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Abstract
New therapies are needed for patients with Hodgkin or non-Hodgkin lymphomas that are resistant to standard therapies. Indeed, unresponsiveness to standard chemotherapy and relapse after autologous stem-cell transplantation are indicators of an especially poor prognosis. Chimeric antigen receptor (CAR) T cells are emerging as a novel treatment modality for these patients. Clinical trial data have demonstrated the potent activity of anti-CD19 CAR T cells against multiple subtypes of B-cell lymphoma, including diffuse large-B-cell lymphoma (DLBCL), follicular lymphoma, mantle-cell lymphoma, and marginal-zone lymphoma. Importantly, anti-CD19 CAR T cells have impressive activity against chemotherapy-refractory lymphoma, inducing durable complete remissions lasting >2 years in some patients with refractory DLBCL. CAR-T-cell therapies are, however, associated with potentially fatal toxicities, including cytokine-release syndrome and neurological toxicities. CAR T cells with novel target antigens, including CD20, CD22, and κ-light chain for B-cell lymphomas, and CD30 for Hodgkin and T-cell lymphomas, are currently being investigated in clinical trials. Centrally manufactured CAR T cells are also being tested in industry-sponsored multicentre clinical trials, and will probably soon become a standard therapy. Herein, we review the clinical efficacy and toxicity of CAR-T-cell therapies for lymphoma, and discuss their limitations and future directions with regard to toxicity management, CAR designs and CAR-T-cell phenotypes, conditioning regimens, and combination therapies.
Following immune attack, solid tumors upregulate coinhibitory ligands that bind to inhibitory receptors on T cells. This adaptive resistance compromises the efficacy of chimeric antigen receptor (CAR) T cell therapies, which redirect T cells to solid tumors. Here, we investigated whether programmed death-1-mediated (PD-1-mediated) T cell exhaustion affects mesothelin-targeted CAR T cells and explored cell-intrinsic strategies to overcome inhibition of CAR T cells. Using an orthotopic mouse model of pleural mesothelioma, we determined that relatively high doses of both CD28- and 4-1BB-based second-generation CAR T cells achieved tumor eradication. CAR-mediated CD28 and 4-1BB costimulation resulted in similar levels of T cell persistence in animals treated with low T cell doses; however, PD-1 upregulation within the tumor microenvironment inhibited T cell function. At lower doses, 4-1BB CAR T cells retained their cytotoxic and cytokine secretion functions longer than CD28 CAR T cells. The prolonged function of 4-1BB CAR T cells correlated with improved survival. PD-1/PD-1 ligand [PD-L1] pathway interference, through PD-1 antibody checkpoint blockade, cell-intrinsic PD-1 shRNA blockade, or a PD-1 dominant negative receptor, restored the effector function of CD28 CAR T cells. These findings provide mechanistic insights into human CAR T cell exhaustion in solid tumors and suggest that PD-1/PD-L1 blockade may be an effective strategy for improving the potency of CAR T cell therapies.
Genetically engineered T cells are powerful new medicines, offering hope for curative responses in patients with cancer. Chimaeric antigen receptors (CARs) are a class of synthetic receptors that reprogram lymphocyte specificity and function. CARs targeting CD19 have demonstrated remarkable potency in B cell malignancies. Engineered
High-dose chemotherapy followed by autologous bone marrow transplantation is a therapeutic option for patients with chemotherapy-sensitive non-Hodgkin's lymphoma who have relapses. In this report we describe a prospective randomized study of such treatment. A total of 215 patients with relapses of non-Hodgkin's lymphoma were treated between July 1987 and June 1994. All patients received two courses of conventional chemotherapy. The 109 patients who had a response to chemotherapy were randomly assigned to receive four courses of chemotherapy plus radiotherapy (54 patients) or radiotherapy plus intensive chemotherapy and autologous bone marrow transplantation (55 patients). The overall rate of response to conventional chemotherapy was 58 percent; among patients with relapses after chemotherapy, the response rate was 64 percent, and among those with relapses during chemotherapy, the response rate was 21 percent. There were three deaths from toxic effects among the patients in the transplantation group, and none among those in the group receiving chemotherapy without transplantation. The two groups did not differ in terms of prognostic factors. The median follow-up time was 63 months. The response rate was 84 percent after bone marrow transplantation and 44 percent after chemotherapy without transplantation. At five years, the rate of event-free survival was 46 percent in the transplantation group and 12 percent in the group receiving chemotherapy without transplantation (P = 0.001), and the rate of overall survival was 53 and 32 percent, respectively (P = 0.038). As compared with conventional chemotherapy, treatment with high-dose chemotherapy and autologous bone marrow transplantation increases event-free and overall survival in patients with chemotherapy-sensitive non-Hodgkin's lymphoma in relapse.
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