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.

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Cyclophosphamide and Fludarabine Conditioning Chemotherapy Induces a Key Homeostatic Cytokine Profile in Patients Prior to CAR T Cell Therapy

Blood ◽

10.1182/blood.v126.23.4426.4426 ◽

2015 ◽

Vol 126 (23) ◽

pp. 4426-4426 ◽

Cited By ~ 9

Author(s):

Adrian Bot ◽

John M. Rossi ◽

Yizhou Jiang ◽

Lynn Navale ◽

Yueh-wei Shen ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Cell Therapy ◽

Fold Increase ◽

Employment Equity ◽

T Cell Therapy ◽

Car T Cells ◽

Car T Cell ◽

Car T ◽

Equity Ownership

Abstract This study is supported in part by funding from the Cooperative Research and Development Agreement (CRADA) between the National Cancer Institute and Kite Pharma Introduction: CAR-engineered autologous T-cell therapy has shown promising activity in relapsed/refractory B-cell malignancies in an ongoing phase 1 study (Kochenderfer et al. J Clin Oncol 2014). Lymphodepleting conditioning chemotherapy is critical for optimal CAR T-cell activity in animal models. We evaluated the effects of conditioning chemotherapy on cytokine and chemokine levels in patients dosed with anti-CD19 CAR T cells. Methods: In this National Cancer Institute clinical trial (NCT00924326), patients with relapsed/refractory B-cell malignancies received conditioning with cyclophosphamide and fludarabine daily for 3 days starting on day -5; followed by anti-CD19 CAR T cells engineered with a CAR comprising CD28 and CD3-zeta signaling domains. Forty one cytokines, chemokines and immune response related markers were measured in the blood of patients pre (day -5) and post conditioning (day 0) by using EMD Millipore Luminex® xMAP® multiplex assays. Data acquisition and analysis were performed using a Luminex 200™ instrument and xPONENT® 3.1 data analysis software. Increases in cytokine and chemokine levels were analyzed pre- and post- conditioning, and the fold-changes in cytokine and chemokine levels were analyzed relative to clinical outcome subsequent to infusion with anti-CD19 CAR T cells. Analyses were performed with the Wilcoxon rank sum test adjusted for multiplicity with a Bonferroni correction, using a nominal level of 0.006 for significance. Results: Samples from 15patients have been evaluated. There were significant increases pre- to post-conditioning in the levels of interleukin 15 (IL-15; p=0.001), interleukin 7 (IL-7; p=0.0002), and monocyte chemoattractant protein-1 (MCP-1; p<0.0025) in blood, five days after the initiation of conditioning chemotherapy. Levels of interferon-gamma induced protein 10 (IP-10) were elevated post-conditioning, but did not meet the threshold for significance (p=0.048). Compared with baseline, levels of IL-15 increased on average 13 fold and levels of IL-7, IP-10 and MCP-1, about 2 fold. Comparison of the fold-increases in IL-15 upon conditioning between responders and non-responders approached significance (p=0.01), but did not meet the threshold after multiplicity adjustment. Larger fold-change increases for responders versus non-responders were also observed with placental growth factor (PLGF) (median fold increase 2.6 v. 1.6, average fold increase 32 v 4.2), C-reactive protein (CRP) (median fold increase 3.5 v 2.4, average fold increase 6.6 v. 2.0), IP-10 (median fold increase 2.1 v. 0.7, average fold increase 2.6 v. 2.8), and interleukin 10 (IL-10) (median fold increase 1.8 v. 0.4, average fold increase 3.1 v. 2.0), but did not meet the threshold for significance. In addition to ongoing analysis of conditioning-mediated cytokine induction and clinical response, we are evaluating the impact of conditioning chemotherapy dose on cytokine levels, as well as the relationship between conditioning-related cytokines and CAR T-cell expansion and persistence. Conclusions: The data obtained to date support the hypothesis that cytokines such as IL-15 play a key role in the clinical outcomes to anti-CD19 CAR T-cell therapy. Our results demonstrate that conditioning chemotherapy significantly increases the levels of homeostatic cytokines known to regulate T-cell expansion, as well as specific pro-inflammatory cytokines and chemokines. Optimization of conditioning chemotherapy is critical to the activity of CAR T-cell therapies. Disclosures Bot: Kite Pharma: Employment, Equity Ownership. Rossi:Amgen: Equity Ownership; Kite Pharma: Employment, Equity Ownership. Jiang:Kite Pharma: Employment, Equity Ownership. Navale:Amgen: Equity Ownership; Kite Pharma: Employment, Equity Ownership. Shen:Kite Pharma: Employment, Equity Ownership. Sherman:Amgen: Equity Ownership; Kite Pharma: Employment, Equity Ownership. Mardiros:Kite Pharma: Employment, Equity Ownership. Yoder:Kite Pharma: Employment, Equity Ownership. Go:Amgen: Equity Ownership; Kite Pharma: Employment, Equity Ownership. Rosenberg:Kite Pharma: Other: CRADA between Surgery Branch-NCI and Kite Pharma. Wiezorek:Kite Pharma: Employment, Equity Ownership, Other: Officer of Kite Pharma. Chang:Kite Pharma: Employment, Equity Ownership, Other: Officer of Kite Pharma. Roberts:Kite Pharma: Employment, Equity Ownership, Other: Officer of Kite Pharma.

