Durable Responses and Low Toxicity After Fast Off-Rate CD19 Chimeric Antigen Receptor-T Therapy in Adults With Relapsed or Refractory B-Cell Acute Lymphoblastic Leukemia

Abstract

Purpose: Prognosis for adult B-cell acute lymphoblastic leukemia (B-ALL) is poor, and there are currently no licensed CD19 chimeric antigen receptor (CAR) therapeutics. We developed a novel second-generation CD19-CAR (CAT19-41BB-Z) with a fast off rate, designed for more physiologic T-cell activation to reduce toxicity and improve engraftment. We describe the multicenter phase I ALLCAR19 (NCT02935257) study of autologous CAT19-41BB-Z CAR T cells (AUTO1) in relapsed or refractory (r/r) adult B-ALL.

Methods: Patients age ≥ 16 years with r/r B-ALL were eligible. Primary outcomes were toxicity and manufacturing feasibility. Secondary outcomes were depth of response at 1 and 3 months, persistence of CAR-T, incidence and duration of hypogammaglobulinemia and B-cell aplasia, and event-free survival and overall survival at 1 and 2 years.

Results: Twenty-five patients were leukapheresed, 24 products were manufactured, and 20 patients were infused with AUTO1. The median age was 41.5 years; 25% had prior blinatumomab, 50% prior inotuzumab ozogamicin, and 65% prior allogeneic stem-cell transplantation. At the time of preconditioning, 45% had ≥ 50% bone marrow blasts. No patients experienced ≥ grade 3 cytokine release syndrome; 3 of 20 (15%) experienced grade 3 neurotoxicity that resolved to ≤ grade 1 within 72 hours with steroids. Seventeen of 20 (85%) achieved minimal residual disease-negative complete response at month 1, and 3 of 17 underwent allogeneic stem-cell transplantation while in remission. The event-free survival at 6 and 12 months was 68.3% (42.4%-84.4%) and 48.3% (23.1%-69.7%), respectively. High-level expansion (Cmax 127,152 copies/µg genomic DNA) and durable CAR-T persistence were observed with B-cell aplasia ongoing in 15 of 20 patients at last follow-up.

Conclusion: AUTO1 demonstrates a tolerable safety profile, high remission rates, and excellent persistence in r/r adult B-ALL. Preliminary data support further development of AUTO1 as a stand-alone treatment for r/r adult B-ALL.

Conflict of interest statement

Claire RoddieHonoraria: Novartis Pharmaceuticals UK Ltd, Gilead SciencesConsulting or Advisory Role: Novartis Pharmaceuticals UK LtdSpeakers' Bureau: Novartis Pharmaceuticals UK Ltd, Gilead SciencesTravel, Accommodations, Expenses: Gilead Sciences Maeve A. O'ReillyHonoraria: Kite/Gilead, NovartisConsulting or Advisory Role: Kite/GileadTravel, Accommodations, Expenses: Kite/Gilead Ketki VisputeEmployment: Quell TherapeuticsStock and Other Ownership Interests: Quell TherapeuticsTravel, Accommodations, Expenses: Quell Therapeutics John A. HartleyEmployment: AstraZenecaStock and Other Ownership Interests: ADC TherapeuticsConsulting or Advisory Role: ADC TherapeuticsResearch Funding: ADC TherapeuticsPatents, Royalties, Other Intellectual Property: Several patents with ADC Therapeutics Laura Clifton-HadleyResearch Funding: Various pharmaceutical companies Graham WheelerHonoraria: AstraZeneca Adrian BloorHonoraria: AbbVie, Janssen, Novartis, Gilead SciencesConsulting or Advisory Role: AbbVieSpeakers' Bureau: Novartis, AbbVieTravel, Accommodations, Expenses: AbbVie, Novartis, Gilead Sciences, Janssen David IrvineHonoraria: Kite, a Gilead companyConsulting or Advisory Role: Novartis Pharmaceuticals UK LtdTravel, Accommodations, Expenses: Novartis Pharmaceuticals UK Ltd, Jazz Pharmaceuticals Leigh WoodHonoraria: Gilead Sciences, Celgene Farzin FarzanehEmployment: ViroCell BiologicsStock and Other Ownership Interests: Autolus Therapeutics, Dawn Therapeutics, ViroCell Biologics LtdConsulting or Advisory Role: Autolous Therapeutics, Dawn TherapeuticsPatents, Royalties, Other Intellectual Property: IP payments received by my Employer (King's College London), a proportion of which was transferred to me, in line with my employer's established policies Mark LowdellEmployment: Autolomous, INmune Bio Inc, Achilles TherapeuticsStock and Other Ownership Interests: INmune Bio Inc, Achilles TherapeuticsConsulting or Advisory Role: Avectas Ltd, Autolus Ltd, Northwest Bio IncResearch Funding: INmune Bio David LinchEmployment: Autolus LtsLeadership: Autous LtdStock and Other Ownership Interests: Autolus LtdConsulting or Advisory Role: Autolus Ltd Martin A. PuleEmployment: Autolus TherapeuticsLeadership: AutolusStock and Other Ownership Interests: Autolus Therapeutics, Mana TherapeuticsConsulting or Advisory Role: Mana TherapeuticsResearch Funding: Autolus TherapeuticsPatents, Royalties, Other Intellectual Property: Royalty share from patents filed by UCL, some of which have been licensed to Autolus Therapeutics, Cellectis, and TC Biopharm Karl S. PeggsEmployment: Achilles TherapeuticsLeadership: Achilles TherapeuticsStock and Other Ownership Interests: Achilles Therapeutics, AutolusConsulting or Advisory Role: AutolusPatents, Royalties, Other Intellectual Property: Patent related to the use of depleting nonblocking anti-CD25 antibody filed by UCL, now under development by RocheNo other potential conflicts of interest were reported.

