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Malignant pleural diseases, comprising metastatic lung and breast cancers and malignant pleural mesothelioma (MPM), are aggressive solid tumors with poor therapeutic response. We developed and conducted a first-in-human, phase I study of regionally delivered, autologous, mesothelin-targeted chimeric antigen receptor (CAR) T-cell therapy. Intrapleural administration of 0.3M to 60M CAR T cells/kg in 27 patients (25 with MPM) was safe and well tolerated. CAR T cells were detected in peripheral blood for >100 days in 39% of patients. Following our demonstration that PD-1 blockade enhances CAR T-cell function in mice, 18 patients with MPM also received pembrolizumab safely. Among those patients, median overall survival from CAR T-cell infusion was 23.9 months (1-year overall survival, 83%). Stable disease was sustained for ≥6 months in 8 patients; 2 exhibited complete metabolic response on PET scan. Combination immunotherapy with CAR T cells and PD-1 blockade agents should be further evaluated in patients with solid tumors.Significance:Regional delivery of mesothelin-targeted CAR T-cell therapy followed by pembrolizumab administration is feasible, safe, and demonstrates evidence of antitumor efficacy in patients with malignant pleural diseases. Our data support the investigation of combination immunotherapy with CAR T cells and PD-1 blockade agents in solid tumors.See related commentary by Aldea et al., p. 2674.This article is highlighted in the In This Issue feature, p. 2659

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Malignant pleural diseases, comprising metastatic lung and breast cancers and malignant pleural mesothelioma (MPM), are aggressive solid tumors with poor therapeutic response. We developed and conducted a first-in-human, phase I study of regionally delivered, autologous, mesothelin-targeted chimeric antigen receptor (CAR) T-cell therapy. Intrapleural administration of 0.3M to 60M CAR T cells/kg in 27 patients (25 with MPM) was safe and well tolerated. CAR T cells were detected in peripheral blood for >100 days in 39% of patients. Following our demonstration that PD-1 blockade enhances CAR T-cell function in mice, 18 patients with MPM also received pembrolizumab safely. Among those patients, median overall survival from CAR T-cell infusion was 23.9 months (1-year overall survival, 83%). Stable disease was sustained for ≥6 months in 8 patients; 2 exhibited complete metabolic response on PET scan. Combination immunotherapy with CAR T cells and PD-1 blockade agents should be further evaluated in patients with solid tumors. Significance: Regional delivery of mesothelin-targeted CAR T-cell therapy followed by pembrolizumab administration is feasible, safe, and demonstrates evidence of antitumor efficacy in patients with malignant pleural diseases. Our data support the investigation of combination immunotherapy with CAR T cells and PD-1 blockade agents in solid tumors. See related commentary by Aldea et al., p. 2674. This article is highlighted in the In This Issue feature, p. 2659

CD19-targeted chimeric antigen receptor (CAR) T-cell therapy has become a breakthrough treatment of patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL). However, despite the high initial response rate, the majority of adult patients with B-ALL progress after CD19 CAR T-cell therapy. Data on the natural history, management, and outcome of adult B-ALL progressing after CD19 CAR T cells have not been described in detail. Herein, we report comprehensive data of 38 adult patients with B-ALL who progressed after CD19 CAR T therapy at our institution. The median time to progression after CAR T-cell therapy was 5.5 months. Median survival after post–CAR T progression was 7.5 months. A high disease burden at the time of CAR T-cell infusion was significantly associated with risk of post–CAR T progression. Thirty patients (79%) received salvage treatment of post–CAR T disease progression, and 13 patients (43%) achieved complete remission (CR), but remission duration was short. Notably, 7 (58.3%) of 12 patients achieved CR after blinatumomab and/or inotuzumab administered following post–CAR T failure. Multivariate analysis revealed that a longer remission duration from CAR T cells was associated with superior survival after progression following CAR T-cell therapy. In summary, overall prognosis of adult B-ALL patients progressing after CD19 CAR T cells was poor, although a subset of patients achieved sustained remissions to salvage treatments, including blinatumomab, inotuzumab, and reinfusion of CAR T cells. Novel therapeutic strategies are needed to reduce risk of progression after CAR T-cell therapy and improve outcomes of these patients.

Immune effector cell (IEC) therapies offer durable and sustained remissions in significant numbers of patients with hematological cancers. While these unique immunotherapies have improved outcomes for pediatric and adult patients in a number of disease states, as ‘living drugs,’ their toxicity profiles, including cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS), differ markedly from conventional cancer therapeutics. At the time of article preparation, the US Food and Drug Administration (FDA) has approved tisagenlecleucel, axicabtagene ciloleucel, and brexucabtagene autoleucel, all of which are IEC therapies based on genetically modified T cells engineered to express chimeric antigen receptors (CARs), and additional products are expected to reach marketing authorization soon and to enter clinical development in due course. As IEC therapies, especially CAR T cell therapies, enter more widespread clinical use, there is a need for clear, cohesive recommendations on toxicity management, motivating the Society for Immunotherapy of Cancer (SITC) to convene an expert panel to develop a clinical practice guideline. The panel discussed the recognition and management of common toxicities in the context of IEC treatment, including baseline laboratory parameters for monitoring, timing to onset, and pharmacological interventions, ultimately forming evidence- and consensus-based recommendations to assist medical professionals in decision-making and to improve outcomes for patients.

Patients who develop chimeric antigen receptor (CAR) T-cell–related severe cytokine release syndrome (CRS) and immune effector cell–associated neurotoxicity syndrome (ICANS) exhibit hemodynamic instability and endothelial activation. The EASIX (Endothelial Activation and Stress Index) score (lactate dehydrogenase [LDH; U/L] × creatinine [mg/dL]/platelets [PLTs; 109 cells/L]) is a marker of endothelial damage that correlates with outcomes in allogeneic hematopoietic cell transplantation. Elevated LDH and low PLTs have been associated with severe CRS and ICANS, as has C-reactive protein (CRP), while increased creatinine is seen only in a minority of advanced severe CRS cases. We hypothesized that EASIX and 2 new modified EASIX formulas (simplified EASIX, which excludes creatinine, and modified EASIX [m-EASIX], which replaces creatinine with CRP [mg/dL]), calculated peri-CAR T-cell infusion, would be associated with development of severe (grade ≥ 3) CRS and ICANS. We included 118 adults, 53 with B-acute lymphoblastic leukemia treated with 1928z CAR T cells ({"type":"clinical-trial","attrs":{"text":"NCT01044069","term_id":"NCT01044069"}}NCT01044069) and 65 with diffuse large B-cell lymphoma treated with axicabtagene ciloleucel or tisagenlecleucel. The 3 formulas showed similar predictive power for severe CRS and ICANS. However, low PLTs and high CRP values were the only variables individually correlated with these toxicities. Moreover, only m-EASIX was a significant predictor of disease response. m-EASIX could discriminate patients who subsequently developed severe CRS preceding the onset of severe symptoms (area under the curve [AUC] at lymphodepletion, 80.4%; at day −1, 73.0%; and at day +1, 75.4%). At day +3, it also had high discriminatory ability for severe ICANS (AUC, 73%). We propose m-EASIX as a clinical tool to potentially guide individualized management of patients at higher risk for severe CAR T-cell–related toxicities.

