Autologous Chimeric Antigen Receptor Research Articles

Phase I trial of autologous cMET-directed CAR-t cells administered intravenously in patients with melanoma & breast carcinoma.

10035 Background: Advanced relapsed/refractory melanoma and metastatic triple-negative breast cancer are lethal diseases for which effective therapies are limited. We conducted a pilot phase I clinical trial (NCT03060356) to establish the safety and feasibility of intravenous autologous chimeric antigen receptor (CAR) T cell immunotherapy targeting cMET, a cell-surface antigen that is highly expressed in these cancers. Methods: Subjects had metastatic or unresectable melanoma (Mel) or triple-negative breast cancer (BC) with ≥30% expression of cMET on archival tissue or screening biopsy. Eligible subjects had measurable disease and progression on at least 1 prior therapy. Patients (pts) received up to 6 doses (1x108 total T-cells per dose) of RNA electroporated anti-cMET CAR T cells over a 2-week period without antecedent lymphodepleting chemotherapy. Subjects underwent pre- and post-infusion biopsies. The primary objective was to determine feasibility and safety of treatment. Results: 77 subjects (39 mel, 38 BC) were prescreened for tumor cMET expression and 37 (17 mel, 20 BC) met the eligibility threshold. Seven pts (4 BC, 3 Mel) received cMET-directed CAR T infusions on study. Mean age was 50 years (35-64); median (M) ECOG 0 (0-1); M prior lines of chemotherapy/immunotherapy were 4/0 for BC pts and 1/3 for Mel pts. 6 of 7 pts received all planned CAR T cell infusions, and 1 received 5 infusions. 5 pts experienced grade (G) 1 or G 2 toxicity that was possibly or definitely related to study. Toxicities occurring in ≥1 pt included: anemia (n = 3), fatigue (n = 2), and malaise (n = 2). No G ≥3 toxicities or cytokine release syndrome were observed. No pts discontinued therapy due to toxicity. Best response was stable disease in 4 pts (2 BC, 2 Mel) and PD in 3 pts (2 BC, 1 Mel). Messenger RNA signals corresponding to CAR T cells were detected by RT-PCR in the peripheral blood of all pts during the infusion period and in 2 pts after the infusion period. 6 pts underwent baseline biopsy and 4 pts underwent post-infusion biopsy. Immunohistochemical stains of CD3, CD4, CD8, CD163, L26, PD1, PDL1, Foxp3, Ki67, Granzyme B and Phospho-S6 were performed on pre- and post-treatment tissue biopsies and are being evaluated. Conclusions: Intravenous administration of RNA-electroporated cMET-directed CAR T cells was safe and feasible. Future directions include examination of this target using a lentiviral construct in combination with lymphodepleting chemotherapy. Clinical trial information: NCT03060356.

First-in-human data of ALLO-501 and ALLO-647 in relapsed/refractory large B-cell or follicular lymphoma (R/R LBCL/FL): ALPHA study.

8002 Background: Allogeneic (off the shelf) chimeric antigen receptor (CAR) T cell therapy addresses the logistical challenges and variable product quality of autologous CAR T therapy. ALLO-501 is a genetically modified anti-CD19 CAR T cell product in which the TCR alpha constant gene is disrupted to reduce the risk of graft-versus-host disease (GvHD) and the CD52 gene is disrupted to permit the use of ALLO-647, an anti-CD52 mAb, for selective and prolonged host lymphodepletion. Methods: This is an open-label, Phase 1 trial (NCT03939026) in adults with R/R LBCL/FL who have received ≥ 2 prior lines of therapy; prior anti-CD19 cell therapy is allowed. Patients (pts) receive fludarabine (flu) 90 mg/m2, cyclophosphamide (cy) 900 mg/m2, and ALLO-647 39 or 90 mg followed by ALLO-501 at 1 of 3 dose levels (DL) in a 3+3 design: 40, 120, and 360 × 106 CAR+ T cells. Results: As of 20 January 2020, 12 pts were enrolled: 9 received ALLO-501 at 3 DLs (4, 4 & 1 pts in DL1, DL2 and DL3 respectively), 1 pt discontinued due to kidney injury prior to lymphodepletion and 2 are starting treatment. Of the 9 treated pts aged 42 to 70 years: 5 had LBCL, 2 were female, 3 had primary refractory disease, and 3 had prior autologous stem cell transplants. The median number of prior lines of therapies was 3 (range 2 to 4). All treated pts received 39 mg of ALLO-647. No DLTs or GvHD have been observed to date. Most common Grade (Gr) ≥ 3 adverse events were neutropenia (55.6%), leukopenia (33.3%) and anemia (22.2%). Two pts (22.2%) developed cytokine release syndrome (1 Gr1 and 1 Gr2) that resolved within 72 hrs without steroids or tocilizumab. One pt developed Gr1 neurotoxicity that resolved without treatment. Infections included upper respiratory tract infection (Gr2), CMV (Gr3) and EBV viremia (Gr1), all reported in a single pt and resolved. One pt had a Gr2 infusion reaction to ALLO-647 which resolved with antihistamines. The overall response rate is 78% (95% exact CI: 40%, 97%): 3 complete and 4 partial responses. With a median follow up of 2.7 mos, 4 pts have ongoing responses and 3 pts progressed at 2, 4 and 6 mos. ALLO-501 cell expansion by qPCR was observed in 4 of 6 pts in varying degrees. Conclusions: These early data suggest that ALLO-501 and ALLO-647 have a manageable safety profile. ALLO-647 may be an effective and selective lymphodepleting agent with CD52 gene editing, and ALLO-501 shows evidence of clinical activity in pts with advanced NHL. Enrollment is ongoing, and updated safety, efficacy, PK/PD data will be presented including pts treated with increasing doses of ALLO-647. Clinical trial information: NCT03939026 .