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Phase I Study of AUTO3, a Bicistronic Chimeric Antigen Receptor (CAR) T-Cell Therapy Targeting CD19 and CD22, in Pediatric Patients with Relapsed/Refractory B-Cell Acute Lymphoblastic Leukemia (r/r B-ALL): Amelia Study

Blood ◽

10.1182/blood-2019-123424 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 2620-2620 ◽

Cited By ~ 7

Author(s):

Persis J Amrolia ◽

Robert Wynn ◽

Rachael E Hough ◽

Ajay Vora ◽

Denise Bonney ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Employment Equity ◽

T Cell Therapy ◽

Car T Cells ◽

Car T Cell ◽

Car T Cell Therapy ◽

Car T ◽

Equity Ownership

Introduction CAR T-cell therapies directed against CD19 or CD22 have shown remarkable activity in r/r B-ALL but relapse due to target antigen down-regulation/loss has been the major cause of treatment failure. To address this, we developed AUTO3, a CAR T-cell therapy designed to target CD19 and CD22 simultaneously. Preliminary results of this study showed an acceptable safety profile and encouraging efficacy in pediatric r/r B-ALL (all 6 patients treated in active doses ≥3 x 106 CAR T-cells/ Kg achieved complete remission (CR) with negative minimal residual disease (MRD) (Amrolia et al, Blood 2018 132:279). Here we present the updated results of CAR naïve patients treated at the active doses. Methods & Patients We constructed a bicistronic retroviral vector encoding both an anti-CD19 CAR and an anti-CD22 CAR. This second-generation CAR incorporated an OX40 co-stimulatory domain for the CD19 CAR and a 41BB for the CD22 CAR. The cell product was manufactured on a semi-automated/closed process. Patients (aged 1‒24 years) with high risk relapsed (IBFM criteria) or refractory B-ALL, adequate performance score/organ function, an absolute lymphocyte count ≥0.5 x 109/L are eligible. Patients with CNS Grade 3 disease, active graft versus host disease are excluded. Patients receive lymphodepletion with 30 mg/m2/day fludarabine x 4 days and 500 mg/m2/day cyclophosphamide x 2 days prior to AUTO3 infusion. Three dose levels were explored (1 x 106, 3 x 106, and 5 x 106 cells/kg), CAR T cells are infused as a single (for <25% blasts) or split (for ≥25% blasts) dose based on leukemia burden. Bridging therapy is allowed during the manufacturing period. The primary endpoint is the frequency of dose-limiting toxicities (DLTs) and key secondary endpoints include morphological/MRD negative CR rate, disease-free survival, overall survival, as well as AUTO3 levels and persistence in blood and bone marrow. Results As of the data cut-off date (June 17, 2019), 10 patients received AUTO3 at 3 x 106 cells/Kg (n= 5, of whom 1 received split dose) or 5 x 106 CAR T-cells/Kg (n= 5, all of them received single infusion). The median transduction efficiency was 15.5% (range 8.6‒39.3%). Median age was 8.5 years (range 5‒16 years) and 5 (50%) patients had prior haemopoietic stem cell transplant (HSCT). One patient (10%) had prior anti-CD19 CAR-T cells. The disease burden at Day ‒7 ranged from 0 to 38% (median 7.5%) blasts. Among the 10 treated patients, 2 have not completed the 30 days post-infusion DLT observation period as of the cut-off date. No deaths or DLTs were observed. MTD has not yet been reached. The most common grade (Gr) ≥3 adverse events were neutropenia (60%), anaemia (50%), pyrexia (40%), febrile neutropenia (40%) and thrombocytopenia (30%). Eight patients (80%) had Gr 1 cytokine release syndrome (CRS), one (10%) had Gr 2 CRS; no ≥Gr 3 CRS was observed. Only one patient was treated with tocilizumab and none required admission to ICU due to CRS. One patient (10%) experienced Gr 1 neurotoxicity; no ≥ Gr 2 neurotoxicity was reported. Among the 9 CAR naïve patients, 7 (4 in the 3 x 106 cells/Kg dose cohort, 3 in the 5 x 106 cells/Kg dose cohort) had a minimum of 8 weeks' follow up and were evaluable for efficacy analysis. All 7 patients achieved CR/CRi (100%) following AUTO3 infusion as well as molecular negative remission (100%). After a median follow-up of 8 months (range 2-12), emergence of MRD by PCR occurred in four patients, lack of persistence of circulating CAR T-cells was observed in 3 of the 4 patients. Three relapses were reported including one with CD19 negative/CD22 low expression at 1 year after treatment. One patient in ongoing molecular remission proceeded to HSCT. All the remaining 4 patients in ongoing CR/CRi maintain B-cell aplasia. The median CAR T-cell expansion (expressed as vector copy number per microgram of DNA) at peak was 102K (range 56-128). The median persistence of CAR-T cells in blood was 180 days (range 21-330). Updated data with longer follow up and additional patient data will be presented. Conclusion This interim data analysis demonstrates that AUTO3 at ≥3 x 106 cells dose achieved 100% molecular remission rate with a favourable safety profile, no ≥ Gr 3 CRS or ≥ Gr 2 neurotoxicity was reported. The most common cause of relapse was antigen positive relapse due to lack of CAR T cell persistence. Evaluation of patients with a modified manufacturing process is planned. Disclosures Amrolia: UCLB: Patents & Royalties. Clark:Autolus Ltd: Employment, Equity Ownership. Al-Hajj:Autolus Therapeutics: Employment, Equity Ownership. Cordoba:Autolus: Employment, Equity Ownership. Kotsopoulou:Autolus Therapeutics: Employment, Equity Ownership. Khokhar:Autolus Therapeutics: Employment, Equity Ownership. Pule:Autolus: Employment, Equity Ownership, Patents & Royalties. Peddareddigari:Autolus Therapeutics: Employment, Equity Ownership.

