In vivo generation of CAR T cells: biology, delivery platforms, clinical promise, and translational challenges

The in vivo generation of CAR T-cells represents a potentially transformative advancement in adoptive immunotherapy, offering a promising alternative to conventional ex vivo manufacturing. By delivering CAR transgenes directly into circulating T-cells within the patient’s body, this approach aims to streamline treatment logistics, reduce production costs, and broaden accessibility. A variety of gene delivery platforms are under active investigation, including viral vectors such as lentivirus and adeno-associated virus (AAV), as well as non-viral systems like lipid nanoparticles (LNPs). These technologies are being optimized to enhance the specificity, efficiency, and safety of gene transfer. Several challenges will arise as in vivo CAR T-cell generation is translated to the clinic. These include relatively novel risks such as specificity (risk of off-target genetic modification) and efficiency (low number of genetically modified cells), along with more conventional risks such as redirection of T-cells against undesired targets and long-term depletion of healthy cellular counterparts. Strategies under development to mitigate these concerns include the use of transient expression systems (e.g., mRNA), targeted delivery mechanisms to minimize off-target activity, and the incorporation of immune-evasive features to reduce vector clearance. Additionally, ensuring compatibility with scalable and GMP-compliant manufacturing pipelines is essential for clinical development. Ongoing preclinical research is focused on refining delivery precision, minimizing adverse immune responses, and establishing long-term safety profiles. If these efforts prove successful, in vivo CAR T-cell therapies could overcome many of the current limitations of ex vivo approaches and redefine the landscape of cell-based cancer treatment by offering more accessible treatment options.