Myeloid cells in peripheral blood mononuclear cell concentrates inhibit the expansion of chimeric antigen receptor T cells

Abstract

Background aims Autologous chimeric antigen receptor (CAR) T-cell therapies have shown promising clinical outcomes, but T-cell yields have been variable. CD19- and GD2-CAR T-cell manufacturing records were reviewed to identify sources of variability. Methods CD19-CAR T cells were used to treat 43 patients with acute lymphocytic leukemia or lymphoma and GD2-CAR T cells to treat eight patients with osteosarcoma and three with neuroblastoma. Both types of CAR T cells were manufactured using autologous peripheral blood mononuclear cells (PBMC) concentrates and anti-CD3/CD28 beads for T-cell enrichment and simulation. Results A comparison of the first 6 GD2- and the first 22 CD19-CAR T-cell products manufactured revealed that GD2-CAR T-cell products contained fewer transduced cells than CD19-CAR T-cell products (147 ± 102 × 106 vs 1502 ± 1066 × 106; P = 0.0059), and their PBMC concentrates contained more monocytes (31.4 ± 12.4% vs 18.5 ± 13.7%; P = 0.019). Among the first 28 CD19-CAR T-cell products manufactured, four had poor expansion yielding less than 1 × 106 transduced T cells per kilogram. When PBMC concentrates from these four patients were compared with the 24 others, PBMC concentrates of poorly expanding products contained greater quantities of monocytes (39.8 ± 12.9% vs. 15.3 ± 10.8%, P = 0.0014). Among the patients whose CD19-CAR T cells expanded poorly, manufacturing for two patients was repeated using cryopreserved PBMC concentrates but incorporating a monocyte depleting plastic adherence step, and an adequate dose of CAR T cells was produced for both patients. Conclusions Variability in CAR T-cell expansion is due, at least in part, to the contamination of the starting PBMC concentrates with monocytes.

Mechanisms of resistance to CAR T cell therapy

“…Other cellular components in the apheresis product can affect CAR T cell manufacturing; this might be a particular challenge given patient heterogeneity and the presence of circulating blasts and nonmalignant cells, such as myeloid-derived suppressor cells, which can inhibit T cell growth 37 . A report of the incidental CAR transduction of B cells, which conferred resistance to subsequent CAR T cell therapy 38 , highlights the importance of having a purified starting product.…”

Toward precision manufacturing of immunogene T-cell therapies

“…Therefore, the presence of non-T-cell components, such as myeloid cells [35][36][37], and differences in T-cell composition (e.g., increased numbers of regulatory T cells [38]) or intrinsic qualities (i.e., elevated numbers of pseudoexhausted/exhausted T cells [30]) may hamper the stimulation and subsequent expansion steps during the cellular manufacturing process.…”

Open access? Widening access to chimeric antigen receptor (CAR) therapy for ALL

“…cytokines, activating beads, such that measures to remove monocytes and neutrophils e.g. elutriation, T cell selection or plastic adherence 63 can improve the feasibility of generating an effective CAR T cell dose in all patients. Optimisation of relapse protocols incorporating CAR T cell therapy is required.…”