Background: BCMA targeted CAR T cell therapy has shown promising results in patients with relapsed/refractory multiple myeloma (RRMM), but relapses are common. Additional treatment options with novel therapeutic targets or mechanisms of action are needed. Here we report on the safety and efficacy of MCARH109, the first-in-class G Protein Coupled Receptor Class C Group 5 Member D (GPRC5D) targeted CAR T cell therapy (Smith EL et al. Sci. Trans Med 2019) in RRMM including patients who relapsed post BCMA targeted CAR T cell therapy. Methods: This is a phase I first-in-human, dose escalation trial of MCARH109; patients received lymphodepleting chemotherapy with fludarabine 30 mg/m 2 daily and cyclophosphamide 300 mg/m 2 daily for 3 days followed by a single infusion of MCARH109. The trial followed a standard 3+3 design with the following dose cohorts to date: 25X10 6, 50X10 6, 150X10 6, 450X10 6 viable CAR + T cells. The primary objective is to assess safety of MCARH109; secondary objectives include anti-myeloma efficacy, expansion and persistence of MCARH109 using quantitative polymerase chain reaction (qPCR) on peripheral blood and bone marrow samples. Results: 18 patients with RRMM were enrolled and underwent apheresis between September 15, 2020 and July 14, 2021. 12 patients have completed MCARH109 infusion to date, with 6 patients currently undergoing manufacturing and pending treatment. Of the 12 patients treated, median age was 59 (37-76) years and patients received a median of 8 (4-14) lines of therapy. 11 (92%) were penta-exposed, all patients were triple refractory, and 7 (58%) had prior treatment with BCMA targeted therapy including 6 (50%) who received prior BCMA CAR T therapy. 3 (25%) patients had non-secretory myeloma and 6(50%) patients had extramedullary plasmacytoma at baseline. 11 (92%) were refractory to last line of therapy and 11 (92%) patients received bridging therapy after apheresis prior to MCARH109 infusion; all patients were refractory to bridging therapy. There were no dose limiting toxicities. Cytokine release syndrome (CRS) grade 1-3 occurred in 11 (92%) patients with only one patient with grade 3 event; 4 (25%) patients received tocilizumab and 1 (8%) received dexamethasone for the treatment of CRS (Table). There were no neurologic toxicities reported to date; 3 (25%) patients had grade 1 nail changes possibly related to MCARH109 (Table). As of July 28, 2021, all treated patients have been followed for at least 2 weeks (median: 13.0 weeks; range: 2.0-39.1 weeks) and 10 (83%) had at least a minimal response or better (2 responses unconfirmed): 2 minimal response, 3 partial response, 3 very good partial response, 2 stringent complete response (sCR). 5 (56%) of the first 9 patients were minimal residual disease (MRD) negative in the bone marrow by multicolor flow cytometry (sensitivity: 10 -5). 6 (100%) patients with prior BCMA CAR T therapy had a response with 2 patients achieving sCR. We also noted robust MCARH109 expansion in the peripheral blood using qPCR across the first 3 dose levels with available data (peak expansion vector copy number/mL, median: 404,467; range: 44,670- 3,560,000; Table). With a median follow-up of 13 weeks, 9 (75%) patients are progression free and followed without additional therapy. Conclusions: MCARH109 is the first-in-class GPRC5D targeted CAR T cell therapy for MM and has a very manageable safety profile with no serious or unexpected toxicities; this dose escalation study is ongoing with additional patients planned for treatment at higher doses. Efficacy is promising in heavily pre-treated RRMM, reflected in high rates of clinical response as well as MRD-negativity, including at doses as low as 25x10 6 CAR T cells. Clinically important, all 6 patients who relapsed after BCMA CAR T therapy responded to GPRC5D targeted CAR T therapy, including 2 patients who achieved sCR. Figure 1 Figure 1. Disclosures Mailankody: Allogene Therapeutics: Research Funding; Physician Education Resource: Honoraria; Bristol Myers Squibb/Juno: Research Funding; Takeda Oncology: Research Funding; Fate Therapeutics: Research Funding; Jansen Oncology: Research Funding; Evicore: Consultancy; Legend Biotech: Consultancy; Plexus Communications: Honoraria. Shah: Janssen: Research Funding; Celgene/BMS: Research Funding. Lesokhin: pfizer: Consultancy, Research Funding; Iteos: Consultancy; Trillium Therapeutics: Consultancy; Genetech: Research Funding; Serametrix, Inc: Patents & Royalties; bristol myers squibb: Research Funding; Janssen: Honoraria, Research Funding; Behringer Ingelheim: Honoraria. Korde: Medimmune: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding. Hassoun: Celgene, Takeda, Janssen: Research Funding. Hultcrantz: GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Research Funding; Daiichi Sankyo: Research Funding; Intellisphere LLC: Consultancy; Curio Science LLC: Consultancy. Shah: Amgen: Research Funding; Janssen: Research Funding. Landau: Takeda, Janssen, Caelum Biosciences, Celgene, Pfizer, Genzyme: Membership on an entity's Board of Directors or advisory committees; Takeda: Research Funding; Genzyme: Honoraria. Scordo: Angiocrine Bioscience: Consultancy, Research Funding; Omeros Corporation: Consultancy; Kite - A Gilead Company: Membership on an entity's Board of Directors or advisory committees; i3 Health: Other: Speaker; McKinsey & Company: Consultancy. Roshal: Auron Therapeutics: Other: Ownership / Equity interests; Provision of services; Celgene: Other: Provision of services; Physicians' Education Resource: Other: Provision of services. Landgren: Janssen: Other: IDMC; Janssen: Honoraria; Janssen: Research Funding; Amgen: Honoraria; Celgene: Research Funding; Amgen: Research Funding; Takeda: Other: IDMC; GSK: Honoraria. Dogan: Physicians' Education Resource: Honoraria; Seattle Genetics: Consultancy; Peer View: Honoraria; Takeda: Consultancy, Research Funding; Roche: Consultancy, Research Funding; EUSA Pharma: Consultancy. Giralt: Actinnum: Membership on an entity's Board of Directors or advisory committees; JENSENN: Membership on an entity's Board of Directors or advisory committees; GSK: Membership on an entity's Board of Directors or advisory committees; AMGEN: Membership on an entity's Board of Directors or advisory committees; CELGENE: Membership on an entity's Board of Directors or advisory committees; PFIZER: Membership on an entity's Board of Directors or advisory committees; JAZZ: Membership on an entity's Board of Directors or advisory committees; SANOFI: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees. Park: Autolus: Consultancy; Kite Pharma: Consultancy; PrecisionBio: Consultancy; Minerva: Consultancy; Curocel: Consultancy; Intellia: Consultancy; Amgen: Consultancy; Affyimmune: Consultancy; Innate Pharma: Consultancy; Novartis: Consultancy; Servier: Consultancy; Kura Oncology: Consultancy; Artiva: Consultancy; BMS: Consultancy. Rivière: FloDesign Sonics: Other: Provision of Services; Juno Therapeutics: Patents & Royalties; The Georgia Tech Research Corporation (GTRC): Other: Provision of Services (uncompensated); Centre for Commercialization of Cancer Immunotherapy: Other: Provision of Services; Fate Therapeutics: Other: Provision of Services, Patents & Royalties. Brentjens: BMS: Consultancy, Patents & Royalties, Research Funding; Gracell Biotechnologies, Inc: Consultancy, Ended employment in the past 24 months; sanofi: Patents & Royalties; Caribou: Patents & Royalties. Smith: Eureka Therapeutics: Consultancy; Fate Therapeutics: Research Funding; Chimeric Therapeutics: Consultancy; Novarits: Consultancy; Sanofi: Patents & Royalties: GPRC5D antibody based therapies; BMS: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: CAR T cells for MM. OffLabel Disclosure: MCARH109 is an experimental GPRC5D targeted CART therapy

Background: Autologous CAR T cell therapy targeting the B-cell specific surface antigen CD19 has demonstrated favorable clinical responses in relapsed or refractory (R/B) B-cell lymphomas (BCL). However, despite 40-60% initial complete response (CR) rates, only a subset of patients experience durable remissions, and there is a need to further improve the efficacy of CAR therapies by preventing relapse and attaining a deeper CR. We hypothesized that the redundancy of CD28 and CD3V signaling in a CAR design incorporating all 3 CD3Vimmunoreceptor tyrosine-based activation motifs (ITAMs) might foster counterproductive T cell differentiation and exhaustion, and therefore created a new CD19 CAR construct with calibrated CAR activation potential by mutating 2 of the 3 ITAMs, termed 1XX. In systemic ALL mouse models, 19-28z1XX CAR induced effective tumor eradication at low CAR T cell doses with improved survival compared to conventional 19-28z CAR. Further preclinical studies demonstrated that the enhanced therapeutic benefit resulted from the reduced strength of activation mediated by the 19-28z1XX CAR, achieving a favorable balance of effector and memory functions, thereby enhancing persistence of functional CAR T cells and promoting effective elimination of CD19+ leukemia at lower T cell doses than needed with 19-28z CAR T cells (Feucht J et al. Nat Med 2019). To further improve the persistence of functional CAR T cells, we screened different humanized CD19-directed scFv in the context of a 19-28z1XX CAR design and proved high specificity and functionality of 19-28z1XX CARs containing a novel humanized scFv T2 - termed 19(T2)28z1XX. Study Design and Methods: This study is a single center Phase I clinical trial of 19(T2)28z1XX in patients with R/R B-cell malignancies at Memorial Sloan Kettering Cancer Center (NCT04464200). Key disease eligibility criteria include R/R diffuse large B cell lymphoma (DLBCL), high grade BCL, primary mediastinal BCL, indolent BCL and chronic lymphocytic leukemia (CLL). Patients with prior CD19 CAR therapies are eligible as long as expression of CD19 is confirmed. Key exclusion criteria include ongoing immunosuppression such as systemic GvHD therapy and active CNS disease. The study uses a 3+3 dose-escalation design to identify the maximum tolerated dose for BCL. There are 5 planned flat-dose levels. Patients will receive conditioning chemotherapy consisting of 3 days of fludarabine and cyclophosphamide followed by a single infusion of 19(T2)28z1XX CAR T cells. In the dose-escalation phase, patients with DLBCL, high grade BCL, and primary mediastinal BCL are eligible to participate. Once the recommended phase 2 dose (RP2D) is determined, the study will open to dose expansion phase with two cohorts. Cohort 1 includes DLBCL, high grade BCL and primary mediastinal BCL (i.e. same eligibility criteria as the dose-escalation phase). Cohort 2 will include patients with indolent BCL, CLL, and Richter's transformation. The dose-expansion part of the trial is designed to further characterize the safety, efficacy, and pharmacokinetics of 19(T2)28z1XX CAR in multiple indications. The primary objective of the trial is to evaluate safety and tolerability and determine the recommended Phase 2 dose of 19(T2)28z1XX. Key secondary objectives include evaluation of 19(T2)28z1XX's efficacy and cellular kinetics. Exploratory objectives include assessment of B cell aplasia, and analysis of serum cytokines. The trial has begun enrollment in August 2020. The investigators are hopeful this study will lead to development of improved CD19 CAR T cell therapy with enhanced efficacy and favorable toxicity profiles with lower infused T cell dose. Disclosures Park: AstraZeneca: Consultancy; Servier: Consultancy, Research Funding; Autolus: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Novartis: Consultancy; Minverva: Consultancy; Artiva: Membership on an entity's Board of Directors or advisory committees; Fate Therapeutics: Research Funding; Kite: Consultancy, Research Funding; Incyte: Consultancy, Research Funding; Genentech/Roche: Research Funding; Juno Therapeutics: Research Funding; GSK: Consultancy; Intellia: Consultancy; Allogene: Consultancy. Riviere:Fate Therapeutics Inc.: Consultancy, Other: Ownership interest , Research Funding; FloDesign Sonics: Consultancy, Other: Ownership interest; Juno Therapeutics: Other: Ownership interest, Research Funding; Takeda: Research Funding; Atara: Research Funding. Palomba:Genentech: Research Funding; Juno Therapeutics, a Bristol-Meyers Squibb Company: Honoraria, Research Funding; Regeneron: Research Funding; Novartis: Honoraria; Merck: Honoraria; Celgene: Honoraria; Pharmacyclics: Honoraria. Brentjens:BMS: Research Funding; Gracell Therapeutics: Consultancy; Juno Therapeutics (a Bristol Myers Squibb company): Patents & Royalties. Sadelain:Atara: Patents & Royalties, Research Funding; Fate Therapeutics: Patents & Royalties, Research Funding; Minerva: Other: Biotechnologies , Patents & Royalties; Mnemo: Patents & Royalties; Takeda: Patents & Royalties, Research Funding. OffLabel Disclosure: Cyclophosphamide and fludarabine will be used as conditioning therapy prior to 19(T2)28z1XX CAR T cell administration.