Pre-clinical assessment of chimeric antigen receptor t cell therapy targeting CD19+ B cell malignancy.

BackgroundAutologous chimeric antigen receptor (CAR) T cell therapy is a promising therapeutic strategy for treating hematologic malignancies. A spectrum of serious complications caused by CAR-T cells has caught great attention. We developed a novel CAR against CD19 namely UWC19, consisting anti-CD19 single-chain variable fragment (scFv) hinged with 4-1BB and CD3z signaling domains. In this study, preclinical assessments of UWC19 were conducted to evaluate the safety and efficacy in vitro and in vivo.MethodsTo evaluate the binding activity of UWC19 cells to CD19, we measured the saturation degree of CAR with human CD19 molecules using flow cytometry in vitro. The antitumor efficacy of UWC19 cells was determined by in vitro cytotoxicity assay against CD19 positive cells and in vivo using a xenograft mouse model. Cross tissue reactivity of UWC19 cells was examined by co-culturing with cell lines from difference human tissues. Tumorigenicity was determined by subcutaneously injecting UWC19 in immunodeficient mice. Persistence was analyzed using quantitative PCR.ResultsWe showed that UWC19 CAR T cells exerted highly specific binding affinity and cytotoxicity against CD19+ cells in vitro. In vivo, UWC19 CAR T cells are able to fully control disease progression in a Raji-xenografted immunodeficient mouse model. UWC19 exerted no obvious effects on the mean body mass and graft versus host disease were observed in surviving mice. We showed that UWC19 cells specifically recognized and eliminated CD19 positive cells, whereas CD19 negative cells were much less affected. No tumorigenicity of UWC19 in immunodeficient mice was observed.ConclusionsUWC19 treatment effectively eliminated CD19 positive tumor cells with favorable toxicity profile. The findings suggest encouraging clinical prospects for its use in patients with CD19 positive B cell malignancies. Our study presented an alternative evaluation strategy for CAR-T cell products.

Predictive Modeling Demonstrating a Two-Factor Signature As Early As a Week Prior to Harvest For Chimeric Antigen Receptor (CAR) T-Cell Manufacturing Growth

Background & Aim CAR T-cell therapies have shown remarkable promise in treating patients (PTs) diagnosed with advanced B cell malignancies. CAR T-cell therapies are living drug characterized by robust proliferation and persistence. We reported previously that high T cell expansion ex vivo during clinical manufacturing (MFG) correlated with high in vivo expansion following infusion, which was also associated with favorable clinical outcomes in PTs receiving CAR T-cells to treat chronic lymphocytic leukemia (CLL) and multiple myeloma (MM). There is no known single quantitative parameter can accurately predict high proliferative potential of the T-cells during the clinical MFG process. Therefore, we conducted multivariate analysis of historical data to investigate combinatorial signatures to predict high proliferative capacity during MFG. Methods, Results & Conclusion We pooled data from a total of 297 PTs (n=248 blood cancers, n=49 solid tumors) from 16 different clinical trials receiving autologous CAR T cell products manufactured at the University of Pennsylvania. We evaluated 70 variables including PT data, phenotype of starting material, and MFG performance to determine signatures that could predict with high accuracy when a population doubling level greater than 4 on day 9 of the clinical MFG process (PDL9>4) could be achieved. We performed logistic regression to assess 70 early variables to predict T cell expansion at least 5-7 days ahead of harvest. We successfully identified a 2-factor signature that predicts PDL9>4 with high sensitivity and specificity (S/S) above 79%. The model was validated from 48 available CAR T cell products that were not used for generating the model, resulting in S/S at least 79% and 67%, respectively. This information can be useful in implementing processes/mitigation strategies to increase proliferative capacity ex vivo and MFG success rate for the product itself, provide lead time with potential alternative therapy strategies for PT. Ongoing investigation is assessing the possibility of identifying a signature of factors prior to manufacture and predict clinical response at day 28. This work provides a methodology for further studies for assessing the impact of extrinsic/intrinsic factors on PTs’ CAR T cell growth and efficacy and directing process development activities and decision algorithms in PT candidates for CAR T therapies.

Exploring the Dilemma of Allogeneic Hematopoietic Cell Transplantation after Chimeric Antigen Receptor T Cell Therapy: To Transplant or Not?

Patients with refractory or relapsed (R/R) B cell acute lymphoblastic leukemia (B-ALL) and highly aggressive B cell non-Hodgkin lymphoma (B-NHL) have a very dismal prognosis and limited treatment options. The advent of chimeric antigen receptor (CAR) T cell therapy constitutes a milestone in current cell and gene therapies, covering the unmet need of treatment of high-risk patients and bringing immunotherapies one step closer toward cancer therapeutics, including hematologic malignancies. CAR T cells targeting CD19 antigen have shown startling remission rates in heavily pretreated B-ALL and B-NHL patients, in whom CAR T cell therapy may sometimes be their last-resort treatment. However, a high proportion of these patients evade immune surveillance by CAR T cells losing their initial deep responses, which leads to disease recurrence as either CD19-positive or CD19-negative relapse. As a result, many investigators have questioned the need for consolidative allogeneic hematopoietic stem cell transplantation (allo-HCT) after CAR T cell therapy, once a patient has achieved remission. There remains much controversy regarding whether CAR T cells should be a bridge therapy to allo-HCT or a definitive treatment, owing to the paucity of strong evidence-based data. In this context, here we review the existing data regarding the necessity, safety, and outcomes of allo-HCT performed after autologous anti-CD19 CAR T cell therapy in B-ALL and B-NHL patients.

