Preliminary Data on Safety, Cellular Kinetics and Anti-Leukemic Activity of UCART19, an Allogeneic Anti-CD19 CAR T-Cell Product, in a Pool of Adult and Pediatric Patients with High-Risk CD19+ Relapsed/Refractory B-Cell Acute Lymphoblastic Leukemia
Authors: Benjamin Reuben , Graham Charlotte , Yallop Deborah , Jozwik Agnieszka , Ciocarlie Oana , Jain Nitin , Jabbour Elias J. , Maus Marcela V. , Frigault Matthiew , Boissel Nicolas , Larghero Jerome , Baruchel Andre , Mohty Mohamad , De Moerloose Barbara , Bloor Adrian , Frey Noelle V. , Zinaï Amina , Balandraud Svetlana , Philippe Anne , Fouliard Sylvain , Gauthier Ludiane , Pauly Jeanne , Konto Cyril , Bermingham Candy , Veys Paul , Qasim Waseem 
Published: October 2019

Abstract
Background
UCART19 is an allogeneic, genetically modified CAR T-cell product (anti-CD19 scFv- 41BB-CD3ζ) manufactured from healthy donor T cells, in which TRAC and CD52 genes have been knocked out to allow its administration in non-HLA matched patients (pts).
Aims
Preliminary safety/anti leukemic and cellular kinetics data of UCART19 administered to pediatric and adult patients with R/R B-ALL are reported.
Methods
Data of patients included in the ongoing CALM study (adult) and PALL study (pediatric) have been pooled. CALM is a dose-escalation study (approximate dose level [DL] 1: 1x105 cells/kg,DL2: 1x106 cells/kg, DL3: 3x106 cells/kg) and PALL is testing a unique dose of 1.1 to 2.3x106 cells/kg. Eligible patients presented with a morphological disease (>5%) or MRD load ≥1x10-3. A lymphodepleting regimen (LD) combining cyclophosphamide (1500 mg/m² in CALM, 120 mg/kg in PALL) and fludarabine (90 mg/m2 in CALM, 150 mg/m2 in PALL) without (FC) or with alemtuzumab (FCA) (1 mg/kg) was administered one week before UCART19 infusion on Day 0 (D0). Cellular kinetics of UCART19 was assessed by flow cytometry (flow) in CALM and by vector copy number in PALL.
Results
As of 15 July 2018, 20 pts had received at least one UCART19 infusion, including 13 pts in CALM (6 at DL1; 6 at DL2 and 1 at DL3) and 7 pts in PALL. Seventeen pts had completed D28 evaluation (1 pt died at D15, 2 pts have not reached D28 yet). Prior to LD, blasts % in the bone marrow (median [range]) was 6% [0-68%] in PALL and 25% [0-96%] in CALM. Seventeen pts received LD with FCA and 3 pts received LD with FC.
Safety was evaluable in 18/20 pts. Cytokine release syndrome (CRS) was reported in 17/18 pts and was mild and reversible in the majority of cases (2 G1, 12 G2, 2 G3, 1 G4). One pt died in context of CRS G4 and neutropenic sepsis. According to data available to date, the severity of CRS does not seem to follow the levels of serum cytokines (IL-6, IL-10 and IFNγ). Mild self-limited neurotoxicity events were reported in 6 pts (5 G1 and 1 G2). Two pts (1 infant and 1 adult) developed G1 acute skin GvHD (non-biopsy proven for 1 pt) that was reversible with steroids.
Grade 1-4 viral infections were reported in 8/18 pts. The majority of events recovered, except in 2 pts who died after allo-SCT in context of prolonged cytopenia (defined as persistent G4 beyond D42 post UCART19 infusion): 1 child with BK virus infection and 1 adult with adenovirus infection.
A further 4 pts developed prolonged cytopenia and all recovered after allo-SCT.
Cellular kinetic data was available for 18/20 pts. UCART19 was detectable in blood from D7. Peak expansion was observed in 72% (13/18) pts between D10 and D17, mostly at D14, with a median persistence duration of 28 days. Expansion occurred at each dose tested; without consistent relationship between administered dose and magnitude of expansion. One patient treated at DL2 presented a high expansion and a long persistence (very low detection by flow at D120). UCART19 persistence could not be assessed beyond D42-D56 in 3 pts because the remaining CARs were ablated by the transplant conditioning regimen. No expansion was observed in 5/18 pts in whom early lymphocyte recovery was detected from D14. Of these 5 pts, 3 did not receive alemtuzumab. The role of clinical status, tumor burden and lymphodepleting regimen on UCART19 expansion is under investigation.