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Knockout of CBLB Greatly Enhances Anti-Tumor Activity of CAR T Cells

Blood ◽

10.1182/blood-2018-99-119247 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 338-338

Author(s):

Kathryn Hooper ◽

Kyle Havens ◽

Anne-Rachel Krostag ◽

Michael S Magee ◽

Unja Martin ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Target Cells ◽

Employment Equity ◽

Car T Cells ◽

Highly Efficient ◽

Car T Cell ◽

Car T ◽

Equity Ownership

Abstract Chimeric antigen receptor (CAR) T cell therapies continue to show excellent outcomes in hematological cancers. Achieving success in additional tumor indications, however, will likely require modulating inhibitory pathways that limit CAR T cell potency. We developed a megaTAL nuclease targeting the gene encoding Casitas B-lineage lymphoma proto-oncogene-b (CBLB), a ubiquitin ligase that serves as an intracellular checkpoint that negatively regulates T cell activation. The megaTAL nuclease platform has been previously shown to drive highly efficient genome editing in primary T cells. Electroporation of primary T cells with mRNA encoding the CBLB megaTAL resulted in >90% indels at the target locus and a concomitant reduction of Cbl-b protein levels. Specificity characterization studies revealed three detectable non-exonic off-target sites with near negligible indel frequencies. We next assessed the functional impact of CBLB disruption in CAR T cells engineered to target the epidermal growth factor receptor (EGFR). When co-cultured with EGFR+ target cells, CAR T cells with megaTAL-mediated CBLB gene knockout had a 2-fold increase in pro-inflammatory cytokine production compared with mock-treated CAR T cells. We developed an A549 tumor xenograft model to test the activity of CBLB megaTAL-treated CAR T cells in vivo. While mock-treated CAR T cells had a transient impact on tumor growth, we observed complete and durable tumor elimination in mice infused with the CBLB megaTAL-treated CAR T cells. Improved responses in the megaTAL treated animals were particularly pronounced at lower CAR T cell doses, suggesting that CBLB knockout enhances the potency of CAR T cells. In summary, the CBLB megaTAL is a highly efficient and specific gene editing nuclease that enhances CAR T cell anti-tumor responses in vitro and in vivo, and thus could potentially improve the efficacy of CAR T therapy. Disclosures Hooper: bluebird bio: Employment, Equity Ownership. Havens:bluebird bio: Employment, Equity Ownership. Krostag:bluebird bio: Employment, Equity Ownership. Magee:bluebird bio: Employment, Equity Ownership. Martin:bluebird bio: Employment, Equity Ownership. Gupta:bluebird bio: Employment, Equity Ownership. Smurnyy:bluebird bio: Employment, Equity Ownership. Pechilis:bluebird bio: Employment, Equity Ownership. Rode:bluebird bio: Employment, Equity Ownership. Chavkin:bluebird bio: Employment, Equity Ownership. Grande:bluebird bio: Employment, Equity Ownership. Morgan:bluebird bio: Employment, Equity Ownership. Jarjour:bluebird bio: Employment, Equity Ownership. Astrakhan:bluebird bio: Employment, Equity Ownership.

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Enhancing co-stimulation of CAR T cells to improve treatment outcomes in solid cancers

Immunotherapy Advances ◽

10.1093/immadv/ltab016 ◽

2021 ◽

Author(s):

Aaron J Harrison ◽

Xin Du ◽

Bianca von Scheidt ◽

Michael H Kershaw ◽

Clare Y Slaney

Keyword(s):

T Cells ◽

T Cell ◽

Cell Biology ◽

Tumour Microenvironment ◽

Solid Tumours ◽

T Cell Therapy ◽

Cell Therapies ◽

Car T Cells ◽

Car T Cell ◽

Car T

Abstract Co-stimulation is a fundamental component of T cell biology and plays a key role in determining the quality of T cell proliferation, differentiation and memory formation. T cell-based immunotherapies, such as chimeric antigen receptor (CAR) T cell immunotherapy, are no exception. Solid tumours have largely been refractory to CAR T cell therapy owing to an immunosuppressive microenvironment which limits CAR T cell persistence and effector function. In order to eradicate solid cancers, increasingly sophisticated strategies are being developed to deliver these vital co-stimulatory signals to CAR T cells, often specifically within the tumour microenvironment. These include designing novel co-stimulatory domains within the CAR or other synthetic receptors, arming CAR T cells with cytokines or using CAR T cells in combination with agonist antibodies. This review discusses the evolving role of co-stimulation in CAR T cell therapies and the strategies employed to target co-stimulatory pathways in CAR T cells, with a view to improve responses in solid tumours.

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Preclinical Development of CTX120, an Allogeneic CAR-T Cell Targeting Bcma

Blood ◽

10.1182/blood-2018-99-116443 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 1921-1921 ◽

Cited By ~ 2

Author(s):

Henia Dar ◽

Daniel Henderson ◽

Zinkal Padalia ◽

Ashley Porras ◽

Dakai Mu ◽

...

Keyword(s):

Multiple Myeloma ◽

T Cells ◽

T Cell ◽

Cell Targeting ◽

Employment Equity ◽

Term Survival ◽

Car T Cells ◽

Car T Cell ◽

Car T ◽

Equity Ownership

Abstract Autologous CAR-T cells targeting BCMA have induced robust and durable responses in patients with relapsed/refractory multiple myeloma. However, autologous cell therapies face several challenges which will likely limit the number of patients that will have access to these therapies. These limitations include manufacturing failure rates, wait time and supply constraints in addition to other factors such as reimbursement. Allogeneic CAR-T cells can potentially overcome these access challenges, and may have several other advantages over autologous therapies. Allogeneic CAR-T cells are derived from robust healthy donor T cells through a batch manufacturing process, which may result in a highly consistent product with greater potency and enable better safety management. Here we show further development and preclinical data for CTX120, an allogeneic "off the shelf" CAR-T cell targeting BCMA. CTX120 is produced using the CRISPR/Cas9 system to eliminate TCR and MHC class I, coupled with specific insertion of the CAR at the TRAC locus. CTX120 shows consistent and high percent CAR expression from this controlled insertion and exhibits target-specific cytotoxicity and cytokine secretion in response to BCMA positive cell lines. CTX120 CAR-T cells retain their cytotoxic capacity over multiple in vitro re-challenges, demonstrating durable potency and lack of exhaustion. In mouse models of multiple myeloma, CTX120 showed typical CAR-T persistence and eliminated tumors completely, resulting in long-term survival as compared to untreated animals. These data support the ongoing development of CTX120 for treatment of patients with multiple myeloma and further demonstrate the potential for our CRISPR/Cas9 engineered allogeneic CAR-T platform to generate potent CAR-T cells targeting different tumor antigens. Disclosures Dar: CRISPR Therapeutics: Employment, Equity Ownership. Henderson:CRISPR Therapeutics: Employment, Equity Ownership. Padalia:CRISPR Therapeutics: Employment, Equity Ownership. Porras:CRISPR Therapeutics: Employment, Equity Ownership. Mu:CRISPR Therapeutics: Employment, Equity Ownership. Kyungah:CRISPR Therapeutics: Employment, Equity Ownership. Police:CRISPR Therapeutics: Employment, Equity Ownership. Kalaitzidis:CRISPR Therapeutics: Employment, Equity Ownership. Terrett:CRISPR Therapeutics: Employment, Equity Ownership. Sagert:CRISPR Therapeutics: Employment, Equity Ownership.

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Development and Evaluation of a Human Single Chain Variable Fragment (scFv) Derived Bcma Targeted CAR T Cell Vector Leads to a High Objective Response Rate in Patients with Advanced MM

Blood ◽

10.1182/blood.v130.suppl_1.742.742 ◽

2017 ◽

Vol 130 (Suppl_1) ◽

pp. 742-742 ◽

Cited By ~ 1

Author(s):

Eric L Smith ◽

Sham Mailankody ◽

Arnab Ghosh ◽

Reed Masakayan ◽

Mette Staehr ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Research Funding ◽

Employment Equity ◽

Advisory Committees ◽

Car T Cells ◽

Car T Cell ◽

Car T ◽

Equity Ownership

Abstract 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 p<0.05). Tumor and CAR T cells were imaged in vivo by taking advantage of luciferase constructs with different substrates. Results show rapid tumor clearance, peak (>10,000 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.

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Prophylactic Itacitinib (INCB039110) for the Prevention of Cytokine Release Syndrome Induced By Chimeric Antigen Receptor T-Cells (CAR-T-cells) Therapy

Blood ◽

10.1182/blood-2019-128288 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 1934-1934 ◽

Cited By ~ 3

Author(s):

Eduardo Huarte ◽

Roddy S O'Connor ◽

Melissa Parker ◽

Taisheng Huang ◽

Michael C. Milone ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Cytokine Release ◽

Employment Equity ◽

Car T Cells ◽

Car T Cell ◽

Car T ◽

Equity Ownership

Background: T-cells engineered to express a chimeric antigen receptor (CAR-T-cells) are a promising cancer immunotherapy. Such targeted therapies have shown long-term relapse survival in patients with B cell leukemia and lymphoma. However, cytokine release syndrome (CRS) represents a serious, potentially life-threatening, side effect often associated with CAR-T cells therapy. The Janus kinase (JAK) tyrosine kinase family is pivotal for the downstream signaling of inflammatory cytokines, including interleukins (ILs), interferons (IFNs), and multiple growth factors. CRS manifests as a rapid (hyper)immune reaction driven by excessive inflammatory cytokine release, including IFN-g and IL-6. Itacitinib is a potent, selective JAK1 inhibitor which is being clinically evaluated in several inflammatory diseases. Aims: To evaluate in vitro and in vivo the potential of itacitinib to modulate CRS without impairing CAR-T cell anti-tumor activity. Materials and Methods: In vitro proliferation and cytotoxic activity of T cells and CAR-T cells was measured in the presence of increasing concentrations of itacitinib or tocilizumab (anti-IL-6R). To evaluate itacitinib effects in vivo, we conducted experiments involving adoptive transfer of human CD19-CAR-T-cells in immunodeficient animals (NSG) bearing CD19 expressing NAMALWA human lymphoma cells. The effect of itacitinib on cytokine production was studied on CD19-CAR-T-cells expanded in the presence of itacitinib or tocilizumab. Finally, to study whether itacitinib was able to reduce CRS symptoms in an in vivo setting, naïve mice were stimulated with Concanavalin-A (ConA), a potent T-cell mitogen capable of inducing broad inflammatory cytokine releases and proliferation. Results: In vitro, itacitinib at IC50 relevant concentrations did not significantly inhibit proliferation or anti-tumor killing capacity of human CAR-T-cells. Itacitinib and tocilizumab (anti-IL-6R) demonstrated a similar effect on CAR T-cell cytotoxic activity profile. In vivo, CD19-CAR-T-cells adoptively transferred into CD19+ tumor bearing immunodeficient animals were unaffected by oral itacitinib treatment. In an in vitro model, itacitinib was more effective than tocilizumab in reducing CRS-related cytokines produced by CD19-CAR-T-cells. Furthermore, in the in vivo immune hyperactivity (ConA) model, itacitinib reduced serum levels of CRS-related cytokines in a dose-dependent manner. Conclusion: Itacitinib at IC50 and clinically relevant concentrations did not adversely impair the in vitro or in vivo anti-tumor activity of CAR-T cells. Using CAR-T and T cell in vitro and in vivo systems, we demonstrate that itacitinib significantly reduces CRS-associated cytokines in a dose dependent manner. Together, the data suggest that itacitinib may have potential as a prophylactic agent for the prevention of CAR-T cell induced CRS. Disclosures Huarte: Incyte corporation: Employment, Equity Ownership. Parker:Incyte corporation: Employment, Equity Ownership. Huang:Incyte corporation: Employment, Equity Ownership. Milone:Novartis: Patents & Royalties: patents related to tisagenlecleucel (CTL019) and CART-BCMA; Novartis: Research Funding. Smith:Incyte corporation: Employment, Equity Ownership.

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Initial Results from a Phase 1 Clinical Study of bb21217, a Next-Generation Anti Bcma CAR T Therapy

Blood ◽

10.1182/blood-2018-99-116953 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 488-488 ◽

Cited By ~ 41

Author(s):

Nina Shah ◽

Melissa Alsina ◽

David S Siegel ◽

Sundar Jagannath ◽

Deepu Madduri ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Board Of Directors ◽