Introduction Cytokine release syndrome (CRS) and immune effector cells associated neurotoxicity syndrome (ICANS) are common CAR T cells toxicities. Various grading systems that attribute different grades of severity to symptoms are currently used, preventing comparisons of different products and possibly leading to management implications. Methods We included 53 patients (pts) with B acute lymphoblastic leukemia (B-ALL) treated with 1928z CAR T cells (NCT01044069) and 49 pts with diffuse large B cell lymphoma (DLBCL) who received axicabtagene ciloleucel (axi-cel, n=36) or tisagenlecleucel (tisa-cel, n=13) after FDA approval. CRS and ICANS were retrospectively graded according to the new ASTCT consensus grading system, for comparison with other available systems: Lee, Penn, Memorial Sloan Kettering Cancer Center, CARTOX and CTCAEv5.0 for CRS; CTCAEv4.03 and CARTOX for ICANS. We then used ASTCT grades to predict management according to current guidelines for DLBCL pts (axi-cel and tisa-cel insert packages, CARTOX and NCCN guidelines) and compare it to the actual treatment received at our center. Results According to the ASTCT grading, B-ALL pts had 87% CRS (28% grade ≥3), while DLBCL pts had 86% CRS (14% grade ≥3) with axi-cel, and 54% (no grade ≥3) with tisa-cel. B-ALL pts had 55% ICANS (45% grade ≥3), while DLBCL pts had 55% ICANS (33% grade ≥3) with axi-cel, and 15% with tisa-cel (no grade ≥3) (fig. 1). When comparing grading systems, agreement on CRS and ICANS diagnosis was found in 99% and 91% cases, respectively. However, when evaluating toxicities grade by grade, only 27% pts had the same grade in each system for CRS, and 55% for ICANS (fig. 2). When predicting management for DLBCL pts, we found some relevant differences across current guidelines (fig. 3). At our center 58% and 13% of patients with CRS received tocilizumab (toci) and steroids, respectively, similarly to what predicted according to axi-cel's, CARTOX and NCCN guidelines, but differently from tisa-cel's label (10% and 5%). For ICANS, while tisa-cel's label does not provide any recommendations, other guidelines-based predictions were mostly overlapping. Indications for treatment vary across current guidelines, which were developed on single products and different grading systems, thus, should not be universally applied. This discrepancy becomes particularly relevant for cases with discordant CRS/ICANS grades. As such, we gave toci to 66% pts upgraded to grade 3 by Penn (grade 2 by ASTCT), while they would receive both toci and steroids according to axi-cel/CARTOX/NCCN guidelines, but would not be treated according to tisa-cel's. Conclusions Different grading systems provide inconsistent CRS/ICANS scores. To avoid discrepancies in assessing and managing toxicities of different products, a unified grading should be used and paired management guidelines with product-specific indications should be developed.

Background Cytopenias are observed post-CAR T, yet there is minimal data delineating the pathobiology and trends thereof. We report the largest series to our knowledge thus far, of hematopoietic recovery post-CAR T and factors affecting this recovery. Methods We retrospectively reviewed 115 adult patients who received CAR T, at our center, for relapsed/refractory (R/R) B cell lymphomas after FDA approval, R/R B cell acute lymphoblastic leukemia (ALL, NCT01044069) and multiple myeloma (MM, NCT03070327). Blood counts were collected for 12 months or until censored for relapse, progression or initiation of chemotherapy/ conditioning for autologous or allogeneic stem cell transplantation (HCT)/ subsequent treatment with CAR T. Only patients with follow-up > 30 days were included. "Recovery" for the respective blood count was defined to signify absence of transfusions or risk of infections: hemoglobin > 8g/dL and platelets > 50,000/µL without transfusion support in 2 weeks and 1 week, respectively; absolute neutrophil count (ANC) > 1,000/µL and white cell count (WBC) > 3,000/µL without growth factor support in 2 weeks. "Complete countrecovery" refers to recovery per above criteria in all 4 counts. Results Eighty three patients were included (Figure 1). By 1 month (n = 83), hemoglobin, platelets, ANC and WBC recovery was noted in 61%, 51%, 33% and 28%, respectively. At 3 months (n = 41), these were 93%, 90%, 81% and 59%. Figure 2 shows recovery at subsequent months. Upon examination of potential variables in a univariate model, lack of recovery of hemoglobin, platelets, ANC and complete count recovery at 1 month was statistically significantly associated with type of CAR construct, higher grade (3-4 vs 1-2 vs none) cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) as well as a higher peak CRP and ferritin (data for complete count recovery in Figure 3). Additionally, lack of hemoglobin recovery at 1 month was associated with lymphodepletion using high dose cyclophosphamide (recovered vs no recovery in 58% vs 42%, p = 0.01) and diagnosis of ALL (65% vs 35%, p = 3 prior lines of therapy (78% vs 22%, p = 0.04). At 3 months, absence of complete count recovery was associated only with the CAR T construct utilized. We also performed a sensitivity analysis using data for all 115 patients and no significant difference in univariate analysis was seen. Conclusions Our study shows that blood counts recover in most patients who have not progressed or received additional therapy by 3 months following CAR T. The association of count recovery with severity of CRS, ICANS as well as inflammatory marker levels indicates that inflammatory response post-CAR T influences hematological recovery in these patients.

BACKGROUND The introduction of chimeric antigen receptor (CAR) T-cell therapy has created challenges and opportunities for nurses. Clinical nurses must be educated on new treatment modalities to recognize toxicity symptoms and to support the therapy moving forward. . OBJECTIVES This article will discuss nursing leadership and interventions to standardize care and ensure patient safety while receiving CAR T cells. . METHODS Using evolving experience, an interprofessional team created standards of care and identified common toxicities and best practices for their management. Electronic documentation forms were designed, which led to the development of a new research infrastructure to care for patients. . FINDINGS The ability to safely manage patients on CAR T-cell treatments has improved. The new infrastructure supported clinicians and scientists in transforming the outcomes of diseases with bleak prognoses, which is possible only with strong nursing leadership. .

Introduction Chimeric Antigen Receptor (CAR) T cells are associated with unique toxicities, including cytokine release syndrome (CRS) and immune effector cells-associated neurotoxicity syndrome (ICANS). Patients (pts) with severe CRS and ICANS exhibit hemodynamic instability and coagulopathy with evidence of endothelial activation and increased blood brain barrier permeability. Increases in inflammatory cytokines and biomarkers of endothelial activation in serum and CSF have been associated with severe CRS and ICANS. The EASIX (Endothelial Activation and Stress Index) score [lactate dehydrogenase (LDH) (U/L) × creatinine (mg/dl) / platelets (PLT) (109 cells/L)] correlates with severe fluid overload and survival in allogeneic transplant pts. Elevated LDH and low PLT levels have been associated with severe ICANS development, and high IL-6 levels are seen in severe CRS and ICANS. We hypothesized that the EASIX and a newly proposed version of it, the modified-EASIX (mEASIX), in which creatinine is replaced by CRP (mg/dL) as an easily available surrogate for IL6, would be associated with CRS and ICANS in CAR T cells pts. Methods We analyzed 2 different populations of adult CAR T cells pts treated at our institution: 1) B-cell acute lymphoblastic leukemia (B-ALL) pts treated with CD1928z CAR T cells from 2010 to 2016 (NCT01044069), and 2) aggressive diffuse large B-cell lymphoma (DLBCL) pts treated with axicabtagene ciloleucel (axi-cel) or tisagenlecleucel (tisa-cel) after FDA approval starting from 2018. EASIX and mEASIX scores were calculated for each patient daily from start of lymphodepletion conditioning to day +14. A log transformation using base 2 (log2) was applied to all EASIX/mEASIX variables to reduce skew. CRS and ICANS were graded according to the ASTCT grading system. Results 87 pts, B-ALL (n=53) and DLBCL (n=34), were analyzed. According to ASTCT grading, 83% (72/87) experienced CRS and 54% (47/87) developed ICANS, grade ≥3 in 23% (20/87) and 40% (35/87) of pts, respectively. When analyzed by disease, CRS and ICANS rates were 87% (46/53) and 55% (29/53) for B-ALL and 76% (26/34) and 53% (18/34) for DLBCL, respectively. CRS and ICANS were grade ≥3 in 28% (15/53) and 45% (24/53) of B-ALL pts and in 15% (5/34) and 32% (11/34) of DLBCL pts, respectively. Median time of onset of CRS after CAR T cell infusion was day +2 and median onset of ICANS was day +6 for the overall population and the subgroups. High EASIX and mEASIX scores at start of conditioning were both associated with development of any grade CRS [OR=1.81 (95% CI 1.09-3.36) p=0.038 and OR=1.94 (95% CI 1.32-3.38) p=0.005] and grade ≥3 CRS [OR=1.47 (95% CI 1.05-2.29) p=0.049 and OR=1.34 (95% CI 1.07-1.80) p=0.024], respectively (Table). Following CAR T cell infusion, high scores of both EASIX [OR=1.60 (95% CI 1.12-2.43) p=0.017] and mEASIX [OR=1.32 (95% CI 1.07-1.69) p=0.014] on day +1 were associated with development of grade ≥3 CRS. Moreover, both high EASIX [OR=1.43 (95% CI 1.08-1.96) p=0.018] and mEASIX [OR=1.29 (95% CI 1.07-1.60) p=0.010] scores on day +3 were associated with grade ≥3 ICANS. When analyzed by disease, results were confirmed for severe CRS and ICANS in B-ALL patients, while in the DLBCL group only mEASIX at start of conditioning and at day +1 was associated with development of any grade CRS. EASIX and mEASIX scores were not associated with response rates to CAR T cells therapy. Conclusions EASIX and mEASIX scores calculated at baseline (before lymphodepletion) are associated with development of CRS and severe CRS. Moreover, both high EASIX and mEASIX scores on day +1 and day +3 are associated with occurrence of grade ≥3 CRS and grade ≥3 ICANS, respectively. We conclude that EASIX and mEASIX, as markers of endothelial damage and inflammation, could be useful as early predictors in guiding treatment decisions before the onset of severe symptoms. Table Disclosures Batlevi: Juno Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Brentjens:JUNO Therapeutics: Consultancy, Patents & Royalties, Research Funding; Celgene: Consultancy. Giralt:Miltenyi: Research Funding; Spectrum Pharmaceuticals: Consultancy; Novartis: Consultancy; Jazz Pharmaceuticals: Consultancy; Celgene: Consultancy, Research Funding; Johnson & Johnson: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Actinium: Consultancy, Research Funding; Kite: Consultancy. Palomba:Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Noble Insights: Consultancy; Seres Therapeutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; STRAXIMM: Membership on an entity's Board of Directors or advisory committees; Kite Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Evelo: Equity Ownership; MSK (IP for Juno and Seres): Patents & Royalties; Hemedicus: Speakers Bureau; Merck & Co Inc.: Consultancy. Santomasso:Kite/Gilead: Consultancy; Juno/Celgene: Consultancy; Novartis: Consultancy. Sauter:GSK: Consultancy; Kite/Gilead: Consultancy; Celgene: Consultancy; Juno Therapeutics: Consultancy, Research Funding; Sanofi-Genzyme: Consultancy, Research Funding; Spectrum Pharmaceuticals: Consultancy; Novartis: Consultancy; Genmab: Consultancy; Precision Biosciences: Consultancy. Scordo:Angiocrine Bioscience, Inc.: Consultancy; McKinsey & Company: Consultancy. Shah:Amgen: Research Funding; Janssen Pharmaceutica: Research Funding. Park:Allogene: Consultancy; Amgen: Consultancy; AstraZeneca: Consultancy; Autolus: Consultancy; GSK: Consultancy; Incyte: Consultancy; Kite Pharma: Consultancy; Novartis: Consultancy; Takeda: Consultancy. Perales:Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bellicum: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Meyers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Servier: Membership on an entity's Board of Directors or advisory committees; Kyte/Gilead: Research Funding; Miltenyi: Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Omeros: Honoraria, Membership on an entity's Board of Directors or advisory committees; Nektar Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy, Honoraria; Medigene: Membership on an entity's Board of Directors or advisory committees; NexImmune: Membership on an entity's Board of Directors or advisory committees; MolMed: Membership on an entity's Board of Directors or advisory committees.

Background: CAR T therapy is FDA approved for specific relapsed/ refractory (R/R) B cell lymphomas and acute lymphoblastic leukemia (ALL), and clinical trials are ongoing for R/R multiple myeloma (MM). Cytopenias have been observed post-CAR T, yet there is minimal data delineating the pathobiology and trends. We report the largest series to our knowledge thus far, of hematological recovery and factors affecting count recovery after CAR T. Methods: We retrospectively reviewed adult patients who received CAR T for R/R B cell lymphomas after FDA approval and those treated for R/R B cell ALL (NCT01044069) and MM (NCT03070327) at our center. Blood counts were collected for up to 12 months or until censored for relapse, progression or initiation of chemotherapy/ conditioning for autologous or allogeneic stem cell transplantation (HCT)/ subsequent treatment with CAR T. Only patients with follow-up > 30 days were included. "Recovery" for the respective blood count was defined as hemoglobin > 8g/dL and platelets > 50,000/µL without transfusion support in 2 weeks and 1 week, respectively; absolute neutrophil count (ANC) > 1,000/µL and white cell count (WBC) > 3,000/µL without growth factor support in 2 weeks. "Normalization" was defined as normal range for the laboratory; hemoglobin > 11.2g/dL in women and 12.5g/dL in men, platelets > 160,000/µL, ANC > 1,500/µL and WBC > 3,000/µL without transfusion support as above. "Complete count recovery" refers to recovery per above criteria in all 4 counts. Categorical variables were compared using Fisher's exact test and continuous variables using the Wilcoxon rank-sum test. Results: Eighty three patients were included (Table 1). Using the noted nadir values, grade 1-2 and 3-4 anemia was seen in 22% and 78%, thrombocytopenia in 29% and 66%, neutropenia in 3% and 96% while leucopenia in 0% and 100%, respectively. During the follow-up, 66% patients received packed red cell transfusion, 52% received platelet transfusion and 62% received growth factor support. By 1 month (n=83), recovery of hemoglobin, platelets, ANC and WBC was noted in 61%, 51%, 33% and 28%, respectively. At 3 months (n=41), these respective percentages were 93%, 90%, 81% and 59%. All patients had recovered hemoglobin and platelet count by 4 months (n=17), and ANC by 9 months (n=14). By 3 months, normalization of hemoglobin, platelets, ANC and WBC was noted in 39%, 34%, 71%, and 39%, respectively. Upon examination of potential variables in a univariate model, lack of recovery of hemoglobin, platelets, ANC and complete counts recovery at 1 month was statistically significantly associated with type of CAR construct, higher grade (grade 3-4 vs grade 1-2 vs none) cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) as well as a higher peak CRP and ferritin (data for complete count recovery in Table 2). Additionally, lack of hemoglobin recovery at 1 month was associated with lymphodepletion using high dose cyclophosphamide (recovered vs no recovery in 58% vs 42%, p=0.01) and diagnosis of ALL (65% vs 35%, p = 3 prior lines of therapy (78% vs 22%, p = 0.04). At 3 months, absence of complete count recovery was associated only with the CAR T construct utilized. A multivariate logistic regression model resulted in wide confidence intervals due to small size of subgroups, hence leading to unreliable point estimates (data not shown). Conclusions: Our study shows that blood counts recover in most patients who have not progressed or received additional therapy by 3 months post-CAR T. The association of count recovery with severity of CRS, ICANS as well as inflammatory marker levels indicates that inflammatory response post-CAR T influences hematological recovery in these patients. The association of count recovery and CAR construct can be influenced by underlying diagnosis as specific CAR constructs were used for specific diagnosis. Since patients with no disease response were excluded and were censored at progression, these effects are less likely to be affected by disease response; however the association of depth of response could not be evaluated in this study. These results warrant future studies to understand underlying mechanisms of inadequate recovery. Disclosures Scordo: McKinsey & Company: Consultancy; Angiocrine Bioscience, Inc.: Consultancy. Sauter:Kite/Gilead: Consultancy; Precision Biosciences: Consultancy; Genmab: Consultancy; Celgene: Consultancy; GSK: Consultancy; Juno Therapeutics: Consultancy, Research Funding; Sanofi-Genzyme: Consultancy, Research Funding; Spectrum Pharmaceuticals: Consultancy; Novartis: Consultancy. Santomasso:Novartis: Consultancy; Kite/Gilead: Consultancy; Juno/Celgene: Consultancy. Palomba:Noble Insights: Consultancy; Hemedicus: Other: Immediate Family Member, Speakers Bureau ; Evelo: Other: Immediate family member, Equity Ownership; MSK (IP for Juno and Seres): Other: Immediate Family Member, Patents & Royalties - describe: intellectual property rights ; Kite Pharmaceuticals: Other: Immediate Family Member, Membership on an entity's Board of Directors or advisory committees; Merck & Co Inc.: Other: Immediate Family Member, Consultancy (includes expert testimony); Seres Therapeutics: Other: Immediate Family Member, Equity Ownership and Membership on an entity's Board of Directors or advisory committees; STRAXIMM: Other: Immediate Family Member, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees. Shah:Amgen: Research Funding; Janssen: Research Funding. Batlevi:Juno Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Smith:Celgene: Consultancy, Patents & Royalties, Research Funding; Fate Therapeutics and Precision Biosciences: Consultancy. Giralt:Celgene: Consultancy, Research Funding; Takeda: Consultancy; Sanofi: Consultancy, Research Funding; Amgen: Consultancy, Research Funding. Brentjens:Celgene: Consultancy; JUNO Therapeutics: Consultancy, Patents & Royalties, Research Funding. Park:Takeda: Consultancy; Novartis: Consultancy; Kite Pharma: Consultancy; Incyte: Consultancy; Allogene: Consultancy; Amgen: Consultancy; AstraZeneca: Consultancy; Autolus: Consultancy; GSK: Consultancy. Perales:Bristol-Meyers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Nektar Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Omeros: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy, Honoraria; Medigene: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees; Kyte/Gilead: Research Funding; Miltenyi: Research Funding; MolMed: Membership on an entity's Board of Directors or advisory committees; NexImmune: Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bellicum: Honoraria, Membership on an entity's Board of Directors or advisory committees. Mailankody:Celgene: Research Funding; Juno: Research Funding; Janssen: Research Funding; Takeda Oncology: Research Funding; CME activity by Physician Education Resource: Honoraria.

Introduction: Autologous chimeric antigen receptor (CAR) T cell therapy has shown to be effective in CD19+ relapsed or refractory (R/R) B-ALL patients (pts). However, relapses are common and the role of post-CAR allogeneic hematopoietic stem cell transplant (alloHSCT) remains unclear, particularly in adults with relapsed B-ALL. We previously reported that there was no survival benefit with post-CAR alloHSCT in overall adult ALL population (Park J et al. NEJM 2018), but it is unclear whether there is a subset of pts who may benefit the most from post-CAR alloHSCT. Therefore, we sought to identify clinical features that are associated with a better long-term survival in adult B-ALL pts treated with CD19 CAR T cells followed by alloHSCT. Methods: We performed a retrospective chart review of adult pts with R/R ALL treated with 19-28z CAR T therapy at MSKCC (NCT01044069), with a particular focus on pts who achieved minimal residual disease (MRD) negative CR to the CAR therapy and subsequently proceeded to alloHSCT. Clinical data was updated with the data cutoff date of July 15, 2019. We examined the association between overall survival and the following clinical factors: impact of age, prior HSCT status, presence of Philadelphia chromosome (Ph), disease status at the time of CAR therapy (MRD vs. morphologic), severity of cytokine release syndrome (CRS) and neurotoxicity (NTX) experienced during CAR therapy. Survival was calculated from the time of CAR T cell infusion. Continuous variables were analyzed univariately using cox PH models. Categorical variables were analyzed using Kaplan Meier methodology and log rank tests. Results: Of the 53 pts who received 1928z CAR T cells, 16 pts proceeded to alloHSCT after achieving MRD negative CR to the CAR therapy. The median age of these pts was 38 (range, 23-66), and baseline disease and pt characteristics as well as response and toxicity to CAR T therapy are listed in Table 1. Of the 16 pts, 6 pts remain alive in remission; 4 pts died of relapse (median time to relapse: 104.5 days, 57-194), and 6 pts died of transplant-related mortality (TRM) in remission (n=4, infection; n=1, pulmonary VOD; n=1, respiratory failure of unclear etiology). Detailed disease and treatment characteristics by the outcome categories are listed in Table 2. For those pts who are alive in remission, the median survival is 47.5 months (range, 39.7-92.4). Among the examined clinical variables, we found younger age and no severe NTX (i.e. grade 0-2) after CAR therapy to be significantly associated with improved overall survival (p=0.014 and 0.05, respectively) but prior lines of therapy, time to HSCT, prior HSCT, Ph chromosome, disease status at the time of T cell therapy and severity of CRS did not impact the survival after alloHSCT. Conclusions: In this retrospective analysis, we found that younger age and no severe NTX to CD19 CAR therapy were associated with improved overall survival following alloHSCT. Number of relapses following alloHSCT (4 of 16 pts) appears to be lower compared to the previously reported number of relapse in the adult ALL cohort without alloHSCT (17 of 26 pts). However, the occurrence of TRM due to infection is high, likely a reflection of heavily pretreated pt population and possibly further immunosuppression from CAR + alloHSCT. The link between severe NTX and worse survival is unclear but could be related to prolonged corticosteroid use and high disease burden. While no definitive conclusion can be drawn due to a small sample size, our data suggests a certain subset of adult pts with R/R B-ALL may benefit more from alloHSCT as a consolidation therapy following CD19 CAR T cells, and acute and late infectious complications following alloHSCT should be carefully monitored. These findings should be validated prospectively and compared between different CAR constructs. Disclosures Park: Allogene: Consultancy; Amgen: Consultancy; AstraZeneca: Consultancy; Autolus: Consultancy; GSK: Consultancy; Incyte: Consultancy; Kite Pharma: Consultancy; Novartis: Consultancy; Takeda: Consultancy. Riviere:Fate Therapeutics: Consultancy; Juno Therapeutics: Consultancy, Equity Ownership, Research Funding; Memorial Sloan Kettering Cancer Center: Employment. Sadelain:Memorial Sloan Kettering Cancer Center: Employment; Fate Therapeutics: Consultancy, Patents & Royalties; Juno Therapeutics: Consultancy, Patents & Royalties, Research Funding. Brentjens:JUNO Therapeutics: Consultancy, Patents & Royalties, Research Funding; Celgene: Consultancy.