Chimeric antigen receptor T-cell therapies: Optimising the dose.

Lymphocytes such as T-cells can be genetically transduced to express a synthetic chimeric antigen receptor (CAR) that re-directs their cytotoxic activity against a tumour-expressed antigen of choice. Autologous (patient-derived) CAR T-cells have been licensed to treat certain relapsed and refractory B-cell malignancies, and numerous CAR T-cell products are in clinical development. As living gene-modified cells, CAR T-cells exhibit unique pharmacokinetics, typically proliferating within the recipient during the first 14 days after administration before contracting in number, and sometimes exhibiting long-term persistence. The relationship between CAR T-cell dose and exposure is highly variable, and may be influenced by CAR design, patient immune function at the time of T-cell harvest, phenotype of the CAR T-cell product, disease burden, lymphodepleting chemotherapy and subsequent immunomodulatory therapies. Recommended CAR T-cell doses are typically established for a specific product and indication, although for some products, stratification of dose based on disease burden may mitigate toxicity while maintaining efficacy. Re-evaluation of CAR T-cell dosing may be necessary following changes to the lymphodepleting regimen, for different disease indications, and following significant manufacturing changes, if product comparability cannot be demonstrated. Dose escalation trials have typically employed 3 + 3 designs, although this approach has limitations, and alternative phase I trial designs may facilitate the identification of CAR T-cell doses that strike an optimal balance of safety, efficacy and manufacturing feasibility.

Abstract IA13: Reprogramming the epigenome for enhancing CAR T-cell antitumor efficacy

Abstract Many studies indicate that adoptive cell transfer therapy with autologous chimeric antigen receptor (CAR) T cells is a powerful approach for the treatment of cancer. CAR-modified T cells have shown activity in several clinical trials including our own at the University of Pennsylvania, with complete response rates as high as 80-90% in certain malignancies. However, the effectiveness of this approach for cancers involving T-cell defects, such as multiple myeloma, pancreatic cancer, and chronic lymphocytic leukemia (CLL), is much lower. The key questions currently facing the field are how to: i) enhance the potency and sustain the in vivo function of CAR T cells for such indications and ii) develop strategies to increase the resistance of CAR T cells to intrinsic and extrinsic dysfunction (e.g., immunosenescence, exhaustion, or other disease-specific defects). Because cell fate determination programs encoded in DNA are interpreted, modified, transmitted, and expanded as chromatin, we hypothesize that immunotherapy and reversal of T-cell dysfunction in cancer can be improved by broadly or specifically targeting appropriate epigenetic pathways. In this vein, we explore manipulation of the “writers” and “readers” of the histone code using genetic editing tools (e.g., CRISPR/Cas9) and chemical modifiers to convert poorly functional T cells to a state that renders these lymphocytes effective at tumor elimination. The basic understanding of T-cell biology in the context of epigenetic regulation may result in enhancement of cellular immunotherapy strategies, including the discovery of several actionable improvements to CAR T-cell therapy. Citation Format: Joseph A. Fraietta. Reprogramming the epigenome for enhancing CAR T-cell antitumor efficacy [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2019 Nov 17-20; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(3 Suppl):Abstract nr IA13.

Advances in pediatric psychooncology.

This article reviews the current literature on psychosocial care of children with cancer with particular focus on evidence-based standards of care, including developments in systematic distress screening, utilization of patient-reported outcomes, evidence-based interventions, survivorship, palliative care and bereavement. Although attention to the psychosocial needs of the child and family is increasingly recognized as an essential element of care for children with cancer, implementing evidence-based care remains suboptimal. Recent efforts have focused on utilizing technology to improve the reach of these interventions and to enhance engagement with special populations, such as adolescents and young adults. Increasing data elucidate the long-term psychological and physical late effects of childhood cancer survivorship and the impact of cancer on siblings and the family. Gaps in clinical care and important directions for future research include the needs of infants and toddlers, overlooked minorities, and patients with hereditary tumor predisposition syndromes, and attention to the psychosocial impact of exciting new treatments, such as autologous chimeric antigen receptor (CAR) T-cell therapy. The evidence base for the psychosocial standards of care for children with cancer and their families continues to grow, but more work is needed to successfully implement these standards across pediatric cancer centers.

CAR T-cell therapy in diffuse large B-cell lymphoma

SummaryDiffuse large B‑cell lymphoma (DLBCL) comprises 30–40% of non-Hodgkin’s lymphoma. Clinical factors such as a high International Prognostic Index (IPI) or molecular factors as cell of origin (COO) have an influence on the clinical outcome after conventional immunochemotherapy. Patients with resistant or relapsed (r/r) DLBCL have a poor prognosis with a median overall survival of 6,3 months and low complete response rates (CR 7%) to salvage chemoimmunotherapy. Currently, therapy with autologous chimeric antigen receptor T‑cells (CAR T‑cells) provide encouraging complete responses (CR) of up to 50%. However, high costs for approved products and elaborate logistics have to be encountered.