Research Funding ◽

Phase 1 ◽

Employment Equity ◽

Car T Cells ◽

Car T Cell ◽

Car T ◽

Equity Ownership

Abstract Introduction: Immunomodulatory chimeric antigen receptor (CAR) T cell therapy directed against B-cell maturation antigen (BCMA) has shown promising results for the treatment of relapsed refractory multiple myeloma (RRMM) in several phase 1 clinical studies in patients with advanced disease. Persistence of CAR T cells post infusion may be one determinant of duration of response. bb21217 is a next-generation anti-BCMA CAR T cell therapy based on investigational therapy bb2121 (Friedman 2018, Hum Gene Ther 29:585). It uses the same scFv, 4-1BB costimulatory motif and CD3-zeta T cell activation domain as bb2121 with the addition of phosphoinositide 3 kinase inhibitor bb007 during ex vivo culture to enrich the drug product for T cells displaying a memory-like phenotype. Evidence suggests that CAR T cells with this phenotype may be more persistent and more potent than unselected CAR T cells. CRB-402 is a first-in-human clinical study of bb21217 in patients with RRMM designed to assess the safety, pharmacokinetics, efficacy and duration of effect of bb21217. Methods: CRB-402 (NCT03274219) is an ongoing, multi-center phase 1 dose escalation trial of bb21217 in approximately 50 patients with RRMM who have received ≥ 3 prior regimens, including a proteasome inhibitor and an immuno-modulatory agent, or are double-refractory. During dose escalation, enrollment is restricted to patients with ≥ 50% BCMA expression by IHC on malignant plasma cells. Peripheral blood mononuclear cells are collected via leukapheresis and sent to a central facility for transduction, expansion and release testing prior to being returned to the site for infusion. Patients undergo lymphodepletion with fludarabine (30 mg/m2) and cyclophosphamide (300 mg/m2) daily for 3 days, then receive bb21217 as a single infusion. Planned dose levels are 150, 450, 800, and 1,200 x 106 CAR+ T cells. The primary outcome measure is incidence of adverse events (AEs), including dose-limiting toxicities (DLTs). Additional outcome measures are quality and duration of clinical response assessed according to the IMWG Uniform Response Criteria for MM, evaluation of minimal residual disease (MRD), progression-free and overall survival, and quantification of CAR+ cells in blood. Results: Asof June 15, 2018, 8 patients (median age 64 [min;max 54 to 70]) have received bb21217. All patients to date received a dose of 150 x 106 CAR+ T cells. Four had high tumor burden, defined as ≥ 50% bone marrow plasma cells pre-infusion. Patients had a median of 9 (min;max 4 to 17) prior lines of therapy and 7/8 had prior autologous stem cell transplant; 50% had high-risk cytogenetics. Four of 8 (50%) had previously received Bort/Len/Car/Pom/Dara. Median follow-up after bb21217 infusion was 16 weeks (2 to 27 weeks) and 7 patients were evaluable for initial (1-month) clinical response. As of data cut-off, 5 of 8 patients developed cytokine release syndrome (CRS; 1 Grade 1, 3 Grade 2, 1 Grade 3) and responded to supportive care or tocilizumab. This included 1 patient with high tumor burden who experienced DLTs consisting of grade 3 CRS and grade 4 encephalopathy with signs of posterior reversible encephalopathy syndrome on MRI. This patient received tocilizumab, corticosteroids and cyclophosphamide, improved neurologically and achieved a sCR. Following this event, the dose escalation cohort was divided into two groups based on tumor burden and dosing continued at 150x106 CAR+ T cells. No deaths occurred. With 1 to 6 months since treatment, 6 of 7 patients had demonstrated clinical response per IMWG criteria: currently 1 sCR, 3 VGPR, 2 PR. MRD negative results at 10-5 nucleated cells were obtained by next-generation sequencing in 3 of 3 evaluable responders. Robust CAR+ T cell expansion during the first 30 days was observed in 7 of 7 evaluable patients. Two of 2 patients evaluable at 6 months had detectable CAR vector copies. Conclusions: Early efficacy results with bb21217 CAR T therapy in RRMM at a dose of 150 x 106 CAR+ T cells are encouraging, with 6 of 7 patients demonstrating clinical responses. The adverse events observed to date are consistent with known toxicities of CAR T therapies. CAR+ T cells were measurable at 6 months post treatment in both evaluable patients. Enrollment in the study is ongoing; longer follow-up and data in more patients will establish whether treatment with bb21217 results in sustained CAR+ T cell persistence and responses. Disclosures Shah: Kite: Consultancy; Indapta Therapeutics: Consultancy; University of California San Francisco: Employment; Nekktar: Consultancy; Teneobio: Consultancy; Sanofi: Consultancy; Janssen: Research Funding; Indapta Therapeutics: Equity Ownership; Amgen: Consultancy; Bluebird: Research Funding; Celgene: Research Funding; Bristol Myers Squibb: Consultancy; Takeda: Consultancy; Sutro Biopharma: Research Funding; Nkarta: Consultancy. Siegel:Takeda: Consultancy, Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Karyopharm: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Amgen: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; Merck: Consultancy, Honoraria, Speakers Bureau; Janssen: Consultancy, Honoraria, Speakers Bureau. Jagannath:Multiple Myeloma Research Foundation: Speakers Bureau; Merck: Consultancy; Novartis: Consultancy; Bristol-Myers Squibb: Consultancy; Celgene: Consultancy; Medicom: Speakers Bureau. Kaufman:Karyopharm: Other: data monitoring committee; BMS: Consultancy; Janssen: Consultancy; Abbvie: Consultancy; Roche: Consultancy. Turka:bluebird bio, Inc: Employment, Equity Ownership. Lam:bluebird bio, Inc: Employment, Equity Ownership. Massaro:bluebird bio, Inc: Employment, Equity Ownership. Hege:Celgene Corporation: Employment, Equity Ownership, Patents & Royalties: multiple; Mersana: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; SITC: Membership on an entity's Board of Directors or advisory committees; Arcus Biosicences: Membership on an entity's Board of Directors or advisory committees. Petrocca:bluebird bio, Inc: Employment, Equity Ownership. Berdeja:Glenmark: Research Funding; Novartis: Research Funding; Genentech: Research Funding; Janssen: Research Funding; Bristol-Myers Squibb: Research Funding; Bluebird: Research Funding; Amgen: Research Funding; Celgene: Research Funding; Poseida Therapeutics, Inc.: Research Funding; Takeda: Research Funding; Teva: Research Funding; Sanofi: Research Funding. Raje:AstraZeneca: Research Funding; Takeda: Consultancy; Merck: Consultancy; Janssen: Consultancy; Celgene: Consultancy; BMS: Consultancy; Amgen Inc.: Consultancy; Research to Practice: Honoraria; Medscape: Honoraria.

