Honoraria. Morschhauser: Servier: Consultancy; Incyte: Membership on an entity's Board of Directors or advisory committees; Chugai: Honoraria; AbbVie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genmab: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees; AstraZenenca: Membership on an entity's Board of Directors or advisory committees; Epizyme: Consultancy, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Speakers Bureau; F. Hoffmann-La Roche Ltd: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Genentech, Inc.: Consultancy; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees.