Current approaches to develop "off-the-shelf" chimeric antigen receptor (CAR)-T cells for cancer treatment: a systematic review

Abstract

Chimeric antigen receptor (CAR)-T cell therapy is one of the most promising advances in cancer treatment. It is based on genetically modified T cells to express a CAR, which enables the recognition of the specific tumour antigen of interest. To date, CAR-T cell therapies approved for commercialisation are designed to treat haematological malignancies, showing impressive clinical efficacy in patients with relapsed or refractory advanced-stage tumours. However, since they all use the patient´s own T cells as starting material (i.e. autologous use), they have important limitations, including manufacturing delays, high production costs, difficulties in standardising the preparation process, and production failures due to patient T cell dysfunction. Therefore, many efforts are currently being devoted to contribute to the development of safe and effective therapies for allogeneic use, which should be designed to overcome the most important risks they entail: immune rejection and graft-versus-host disease (GvHD). This systematic review brings together the wide range of different approaches that have been studied to achieve the production of allogeneic CAR-T cell therapies and discuss the advantages and disadvantages of every strategy. The methods were classified in two major categories: those involving extra genetic modifications, in addition to CAR integration, and those relying on the selection of alternative cell sources/subpopulations for allogeneic CAR-T cell production (i.e. γδ T cells, induced pluripotent stem cells (iPSCs), umbilical cord blood T cells, memory T cells subpopulations, virus-specific T cells and cytokine-induced killer cells). We have observed that, although genetic modification of T cells is the most widely used approach, new approaches combining both methods have emerged. However, more preclinical and clinical research is needed to determine the most appropriate strategy to bring this promising antitumour therapy to the clinical setting.

Keywords: Advanced therapy medicinal products (ATMPs); Allogeneic treatment; Allorejection; Cancer immunotherapy; Chimeric antigen receptor (CAR)-T cells; Genetic engineering; Graft-versus-host disease (GvHD); Systematic review; “Off-the-shelf” adoptive T cell therapy.

Fig. 1

Overview of general autologous/allogeneic CAR-T cell production and application process. (1) T cell isolation from different sources (depending on autologous or allogeneic use); (2) T cell activation for ex vivo culture (usually through CD3 and CD28 stimulation); (3) genetic modification for inducing CAR expression (commonly 2^nd generation CARs); (4) expansion to obtain the desired number of cells (usually either IL-2 or IL-7 and IL-15 supplementations); (5) CAR-T cell therapy quality controls (in-process and final product controls); (6) administration to the patient/s; and (7) elimination of tumour cells triggered by CAR antigen recognition. QC: quality control. TM: transmembrane. Created with BioRender.com.

Fig. 2

Flow diagram summarizing the selection process for studies included in the systematic review

Fig. 3

Representative examples of the main strategies to produce antitumour allogeneic CAR-T cells: (A) Performing additional genetic modifications (besides CAR transgene introduction) on donor αβ T cells, or using different cell sources such as (B) γδ T cells, (C) induced pluripotent stem cells (iPSCs), (D) umbilical cord blood T cells, (E) central memory T cells, or (F) virus-specific T cells. Created with BioRender.com.