Beyond autologous ex vivo CAR-expressing cell therapies: Toward allogeneic and nucleated cell-free delivery systems of CAR

The success of <i>ex vivo</i> chimeric antigen receptor (CAR)-T cell therapies has transformed the treatment of hematologic malignancies but remains limited by individualized manufacturing complexity and cost. Emerging <i>in situ</i> and <i>in vivo</i> CAR engineering platforms aim to overcome these barriers by programming patient immune cells directly within the body. Targeted lipid nanoparticles, synthetic DNA nanocarriers, and viral and non-viral delivery systems have demonstrated the ability to generate functional CAR-T cells without <i>ex vivo</i> manipulation, enabling scalable, on-demand immunotherapy. In parallel, advances in allogeneic "off-the-shelf" cellular therapies provide donor-derived products that can be manufactured at scale, cryopreserved, and delivered rapidly. Additional cell types are also being explored as vehicles for <i>in vivo</i> CAR delivery. Hybrid approaches that leverage allogeneic cells as carriers for CAR constructs may combine the scalability of off-the-shelf products with the speed and flexibility of <i>in vivo</i> engineering. Despite this promise, challenges remain, including cell-specific targeting, control of transgene persistence, immunogenicity, and regulatory considerations. Together, these innovations signal a paradigm shift in the generation and deployment of CAR-based cellular immunotherapies.