Chimeric Antigen Receptor-T Cells: A Pharmaceutical Scope

Abstract

Cancer is among the leading causes of death worldwide. Therefore, improving cancer therapeutic strategies using novel alternatives is a top priority on the contemporary scientific agenda. An example of such strategies is immunotherapy, which is based on teaching the immune system to recognize, attack, and kill malignant cancer cells. Several types of immunotherapies are currently used to treat cancer, including adoptive cell therapy (ACT). Chimeric Antigen Receptors therapy (CAR therapy) is a kind of ATC where autologous T cells are genetically engineered to express CARs (CAR-T cells) to specifically kill the tumor cells. CAR-T cell therapy is an opportunity to treat patients that have not responded to other first-line cancer treatments. Nowadays, this type of therapy still has many challenges to overcome to be considered as a first-line clinical treatment. This emerging technology is still classified as an advanced therapy from the pharmaceutical point of view, hence, for it to be applied it must firstly meet certain requirements demanded by the authority. For this reason, the aim of this review is to present a global vision of different immunotherapies and focus on CAR-T cell technology analyzing its elements, its history, and its challenges. Furthermore, analyzing the opportunity areas for CAR-T technology to become an affordable treatment modality taking the basic, clinical, and practical aspects into consideration.

Keywords: CAR-T cells therapy; advanced cell therapy; cell and gene therapy; cell manufacturing process; immunotherapy.

FIGURE 1

Development of CAR generations. (A) Archetype of a CAR. The four main domains that make up a CAR are distinguished: the recognition domain, the hinge domain, the transmembrane domain, and the intracellular domain. (B) CARs generations. First-generation CARs only own the CD3ζ in the intracellular domain; the second-generation CARs incorporate a costimulatory domain; the third-generation CARs include two costimulatory domains; and fourth-generation CARs are reinforced with genes that allow the expression of cytokines.

FIGURE 2

The major challenges in CAR-T immunotherapy. Nowadays, the novel CAR-T cells therapy does face some significant challenges, such as side effects, a hostile tumor microenvironment (TME), and T-cell exhaustion. In addition, the challenge of scaling-up the manufacture of clinical-grade cell therapies needs to be addressed to make them available and affordable for more patients worldwide.

FIGURE 3

A brief diagram of the CAR-T cells manufacturing process. After enough leukocytes have been harvested from a patient’s blood via leukapheresis, T cells are shipped to a biopharmaceutical company where they are genetically engineered to express a CAR on the T cell surface. Then, the CAR-T cells are amplified in vitro; after that, the CAR-T cells are returned to the hospital for administration into the patient.

FIGURE 4

Quality control during CAR-T cell therapy. The median of total nucleated cells (TNC) is 98 × 10⁸ (range 9 - 341 × 10⁸) with a viability analysis of 98% for quality control (QC) in the leukapheresis products. However, the QC could be set in 10× 10⁸ CD3⁺ T cells with a viability analysis of 98% (99.6–100%) in a median volume of 237 ml (136–310 ml) for CD3⁺ T cell isolation (Data based in the report of Korell et al., 2020). The normal transduction rate is around 20–60% using lentiviral vectors. A 2:1 ratio immunophenotype of CD4+: CAR-T (29 ± 18.1%) and CD8+: CAR-T (71 ± 18.1%) is recommended for clonal CAR-T cell expansion under GMP conditions. Clonal expansion must reach 3.1×10⁶ transduced viable T cells per kilogram of body weight (range, 0.2×10⁶ to 5.4×10⁶ cells per kilogram); this CAR-T cells product is ready for cryopreservation. Cold chain must be controlled during transportation using liquid nitrogen. Prior infusion lymphodepleting chemotherapy with fludarabine and cyclophosphamide it is used. Finally, rate a CAR-T subclone identification followed by genome sequency should be evaluated for measure the molecular remission.