Relationship of CRP and Ferritin Levels and Length of ICU Stay in Patients with B-Cell Lymphomas Treated with Axicabtagene Ciloleucel (axi-cel)

Background Axicabtagene ciloleucel (Axi-cel) is an autologous chimeric antigen receptor (CAR) T-cell therapy which is effective in relapsed/refractory (R/R) anti-CD19 B-cell leukemia and lymphomas. Axi-cel is associated with unique toxicities, including cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Management of these toxicities often requires ICU admission. Scoring systems have been developed to grade severity of these toxicities and help guide treatment escalation as needed; however, they provide little insight into duration of ICU stay. C-reactive protein (CRP) and ferritin are serum inflammatory markers associated with onset and persistence of CAR-T cell related toxicity. Here, we examine the relationship between these serum inflammatory markers and the duration of ICU stay in CAR-T Cell therapy recipients. Methods We conducted a retrospective analysis of patients (pts) treated with axi-cel across two Mayo Clinic campuses (Jacksonville and Phoenix) from 06/01/2018 until 07/01/2019. Primary objective was to examine the relationship between serum ferritin and CRP levels with need for and length of ICU stay in axi-cel treated pts. Results Our study population consisted of 18 pts (11 males, 61%), median age of 51 (26-67) years. Nine were admitted to the ICU during their initial hospitalization. The median time from axi-cel infusion to ICU admission was 4 (2-8) days with a median ICU length of stay of 4 (2-24) days. All 9 admitted pts developed CRS: grade 1 (1), grade 2 (7), and grade 3 (1); 7 pts developed ICANS: grade 2 (1), grade 3 (1) and grade 4 (5). Eight of the 9 non-ICU pts developed CRS: grade 1 (5) and grade 2 (3). Three pts developed grade 1 ICANS. Grade of CRS and ICANS were higher in ICU pts vs non-ICU pts (p=0.01 and p=0.001, respectively). There was no correlation between the severity of CRS and length of ICU stay (correlation of 0.07, p=0.86) or severity of ICANS and length of ICU stay (correlation of 0.36, p=0.35). Initial median CRP level at infusion was higher in ICU vs. non-ICU pts (25.2 mg/L vs. 13.9 mg/L); however, this difference was not significant, p=0.38. Initial ferritin levels at infusion were over 2-fold higher, albeit not statistically significant, in ICU pts (837 mcg/L vs 387 mcg/L, p=0.21). The median CRP at the time of ICU admission was 54.1 mg/L (3.2-341) mg/L. There was no significant correlation between CRP levels at time of ICU admission and length of ICU stay (correlation of 0.067, p = 0.86). The median ferritin level at the time of ICU admission was 2010mcg/L (344-10943). There was a strong direct correlation between serum ferritin levels and length of ICU stay (correlation of 0.93, p = 0.0003). Conclusions This study showed that an elevated ferritin level at the time of escalation of medical care may be indicative of anticipated prolonged ICU hospitalization in axi-cel recipients.

KTE-X19, an Anti-CD19 Chimeric Antigen Receptor (CAR) T Cell Therapy, in Patients (Pts) with Relapsed/Refractory Mantle Cell Lymphoma (R/R MCL): Results of the Phase 2 ZUMA-2 Study

Introduction Outcomes with salvage regimens in pts with MCL who progress after Bruton tyrosine kinase inhibitor (BTKi) therapy are poor. ZUMA-2 is a Phase 2, registrational, multicenter study evaluating KTE-X19, an autologous anti-CD19 CAR T cell therapy, in pts with R/R MCL (1-5 therapies, including a BTKi). We present interim efficacy and safety results. Objectives Evaluate efficacy and safety of KTE-X19 in R/R MCL. Methods Eligible pts (≥ 18 y) with R/R MCL had an ECOG of 0-1 and ≤ 5 prior therapies, including chemotherapy, an anti-CD20 antibody, and a BTKi. Pts underwent leukapheresis and conditioning chemotherapy followed by KTE-X19 infusion at 2 × 106 cells/kg. Bridging therapy with dexamethasone, ibrutinib, or acalabrutinib was permitted. The primary endpoint was objective response rate (ORR; complete response [CR] + partial response) assessed by an Independent Review Committee per the Lugano Classification (Cheson, et al. J Clin Oncol. 2014). Interim efficacy endpoints were investigator-assessed using the revised IWG Response Criteria for Malignant Lymphoma (Cheson, et al. J Clin Oncol. 2007). Key secondary endpoints were duration of response (DOR), progression-free survival (PFS), overall survival (OS), frequency of adverse events (AEs), and blood levels of CAR T cells and cytokines. Sixty pts received KTE-X19; here, we present results in pts with ≥ 1 y follow-up. Updated results in all 60 pts will be reported in the presentation. Results As of May 30, 2018, 28 pts received KTE-X19 with ≥ 1 y follow-up (median, 13.2 mo). The median age was 65 y; 43% of pts had an ECOG score of 1; 21% had blastoid morphology; 82% had stage IV disease; 50% had intermediate/high-risk MIPI; and 86% received a median of 4 prior therapies. In 20 of 28 pts with available data, the median Ki-67 index was 38%. Eight pts received bridging therapy; all had disease present post-bridging. Investigator-assessed ORR was 86% (95% CI, 67-96) with a CR rate of 57% (95% CI, 37-76). As of May 30, 2018, 75% of responders remained in response, and 64% of treated pts had ongoing responses. The 12-month rates of DOR, PFS, and OS were 83% (95% CI, 60-93), 71% (95% CI, 50-84), and 86% (95% CI, 66-94), respectively; medians were not reached. The most common Grade ≥ 3 AEs were anemia (54%), platelet count decreased (39%), and neutropenia (36%). Grade 3/4 cytokine release syndrome (CRS) assessed by Lee et al. (Blood. 2014) and Grade 3/4 neurologic events (NE) occurred in 18% and 46% of pts, respectively, with no Grade 5 events. CRS and NE were generally reversible. There was 1 Grade 5 AE of organizing pneumonia. Median CAR T cell levels measured by peak and area under the curve were 99 cells/µL (range, 0.4-2589) and 1542 cells/µL (range, 5.5-27239), respectively. Conclusion With ≥ 1 y follow-up, KTE-X19 demonstrated significant and durable clinical benefit, with a manageable safety profile in pts with R/R MCL for whom there are no curative treatment options.

