Cancer Immunotherapy Using CAR-T Cells: From the Research Bench to the Assembly Line

Abstract

The focus of cancer treatment has recently shifted toward targeted therapies, including immunotherapy, which allow better individualization of care and are hoped to increase the probability of success for patients. Specifically, T cells genetically modified to express chimeric antigen receptors (CARs; CAR-T cells) have generated exciting results. Recent clinical successes with this cutting-edge therapy have helped to push CAR-T cells toward approval for wider use. However, several limitations need to be addressed before the widespread use of CAR-T cells as a standard treatment. Here, a succinct background on adoptive T-cell therapy (ATCT)is given. A brief overview of the structure of CARs, how they are introduced into T cells, and how CAR-T cell expansion and selection is achieved in vitro is then presented. Some of the challenges in CAR design are discussed, as well as the difficulties that arise in large-scale CAR-T cell manufacture that will need to be addressed to achieve successful commercialization of this type of cell therapy. Finally, developments already on the horizon are discussed.

Keywords: T cells; chimeric antigen receptors; genetic engineering; immunotherapy; manufacturing.

Figure 1. Schematic representation of a Chimeric Antigen Receptor (CAR)

CARs currently in clinical use have an extracellular antigen recognition domain (here represented by an antibody-derived single-chain variable fragment, scFv), one or more co-stimulatory domains (signal 2), and CD3ζ (signal 1).

Figure 2. Schematic representation of the manufacture process of CAR-T cells used in clinical trials

T cells are collected from the patient usually through leukapheresis (1) and then activated (2) and transduced with a retroviral vector (3). CAR-T cells are then expanded (4) to obtain sufficient numbers to infuse back into the patient a few days or weeks later (5).

Figure 3. Workflow of CAR-T cell manufacturing

Starting with blood collection, T cells undergo a complex process evolving multiple sequential steps until infusion into the patient. Each step is performed in GMP conditions with several alternatives from institute to institute. Steps in blue are usually required for generation of “off-the-shelf” CAR T cells