Background: Malignant pleural disease (MPD) from primary malignant pleural mesothelioma (MPM) or secondary metastatic disease (lung and breast cancers) affects more than 150,000 patients a year in the US alone. We developed chimeric antigen receptors (CARs) to target mesothelin (MSLN), a cell-surface antigen that we have shown is highly expressed in MPD, is associated with aggressiveness and poor survival, and has low expression in normal tissues. Methods: Using a second-generation CD28-costimulated MSLN CAR with the Icaspase-9 safety gene (IcasM28z), we initiated a phase I clinical trial (NCT02414269) to determine the safety and maximum tolerated dose of intrapleurally administered CAR T cells. Patients with biopsy-proven MPD expressing MSLN were eligible for the study. A single dose of IcasM28z CAR T cells was administered intrapleurally (with or without cyclophosphamide preconditioning) by either pleural catheter or an interventional radiology procedure. On-target, off-tumor toxicity, serial serum soluble MSLN-related peptide (SMRP) levels and C-reactive protein levels were assessed, and CT and PET scans were performed, in addition to routine clinical and laboratory tests. Results: Twenty-one patients with MPD (19 MPM, 1 lung cancer, 1 breast cancer) were treated (40% received ≥3 lines of prior therapy). Eighteen of the 21 patients received cyclophosphamide preconditioning (3E5 - 1E7 CAR T cells/kg); the first cohort did not receive cyclophosphamide. Twelve patients were administered CAR T cells using an interventional radiology procedure. One patient had febrile neutropenia (grade 3) related to cyclophosphamide. No CAR T-cell-related toxicities higher than grade 2 were observed. The last cohorts of patients were admitted 2 weeks after infusion with a temperature of 101°F and fatigue. Intense monitoring for on-target, off-tumor toxicity by clinical (chest or abdominal pain), radiological (CT/PET or echocardiogram for pericardial effusion, ascites), laboratory (troponin elevation), and other (electrocardiogram) evaluation found no evidence of toxicity. One patient successfully underwent curative-intent surgical resection 6 weeks after CAR T-cell infusion. CAR T cells were detected in the peripheral blood of 13 patients (day 1 to 38 weeks), as evidenced by vector copy number. T-cell persistence was associated with decreased serum SMRP levels (>50% compared to pretreatment) and evidence of tumor regression on imaging studies. Once lack of toxicity had been established (6-17 weeks after CAR T-cell infusion), 14 patients received anti-PD1 checkpoint blockade agents (1-21 cycles), off protocol, with no toxicity. The best response among the 19 MPM patients (13 patients received anti-PD1 agent; PD-L1 Conclusion: In this phase I clinical trial, intrapleurally administered MSLN-targeted CAR T cells had no evidence of on-target, off-tumor or therapy related toxicity, and there was evidence of CAR T-cell antitumor activity. MSLN-targeted CAR T-cell therapy combined with anti-PD1 agents shows encouraging clinical outcomes, thus a combination therapy trial is planned to recruit patients in the second quarter of 2019. Citation Format: Prasad S. Adusumilli, Marjorie G. Zauderer, Valerie W. Rusch, Roisin E. O'Cearbhaill, Amy Zhu, Daniel A. Ngai, Erin McGee, Navin K. Chintala, John C. Messinger, Alain Vincent, Elizabeth F. Halton, Claudia Diamonte, John Pineda, Shanu Modi, Stephen B. Solomon, David R. Jones, Renier J. Brentjens, Isabelle Rivière, Michel Sadelain. A phase I clinical trial of malignant pleural disease treated with regionally delivered autologous mesothelin-targeted CAR T cells: Safety and efficacy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT036.

2520 Background: Autologous chimeric antigen receptor (CAR) T cell therapy has shown to be effective in CD19+ relapsed or refractory (R/R) B-ALL but requires a 2-4 week period of cell processing and manufacture. During this “bridging period,” patients are vulnerable to disease progression and complications. We sought to characterize bridging strategies in our published study of CD19 CAR T cell therapy in adults with R/R ALL (Park et al., NEJM, 2018). Methods: We performed a retrospective review of adult patients with R/R ALL treated with 19-28z CAR T therapy at MSKCC. Bridging therapy was defined as any therapy given from trial enrollment to cell infusion and classified as either high intensity (remission-inducing or myelosuppressive regimens, eg hyper-CVAD or high-dose cytarabine based regimens) or low intensity (maintenance and/or less myelosuppressive regimens, eg POMP, Blinatumomab, TKI). Results: Of 53 patients who received CAR T cell infusion, 19 were bridged with a high intensity regimen and 34 with a low intensity regimen. There was no difference in number of prior therapies, pre-bridging chemotherapy disease burden, and prior transplant status between groups. High intensity therapy was associated with a higher rate of Gr3-4 infectious complications during the bridging period (78% vs 32%, p < 0.002 by Fisher’s Exact) but not with response to bridging or CAR T cell therapy, relapse free survival, post-CAR Gr3-4 cytokine release syndrome (CRS) or neurotoxicity (NT). Patients in both groups who converted from morphologic to molecular disease during bridging (n=9) had a decreased rate of eventual severe CRS (0% vs 41%, p=0.01) or NT (0% vs 55%, p 0.05) or a combined endpoint of CAR T cell infusion or alternative therapy including transplant (80% vs 86%, p> 0.05). Conclusions: High intensity bridging therapy is associated with a high risk of infectious complications without a clear benefit in outcome in R/R ALL receiving CD19 CAR T cells. Selection of bridging regimen therefore requires consideration of previous treatments and patient status to maximize the efficacy and safety. Clinical trial information: NCT01044069.

2511 Background: We conducted a phase I dose escalation trial of first-in-human autologous chimeric antigen receptor (CAR) T-cell immunotherapy targeting mesothelin (MSLN), a cell-surface antigen that is highly expressed in pleural cancers- malignant pleural mesothelioma (MPM) and metastatic lung and breast cancers. Methods: A single dose of CD28-costimulated MSLN CAR T cells with the I-caspase-9 safety gene was administered intrapleurally in patients with MSLN-expressing pleural tumors. Following a 3+3 design, patients were treated in dose escalating cohorts (dose range 3E5 to 1E7 CAR T cells/kg) following IV cyclophosphamide lymphodepletion (first 3 patients did not receive cyclophosphamide). A subset of MPM patients received subsequent anti-PD-1 therapy, off-protocol, which we have shown to prolong CAR T-cell functional persistence in preclinical models. Results: Twenty patients (18 MPM, 1 lung cancer, 1 breast cancer) were treated (prior lines of therapy 1–8, 35% received ≥3 lines of therapy). No CAR T-cell–related toxicities higher than grade 1 were observed. Intense monitoring for on-target, off-tumor toxicity by clinical (chest or abdominal pain), radiological (CT/PET or echocardiogram for pericardial effusion, ascites), laboratory (troponin elevation), and EKG evaluation found no evidence of toxicity. Fourteen MPM patients received subsequent anti-PD1 therapy (1–21 cycles, pretreatment tumor PD-L1 < 10% in all patients except one), with 1 patient developing grade 3 pneumonitis that responded to steroid treatment. CAR T cells were detected in the peripheral blood of 13 of 14 patients (1-39 weeks). At data cut-off date (Jan 31, 2019), among 14 MPM patients that received combination therapy (follow-up 13-77 weeks, median 31 weeks), best responses included 2 patients with complete metabolic response on PET (62 and 39 weeks ongoing); 5 partial responses and 4 stable disease by investigator assessment. Conclusions: Intrapleurally administered MSLN-targeted CAR T cells were safe. Encouraging antitumor activity of MSLN-targeted CAR T-cell therapy was observed when combined with anti-PD1 therapy and shows promise for future development of this approach. Clinical trial information: NCT02414269.

