Advancements and challenges in developing in vivo CAR T cell therapies for cancer treatment

Abstract

The Chimeric Antigen Receptor (CAR) T cell therapy has emerged as a ground-breaking immunotherapeutic approach in cancer treatment. To overcome the complexity and high manufacturing cost associated with current ex vivo CAR T cell therapy products, alternative strategies to produce CAR T cells directly in the body have been developed in recent years. These strategies involve the direct infusion of CAR genes via engineered nanocarriers or viral vectors to generate CAR T cells in situ. This review offers a comprehensive overview of recent advancements in the development of T cell-targeted CAR generation in situ. Additionally, it identifies the challenges associated with in vivo CAR T method and potential strategies to overcome these issues.

Keywords: Cancer; Gene delivery; Gene editing; In vivo CAR-T.

Fig. 1

Overview of CAR structure. All five generations of CAR constructs share common structures with 4 domains: an extracellular domain targeting tumour-specific antigens (ScFV), a hinge region, transmembrane domain (TM), and finally an intracellular domain. As demonstrated, the structure of CAR intracellular domain indicates CAR generation as well as its functional activity. For instance, the CD3ζ domain initiates essential signal transduction pathways necessary for T-cell activation, proliferation, cytokine production, and cytotoxicity. Meanwhile, the CD28 and 4-1BB domains function as co-stimulatory signals, augmenting T-cell activation, persistence, and functionality. The IL-12 inducer domain is employed to prompt cytokine release within the tumour microenvironment, and the IL-2R beta chain mimics IL-2 signalling, enhancing CAR-T cell survival, proliferation, and persistence.

Fig. 2

Process of ex vivo CAR T therapies.Ex vivo CAR T-cell therapy involves isolating a patient’s or healthy donor’s T-cells via leukapheresis, genetically modifying them with a CAR construct designed for specific cancer antigens. These modified cells are then cultured and expanded. The expanded and modified T-cells are reintroduced into the patient via infusion. Activated CAR T-cells recognise and destroy cancer cells expressing the targeted antigen, potentially providing long-term immunity against cancer recurrence.

Fig. 3

Schematic explanation of the in vivo CAR T therapy for cancer treatment. The in vivo CAR T therapy simplifies ex vivo CAR T method by systemic administration of the CAR gene editing construct enveloped in viral vectors or nanoparticles. These carriers specifically target T cells to unload gene editing cargo, thus inducing the expression of the CAR construct on the T cell surface. The resulting CAR T cells can then specifically detect cancer cells, thus activating themselves and expanding to effectively eliminate cancer cells in the bloodstream or malignant tumours.

Fig. 4

Delivery vehicles for in vivo CAR T generation. a. Viral vectors: Adeno-associated virus, lentivirus and retrovirus; b. Nanocarriers: Polymer nanocarriers, lipid nanoparticles and exosome.