Significant Advancements and Evolutions in Chimeric Antigen Receptor Design

Abstract

Recent times have witnessed remarkable progress in cancer immunotherapy, drastically changing the cancer treatment landscape. Among the various immunotherapeutic approaches, adoptive cell therapy (ACT), particularly chimeric antigen receptor (CAR) T cell therapy, has emerged as a promising strategy to tackle cancer. CAR-T cells are genetically engineered T cells with synthetic receptors capable of recognising and targeting tumour-specific or tumour-associated antigens. By leveraging the intrinsic cytotoxicity of T cells and enhancing their tumour-targeting specificity, CAR-T cell therapy holds immense potential in achieving long-term remission for cancer patients. However, challenges such as antigen escape and cytokine release syndrome underscore the need for the continued optimisation and refinement of CAR-T cell therapy. Here, we report on the challenges of CAR-T cell therapies and on the efforts focused on innovative CAR design, on diverse therapeutic strategies, and on future directions for this emerging and fast-growing field. The review highlights the significant advances and changes in CAR-T cell therapy, focusing on the design and function of CAR constructs, systematically categorising the different CARs based on their structures and concepts to guide researchers interested in ACT through an ever-changing and complex scenario. UNIVERSAL CARs, engineered to recognise multiple tumour antigens simultaneously, DUAL CARs, and SUPRA CARs are some of the most advanced instances. Non-molecular variant categories including CARs capable of secreting enzymes, such as catalase to reduce oxidative stress in situ, and heparanase to promote infiltration by degrading the extracellular matrix, are also explained. Additionally, we report on CARs influenced or activated by external stimuli like light, heat, oxygen, or nanomaterials. Those strategies and improved CAR constructs in combination with further genetic engineering through CRISPR/Cas9- and TALEN-based approaches for genome editing will pave the way for successful clinical applications that today are just starting to scratch the surface. The frontier lies in bringing those approaches into clinical assessment, aiming for more regulated, safer, and effective CAR-T therapies for cancer patients.

Keywords: ATMP; CAR-T cells; CAR-T therapy; adoptive cell therapy; immunotherapy.

Figure 1

Schematic representation of the CAR-T cell production process. Autologous chimeric antigen receptor (CAR) T cell therapy, which is currently approved, works by modifying a patient’s own T cells ex vivo and then administering them back to the same person. The production process is carried out in accordance with Good Manufacturing Practice (GMP) guidelines and is overseen by multiple quality assessments. The first step in autologous CAR-T cell production is the isolation of T cells from the patient’s peripheral blood. Isolated T cells are then activated and genetically engineered via viral transduction to express the CAR molecule. CAR-T cells are subsequently expanded in culture to up to billions of cells. The modified CAR-T cells are typically cryopreserved and later re-infused into the patient to specifically target and eliminate cancer cells. Created in BioRender. Gaimari, A. (2022).

Figure 2

Schematic overview of CAR-T cell engineering strategies and recent innovations. The figure is divided into two main parts. Panel (A) shows various chimeric antigen receptor (CAR) T cell constructs, including UNIVERSAL CAR, DUAL CAR, SUPRA CAR, and Tandem CAR designs, highlighting structural modifications aimed at enhancing therapeutic specificity and efficacy. Additionally, non-design-based modifications, such as the incorporation of enzymes like heparanase or catalase, are shown as strategies to improve CAR-T cell performance. Panel (B) explores approaches driven by external stimuli, such as light, ultrasound, or small molecules (e.g., resveratrol, AP1903). The figure also highlights cutting-edge developments, including the use of synthetic nanomaterials and nanovesicles, which represent emerging tools to further refine CAR-T cell therapy, enhancing its safety and effectiveness in clinical applications. (scFv, single-chain variable fragment; FITC, fluorescein isothiocyanate; zipFv, tumour-targeting scFv adaptor; CCR4, C-C chemokine receptor type 4; CXCR3, C-X-C motif chemokine receptor type 3). Created in BioRender. Mazza, M. (2024), https://BioRender.com/p17t758 (accessed on 5 November 2024).