BackgroundWith its roots in principles of basic immunology, synthetic biology and genetic engineering, the field of adoptive cell transfer (ACT) has quickly become one of the most promising and innovative approaches to treat cancer, viral infections and other immune-modulated diseases. There are currently three main types of ACT using effector cells 1 : administration of tumour infiltrating lymphocytes (TILs), and gene transfer-based strategies relying on T-cell manipulation for expression of either chimeric antigen (Ag) receptors (CARs) -composed of antibody (Ab)-binding domains fused to T-cell signalling domains -or engineered T-cell receptor (TCR) α/β heterodimers. Genetic modification of autologous T cells to target specific tumour antigens has been developed to overcome the consequences of immune tolerance and offers the possibility to endow the immune system with reactivities that are not naturally present. This approach has the additional benefit of rapid tumour eradication, which is usually observed with cytotoxic chemotherapy or with targeted therapies, and it contrasts to the delayed effects that are usually observed with vaccines and T-cell checkpoint therapies. Lasting anticancer responses have been extensively reported for CARs targeting CD19 on chronic lymphocytic leukemia (CLL), acute lymphoblastic leukemia (ALL) and B-cell lymphoma 2 , and the US Food and Drug Administration (FDA) has recently approved two genetically engineered CAR T-cell products, tisagenlecleucel (Kymriah) 3 and axicabtagene ciloleucel (Yescarta) 4 , for clinical application. Although not having yet provided such a dramatic evidence of effectiveness, therapeutic TCR genemodified T cells have also shown clinical activity and significantly reduce tumour burden 2 . Furthermore, they feature particularities that render them a more suitable approach for specific types of malignancies, including solid tumours. This review will focus on the main characteristics of TCR gene-modified cells, their potential clinical application and promise to the field of ACT, basic manufacturing procedures and characterisation protocols, and overall challenges that need to be overcome so that redirection of TCR specificity may be successfully translated into clinical practice. TCR structure and signallingThe TCR is a heterodimeric protein, typically consisting of an alpha (α) and a beta (β) chain, expressed on the cell surface as part of a complex with CD3 molecules. A minority of T cells can express an alternate receptor formed by gamma (γ) and delta (δ) chains (γδ T cells). TCR activation depends on the binding to a processed intracellular peptide presented by a major histocompatibility complex (MHC) molecule (the peptide-MHC antigen) on the target cells, followed by proper signal initiation and amplification, processes that involve an array of cell surface molecules. Each αβ subunit contains variable (V) and constant (C) regions, with the latter being followed by a transmembrane region. Each V domain contains three loops which interact with the pepti...

