Use of CAR-Transduced Natural Killer Cells in CD19-Positive Lymphoid Tumors

Abstract

Background: Anti-CD19 chimeric antigen receptor (CAR) T-cell therapy has shown remarkable clinical efficacy in B-cell cancers. However, CAR T cells can induce substantial toxic effects, and the manufacture of the cells is complex. Natural killer (NK) cells that have been modified to express an anti-CD19 CAR have the potential to overcome these limitations.

Methods: In this phase 1 and 2 trial, we administered HLA-mismatched anti-CD19 CAR-NK cells derived from cord blood to 11 patients with relapsed or refractory CD19-positive cancers (non-Hodgkin's lymphoma or chronic lymphocytic leukemia [CLL]). NK cells were transduced with a retroviral vector expressing genes that encode anti-CD19 CAR, interleukin-15, and inducible caspase 9 as a safety switch. The cells were expanded ex vivo and administered in a single infusion at one of three doses (1×10⁵, 1×10⁶, or 1×10⁷ CAR-NK cells per kilogram of body weight) after lymphodepleting chemotherapy.

Results: The administration of CAR-NK cells was not associated with the development of cytokine release syndrome, neurotoxicity, or graft-versus-host disease, and there was no increase in the levels of inflammatory cytokines, including interleukin-6, over baseline. The maximum tolerated dose was not reached. Of the 11 patients who were treated, 8 (73%) had a response; of these patients, 7 (4 with lymphoma and 3 with CLL) had a complete remission, and 1 had remission of the Richter's transformation component but had persistent CLL. Responses were rapid and seen within 30 days after infusion at all dose levels. The infused CAR-NK cells expanded and persisted at low levels for at least 12 months.

Conclusions: Among 11 patients with relapsed or refractory CD19-positive cancers, a majority had a response to treatment with CAR-NK cells without the development of major toxic effects. (Funded by the M.D. Anderson Cancer Center CLL and Lymphoma Moonshot and the National Institutes of Health; ClinicalTrials.gov number, NCT03056339.).

Figure 1.. Clinical Response to CAR-NK Therapy and Postremission Treatments.

Shown are the clinical outcomes and subsequent therapies for the 11 patients who were treated with anti-CD19 chimeric antigen receptor (CAR) natural killer (NK) cells in our study. Responses were confirmed and assessed according to the 2018 criteria of the International Workshop on Chronic Lymphocytic Leukemia and the 2014 Lugano classification for non-Hodgkin’s lymphoma. The indicated responses include partial response (PR) and complete response (CR); MRD denotes minimal residual disease, as assessed on multiparameter flow cytometry, with or without bone marrow (BM) infiltration. Patient 3 received four doses (×4) of rituximab; for Patients 5 and 7, the dashed white line indicates the duration of postremission therapy. HSCT denotes hematopoietic stem-cell transplantation.

Figure 2.. Persistence of CAR-NK Cells after Infusion.

Panel A shows measurements of CAR-NK cells in peripheral-blood samples, as assessed on quantitative polymerase-chain-reaction assay, according to the dose of CAR-NK cells received by the patient. The horizontal gray line at 3 copies per microgram of DNA represents the lower limit of quantification for this assay. The solid horizontal bars indicate the median copy numbers at the various time points for each dose level. After a single infusion of CAR-NK cells, CAR sequences could be detected in all 11 patients. The values increased and remained detectable in peripheral blood for up to 1 year after infusion, regardless of the dose level. No relationship was observed between the administered cell dose and the CAR-NK copy number beyond day 14 after infusion, which suggests that the persistence of CAR-NK cells was driven by in vivo proliferation of the infused cells. The length of follow-up varied among the patients. Panel B shows the peak copy numbers of CAR-NK cells in the first 28 days after infusion for the 11 patients, according to their response to therapy. Patients who had a response at day 30 had a significantly higher copy-number peak of CAR-NK cells after the infusion than those who did not have a response (median value, 31,744 vs. 903 copies per microgram; P = 0.02). The black horizontal bars indicate median values.