Anti-leukemic activity was evaluable in 16/20 pts (1 pt died at D15, 1 pt was not assessed at D28, 2 pts have not yet reached D28). After UCART19 infusion, 88% of evaluable pts (14/16) achieved CR or CRi by D28 or D42 and 86% (12/14) of these pts were MRD negative (MRD- stands for < 1x10-4 copies) by flow or qPCR. Two out of 16 pts had no expansion and showed refractory disease. Among 12 pts achieving MRD-, 5 pts remain in molecular remission 4.5 to 16.4 months post UCART19. In total, 11 pts underwent allo-SCT (5 in PALL and 6 in CALM). Preliminary data suggests that in the majority of pts, anti-leukemic activity is linked with CAR expansion.
Conclusion
Pooled data of 20 pts show an acceptable and manageable safety profile of UCART19. Severe CRS was reported in 15%. Only 2 G1 cutaneous acute GvHD were observed and no severe neurotoxicity was reported. In this heavily pre-treated population, 88% pts of evaluable pts (14/16) achieved CR or CRi of which 86% (12/14) achieved MRD-. All pts who achieved MRD- had evidence of UCART19 expansion. Updated data, including data for the highest dose level in CALM study, will be presented (NCT 02746952, NCT02808442).

Disclosures
Benjamin: Servier: Research Funding; Amgen: Honoraria; Takeda: Honoraria; Novartis: Honoraria; Gilead: Honoraria; Celgene: Honoraria; Pfizer: Research Funding. Graham:Servier: Research Funding. Yallop:Pfizer: Consultancy; Servier: Other: Travel funding. Jozwik:Servier: Honoraria, Research Funding. Ciocarlie:Servier: Research Funding. Jain:Cellectis: Research Funding; Seattle Genetics: Research Funding; Astra Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Research Funding; ADC Therapeutics: Research Funding; Astra Zeneca: Research Funding; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Infinity: Research Funding; Servier: Research Funding; ADC Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; BMS: Research Funding; Adaptive Biotechnologies: 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; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novimmune: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologioes: Research Funding; Seattle Genetics: Research Funding; Genentech: Research Funding; Astra Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novimmune: Honoraria, Membership on an entity's Board of Directors or advisory committees; Verastem: Research Funding; Adaptive Biotechnologioes: Research Funding; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics: Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Research Funding; Pharmacyclics: Research Funding; Cellectis: Research Funding; Pfizer: Research Funding; Verastem: Research Funding; BMS: Research Funding; Servier: Research Funding; Infinity: Research Funding; Astra Zeneca: Research Funding; Celgene: Research Funding; Genentech: Research Funding; Incyte: Research Funding; Abbvie: Research Funding; Pfizer: Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees. Maus:adaptimmune: Consultancy; novartis: Consultancy; windmil therapeutics: Consultancy; agentus: Consultancy, Research Funding; crispr therapeutics: Consultancy, Research Funding; kite therapeutics: Consultancy, Research Funding. Boissel:Novartis Pharmaceuticals Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Consultancy, Membership on an entity's Board of Directors or advisory committees. Larghero:Gilead: Consultancy. Baruchel:Novartis: Membership on an entity's Board of Directors or advisory committees; Shire: Research Funding; Roche: Consultancy; Jazz Pharmaceuticals: Consultancy, Honoraria, Other: Travel, accommodations or expenses; Amgen: Consultancy; Servier: Consultancy; Celgene: Consultancy. Mohty:Takeda: Honoraria, Speakers Bureau; Molmed: Consultancy; Servier: Consultancy; Jazz Pharmaceuticals: Honoraria, Research Funding, Speakers Bureau; MaaT Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Honoraria; Janssen: Honoraria, Research Funding, Speakers Bureau; Sanofi: Consultancy, Honoraria, Research Funding, Speakers Bureau; Bristol Myers: Consultancy, Research Funding; Amgen: Consultancy, Honoraria. Bloor:Janssen: Research Funding; AbbVie: Research Funding. Frey:Novartis: Consultancy; Servier Consultancy: Consultancy. Konto:Pfizer: Equity Ownership. Veys:Pfizer: Honoraria; Servier: Research Funding; Novartis: Honoraria. Qasim:Bellicum: Research Funding; Autolus: Equity Ownership; Orchard: Equity Ownership; Servier: Research Funding.