Autologous CAR T-cell therapies supply chain: challenges and opportunities?

Chimeric antigen receptor (CAR) T cells are considered a potentially disruptive cancer therapy, showing highly promising results. Their recent success and regulatory approval (both in the USA and Europe) are likely to generate a rapidly increasing demand and a need for the design of robust and scalable manufacturing and distribution models that will ensure timely and cost-effective delivery of the therapy to the patient. However, there are challenging tasks as these therapies are accompanied by a series of constraints and particularities that need to be taken into consideration in the decision-making process. Here, we present an overview of the current state of the art in the CAR T cell market and present novel concepts that can debottleneck key elements of the current supply chain model and, we believe, help this technology achieve its long-term potential.

'Off-the-shelf' allogeneic CAR T cells: development and challenges.

Autologous chimeric antigen receptor (CAR) T cells have changed the therapeutic landscape in haematological malignancies. Nevertheless, the use of allogeneic CAR T cells from donors has many potential advantages over autologous approaches, such as the immediate availability of cryopreserved batches for patient treatment, possible standardization of the CAR-T cell product, time for multiple cell modifications, redosing or combination of CAR T cells directed against different targets, and decreased cost using an industrialized process. However, allogeneic CAR T cells may cause life-threatening graft-versus-host disease and may be rapidly eliminated by the host immune system. The development of next-generation allogeneic CAR T cells to address these issues is an active area of research. In this Review, we analyse the different sources of T cells for optimal allogeneic CAR-T cell therapy and describe the different technological approaches, mainly based on gene editing, to produce allogeneic CAR T cells with limited potential for graft-versus-host disease. These improved allogeneic CAR-T cell products will pave the way for further breakthroughs in the treatment of cancer.

CRISPR/Cas systems to overcome challenges in developing the next generation of T cells for cancer therapy.

Genetically engineered immune cells with chimeric antigen receptors (CAR) or modified T cell receptors (TCR) have demonstrated their potential as a potent class of new cancer therapeutic strategy. Despite the clinical success of autologous CD19 CAR T cells in hematological malignancies, allogeneic T cells exhibit many advantages over their autologous counterparts and have recently gathered widespread attention due to the emergence of multiplex genome editing techniques, particularly CRISPR/Cas systems. Furthermore, genetically engineered T cells face a host of major challenges in solid tumors that are not as significant for blood cancers such as T cell targeted delivery, target specificity, proliferation, persistence, and the immunosuppressive tumor microenvironment. We take this opportunity to analyze recent strategies to develop allogeneic T cells, specifically in consideration of CRISPR/Cas and its delivery systems for multiplex gene editing. Additionally, we discuss the current methods used to delivery CRISPR/Cas systems for immunotherapeutic applications, and the challenges to continued development of novel delivery systems. We also provide a comprehensive analysis of the major challenges that genetically engineered T cells face in solid tumors along with the most recent strategies to overcome these barriers, with an emphasis on CRISPR-based approaches. We illustrate the synergistic prospects for how the combination of synthetic biology and immune-oncology could pave the way for designing the next generation of precision cancer therapy.

Autologous cryopreserved leukapheresis cellular material for chimeric antigen receptor–T cell manufacture

Tisagenlecleucel, a CD19-specific autologous chimeric antigen receptor (CAR)–T cell therapy, is efficacious for the treatment of relapsed/refractory B-cell precursor acute lymphoblastic leukemia and diffuse large B-cell lymphoma. The tisagenlecleucel manufacturing process was initially developed in an academic setting and subsequently transferred to industry for qualification, validation and scaling up for global clinical trials and commercial distribution. Use of fresh leukapheresis material was recognized early on in the transfer process as a challenge with regard to establishing a global supply chain. To maximize manufacturing success rates and to overcome logistical challenges, cryopreservation was adapted into the Novartis manufacturing process from the beginning of clinical trials. Tisagenlecleucel manufactured in centralized facilities with cryopreserved leukapheresis material has been used successfully in global clinical trials at more than 50 clinical centers in 12 countries. Cryopreservation provides flexibility in scheduling leukapheresis when the patient's health is optimal to provide T cells; it also provides protection from external factors, such as shipping delays, and removes manufacturing time constraints. Several studies were performed to establish comparability of fresh versus cryopreserved leukapheresis material, to evaluate and optimize the cryopreservation process, to determine the optimal temperature and maximum hold time prior to cryopreservation and to determine the optimal temperature range for shipment and storage. Using the current validated industry manufacturing process, high success rates were achieved with regard to manufacturing tisagenlecleucel batches that met specifications and were released to patients. Consistent product quality and positive clinical outcomes support the use of cryopreserved non-mobilized peripheral mononuclear blood cells collected using leukapheresis for CAR-T cell manufacturing.

Preclinical Evaluation of ALLO-819, an Allogeneic CAR T Cell Therapy Targeting FLT3 for the Treatment of Acute Myeloid Leukemia

Autologous chimeric antigen receptor (CAR) T cells have achieved unprecedented clinical responses in patients with B-cell leukemias, lymphomas and multiple myeloma, raising interest in using CAR T cell therapies in AML. These therapies are produced using a patient's own T cells, an approach that has inherent challenges, including requiring significant time for production, complex supply chain logistics, separate GMP manufacturing for each patient, and variability in performance of patient-derived cells. Given the rapid pace of disease progression combined with limitations associated with the autologous approach and treatment-induced lymphopenia, many patients with AML may not receive treatment. Allogeneic CAR T (AlloCAR T) cell therapies, which utilize cells from healthy donors, may provide greater convenience with readily available off-the-shelf CAR T cells on-demand, reliable product consistency, and accessibility at greater scale for more patients. To create an allogeneic product, the TRAC and CD52 genes are inactivated in CAR T cells using Transcription Activator-Like Effector Nuclease (TALEN®) technology. These genetic modifications are intended to minimize the risk of graft-versus-host disease and to confer resistance to ALLO-647, an anti-CD52 antibody that can be used as part of the conditioning regimen to deplete host alloreactive immune cells potentially leading to increased persistence and efficacy of the infused allogeneic cells. We have previously described the functional screening of a library of anti-FLT3 single-chain variable fragments (scFvs) and the identification of a lead FLT3 CAR with optimal activity against AML cells and featuring an off-switch activated by rituximab. Here we characterize ALLO-819, an allogeneic FLT3 CAR T cell product, for its antitumor efficacy and expansion in orthotopic models of human AML, cytotoxicity in the presence of soluble FLT3 (sFLT3), performance compared with previously described anti-FLT3 CARs and potential for off-target binding of the scFv to normal human tissues. To produce ALLO-819, T cells derived from healthy donors were activated and transduced with a lentiviral construct for expression of the lead anti-FLT3 CAR followed by efficient knockout of TRAC and CD52. ALLO-819 manufactured from multiple donors was insensitive to ALLO-647 (100 µg/mL) in in vitro assays, suggesting that it would avoid elimination by the lymphodepletion regimen. In orthotopic models of AML (MV4-11 and EOL-1), ALLO-819 exhibited dose-dependent expansion and cytotoxic activity, with peak CAR T cell levels corresponding to maximal antitumor efficacy. Intriguingly, ALLO-819 showed earlier and more robust peak expansion in mice engrafted with MV4-11 target cells, which express lower levels of the antigen relative to EOL-1 cells (n=2 donors). To further assess the potency of ALLO-819, multiple anti-FLT3 scFvs that had been described in previous reports were cloned into lentiviral constructs that were used to generate CAR T cells following the standard protocol. In these comparative studies, the ALLO-819 CAR displayed high transduction efficiency and superior performance across different donors. Furthermore, the effector function of ALLO-819 was equivalent to that observed in FLT3 CAR T cells with normal expression of TCR and CD52, indicating no effects of TALEN® treatment on CAR T cell activity. Plasma levels of sFLT3 are frequently increased in patients with AML and correlate with tumor burden, raising the possibility that sFLT3 may act as a decoy for FLT3 CAR T cells. To rule out an inhibitory effect of sFLT3 on ALLO-819, effector and target cells were cultured overnight in the presence of increasing concentrations of recombinant sFLT3. We found that ALLO-819 retained its killing properties even in the presence of supraphysiological concentrations of sFLT3 (1 µg/mL). To investigate the potential for off-target binding of the ALLO-819 CAR to human tissues, tissue cross-reactivity studies were conducted using a recombinant protein consisting of the extracellular domain of the CAR fused to human IgG Fc. Consistent with the limited expression pattern of FLT3 and indicative of the high specificity of the lead scFv, no appreciable membrane staining was detected in any of the 36 normal tissues tested (n=3 donors). Taken together, our results support clinical development of ALLO-819 as a novel and effective CAR T cell therapy for the treatment of AML. Disclosures Sommer: Allogene Therapeutics, Inc.: Employment, Equity Ownership. Cheng:Allogene Therapeutics, Inc.: Employment, Equity Ownership. Yeung:Pfizer Inc.: Employment, Equity Ownership. Nguyen:Allogene Therapeutics, Inc.: Employment, Equity Ownership. Sutton:Allogene Therapeutics, Inc.: Employment, Equity Ownership. Melton:Allogene Therapeutics, Inc.: Employment, Equity Ownership. Valton:Cellectis, Inc.: Employment, Equity Ownership. Poulsen:Allogene Therapeutics, Inc.: Employment, Equity Ownership. Djuretic:Pfizer, Inc.: Employment, Equity Ownership. Van Blarcom:Allogene Therapeutics, Inc.: Employment, Equity Ownership. Chaparro-Riggers:Pfizer, Inc.: Employment, Equity Ownership. Sasu:Allogene Therapeutics, Inc.: Employment, Equity Ownership.

Investigation of Allocar TTM Targeting CD70 As a Potential Therapy for an Array of Hematological Malignancies