Figures

FIG 1.

ALLCAR19 study design and recruitment. (A) ALLCAR19 trial schema. Red circles with a pink rim symbolize patients with both ≤ 20% and > 20% blasts infused with CAR-T on day 0 and again on day 9. The small pink rectangles indicate the number of fludarabine doses administered (3 doses; 30 mg/m2) and the small red rectangle indicates a single dose of cyclophosphamide (60 mg/kg) was administered. (B) Flow diagram of patients on ALLCAR19. BM, bone marrow; CAR, chimeric antigen receptor; CRS, cytokine release syndrome; EoS, end of study; ICANS, immune effector cell–associated neurotoxicity syndrome.

FIG 2.

Toxicity and cytokine secretion on ALLCAR19. (A) Example flow plots of CAR T cells in the CSF at day 28 in patients with and without a history of grade 3 ICANS; (B) %CAR of CD3 in the CSF at day 28 is significantly higher in patients with ≥ grade 2 ICANS than in those without (Mann-Whitney; **P = .004); (C) cytokine analysis on ALLCAR19 was assessed by cytometric bead array during the first 28 days after AUTO1 infusion in all 20 patients; PB IL-6, IL-10, and IFNg concentrations for individual patients are shown over time to day 28. The y-axis denotes serum level in pg/mL (lower limit of detection, 20 pg/mL). The red lines indicate patients with ≥ 20% blasts pre-LD, and the black lines indicate patients with < 20% blasts. This clearly shows that although the overall cytokine secretion on ALLCAR19 is low, detectable cytokine production is almost exclusively in the context of ≥ 20% blasts. (D) Panel of peak PB cytokine concentration for all patients, illustrating the low cytokine secretion observed in this study. (E) Correlation between peak IL-6 (Mann-Whitney; ***P = .0007) and peak ferritin (Mann-Whitney; **P = .0047) with high disease burden (≥ 20% BM blasts) compared with low disease burden (< 20% BM blasts). BM, bone marrow; CAR, chimeric antigen receptor; D, day; ICANS, immune effector cell–associated neurotoxicity syndrome; IFN, interferon; IL, interleukin; LD, lymphodepletion; PB, peripheral blood; TNF, tumor necrosis factor.

FIG 3.

CAR T-cell persistence on ALLCAR19. (A) CAR T cells in the PB by flow cytometry of an exemplary patient over a 9-month follow-up; (B) transgene-specific qPCR analysis of CAT19-41BB-Z in the PB for all patients; (C) flow cytometric analysis of CAR T cells in the PB for all patients; (D) B-cell aplasia on ALLCAR19; (E) Kaplan-Meier analysis of B-cell aplasia; (F) peak expansion by qPCR was not correlated with total AUTO1 dose but was strongly associated with disease burden (patients with ≥ 20% blasts had significantly higher expansion than those with P ≤ .0001] and with ≥ grade 2 CRS [Mann-Whitney; **P = .011], but not with ≥ grade 2 ICANS). CAR, chimeric antigen receptor; CRS, cytokine release syndrome; D, day; ICANS, immune effector cell–associated neurotoxicity syndrome; IgG, immunoglobulin G; M, month; ns, not significant; PB, peripheral blood; qPCR, quantitative polymerase chain reaction.

FIG 4.

Response rates and survival on ALLCAR19. (A) Swimmers' plot showing responses of individual patients infused with AUTO1, duration of response, and nature of relapse and deaths; the median follow-up was 21.7 months; (B) EFS by morphologic (morph. only) and by morphologic and/or molecular relapse (morph. or mol.), defined as time from date of infusion to date of either morphologic relapse (or molecular relapse) or all-cause mortality, whichever occurred first. Patients were censored at date of last observed follow-up or date of allo-SCT received; (C) Kaplan-Meier plot of OS in all infused patients. For patients still on study and in follow-up, date of data cutoff (February 26, 2021) was used as the date they were last observed for OS and EFS analyses. allo-SCT, allogeneic stem-cell transplantation; CR, complete response; EFS, event-free survival; MRD, minimal residual disease; OS, overall survival; PCR, polymerase chain reaction.