Introduction: In adults, prognosis for B-ALL is poor, patients are more vulnerable to CD19 CAR immunotoxicity and there is currently no CD19 CAR therapeutic with acceptable toxicity and durable efficacy. We have developed a novel second generation CD19CAR (CAT-41BBz CAR), with a faster off-rate but equivalent on rate than the FMC63-41BBz CAR (Kd 116 nM vs 0.9 nM, T1/2 9s vs 4.2 hours) designed to result in more physiological T-cell activation, reduce toxicity and improve engraftment. Preliminary paediatric clinical data of this novel CD19 CAR (AUTO1) supports this assertion. We here describe preliminary data from ALLCAR19 (NCT02935257), a multi-centre, Phase I clinical study of AUTO1 as therapy for r/r adult B-ALL. Methods: Manufacturing: AUTO1 utilises non-mobilised autologous leucapheresate. The first 6 trial products were generated using a standard dynal bead/WAVE Bioreactor process and subsequent products using a semi-automated closed process. Study design: ALLCAR19 is a phase I/II study recruiting subjects 16-65y with r/r B ALL. Lymphodepletion with fludarabine (30mg/m2 x3) and cyclophosphamide (60mg/kg x1) is followed by split dose CAR T cell infusion (Day 0: if ≥20% BM blasts, infuse 10 x 106 CAR T cells ; if <20% BM blasts, infuse 100 x 106 CAR T cells. Day +9: if no Grade 3-5 CRS/CRES, infuse Dose 2, to a total dose of 410 x 106 CAR T cells). Study endpoints include feasibility of manufacture, grade 3-5 toxicity and remission rates at 1 and 3 months Results: As of 24 July 2019, 16 patients have been leukaphresed, 14 products manufactured (one failed leukaphresis and one currently in manufacture) and 13 patients have received at least 1 dose of AUTO1. Of the 16 patients, median age was 35.5 (range 18-63), 10/16 (63%) had prior blinatumomab or inotuzumab ozogamicin and 12/16 (75%) had prior HSCT. At the time of pre-conditioning, 9/13 (69%) patients were in morphological relapse with >5% leukemic blasts of which 6/13 (46%) had ≥50% blast. 9/13 patients (69%) received the total target split dose of 410 x 106 CAR T cells while 1/13 patients (8%) received a reduced split total dose of 51.3 x 106 CAR T cells due to manufacturing constraints. 3/13 patients (23%) received only a first dose of 10 x 106 CAR T cells. The dose was administered safely to date: No patients experienced ≥Grade 3 CRS (using Lee criteria) and only 1/13 (8%) experienced Grade 3 neurotoxicity (dysphasia) that resolved swiftly with steroids. All patients had robust CAR expansion (median peak expansion 172 CAR/uL blood). Of the 13 patients dosed (1/13 pending 28 day follow up), 10/12 (83%) achieved MRD negative CR at 1 month and all patients had ongoing CAR T cell persistence at last follow up. Two patients experienced CD19 negative relapse (one at M3, one at M6), 1 patient died on D17 before first response evaluation, 1 died in molecular CR from sepsis, and 1 died from persistent disease. Currently, 7/12 remain on study and continue in flow/molecular MRD negative remission with a median follow up of 9.0 months (range 1.2-14.8). Conclusions: AUTO1 delivers excellent early remission rates with initial data showing 83% MRD negative CR and robust CAR expansion and persistence. Despite high tumour burden, the safety profile compares favourably to other CD19 CARs, with no cases of severe CRS and only one case of Gr3 neurotoxicity. This is consistent with experience in the paediatric cohort. Updated results will be presented. Disclosures Roddie: Novartis: Consultancy; Gilead: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau. O'Reilly:Kite Gilead: Honoraria. Farzaneh:Autolus Ltd: Equity Ownership, Research Funding. Linch:Autolus: Membership on an entity's Board of Directors or advisory committees. Pule:Autolus: Membership on an entity's Board of Directors or advisory committees. Peggs:Gilead: Consultancy, Speakers Bureau; Autolus: Membership on an entity's Board of Directors or advisory committees.

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Introduction: 2nd generation CD19 CAR T cells show unprecedented efficacy in B-ALL, but several challenges remain: (1) scaling manufacture to meet patient need and (2) feasibility of generating products from lymphopenic patients post allogeneic stem cell transplant (allo-SCT). To overcome these issues we propose: (1) use of the CliniMACS Prodigy (Miltenyi Biotec), a semi-automated cGMP platform that simplifies CAR T cell manufacture and (2) the use of matched donor T cells to overcome the challenge posed by patient lymphopenia, albeit this may come with a heightened risk of graft versus host disease (GvHD). CARD (NCT02893189) is a Phase I study of matched donor derived CD19 CAR T cells generated on the CliniMACS Prodigy in 14 adult patients with relapsed/refractory (r/r) B ALL following allo-SCT. We additionally explore the requirement for lymphodepletion (LD) in the allogeneic CAR T cell setting and report on the incidence of GvHD with this therapy. Methods: Manufacturing: CARD utilises non-mobilised matched donor leucapheresate to manufacture 2nd generation CD19CAR T cells using a closed CliniMACS® Prodigy/ TransACTTM process. Study design: Eligible subjects are aged 16-70y with r/r B ALL following allo SCT. Study endpoints include feasibility of CD19CAR T cell manufacture from allo-SCT donors on the CliniMACS Prodigy and assessments of engraftment and safety including GvHD. To assess the requirement for LD prior to CD19CAR T cells in lymphopenic post-allo-SCT patients, the study is split into Cohort 1 (no LD) and Cohort 2 (fludarabine (30 mg/m2 x3) and cyclophosphamide (300mg/m2 x3)). To mitigate for the potential GvHD risk, cell dosing on study mirrors conventional donor lymphocyte infusion (DLI) schedules and is based on total CD3+ (not CAR T) cell numbers: Dose 1=1x106/kg CD3+ T cells; Dose 2= 3x106/kg CD3+ T cells; Dose 3= 1x107/kg CD3+ T cells. Results: As of 26 July 2019, 17 matched allo SCT donors were leukapheresed and 16 products were successfully manufactured and QP released. Patient demographics are as follows: (1) median patient age was 43y (range 19-64y); (2) 4/17 had prior blinatumomab and 5/17 prior inotuzumab ozogamicin; (3) 7/17 had myeloablative allo SCT and 10/17 reduced intensity allo SCT of which 6/17 were sibling donors and 12/17 were matched unrelated donors. No patients with haploidentical transplant were enrolled. To date, 12/16 patients have received at least 1 dose of CD19CAR T cells: 7/16 on Cohort 1 and 5/16 on Cohort 2 (2/16 are pending infusion on Cohort 2 and 2/16 died of fungal infection prior to infusion). Median follow-up for all 12 patients is 22.9 months (IQR 2.9-25.9; range 0.7 - 25.9). At the time of CAR T cell infusion, 7/12 patients were in morphological relapse with >5% leukemic blasts. Despite this, CD19CAR T cells were administered safely: only 2/12 patients experienced Grade 3 CRS (UPenn criteria), both in Cohort 1, which fully resolved with Tocilizumab and corticosteroids. No patients experienced ≥Grade 3 neurotoxicity and importantly, no patients experienced clinically significant GvHD. In Cohort 1 (7 patients), median peak CAR expansion by flow was 87 CD19CAR/uL blood whereas in Cohort 2 (5 patients to date), median peak CAR expansion was 1309 CD19CAR/uL blood. This difference is likely to reflect the use of LD in Cohort 2. CAR T cell persistence by qPCR in Cohort 1 is short, with demonstrable CAR in only 2/7 treated patients at Month 2. Data for Cohort 2 is immature, but this will also be reported at the meeting in addition to potential mechanisms underlying the short persistence observed in Cohort 1. Of the 10 response evaluable patients (2/12 pending marrow assessment), 9/10 (90%) achieved flow/molecular MRD negative CR at 6 weeks. 2/9 responders experienced CD19 negative relapse (one at M3, one at M5) and 3/9 responders experienced CD19+ relapse (one at M3, one at M9, one at M12). 4/10 (40%) response evaluable patients remain on study and continue in flow/molecular MRD negative remission at a median follow up of 11.9 months (range 2.9-25.9). Conclusions: Donor-derived matched allogeneic CD19 CAR T cells are straightforward to manufacture using the CliniMACS Prodigy and deliver excellent early remission rates, with 90% MRD negative CR observed at Week 6 in the absence of severe CAR associated toxicity or GvHD. Peak CAR expansion appears to be compromised by the absence of LD and this may lead to a higher relapse rate. Updated results from Cohorts 1 and 2 will be presented. Disclosures Roddie: Novartis: Consultancy; Gilead: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau. O'Reilly:Kite Gilead: Honoraria. Farzaneh:Autolus Ltd: Equity Ownership, Research Funding. Qasim:Autolus: Equity Ownership; Orchard Therapeutics: Equity Ownership; UCLB: Other: revenue share eligibility; Servier: Research Funding; Bellicum: Research Funding; CellMedica: Research Funding. Linch:Autolus: Membership on an entity's Board of Directors or advisory committees. Pule:Autolus: Membership on an entity's Board of Directors or advisory committees. Peggs:Gilead: Consultancy, Speakers Bureau; Autolus: Membership on an entity's Board of Directors or advisory committees.

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Introduction: CD19 CAR T therapy has advanced treatment of relapsed/refractory (r/r) Acute Lymphoblastic Leukemia (B-ALL). However, several challenges remain including: (1) considerable toxicity of CD19 CAR therapy; (2) the need for long-term persistence to deliver sustained response; (3) requirement for robust, cost effective manufacture. All current CD19 CARs for B-ALL use a high affinity CD19 binder, fmc63. We hypothesized that a CD19 binder with a lower affinity due to a fast binding off-rate, would result in more physiological T-cell activation, reduce toxicity and improve engraftment. Preliminary pediatric clinical data of a novel CD19 CAR (AUTO1) supports this assertion. In adults, prognosis for B-ALL is poor, patients are more vulnerable to CD19 CAR immunotoxicity and there is currently no CD19 CAR therapeutic with acceptable toxicity and durable efficacy. AUTO1 may be particularly well suited to this patient group. We describe preliminary data testing AUTO1 in adults with r/r B-ALL. Further, to address large-scale manufacture, we compare standard manufacturing with a closed semi-automated manufacture process. Methods: Manufacturing: AUTO1 utilizes non-mobilized autologous leucapheresate. The first 6 trial products were generated using a standard dynal bead/WAVE Bioreactor process and subsequent products using a closed CliniMACS® Prodigy/ TransACTTM process. Study design: ALLCAR19 (NCT02935257) is a phase I/II study recruiting subjects 16-65y with r/r B ALL. Lymphodepletion with fludarabine (30 mg/m2 x3) and cyclophosphamide (60mg/kg x1) is followed by split dose CAR T infusion (Day 0: if ≥20% BM blasts, infuse 10 x 106 CAR T; if <20% BM blasts, infuse 100 x 106 CAR T. Day +9: if no Grade 3-5 CRS/ CRES, infuse Dose 2, to a total dose of 410 x106 CAR T). Study endpoints include feasibility of manufacture, grade 3-5 toxicity and remission rates at 1 and 3 months. Results: To date (data cut off Dec 13 2018), 13 patients of median age 51y (range 18 - 63) were leucapheresed and 12 products manufactured. 9 infused patients (5 with ≥ 70% BM blasts) showed excellent peak CAR T expansion (median 367 CAR/uL blood). 0/9 patients had CRS ≥ Grade 3 by Lee criteria and 1/9 had CRES Grade 3 that resolved with steroids. 1/9 died of sepsis within the first month. Two patients are pending infusion. 7/8 (88%) response evaluable patients achieved CR at 1 month and all 7 had ongoing CAR T persistence and B cell aplasia at last follow up (median follow-up 2.5 months (range 1-7.5)). 1/7 had a CD19 negative relapse, 1/7 in molecular CR died of sepsis but 5/7 remain on study and continue in flow/molecular MRD negative remission. Conclusions: AUTO1 delivers excellent early remission rates and CAR expansion/ persistence. Despite high tumour burden, the safety profile compares favorably to other CD19 CARs, consistent with experience in the pediatric cohort. Updated results will be presented. Citation Format: Claire Roddie, Maeve A. O'Reilly, Juliana Dias Alves Pinto, Ketki Vispute, Fahetullah Syed, Lauren Nickolay, Yashma Pathak, Alexia Gali, Helen Lowe, Kim Champion, Graham Wheeler, Jo Olejnik, Maria Marzolini, Martin A. Pule, Karl S. Peggs. AUTO1, a novel fast off CD19CAR delivers durable remissions and prolonged CAR T cell persistence with low CRS or neurotoxicity in adult ALL [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT105.

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