Adoptive transfer of T cells expressing chimeric antigen receptors (CARs) is an exciting new therapy showing great promise in hematologic malignancies. Recent approval of two CD19-targeting CAR Ts, Kymriah® and Yescarta®, has been followed with promising results from BCMA clinical trials, showing that activity can extend to other targets. While these treatments show excellent potential for patients with an otherwise poor prognosis, a number of patients are still subject to relapse. These data suggest the potential utility of expanding the number of targets available for hematological malignancies. Autologous chimeric antigen receptor (CAR) T therapies use a patient's own T cells to produce the therapy. This approach has inherent challenges, including requiring significant time for production, complex supply chain logistics, separate GMP manufacturing for each patient, and variability in performance of patient-derived cells. Given rapid disease progression, combined with limitations associated with the autologous approach, many patients may not be able to receive CAR T therapy. Allogeneic CAR T (AlloCAR T) cell therapy, or "off-the-shelf" therapy which utilizes cells from healthy donors, may provide greater convenience with readily available CAR T therapy on-demand, reliable product consistency, and accessibility at greater scale for more patients. To create an allogeneic product, mRNAs encoding Transcription Activator-Like Effector Nucleases (TALEN®) designed to specifically disrupt the TRAC and CD52 genes are introduced to CAR Ts. These modifications are intended to minimize the risk of graft-versus-host disease and to confer resistance to ALLO-647, an anti-CD52 antibody that can be used as part of the conditioning regimen to deplete host alloreactive immune cells potentially leading to increased persistence and efficacy of the infused allogeneic cells. CD70 is a TNF superfamily member expressed on subsets of activated lymphocytes and is being explored as a CAR T target for renal cell carcinoma but may also be suitable for targeting hematological malignancies. To evaluate the potential of CD70 as a heme target, expression of CD70 RNA was compared to that of three known targets, CD19, BCMA, and FLT3, across a range of hematological malignancies by interrogating The Cancer Genome Atlas (TCGA) database. CD19 was expressed in lymphomas and leukemias, BCMA was expressed primarily in MM, and FLT3 expression was largely limited to AML. CD70 expression was observed across all 4 cancer types, indicating the potential broad utility CD70 CAR T cells. To determine cell-surface expression of these four targets, flow cytometry and receptor quantification was performed on a panel of heme cell lines. Good correlation was seen between RNA and the cell-surface protein expression of CD70. CAR T cells against each of the 4 targets were generated and evaluated in vitro. All CAR T cells exhibited robust specific activity against cells expressing their corresponding antigens. To ensure clinical relevance of results with cell lines, studies are currently ongoing to evaluate CD70 expression on primary patient samples and activity of CD70 CAR T cells against these same samples. Based on our studies, CD70 has a broad expression profile across a range of hematological malignancies and potent and selective CD70 CAR T activity has been demonstrated. Given these results, an allogeneic CD70 CAR T is expected to be clinically useful against a range of hematological tumor types either as a single agent or in combination with other CAR Ts. Disclosures Panowski: Allogene Therapeutics: Employment, Equity Ownership. Srinivasan:Allogene Therapeutics: Employment, Equity Ownership. Van Blarcom:Allogene Therapeutics, Inc.: Employment, Equity Ownership. Sommer:Allogene Therapeutics, Inc.: Employment, Equity Ownership. Cheng:Allogene Therapeutics, Inc.: Employment, Equity Ownership. Pertel:Allogene Therapeutics: Employment, Equity Ownership. Santaguida:Notable Labs: Employment. Galetto:Cellectis Inc: Employment. Sasu:Allogene Therapeutics, Inc.: Employment, Equity Ownership.

Clinical Factors Associated with Improved Survival Following Allogeneic HSCT after CD19 CAR Therapy in Adult Patients with Relapsed B-ALL

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.

Impact of Bridging Chemotherapy on Clinical Outcomes of CD19 CAR T Therapy in Relapse/Refractory Diffuse Large B- Cell Lymphoma in Real World Experience

Background: Autologous chimeric antigen receptor (CAR) T cell therapy has shown to be effective in relapsed or refractory (R/R) diffuse large B cell lymphoma (DLBCL) but requires in real world and in Europe at least a 4 weeks period of cell processing. During this "bridging period", patients are vulnerable to disease progression and complications. We sought to characterize bridging therapy strategies. Methods: We performed a retrospective review of patients (pts) with R/R DLBCL treated with commercialized CD19 CAR T cells, either Axicabtagene Ciloleucel (Yescarta) or tisagenlecleucel (Kymriah). Bridging therapy (BT) was defined by any therapy given from enrolment to cell infusion. We divided bridging therapy in 2 groups: high intensity BT (HI, including chemotherapy+/-immunotherapy) and low intensity BT (LI, including monoclonal antibodies rituximab, brentuximab, dexamethasone, lenalidomide). We evaluated toxicity (cytokine releasing syndrome (CRS), CAR-related encephalopathy syndrome (CRES), infections) and efficacy (OS, PFS) after infusion according to the intensity of the BT. Results: 46 pts were enrolled for commercialized CAR T cells (Kymriah n=25, Yescarta n=21) including R/R DLBCL (n=35), TFL (n=5) or PMBL (n=6) between June 2018 and April 2019. The median age was 57 (IQR, 42 to 64). Number of pts with aaIPI > 2 was 20. The median number of previous lines was 3 (range 3-5), including 15 autologous stem cell transplants and 2 allotransplants. Median time between enrollment and infusion, and between collection and infusion were 59 (35 to 118) and 40 (32 to 90) days, respectively. Overall, 30 (65%) pts received a HI and 16 (35%) a LI or no bridging therapy. Median number of BT cycles was 2 (range, 1-4). 13 patients had various regimen because of uncontrolled disease. Pts receiving HI presented at enrollment with more elevated LDH (60% vs 31%), more involved extranodal sites (n> 2, 32% vs 0%), higher IPI (>2, 77% vs 43%, p=.049), and higher total metabolic tumor volume (TMTV) measured on FDG PET/CT (median, 90 vs 10, p=.002). After BT, 44 pts were infused. 2 pts died before infusion because of a pulmonary infection (n=1) and a lymphoma progression (n=1), both in the HI group. At infusion response evaluation showed that 25 (57%) pts progressed during BT, without difference in the HI or the LI groups (61 % vs 50%). Median TMTV in HI and LI was 95 (10 -256) vs 18 (8 - 44), respectively. After CAR T infusion, 14 pts (32%) developed an infectious disease (7 in the LI group, 7 in the HI group, p=0.31). Median duration of neutropenia (PNN < 1000) was 8 days, 7 in the LI and 9 in the HI (p= 0.21). In the LI and HI groups, 11 and 19 pts developed a CRS (0 grade 3-4), 1 and 11 pts developed a CRES (1 and 3 grade 3-4), respectively. The HI/LI did not impact the occurrence of CRS (p=1.00) but that of CRES (p=0.03). Pts with abnormal LDH (p=0.02), high number of courses (p=0.03) or PS>0 (p=0.049) had a higher risk of CRS, whereas patients with high IPI (p=0.03), and high values of CRP (P=0.02) or decreased albumin levels (p=0.008) had a higher risk of CRES. After CAR T cells infusion, with a median follow up of 5.7 months, the median PFS was not reached in the LI group, and was of 3 months in the HI group (p=0.06). The median OS was not reached in the LI group, and was of 12.5 months in the HI group (p=0.09). In multivariate analyses, IPI was predictor of better PFS, whereas low IPI and TMTV were predictors of better OS. No evidence of any effect of intensity of the BT on OS or PFS was observed in these multivariate analyses. Conclusion: The type of bridging therapies was very heterogeneous. Its intensity was closely related to tumor burden at enrolment. There was no significant difference in terms of efficacy between the HI and LI groups, but a higher frequency of CRES in the HI group. Disclosures Paillassa: Janssen: Other: Bibliography board with young hematologists. Di Blasi:Novartis: Honoraria. Thieblemont:Roche: Honoraria, Research Funding; Gilead: Honoraria; Novartis: Honoraria; Kyte: Honoraria; Janssen: Honoraria; Celgene: Honoraria; Cellectis: Membership on an entity's Board of Directors or advisory committees.