Cellular therapy with chimeric antigen receptor (CAR) T cells has fundamentally changed the treatment of many cancers. Unfortunately, not all patients who receive this therapy have a favorable response. Additionally, patients may develop toxicity due to cytokine release syndrome (CRS) or neurotoxicity. We hypothesized that the composition of the intestinal microbiota prior to CAR T cell infusion is correlated with efficacy and toxicity. We collected fecal samples from recipients of CAR T cells at Memorial Sloan Kettering Cancer Center (MSKCC) pre-CAR T cell infusion. Microbiota composition was profiled by 16S sequencing. Shotgun metagenomic sequencing was performed on a subset of the samples. Clinical response to assess efficacy was classified as complete response (CR) or no CR. Toxicity was defined as CRS or neurotoxicity of Grade 1 to 4. Linear discriminant analysis effect size (LEfSe) identified differentially abundant bacteria between groups with a linear discriminant analysis (LDA) score threshold >2.5. We analyzed baseline samples from 25 patients treated at MSKCC. The patients were adult recipients of CAR T cells who varied in regard to conditioning regimen, CAR construct and underlying diagnosis, which included hematologic and solid malignancies. LEfSe revealed increased representation of bacterial taxa in the microbiome of CR versus no CR, with Oscilliospiraceae, Ruminococcacaeae and Lachnospiraceae enriched in CR and Peptostreptococcaceae more abundant in no CR (A). A higher abundance of Lachnospiraceae was found in those who experienced toxicity, while Peptostreptococcaceae was more abundant in patients who did not have toxicity (B). We explored shotgun metagenomic sequences from 19 of 25 samples that were functionally annotated using the shortBRED pipeline. We inspected abundances of genes assigned to three pathways that we hypothesized may be immunologically relevant: B vitamin synthesis, bile acid biosynthesis, and short-chain fatty acid production. We observed increased abundance of genes associated with B vitamin biosynthesis in patients who had no CR (C) or toxicity (D). We observe differential abundance of microbiota in patients who achieved a CR or experienced toxicity as compared to those who did not achieve a CR or experience toxicity. We observe that increased B vitamin gene abundance is associated with no CR or toxicity. Overall, this data indicates that features of the microbiota may correlate with outcomes to CAR T cell therapy.

Introduction: BCMA targeted CAR T cell therapy has shown promising results in patients with relapsed/refractory multiple myeloma (MM). Herein, we report on the safety and efficacy of MCARH171, a second generation, human derived BCMA targeted autologous 4-1BB containing CAR T cell therapy, including a truncated epidermal growth factor receptor safety system (Smith EL. Mol Ther 2018). Methods: This is a phase I first in human, dose escalation trial of MCARH171. Patients received conditioning chemotherapy with cyclophosphamide (Cy) 3 gm/m2 as a single dose or fludarabine 30 mg/m2 daily and Cy 300 mg/m2 daily for 3 days followed by MCARH171 infusion in 1-2 divided doses. The trial followed a standard 3+3 design with 4 dose levels where patients received the following mean doses per cohort: (1) 72x106, (2) 137x106, (3) 475x106, (4) 818x106 viable CAR+ T cells. The primary objective was to demonstrate safety, and secondary objectives included efficacy and expansion, and persistence of CAR T cells using PCR from the peripheral blood. The last accrued patient received MCARH171 on Dec 6, 2017 and the data cut-off is July 16, 2018. The study is closed to accrual. Results: 11 patients with relapsed and/or refractory MM were treated. Median number of prior lines of therapy was 6 (range: 4-14), and all patients received prior therapy with a proteasome inhibitor, IMiD, anti-CD38 monoclonal antibody, and high dose melphalan/stem cell transplant. Nine (82%) patients had high-risk cytogenetics and 9 (82%) were refractory to their immediate prior line of treatment. One patient was not evaluable for DLTs given the need for early radiation and steroids for impending spinal cord compression by tumor. There are no DLTs reported. Cytokine release syndrome (CRS) grade 1-2 occurred in 4 patients (40%), grade 3 occurred in 2 (20%), and there was no grade 4-5 CRS. Grade 2 encephalopathy occurred in 1 patient (10%) in the setting of high fevers which resolved in less than 24 hours. There was no grade 3 or higher neurotoxicity observed. Tocilizumab was administered to 3 patients; 2 in cohort 2, and 1 in cohort 3. Laboratory values correlating with CRS reaching grade 3 or requiring Tocilizumab (N=4) compared to those with no or milder CRS (N=6) included peak CRP (mean: 28.5 vs 4.6 mg/dL, p Overall response rate was 64% and the median duration of response was 106 days (range: 17 to 235 days). The peak expansion and persistence of MCARH171 as well as durable clinical responses were dose dependent. Patients who were treated on the first two dose cohorts (≤150 X106 CAR T cells) had a lower peak expansion in the peripheral blood (mean 14,098 copies/µL; N=6), compared to patients who were treated on the third or fourth dose cohort 3-4 (≥450 X106 CAR T cells; N=5), where the mean peak expansion was 90,208 copies/µL (p6 months compared to only 1 of 6 (16.7%) patients who received lower doses. Two patien have ongoing responses (VGPR) at 7.5+ and 10+ months of follow up. To normalize for dose administered we compared the pharmacokinetics of only patients treated at dose levels 3-4 ( ≥450 X106 CAR T cells). Here, we demonstrate that peak expansion correlated to clinical efficacy, with the 3 durable responders all having peak expansion >85,000 copies/µL (mean: 131,732 copies/µL); compared to transient responders, where the maximum peak expansion was 33,213 copies/µL (mean: 27,922; Figure 1). Conclusions: MCARH171 has an acceptable safety profile with no DLTs reported. A dose-response relationship with toxicity was not clearly observed, as noted by distribution of tocilizumab use across dose cohorts. However, a dose-response relationship was observed with promising clinical efficacy at dose levels of ≥450 X106 CAR T cells. Controlling for dose level, peak expansion correlated with durability of response. These results further support the development of CAR T cells for heavily pre-treated patients with relapsed and refractory MM. Disclosures Mailankody: Janssen: Research Funding; Takeda: Research Funding; Juno: Research Funding; Physician Education Resource: Honoraria. Korde:Amgen: Research Funding. Lesokhin:Takeda: Consultancy, Honoraria; Squibb: Consultancy, Honoraria; Janssen: Research Funding; Genentech: Research Funding; Serametrix, inc.: Patents & Royalties: Royalties; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding. Hassoun:Oncopeptides AB: Research Funding. Park:Juno Therapeutics: Consultancy, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; AstraZeneca: Consultancy; Adaptive Biotechnologies: Consultancy; Kite Pharma: Consultancy; Novartis: Consultancy; Shire: Consultancy. Sauter:Juno Therapeutics: Consultancy, Research Funding; Sanofi-Genzyme: Consultancy, Research Funding; Spectrum Pharmaceuticals: Consultancy; Novartis: Consultancy; Precision Biosciences: Consultancy; Kite: Consultancy. Palomba:Pharmacyclics: Consultancy; Celgene: Consultancy. Riviere:Fate Therapeutics Inc.: Research Funding; Juno Therapeutics, a Celgene Company: Membership on an entity's Board of Directors or advisory committees, Research Funding. Landgren:Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; Pfizer: Consultancy; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm: Consultancy; Merck: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Research Funding. Brentjens:Juno Therapeutics, a Celgene Company: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Smith:Celgene: Consultancy, Patents & Royalties: CAR T cell therapies for MM, Research Funding.

Introduction Cellular therapy with chimeric antigen receptor (CAR) T cells has fundamentally changed the treatment of many cancers. Unfortunately, not all patients who receive this therapy have a favorable response. Additionally, some patients may develop toxicity due to cytokine release syndrome (CRS) or neurotoxicity. Recent studies have found a relationship between the intestinal microbiome and the response to immunotherapy with checkpoint blockade. We propose the intestinal microbiota as a factor that influences the efficacy and toxicity of CAR T cells. We hypothesize that the differences in outcomes of patients who receive CAR T cells are related to the composition of their intestinal microbiota at baseline. We report a single-center analysis of pre-CAR T cell infusion microbiota composition. Methods We collected stool samples from recipients of CAR T cells at Memorial Sloan Kettering Cancer Center (MSKCC). A baseline sample was collected prior to CAR T cell infusion. Samples were submitted for 16S RNA sequencing of the V4-V5 region on the Illumina MiSeq platform and the operational taxonomic units (OTUs) were classified using the NCBI Reference Sequence Database. Clinical response to assess efficacy was classified as either complete response (CR) or no complete response. Given the sample size, toxicity was pooled to encompass Grade 1 to 4 CRS and Grade 1 to 4 neurotoxicity. Linear discriminant analysis effect size (LEfSe) was used to identify microbial biomarkers for efficacy and toxicity between groups using relative abundances with a linear discriminant analysis score threshold >2.5. Results We analyzed 24 baseline samples from 24 patients treated at MSKCC. The patients were all adult recipients of cellular therapy with CAR T cells. The patients varied in conditioning regimen, CAR construct and underlying diagnosis, which included solid tumors and hematologic malignancies. First, we assessed the 16S relative abundance of the intestinal microbiota of the patients at baseline. We found that the composition of the microbiota prior to CAR T cell infusion was diverse, as defined by an Inverse Simpson >4 in all of the patients, although the level of diversity amongst the patient samples varied (Fig A). An assessment of the efficacy of CAR T cells with LEfSe analysis found increased abundance in several families of the Clostridiales order (Firmicutes phylum), including Oscillospiraceae, Ruminococcacaeae, and Lachnospiraceae, in those patients who achieved a CR. For the patients who did not achieve a CR, we found an increased abundance of a family in the Clostridiales order (Firmicutes phylum), Peptostreptococcaceae. Patients who experienced toxicity, either CRS or neurotoxicity, had an increased abundance of families within the Clostridiales or Lactobacillales order (Firmicutes phylum), which included Lachnospiraceae and Lactobacillaceae. Finally, patients who did not experience toxicity also had an increased abundance of a family in the Clostridiales order (Firmicutes phylum), Peptostreptococcaceae. Conclusion We demonstrate that our subset of patients had diverse microbial composition prior to receiving CAR T cell therapy despite the fact that many of them were heavily pre-treated. Additionally, we observe the abundance of the family Lachnospiraceae in the patients who achieved a CR and those who experienced toxicity. Many Lachnospiraceae are butyrate producers, whose presence has been found to be protective against Clostridium difficile infection in recipients of allogeneic hematopoietic cell transplant but whose abundance is lower in colon cancer. Conversely, we observe an abundance of the family Peptostreptococcaceae in patients who did not achieve a CR or who did experience toxicity. Peptostreptococcaceae has been found to be more abundant in the intestines of patients with colon cancer. Of note, the intestinal micriobiota that we identify are not congruent with the specific bacteria that have been found to promote anti-tumor immunity to checkpoint blockade. Our data suggests a role for the intestinal microbiota in mediating the response to CAR T cells and proposes that the baseline microbial composition may correlate with efficacy and toxicity. Further studies will investigate biochemical mechanisms to understand the interplay of the intestinal microbiota and the immune system to improve patient outcomes following CAR T cell therapy. Disclosures Park: Adaptive Biotechnologies: Consultancy; Juno Therapeutics: Consultancy, Research Funding; Novartis: Consultancy; AstraZeneca: Consultancy; Kite Pharma: Consultancy; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Shire: Consultancy. O'Cearbhaill:Juno: Research Funding. Mailankody:Juno: Research Funding; Janssen: Research Funding; Takeda: Research Funding; Physician Education Resource: Honoraria. Smith:Celgene: Consultancy, Patents & Royalties: CAR T cell therapies for MM, Research Funding. Palomba:Pharmacyclics: Consultancy; Celgene: Consultancy. Riviere:Fate Therapeutics Inc.: Research Funding; Juno Therapeutics, a Celgene Company: Membership on an entity's Board of Directors or advisory committees, Research Funding. Brentjens:Juno Therapeutics, a Celgene Company: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.

