ALBERT

Description: Autologous T-cells engineered with chimeric antigen receptors (CARs) against CD19 are proving to be an efficacious immunotherapy for patients with relapsed or refractory B-cell acute lymphoblastic leukemia (B-ALL). At present, CAR technology is administered through the custom-made manufacturing of therapeutic products from each patient's own T-cells. However, this patient-specific autologous paradigm is a significant limiting factor in the large-scale deployment of CAR technology. In this study, we utilized allogeneic "off-the-shelf" engineered CAR T-cells from third-party healthy donors. The CD22 surface antigen is commonly expressed in B-ALL patients as well as in healthy B-cells. Here, its potential as a CAR target was investigated using allogeneic off-the shelf engineered CAR T-cells against human CD22 (UCART22). UCART22 cells harbor surface expression of an anti-CD22 CAR (CD22 scFv-41BB-CD3z) and the RQR8 ligand, a safety feature rendering the T-cells sensitive to the monoclonal antibody rituximab. To reduce the potential for alloreactivity, the cell surface expression of the T-cell receptor (TCR) is abrogated through the inactivation of the TCRα constant (TRAC) gene using Cellectis' TALEN® gene-editing technology. The level of CD22 cell surface molecules was measured using BD Quantbrite beads for both patient peripheral blood samples and B-ALL cell lines. B-ALL cell lines (n=8) expressed a greater amount of CD22 molecules per cell than patient samples (n=14) (5,028 +/- 1,342 compared to 951 +/-160 molecules/cell, p=0.044), with highest expression of CD22 in two Ph-like B-ALL cell lines (MUTZ5, shown in Figure1A and MHH-CALL4). The in vitro cytotoxic activity of UCART22 cells was evaluated by co-culturing UCART22 or non-transduced CAR(-) TCRαβ(-) control T-cells (NTD) with B-ALL cell lines and primary human samples, at a maximum 10:1 effector to target ratio (represented in Figure1B). Using flow cytometry, significant antigen-specific cytotoxic activity of UCART22 cells was found compared to NTD controls and correlated with CD22 expression factored by the %kolmogorov-smirnov max difference in CD22-PE fluorescence compared to unstained controls (Pearson correlation r-squared for cell lines= 0.6850, p=0.0001 and r-squared for patient samples=0.6204, p=0.0008). Secretion of 13 cytokines was measured after 1:1 co-incubation of effector and target cells. UCART22 cells stimulated by CD22(+) B-ALL, but not NTD cells, secreted high levels of IFNγ, TNFα, IL-5, IL-17A and IL-17F in the culture supernatants, with cytokine levels being proportionate to CD22 abundance (represented in Figure1C). In addition, immune compromised mice engrafted with Daudi cells, a CD22(+) expressing Burkitt's lymphoma cell line, were treated with UCART22 cells. Treatment doses of 1-10x10^6 cells per mouse reduced disease burden (Figure 1D), measured by bioluminescence imaging, and extended survival in a dose-dependent fashion compared to saline or NTD treated controls. Additional PDX studies using B-ALL patient derived xenografts are ongoing and will be presented. Altogether, these results show supporting evidence for the future use of allogenic UCART22 in B-ALL immunotherapy. Disclosures Schiffer-Manniou: Cellectis SA: Employment. Filipe: Cellectis: Employment. Gouble: Cellectis SA: Employment. Galetto: Cellectis SA: Employment. Jain: ADC Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Verastem: Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Research Funding; Abbvie: Research Funding; Incyte: Research Funding; Genentech: Research Funding; Novimmune: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees. Jabbour: Bristol-Myers Squibb: Consultancy. Smith: Cellectis Inc: Employment.

Description: Introduction: UCART22 is a genetically modified T-cell product manufactured from non-HLA matched healthy donor cells. Donor derived T-cells are transduced using a lentiviral vector to express anti-CD22 CAR (anti-CD22 scFv-41BB-CD3ζ) and are further modified using Cellectis' TALEN® technology to disrupt the T-cell receptor alpha constant (TRAC) and CD52 genes. These modifications minimize the risk of graft versus host disease (GvHD) and allow the use of anti-CD52 directed drugs in the lymphodepletion (LD). UCART22 demonstrated antigen-specific cytotoxic activity against B-ALL cell lines and primary human samples in vitro. In a preclinical in vivo model, immune compromised mice engrafted with Daudi cells, a CD22(+) expressing Burkitt's lymphoma cell line, treated with UCART22 cells demonstrated extended survival in a dose-dependent fashion compared to controls (Wells et al, Blood 2017, abstr. 208). Methods: BALLI-01 (NCT04150497) is a Phase I open-label dose-escalation study designed to assess the safety, the maximum tolerated dose (MTD), and preliminary anti-leukemia activity of UCART22 in patients (pts) with R/R B-ALL. Additional endpoints include characterization of the expansion, trafficking and persistence of UCART22. Eligible pts include adults (18-65 years) with adequate organ function, ECOG PS ≤1, and B-ALL blast CD22 expression ≥ 90% by flow cytometry. Pts must have received at least one standard chemotherapy regimen and one salvage regimen. Protocol therapy includes LD regimens of cyclophosphamide and fludarabine (FC) or FC with alemtuzumab (FCA), followed by a single dose of UCART22 at 1 of 4 dose levels (DL). DLT is assessed at the end of the 28-day DLT observation period. Anti-leukemia activity is based on investigator assessment using NCCN ALL response criteria. UCART22 expansion and persistence are assessed in blood and bone marrow (BM) by flow cytometry, vector copy number and chimerism analysis by qPCR. Immune reconstitution is assessed by flow cytometry. Results: As of 01 July, 2020, 7 pts signed consent, 1 pt failed screening, and 6 pts (4 male; median age 24 [22-52]) were enrolled. Five pts received UCART22 infusion [DL1: 1X105 cells/kg (n=3), DL2: 1x106 cells/kg (n=2)] after FC LD (cyclophosphamide 1g/m2 x 3 days and fludarabine 30 mg/m2 x 4 days). 1 pt discontinued prior to UCART22 administration due to AE (hypoxia due to pneumonitis related to LD). Median number of prior therapies was 3 [2-4]. Median baseline BM blasts % prior to LD was 35% [5-78.4%]. Among 5 pts treated, 4 pts experienced 10 treatment-related treatment-emergent AEs (TEAEs): bilirubin increased (n=1, G4); ALP increased (n=1, G2); hypotension (n=1, G2); CRS (n=2, G2; n=1, G1); headache (n=1, G1); lymph node pain (n=1, G1); fever (n=1, G1); transaminitis (n=1, G1). Two pts experienced serious TEAEs: 1 pt had G3 febrile neutropenia and G3 peri-hepatic hematoma; 1 pt had G4 bleeding and G5 sepsis in the context of PD. No pts had treatment-related serious TEAE, GvHD, ICANS, protocol-defined DLT nor AE of special interest. 2 pts at DL1 achieved best response at day 28 of CR with incomplete hematologic recovery (CRi); and 1 pt at DL2 had initial significant reduction in BM blasts [40% (D -1) to 13% (D 28)] and then progressed. Host T cells recovery was observed in all pts within the DLT period (range D17-D28). Correlative analysis of UCART22 expansion and persistence is ongoing. Conclusion: UCART22 demonstrated no unexpected toxicities at doses of 1x105/kg and 1x106/kg with FC LD regimen. CRS was observed in 3 patients, all grade 1-2, and was manageable. No pts had DLT, GvHD nor ICANS. Two pts achieved CRi. As host immune recovery was observed early, the addition of alemtuzumab to FC LD is now being explored in ongoing treatment cohorts to potentially achieve a deeper and more sustained T-cell depletion and promote expansion and persistence of UCART22. Enrollment is ongoing. Disclosures Jain: Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Research Funding; ADC Therapeutics: Research Funding; Pfizer: Research Funding; BMS: Research Funding; AstraZeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Cellectis: Research Funding; Fate Therapeutics: Research Funding; Precision Bioscienes: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Aprea Therapeutics: Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BeiGene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Roboz:Pfizer: Consultancy; Novartis: Consultancy; Janssen: Consultancy; Celgene: Consultancy; Astex: Consultancy; Amphivena: Consultancy; Agios: Consultancy; MEI Pharma: Consultancy; Abbvie: Consultancy; Array BioPharma: Consultancy; Bayer: Consultancy; Celltrion: Consultancy; Eisai: Consultancy; Jazz: Consultancy; Roche/Genentech: Consultancy; Sandoz: Consultancy; Actinium: Consultancy; Argenx: Consultancy; Astellas: Consultancy; Daiichi Sankyo: Consultancy; AstraZeneca: Consultancy; Orsenix: Consultancy; Otsuka: Consultancy; Takeda: Consultancy; Trovagene: Consultancy; Cellectis: Research Funding; Jasper Therapeutics: Consultancy; Epizyme: Consultancy; Helsinn: Consultancy. Konopleva:Eli Lilly: Research Funding; Amgen: Consultancy; F. Hoffmann La-Roche: Consultancy, Research Funding; Reata Pharmaceutical Inc.;: Patents & Royalties: patents and royalties with patent US 7,795,305 B2 on CDDO-compounds and combination therapies, licensed to Reata Pharmaceutical; Ablynx: Research Funding; Stemline Therapeutics: Consultancy, Research Funding; Ascentage: Research Funding; AstraZeneca: Research Funding; Sanofi: Research Funding; Calithera: Research Funding; Kisoji: Consultancy; Cellectis: Research Funding; AbbVie: Consultancy, Research Funding; Rafael Pharmaceutical: Research Funding; Forty-Seven: Consultancy, Research Funding; Agios: Research Funding; Genentech: Consultancy, Research Funding. Liu:BMS: Research Funding; Karyopharm: Research Funding; Agios: Honoraria, Other: Regional Advisory board meeting. Jabbour:Pfizer: Other: Advisory role, Research Funding; Takeda: Other: Advisory role, Research Funding; Genentech: Other: Advisory role, Research Funding; BMS: Other: Advisory role, Research Funding; Amgen: Other: Advisory role, Research Funding; AbbVie: Other: Advisory role, Research Funding; Adaptive Biotechnologies: Other: Advisory role, Research Funding. Poirot:Cellectis SA: Current Employment. Schiffer-Manniou:Cellectis SA: Current Employment. Gouble:Cellectis SA: Current Employment, Current equity holder in publicly-traded company. Haider:Cellectis SA: Current Employment. Zernovak:Cellectis SA: Current Employment. Larson:Astellas, Celgene, Daiichi Sankyo, Novartis, Rafael Pharmaceuticals, Cellectis, Forty Seven: Research Funding; Novartis, Takeda, CVS/Caremark, Celgene, Amgen, Epizyme: Consultancy. OffLabel Disclosure: UCART22 is not FDA approved