Development of a Genetically-Engineered Allogeneic Anti-CD38 T Cell Therapy Utilizing a Novel Antigen Receptor Structure

Background: Autologous Chimeric Antigen Receptor (CAR) T cell therapy has shown great promise as a treatment modality for a variety of hematological malignancies. But autologous cell therapies still face several practical hurdles, including reliance on patient immune cells and manufacturing difficulties. Sorrento has pioneered an allogeneic T cell therapy approach utilizing genetic engineering of donor-derived T cells to express a Dimeric Antigen Receptor (DAR). The first DAR-T cell therapy being developed is targeted against CD38, a clinically-validated antigen in multiple myeloma. Preclinical data demonstrate potent anti-tumor activity in both in vitro assays and in vivo studies against CD38-expressing lymphoma and multiple myeloma (MM) cell lines. Methods: Anti-CD38 DAR-T cells were generated through genetic engineering of T cells derived from healthy donors inserting the anti-CD38 DAR construct into the TRAC gene locus resulting in loss of endogenous TCR expression while expressing the DAR. Three distinct DAR constructs were utilized differing only in the intracellular signaling components, namely CD28/CD3zeta, 4-1BB/CD3zeta and CD28/4-1BB/CD3zeta. The CD38 DAR-T were expanded and purified for subsequent preclinical studies. Using in vitro assays, the 3 different CD38 DAR-T cells were evaluated against multiple myeloma and lymphoma cell lines for specific cytotoxicity as well as stimulus-induced cytokine secretion and cell expansion. The in vivo anti-tumor activity was assessed using luciferase-expressing RPMI8226 cells in NSG mice in a model of disseminated disease. A single dose of anti-CD38 DAR-T cells or relevant control cells was administered and tumor burden was assessed weekly using bioluminescence imaging. Results: An anti-CD38 DAR gene was efficiently integrated into TRAC locus of T cells from healthy donors by one step knock out/knock in (KOKI) methodology with high efficiency (~40-80% CD38 DAR expression and ~90% TCR knock out). Following a CD3-depletion step, the TCR-positive T cells were less 1%. When co-cultured with CD38-positive tumor cells, anti-CD38 DAR T cells killed as effectively as retroviral anti-CD38 CAR-T cells with similar cytokine secretion profiles while no cytotoxicity was observed against CD38-negative cancer cells. Moreover, in vivo DAR-T cells showed better killing activity against multiple myeloma cell lines than CAR-T cell with anti-CD38 4-1BB/CD3zeta DAR demonstrating the best anti-tumor activity in an NSG mouse model. The anti-CD38 DAR-T cells with 41BB/CD3 zeta internal signals have been selected for clinical development. Conclusions: All tested anti-CD38 DAR-T cells exhibited potent in vitro and in vivo anti-tumor activity. Direct comparison of three different cytoplasmic signaling compositions of the DAR allowed for selection of the most potent construct, namely the anti-CD38 DAR utilizing 4-1BB and CD3zeta signaling domains. Based on these data, further development of CD38 DAR-T therapy for hematological malignancies is warranted. GMP manufacturing of the allogeneic anti-CD38 DAR-T cells has been initiated. Disclosures Ding: Sorrento Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties. Gray:Sorrento Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties. Krapf:Sorrento Therapeutics, Inc.: Employment, Equity Ownership. Zhang:Sorrento Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties. Zhang:Sorrento Therapeutics, Inc.: Employment, Equity Ownership. Deng:Sorrento Therapeutics, Inc.: Employment, Equity Ownership. Wei:Sorrento Therapeutics, Inc.: Employment, Equity Ownership. Knight:Sorrento Therapeutics, Inc.: Employment, Equity Ownership. Zeldis:Sorrento Therapeutics Inc: Employment, Equity Ownership. Kaufmann:Sorrento Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties. Ji:Sorrento Therapeutics Inc: Employment, Equity Ownership, Patents & Royalties; Celularity, Inc.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Guo:Sorrento Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties.