UCART19, a first-in-class allogeneic anti-CD19 chimeric antigen receptor T-cell therapy for adults with relapsed or refractory B-cell acute lymphoblastic leukaemia (CALM): a phase 1, dose-escalation trial.

BACKGROUND: The prognosis for adults with relapsed or refractory B-cell acute lymphoblastic leukaemia remains poor. UCART19, an allogeneic genome-edited anti-CD19 chimeric antigen receptor (CAR) T-cell product derived from healthy donors and available for immediate clinical use, offers a potential therapeutic option for such patients. The CALM trial is a first-in-human study evaluating the safety and antileukaemic activity of UCART19 in adult patients with relapsed or refractory B-cell acute lymphoblastic leukaemia. METHODS: This phase 1, open-label study was conducted at eight centres across France, the UK, the USA, and Japan. Adult patients aged 16-70 years with CD19-positive relapsed or refractory B-cell acute lymphoblastic leukaemia who had morphological relapse or a minimal residual disease level of at least 1 × 10-3 and had exhausted standard treatment options were enrolled in the study, which comprised a dose-escalation phase of up to three UCART19 doses followed by a safety expansion phase. Patients underwent lymphodepletion with fludarabine (30 mg/m2 per day intravenously for 3 days) and cyclophosphamide (500 mg/m2 per day intravenously for 3 days) with or without alemtuzumab (1 mg/kg or 40 mg or 60 mg over 5 days) and received UCART19 doses of 6 × 106, 6-8 × 107, or 1·8-2·4 × 108 total CAR T cells intravenously, followed by safety evaluation and disease response assessments. The primary endpoint was incidence and severity of adverse events. Secondary endpoints were the overall response rate, duration of response, relapse-free survival, progression-free survival, and overall survival. This trial is registered with ClinicalTrials.gov (NCT02746952) and is complete. FINDINGS: Between Aug 1, 2016, and June 30, 2020, 25 patients were enrolled in the study and treated with UCART19. Median duration of follow-up was 12·8 months (IQR 2·8-24·8). Median age was 37 years (IQR 28-45). 14 (56%) patients were male and 11 (44%) female. 17 (68%) patients were White, two (8%) Black, two (8%) Asian, and four (16%) from other racial or ethnic groups. Three patients developed dose-limiting toxicities (one at each dose level); one had grade 4 cytokine release syndrome and two had grade 4 prolonged cytopenias. Grade 3 or higher cytokine release syndrome was reported in six (24%) patients and grade 3 or higher neurological toxicity in one (4%) patient. Grade 3 or higher infections occurred in seven (28%) patients, and grade 4 prolonged cytopenia in four (16%) patients. Two (8%) patients developed grade 1 acute cutaneous graft-versus-host disease. 14 patients died, nine from progressive disease and five from infections or other complications, of which four were considered to be related to UCART19 or lymphodepletion, or both. After a median of follow-up of 12·8 months (IQR 2·8-24·8), overall response rate was 48% (95% CI 28-69; 12 of 25 patients), duration of response and median relapse-free survival were 7·4 months (95% CI 1·8 to not calculable), progression-free survival was 2·1 months (95% CI 1·2-2·8), and overall survival was 13·4 months (95% CI 4·8-23·0). INTERPRETATION: UCART19 had a manageable safety profile, and showed evidence of antileukaemic activity in heavily pretreated adult patients with relapsed or refractory B-cell acute lymphoblastic leukaemia. This study shows that allogeneic off-the-shelf CAR T cells can be used safely to treat patients with relapsed B-cell acute lymphoblastic leukaemia. FUNDING: Servier.

Mechanistic Modeling of the Interplay Between Host Immune System, IL-7 and UCART19 Allogeneic CAR-T Cells in Adult B-cell Acute Lymphoblastic Leukemia.

Chimeric antigen receptor (CAR)-T cell therapies have shown tremendous results against various hematologic cancers. Prior to cell infusion, a host preconditioning regimen is required to achieve lymphodepletion and improve CAR-T cell pharmacokinetic exposure, leading to greater chances of therapeutic success. To better understand and quantify the impact of the preconditioning regimen, we built a population-based mechanistic pharmacokinetic-pharmacodynamic model describing the complex interplay between lymphodepletion, host immune system, homeostatic cytokines, and pharmacokinetics of UCART19, an allogeneic product developed against CD19+ B cells. Data were collected from a phase I clinical trial in adult relapsed/refractory B-cell acute lymphoblastic leukemia and revealed three different UCART19 temporal patterns: (i) expansion and persistence, (ii) transient expansion with subsequent rapid decline, and (iii) absence of observed expansion. On the basis of translational assumptions, the final model was able to capture this variability through the incorporation of IL-7 kinetics, which are thought to be increased owing to lymphodepletion, and through an elimination of UCART19 by host T cells, which is specific to the allogeneic context. Simulations from the final model recapitulated UCART19 expansion rates in the clinical trial, confirmed the need for alemtuzumab to observe UCART19 expansion (along with fludarabine cyclophosphamide), quantified the importance of allogeneic elimination, and suggested a high impact of multipotent memory T-cell subpopulations on UCART19 expansion and persistence. In addition to supporting the role of host cytokines and lymphocytes in CAR-T cell therapy, such a model could help optimizing the preconditioning regimens in future clinical trials. Significance: A mathematical mechanistic pharmacokinetic/pharmacodynamic model supports and captures quantitatively the beneficial impact of lymphodepleting patients before the infusion of an allogeneic CAR-T cell product. Mediation through IL-7 increase and host T lymphocytes decrease is underlined, and the model can be further used to optimize CAR-T cell therapies lymphodepletion regimen.