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ALLO-715, an Allogeneic BCMA CAR T Therapy Possessing an Off-Switch for the Treatment of Multiple Myeloma

Blood ◽

10.1182/blood-2018-99-119227 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 591-591 ◽

Cited By ~ 8

Author(s):

Cesar Sommer ◽

Bijan Boldajipour ◽

Julien Valton ◽

Roman Galetto ◽

Trevor Bentley ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Cell Expansion ◽

Employment Equity ◽

Car T Cells ◽

Car T Cell ◽

Car T ◽

Equity Ownership

Abstract Autologous chimeric antigen receptor (CAR) T cells targeting B-Cell Maturation Antigen (BCMA) have demonstrated promising clinical activity, inducing durable responses in patients with relapsed/refractory multiple myeloma (MM). Development of autologous CAR T therapies is however limited by logistical challenges and the time required for manufacturing, which has to be done for each patient. In addition, manufacturing may not be feasible in some patients. An allogeneic approach that utilizes engineered cells from a healthy donor could potentially expand patient access to these therapies by providing a readily available off-the-shelf product. We have previously described the screening of a library of single chain variable fragments (scFvs) with high affinity to human BCMA and the identification of candidate BCMA CARs with potent antitumor activity. Here we sought to further characterize ALLO-715, our lead allogeneic BCMA CAR T cell product, for its specificity to human BCMA, antitumor efficacy in vitro using a long-term killing assay and in xenograft mouse models with physiologic levels of human IL-7 and IL-15, and suitability for scale-up manufacturing. Allogeneic ALLO-715 CAR T cells were generated by lentiviral transduction with a second generation CAR construct incorporating a novel scFv derived from a fully-human antibody with high affinity to BCMA (KD value ~ 5 nM, determined at 37°C) and featuring a rituximab-driven off-switch. Transduced T cells were then transfected with mRNAs encoding Transcription Activator-Like Effector Nucleases (TALEN®) designed to specifically disrupt the T cell receptor alpha chain and CD52 loci. These modifications result in a cell product with a lower risk of TCR-mediated graft-versus-host disease and resistance to the CD52 antibody alemtuzumab, a lymphodepleting agent. BCMA CAR T cells exhibited robust cell expansion, with low levels of tonic signaling that resulted in minimal differentiation (> 50% Tscm/Tcm phenotype). In in vitro assays, ALLO-715 CAR T cells displayed potent cytotoxic activity when co-cultured with the target cell lines MM.1S, Molp-8, and BCMA-REH but negligible cytotoxicity against BCMA-negative REH cells. The high proliferative potential indicated by the high frequency of memory T cells was validated in long-term killing assays, where ALLO-715 CAR T cells showed substantial expansion in the presence of MM.1S cells with no evidence of exhaustion or diminished cytolytic activity after seven days of continuous exposure to target. The potency of ALLO-715 CAR T cells was unaffected by high concentrations of soluble BCMA (>10 ug/mL), which has been shown previously to interfere with the activity of some BCMA-specific CARs. In MM xenograft mouse models, ALLO-715 CAR T cells were highly efficacious at single dose. High serum IL-15 levels have been associated with CAR T cell expansion in clinical trials. To evaluate the impact of homeostatic cytokines on CAR T cell survival and antitumor activity in our xenograft models, mice were administered adeno-associated viruses (AAV) for the expression of human IL-7 and IL-15. In the presence of physiological concentrations of these cytokines, enhanced BCMA CAR T cell expansion and anti-tumor activity were observed. To assess potential off-target interactions of ALLO-715 CAR, tissue cross-reactivity studies were carried out on standard human tissue panels using a scFv-human IgG fusion protein. Consistent with the limited expression pattern of BCMA, reactivity was seen on scattered cells in lymphoid tissues such as tonsil and abundantly on BCMA-expressing cell lines, but no appreciable staining was detected in other tissues. We examined BCMA CAR T cells manufactured following a proprietary GMP-like clinical scale process and found that cell expansion and viability, T cell phenotype and in vivo antitumor efficacy were preserved. These results demonstrate the potential of ALLO-715 as a novel allogeneic BCMA CAR T therapy for the treatment of relapsed/refractory MM and other BCMA-positive malignancies. Disclosures Sommer: Allogene Therapeutics: Employment, Equity Ownership, Patents & Royalties. Boldajipour:Pfizer Inc.: Employment, Patents & Royalties. Valton:Cellectis.Inc: Employment, Equity Ownership, Patents & Royalties. Galetto:Cellectis SA: Employment, Equity Ownership, Patents & Royalties. Bentley:Allogene Therapeutics: Employment, Equity Ownership. Sutton:Allogene Therapeutics: Employment, Equity Ownership. Ni:Allogene Therapeutics: Employment, Equity Ownership. Leonard:Allogene Therapeutics: Employment, Equity Ownership. Van Blarcom:Allogene Therapeutics: Employment, Equity Ownership. Smith:Cellectis. Inc: Employment, Patents & Royalties. Chaparro-Riggers:Pfizer Inc.: Employment, Patents & Royalties. Sasu:Allogene Therapeutics: Employment, Equity Ownership, Patents & Royalties.