Background: CD19-specific 2nd generation chimeric antigen receptor (CAR) T cell therapy with either CD28 or 41BB co-stimulatory domain has demonstrated complete remission (CR) rates of 30-50% in relapsed or refractory (R/R) NHL and 20-30% in CLL. The lesser activity of CD19 CAR T cells in CLL and NHL relative to ALL may be in part due to diminished intrinsic T cell quality or greater CAR T cell inhibition in the tumor microenvironment. We previously demonstrated that 19-28z CAR T cells that express 4-1BBL achieve greater proliferation, IL-2 secretion and persistence compared to 19-28z or 19-4-1BBz CAR T cells (Zhao et al., Cancer Cell, 2015). Herein, we report on adult patients (pts) with CLL or NHL treated with escalating doses of autologous 19-28z/4-1BBL+ CAR T cells (NCT03085173). Methods: Pts with R/R NHL (DLBCL, follicular lymphoma (FL), transformed FL (tFL), Waldenström's macroglobulinemia (WM)) and CLL including Richter's transformation were eligible for the trial. Pts received conditioning chemotherapy of cyclophosphamide (Cy) alone or combined with fludarabine (Flu) followed by escalating doses of CAR T cells. CAR T cells were administered at dose level (DL) 1 (1x105 CAR T cells/kg), DL2 (3x105 CAR T cells/kg), DL 3 (1x106 CAR T cells/kg), and DL4 (3x106 CAR T cells/kg). The primary objective of the study was to evaluate safety of autologous 19-28z/4-1BBLCAR T cells. Secondary objectives included rates of overall response. Results: 25 pts were enrolled with R/R CLL (n=9), de novo DLBCL (n=6), tFL (n=3), FL and WM (n=4), and Richter's transformation (n=3). Median age of the pts was 70 (range, 53-81), and median number of prior treatments was 5 (range, 2-17). All 10 pts with CLL progressed on ibrutinib and 9 pts were refractory to venetoclax. 3 pts received DL1 CAR T cells, 3 pts DL2 CAR T cells, 3 pts DL3 CAR T cells and remaining 16 pts received DL4 CAR T cells. Of the 9 de novo DLBCL and tFL pts, all were >70 years old, 7/9 were refractory with progressive disease as best response to any line of chemotherapy or relapsed ≤12 mo after ASCT or any line of therapy. Six of 9 pts received R-GemOx as bridging chemotherapy with 2/6 progressing on R-Gemox prior to CAR T cell therapy. 3 pts received conditioning chemotherapy with Cy alone, and 22 pts received Flu + Cy conditioning chemotherapy. No dose-limiting toxicity has been observed. Of the 25 treated pts, 24 pts are at least 2 weeks from T cell infusion and evaluable for toxicity. Overall, 16 pts experienced CRS (67%), all of which were grade 1 (n=13) and grade 2 (n=3). No pts experienced severe CRS. 8 pts (33%) experienced any grade neurotoxicity (NTX), including 6 pts with grade 1-2 and 2 pts with grade 3 NTX. No cerebral edema was observed, and all NTX were transient and reversible. 2 pts (8%) received one dose of tocilizumab and 4 pts (16%) received corticosteroid for NTX. 21 pts had at least 4 weeks of follow-up and were evaluable for response. 12 of 21 pts (57%) achieved CR, including 7 of 8 pts (88%) with large cell lymphoma, 2 of 2 pts with FL, 2 of 9 pts (22%) with CLL and 1 of 2 pts with Richter's transformation (Figure). CR was observed in pts with ≥10cm bulky lymph nodes (n=1), extra nodal disease involving bone, muscle, perineural and CNS (n=3), and extensive bone marrow involvement ≥80% (n=3). With a median follow-up of 93 days (range, 30 - 439), 11 of the 12 CR pts remain in CR. Peak CAR T cell expansion occurred at a median of 9 days after CAR T cell infusion (range, 2-82). While analysis of CAR T cell persistence is ongoing, CAR T cell detection beyond 160 days has been noted. Conclusions: Treatment with 19-28z/41BBL armored CAR T cells appears to be safe. No severe CRS was observed and severe NTX occurred in 8% of the pts with no case of cerebral edema. The overall CR rate of 57% is encouraging with 11 of the 12 pts remaining in CR at the time of this report. CR rates were higher in pts with large cell lymphoma (88%) compared to CLL (22%), though most of CLL pts received lower dose of CAR T cells (7 pts at DL1-3 vs. 2 pts at DL4). Pts with CLL may require higher doses of CAR T cells or incorporation of the CAR therapy in earlier lines of treatments. Detailed cytokine and CAR T cell expansion analysis in comparison to our previous cohort of pts treated with the 2nd generation 1928z CAR T cells will be presented. Figure. Figure. Disclosures Park: Adaptive Biotechnologies: Consultancy; Kite Pharma: Consultancy; Novartis: Consultancy; Shire: Consultancy; Juno Therapeutics: Consultancy, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; AstraZeneca: Consultancy; Pfizer: Consultancy. Palomba:Celgene: Consultancy; Pharmacyclics: Consultancy. Riviere:Fate Therapeutics Inc.: Research Funding; Juno Therapeutics, a Celgene Company: Membership on an entity's Board of Directors or advisory committees, Research Funding. Furman:Pharmacyclics LLC, an AbbVie Company: Consultancy; Acerta: Consultancy, Research Funding; Genentech: Consultancy; Gilead: Consultancy; Incyte: Consultancy, Other: DSMB; Loxo Oncology: Consultancy; Sunesis: Consultancy; TG Therapeutics: Consultancy; Verastem: Consultancy; Janssen: Consultancy; AbbVie: Consultancy. Brentjens:Juno Therapeutics, a Celgene Company: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Sadelain:Fate Therapeutics Inc.: Research Funding; Juno Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.

Patients with relapsed/refractory MM (RRMM) rarely obtain durable remissions with available therapies. Clinical use of BCMA targeted CAR T cell therapy was first reported in 12/2015 for RRMM, and based on small numbers, preliminary results appear promising. Given that host immune anti-murine CAR responses have limited the efficacy of repeat dosing (Turtle C. Sci Trans Med 2016), our goal was to develop a human BCMA targeted CAR T cell vector for clinical translation. We screened a human B cell derived scFv phage display library containing 6x1010 scFvs with BCMA expressing NIH 3T3 cells, and validated results on human MM cell lines. 57 unique and diverse BCMA specific scFvs were identified containing light and heavy chain CDR's each covering 6 subfamilies, with HCDR3 length ranges from 5-18 amino acids. 17 scFvs met stringent specificity criteria, and a diverse set was cloned into CAR vectors with either a CD28 or a 4-1BB co-stimulatory domain. Donor T cells transduced with BCMA targeted CAR vectors that conveyed particularly desirable properties over multiple in vitro assays, including: cytotoxicity on human MM cell lines at low E:T ratios (>90% lysis, 1:1, 16h), robust proliferation after repeat antigen stimulation (up to 700 fold, stimulation q3-4d for 14d), and active cytokine profiling, were selected for in vivo studies using a marrow predominant human MM cell line model in NSG mice. A single IV injection of CAR T cells, either early (4d) or late (21d) after MM engraftment was evaluated. In both cases survival was increased when treated with BCMA targeted CAR T cells vs CD19 targeted CAR T cells (median OS at 60d NR vs 35d p10,000 fold) CAR T expansion at day 6, followed by contraction of CAR T cells after MM clearance, confirming the efficacy of the anti-BCMA scFv/4-1BB containing construct. Co-culture with primary cells from a range of normal tissues did not activate CAR T cells as noted by a lack of IFN release. Co-culture of 293 cells expressing this scFv with those expressing a library of other TNFRSF or Ig receptor members demonstrated specific binding to BCMA. GLP toxicity studies in mice showed no unexpected adverse events. We generated a retroviral construct for clinical use including a truncated epithelial growth factor receptor (EGFRt) elimination gene: EGFRt/hBCMA-41BBz. Clinical investigation of this construct is underway in a dose escalation, single institution trial. Enrollment is completed on 2/4 planned dose levels (DL). On DL1 pts received cyclophosphamide conditioning (3g/m2 x1) and 72x106 mean CAR+ T cells. On DL2 pts received lower dose cyclophosphamide/fludarabine (300/30 mg/m2 x3) and 137x106 mean CAR+ T cells. All pts screened for BCMA expression by IHC were eligible. High risk cytogenetics were present in 4/6 pts. Median prior lines of therapy was 7; all pts had IMiD, PI, high dose melphalan, and CD38 directed therapies. With a data cut off of 7/20/17, 6 pts are evaluable for safety. There were no DLT's. At DL1, grade 1 CRS, not requiring intervention, occurred in 1/3 pts. At DL2, grade 1/2 CRS occurred in 2/3 pts; both received IL6R directed Tocilizumab (Toci) with near immediate resolution. In these 2 pts time to onset of fever was a mean 2d, Tmax was 39.4-41.1 C, peak CRP was 25-27mg/dl, peak IL6 level pre and post Toci were 558-632 and 3375-9071 pg/ml, respectively. Additional serum cytokines increased >10 fold from baseline in both pts include: IFNg, GM CSF, Fractalkine, IL5, IL8, and IP10. Increases in ferritin were limited, and there were no cases of hypofibrinogenemia. There were no grade 3-5 CRS and no neurotoxicities or cerebral edema. No pts received steroids or Cetuximab. Median time to count recovery after neutropenia was 10d (range 6-15d). Objective responses by IMWG criteria after a single dose of CAR T cells were observed across both DLs. At DL1, of 3 pts, responses were 1 VGPR, 1 SD, and 1 pt treated with baseline Mspike 0.46, thus not evaluable by IMWG criteria, had >50% reduction in Mspike, and normalization of K/L ratio. At DL2, 2/2 pts had objective responses with 1 PR and 1 VGPR (baseline 95% marrow involvement); 1 pt is too early to evaluate. As we are employing a human CAR, the study was designed to allow for an optional second dose in pts that do not reach CR. We have treated 2 pts with a second dose, and longer follow up data is pending. Figure 1 Figure 1. Disclosures Smith: Juno Therapeutics: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: BCMA targeted CAR T cells, Research Funding. Almo: Cue Biopharma: Other: Founder, head of SABequity holder; Institute for Protein Innovation: Consultancy; AKIN GUMP STRAUSS HAUER & FELD LLP: Consultancy. Wang: Eureka Therapeutics Inc.: Employment, Equity Ownership. Xu: Eureka Therapeutics, Inc: Employment, Equity Ownership. Park: Amgen: Consultancy. Curran: Juno Therapeutics: Research Funding; Novartis: Consultancy. Dogan: Celgene: Consultancy; Peer Review Institute: Consultancy; Roche Pharmaceuticals: Consultancy; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees. Liu: Eureka Therpeutics Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Brentjens: Juno Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding.