Clinical Pharmacology and Determinants of Response to UCART19, an Allogeneic Anti-CD19 CAR-T Cell Product, in Adult B-cell Acute Lymphoblastic Leukemia.

Background: UCART19 is an "off-the-shelf" genome-edited anti-CD19 chimeric antigen receptor (CAR)-T cell product, manufactured from unrelated healthy donor cells. Methods: UCART19 was administered to 25 adult patients with relapsed or refractory (R/R) B-cell acute lymphoblastic leukemia (B-ALL) in the CALM trial. All patients underwent lymphodepletion with fludarabine and cyclophosphamide ± alemtuzumab and received one of three ascending doses of UCART19. Given the allogeneic nature of UCART19, we analyzed the impact of lymphodepletion, HLA disparities, and host immune system reconstitution on its kinetics, along with other factors known to affect autologous CAR-T cell clinical pharmacology. Results: Responder patients (12/25) had higher UCART19 expansion (C max) and exposure (AUCTlast) than nonresponders (13/25), as measured by transgene levels in peripheral blood. The persistence of CAR+ T cells did not exceed 28 days in 10/25 patients and lasted beyond 42 days in 4/25. No significant correlation was found between UCART19 kinetics and administered cell dose, patient and product characteristics or HLA disparities. However, the number of prior lines of therapy and absence of alemtuzumab negatively impacted UCART19 expansion and persistence. Alemtuzumab exposure positively affected IL7 and UCART19 kinetics, while negatively correlating with host T lymphocyte AUC0-28. Conclusions: UCART19 expansion is a driver of response in adult patients with R/R B-ALL. These results shed light on the factors associated with UCART19 kinetics, which remain highly affected by the impact of alemtuzumab on IL7 and host-versus-graft rejection. Significance: First description of the clinical pharmacology of a genome-edited allogeneic anti-CD19 CAR-T cell product showing the crucial role of an alemtuzumab-based regimen in sustaining UCART19 expansion and persistence through increased IL7 availability and decreased host T lymphocyte population.

Genome-edited, donor-derived allogeneic anti-CD19 chimeric antigen receptor T cells in paediatric and adult B-cell acute lymphoblastic leukaemia: results of two phase 1 studies.

BACKGROUND: Genome-edited donor-derived allogeneic anti-CD19 chimeric antigen receptor (CAR) T cells offer a novel form of CAR-T-cell product that is available for immediate clinical use, thereby broadening access and applicability. UCART19 is one such product investigated in children and adults with relapsed or refractory B-cell acute lymphoblastic leukaemia. Two multicentre phase 1 studies aimed to investigate the feasibility, safety, and antileukaemic activity of UCART19 in children and adults with relapsed or refractory B-cell acute lymphoblastic leukaemia. METHODS: We enrolled paediatric or adult patients in two ongoing, multicentre, phase 1 clinical trials to evaluate the safety and antileukaemic activity of UCART19. All patients underwent lymphodepletion with fludarabine and cyclophosphamide with or without alemtuzumab, then children received UCART19 at 1·1-2·3 × 106 cells per kg and adults received UCART19 doses of 6 × 106 cells, 6-8 × 107 cells, or 1·8-2·4 × 108 cells in a dose-escalation study. The primary outcome measure was adverse events in the period between first infusion and data cutoff. These studies were registered at ClinicalTrials.gov, NCT02808442 and NCT02746952. FINDINGS: Between June 3, 2016, and Oct 23, 2018, seven children and 14 adults were enrolled in the two studies and received UCART19. Cytokine release syndrome was the most common adverse event and was observed in 19 patients (91%); three (14%) had grade 3-4 cytokine release syndrome. Other adverse events were grade 1 or 2 neurotoxicity in eight patients (38%), grade 1 acute skin graft-versus-host disease in two patients (10%), and grade 4 prolonged cytopenia in six patients (32%). Two treatment-related deaths occurred; one caused by neutropenic sepsis in a patient with concurrent cytokine release syndrome and one from pulmonary haemorrhage in a patient with persistent cytopenia. 14 (67%) of 21 patients had a complete response or complete response with incomplete haematological recovery 28 days after infusion. Patients not receiving alemtuzumab (n=4) showed no UCART19 expansion or antileukaemic activity. The median duration of response was 4·1 months with ten (71%) of 14 responders proceeding to a subsequent allogeneic stem-cell transplant. Progression-free survival at 6 months was 27%, and overall survival was 55%. INTERPRETATION: These two studies show, for the first time, the feasibility of using allogeneic, genome-edited CAR T cells to treat patients with aggressive leukaemia. UCART19 exhibited in-vivo expansion and antileukaemic activity with a manageable safety profile in heavily pretreated paediatric and adult patients with relapsed or refractory B-cell acute lymphoblastic leukaemia. The results this study are an encouraging step forward for the field of allogeneic CAR T cells, and UCART19 offers the opportunity to treat patients with rapidly progressive disease and where autologous CAR-T-cell therapy is unavailable. FUNDING: Servier.