Advancing In Vivo Chimeric Antigen Receptor T‐Cell Engineering to Accelerate Clinical Translation

ABSTRACT Chimeric antigen receptor T‐cell (CAR‐T) therapy is a transformative tumor immunotherapy that redirects autologous T cells to eliminate malignant cells. However, its broader clinical translation is constrained by complex and costly ex vivo manufacturing, variable product quality, and limited control over in vivo activity. In vivo CAR‐T engineering enables direct T‐cell programming in the body, reducing reliance on ex vivo manufacturing while improving T‐cell fitness and antitumor efficacy. This approach also enables flexible dosing and may obviate lymphodepletion. This review first summarizes recent advances in in vivo CAR‐T engineering and the evolution of CAR architectures. We then examine viral and non‐viral delivery systems, including lentiviral vectors (LVs), adeno‐associated virus (AAV) vectors, lipid nanoparticles (LNPs), polymeric nanoparticles (PNPs), and emerging platforms, highlighting their distinct advantages and limitations. We further evaluate strategies to facilitate clinical translation, focusing on safety and efficacy. Finally, we discuss emerging opportunities enabled by biomaterials and artificial intelligence to improve scalability and accessibility while broadening therapeutic applications. This review provides a framework for understanding in vivo CAR‐T engineering and highlights key strategies for overcoming translational barriers and advancing next‐generation CAR‐T therapies.