7024 Background: CD19-specific chimeric antigen receptor (CAR) modified T cells produce high anti-tumor activity in relapsed or refractory (R/R) ALL, but can be associated with cytokine release syndrome (CRS) and neurotoxicity (NTX). Herein, we report baseline and post-treatment clinical and laboratory factors associated with severe NTX (≥Grade 3) in our phase I clinical trial of CD19-specific 19-28z CAR T cells for adult patients (pts) with R/R B-ALL (NCT01044069). Methods: 51 adult pts with R/R B-ALL were treated with 19-28z CAR T cells following conditioning chemotherapy at MSKCC. In order to identify clinical and serum biomarkers associated with severe NTX (sNTX), we examined demographic, treatment, and clinical blood parameters as well as in vivo CAR T expansion and serum cytokines, and performed univariate and multivariate analysis. Results: In this cohort of ALL pts, 20, 8, 2, 18 and 3 pts experienced Gr 0, 1, 2, 3, and 4 NTX, respectively. No pt developed grade 5 NTX. Disease burden (≥50% blasts) at the time of T cell infusion (p = 0.0045) and post-treatment ≥Gr3 CRS (p = 0.0010) were significantly associated with sNTX, but we found no association with age, weight, T cell dose, choice of conditioning chemotherapy (Flu/Cy s. Cy), and prior lines of treatment. Among the clinical and blood parameters, fever, low PLT, high ferritin and MCHC as well as elevated GM-CSF, IFNγ, IL-15, IL-5, IL-10, IL-2 at day 3 of T cell infusion at day 3 of T cell infusion were significantly associated with sNTX (all p < 0.01). While some of these cytokines were also elevated in severe CRS cases, IL-5 and IL-2 at day 3 were unique to sNTX. Furthermore, in vivo peak CAR T expansion at day 7 (p = 0.0001) significantly correlated with sNTX (p < 0.01). Lastly, multivariate analysis revealed baseline PLT < 60 or MCHC > 33.2% and morphologic disease ( > 5% blasts) has 95% sensitivity and 70% specificity of identifying sNTX pts. Conclusions: These data provide a characterization of early clinical and serum biomarkers of sNTX in adult pts receiving 19-28z CAR T cells and should help identify appropriate pts for early intervention strategy to mitigate NTX. Clinical trial information: NCT01044069.

TPS7568 Background: Despite the recent progress in the therapy of CLL with BTK, PI3Kδ, and BCL2 inhibitors, CLL remains incurable and patients with high-risk disease features (i.e. del17p, complex karyotype) and patients whose disease progress after treatment with the above targeted agents continue to have extremely poor prognosis. CD19-specific chimeric antigen receptor (CAR) T cell therapy with various 2nd generation CARs (19-28z or 19-41BBz) have demonstrated anti-tumor efficacy in CLL but the complete response (CR) rates in CLL have been suboptimal (20-45%) compared to CR rates in ALL (80-90%). The suboptimal activity of the current 2nd generation CAR T cells can be due to the inhibitory tumor microenvironment (TM) of CLL. We believe one approach to over the hostile TM is through the use of CD19-CAR T cells further modified to express a second costimulatory ligand, 4-1BBL. A binding of 4-1BBL to its cognate receptor enhances T cell proliferation, IL-2 secretion, and survival and cytolytic activity of the T cells compared to 19-28z. 19-41BBz and 1928BBz (Zhao Z et al. Cancer Cell 2015;28:415-428). Methods: This phase I dose escalating trial is a single-center clinical trial (MSKCC) to study the safety and efficacy of autologous EGFRt/19-28z/4-1BBL+ CAR T cells in patients with relapsed CLL. Given the concern for potential systemic toxicity the vector includes a "safety switch" in the form of a gene for the expression of truncated form of human epidermal growth factor receptor (EGFRt). Patients with relapsed CLL are eligible for the trial. Patients will receive conditioning chemotherapy of cyclophosphamide followed by escalating doses of CAR T cells (1x105 – 3x106 CAR T cells/kg). The primary endpoint is safety and maximum tolerated doses of the CAR T ells. Secondary objectives include response assessment by iwCLL criteria. The comprehensive treatment algorithms for CRS and neurotoxicity are based on our CAR T cell experience in other studies. The study will begin enrollment in February 2017 and enroll up to 30 patients. Clinical trial information: Pending.

7008 Background: CD19-specific chimeric antigen receptor (CAR) T cells have demonstrated high initial responses in patients with relapsed B-ALL. However, clinical characteristics associated with the durability of response remain undefined. Herein, we report the results from analysis of our phase I clinical trial of 19-28z CAR T cells in adult patients with relapsed B-ALL (NCT01044069) with a focus to identify those patients who optimally benefit from 19-28z CAR T cell therapy with durable long-term survival and reduced toxicities. Methods: Adults with relapsed B-ALL were infused with autologous T cells expressing the 19-28z CAR following conditioning chemotherapy. Disease burden was assessed by bone marrow biopsy immediately prior to T cell infusion; patients with < 5% blasts were classified as minimal residual disease (MRD) cohort vs. patients ≥5% blasts as morphologic disease cohort. Response assessment occurred at 4 weeks. Median follow-up duration was 18 months (range, 0.2-57.3). Results: 51 adults received 19-28z CAR T cells; 20 in the MRD and 31 in the morphologic cohort. Complete remission (CR) rates were comparable (95% and 77%, respectively). However, median event-free and overall survivals widely diverged among the 42 patients who achieved MRD-negative CR: not reached (NR) (95% confidence interval [CI]: 4.2-NR) vs. 6.3 months (95% CI, 4.8-9.0) (p = 0.0005), and NR (95% CI, 15.3-NR) vs. 17 months (95% CI, 8.5 – 36.2) (p = 0.0189), in the MRD and morphologic cohorts, respectively. Subsequent allogeneic HSCT in either cohort did not improve survival (p = 0.8). MRD cohort patients developed substantially less severe cytokine release syndrome (CRS) and neurotoxicity, both correlating with peak CAR T cell expansion (p = 0.0326 and p = 0.0001, respectively). Conclusions: Despite comparable initial CR rates regardless of pre-treatment disease burden, durability of 19-28z CAR T cell mediated remissions and survival in adult patients with relapsed B-ALL positively correlated to a low disease burden and do not appear to be enhanced by allogeneic transplant. Our findings strongly support the early incorporation of CD19 CAR therapy before morphologic relapse in B-ALL. Clinical trial information: NCT01044069.

3019 Background: CD19-specific chimeric antigen receptor (CAR) modified T cells produce high and durable anti-tumor activity, but can be associated with treatment-related toxicities including cytokine release syndrome (CRS) and neurotoxicity (NTX). NTX is poorly understood and it hasn't been clear where to focus further research. We report cerebrospinal fluid (CSF) data and neuroimaging characteristics of patients (pts) who developed severe NTX (sNTX) during our phase I clinical trial of CD19-specific 19-28z CAR T cells for adult pts with R/R B-ALL, which suggest new avenues for future research. Methods: 51 adult pts with R/R B-ALL were treated with 19-28z CAR T cells following conditioning chemotherapy at MSKCC. We analyzed the incidence and grade of NTX, CRS and correlative biomarkers in blood and CSF. Results: 21/51 treated pts developed sNTX (grade ≥3) complications such as encephalopathy, aphasia, depressed level of consciousness, myoclonus, and seizure. No pt developed grade 5 NTX and, in all but one case, neurologic symptoms fully resolved. We collected CSF by lumbar puncture and blood from 14 pts at the time of peak NTX. sNTX was correlated with pre-infusion disease burden (p = 0.013) and peak CAR T cell expansion in the blood (p = 0.0001), but we found no significant correlation between NTX grade and the CAR T cell concentration in the CSF during NTX. Instead CSF protein level was correlated with neurotoxicity grade (p = 0.0109). The cytokines IL6, IL8, IL10, IFNγ and GCSF were elevated in CSF over serum at the time of NTX and correlated with CSF protein levels (all p < 0.005). These were distinct from serum cytokines significantly associated with sNTX at d3 of T cell infusion: GMCSF, IFNγ, IL15, IL5, IL10, and IL2 (all p < 0.01). 4/21 patients developed a pattern of reversible MRI T2/FLAIR hyperintensity involving the bilateral thalami, dorsal pons, and medulla. Conclusions: NTX is predominantly reversible. MRI findings suggesting transient toxicity to deep grey structures and findings of a CSF-specific cytokine profile expand the hypotheses on the mechanism of NTX. Future studies will focus on determining the etiology of the CSF protein elevation and the distinct cytokine profile. Clinical trial information: NCT01044069.