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Manufacturing an Enhanced CAR T Cell Product By Inhibition of the PI3K/Akt Pathway During T Cell Expansion Results in Improved In Vivo Efficacy of Anti-BCMA CAR T Cells

Blood ◽

10.1182/blood.v126.23.1893.1893 ◽

2015 ◽

Vol 126 (23) ◽

pp. 1893-1893 ◽

Cited By ~ 6

Author(s):

Molly R. Perkins ◽

Shannon Grande ◽

Amanda Hamel ◽

Holly M. Horton ◽

Tracy E. Garrett ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Ex Vivo ◽

Employment Equity ◽

Car T Cells ◽

Car T Cell ◽

Car T ◽

Equity Ownership ◽

Cells Cultured

Abstract Patients treated with chimeric antigen receptor (CAR) T cells targeting CD19 for B cell malignancies have experienced rapid and durable tumor regressions. Manufacture of CAR T cells is challenged by the necessity to produce a unique drug product for each patient. Each treatment requires ex vivo culture of patient T cells to facilitate CAR gene transfer and to achieve therapeutic amounts of T cells. Paradoxically, ex vivo culture with IL-2 also decreases CAR T cell activity. Some investigators have proposed isolating central memory T cells (thought to be enriched for therapeutic T cells), yet isolation techniques are cumbersome and costly to scale commercially. Culture of T cells in IL-7 and IL-15 has also been shown by several investigators to improve therapeutic activity. Here we explored the potential for culture modifications to improve the therapeutic potential of CAR T cells without adding complexity to manufacturing. We tested this hypothesis using CAR T cells specific to B cell maturation antigen (BCMA) manufactured using standard IL-2 culture with an inhibitor of PI3K added to the media, or with IL-7 and IL-15 in place of IL-2. The in vivo activity was studied in NSG mouse models of human Burkitt's lymphoma (Daudi), and multiple myeloma (RPMI-8226), both of which express BCMA. In the lymphoma model, NSG mice were injected intravenously (IV) with 2 x 106 Daudi cells and allowed to accumulate a large tumor burden before being treated with 4 x 106 CAR+ T cells on day 18 post-tumor injection. At this late time point post implantation, mice had highly disseminated Daudi tumor (our goal was to model late stage disease observed in relapsed and refractory lymphoma). In this model of advanced disease, IL-2 cultured anti-BCMA CAR T cells had no effect on tumor growth (p = 0.22) and all mice succumbed to the tumors within two weeks after treatment. Anti-BCMA CAR T cells grown in IL-7 and IL-15 also failed to control tumor growth (p = 0.23). In sharp contrast, all animals treated with anti-BCMA CAR T cells cultured with the PI3K inhibitor survived and experienced complete long-term tumor regression (p=0.003). The same anti-BCMA CAR T cells were used in a model of multiple myeloma. NSG mice were injected subcutaneously (SC) with 107 RPMI-8226 MM cells, and at 22 days post-implantation mice received a single IV administration of anti-BCMA CAR T cells (4 x 105 CAR+ T cells/mouse) cultured under various conditions. In this model, all treatment groups demonstrated tumor regression, regardless of the in vitro culture conditions. To evaluate CAR T cell durability, two weeks after initial tumor clearance, surviving animals were then re-challenged with RPMI-8226 cells on the opposite flank to model tumor relapse. We found that only animals that had been treated with anti-BCMA CAR T cells cultured with PI3K inhibition were immune to subsequent tumor challenge (p=0.005). Given the superior in vivo efficacy of anti-BCMA CAR T cells cultured with PI3K inhibition, we sought to identify phenotypic characteristics associated with the improved therapeutic activity. Anti-BCMA CAR T cells cultured with PI3K inhibition contained an increased frequency of CD62L+ CD8 T cells in the final product (p < 0.001) suggesting improved expansion of a distinct CD8 T cell subset. These data suggest that inhibition of PI3K during ex vivo expansion with IL-2 may generate a superior anti-BCMA CAR T cell product for clinical use. Furthermore, this approach could potentially be used in the manufacture of other T cell therapies. Disclosures Perkins: bluebird bio: Employment, Equity Ownership. Grande:bluebird bio: Employment, Equity Ownership. Hamel:bluebird bio: Employment, Equity Ownership. Horton:bluebird bio: Employment, Equity Ownership. Garrett:bluebird bio: Employment, Equity Ownership. Miller:bluebird bio: Employment, Equity Ownership. Latimer:bluebird bio: Employment, Equity Ownership. Horvath:bluebird bio: Employment, Equity Ownership. Kuczewski:bluebird bio: Employment, Equity Ownership. Friedman:bluebird bio: Employment, Equity Ownership. Morgan:bluebird bio: Employment, Equity Ownership.

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