Efficient in vivo generation of CAR T cells using a retargeted 4th generation lentiviral vector

CAR T cell therapy has proven remarkably successful for the treatment of haematological malignancies. However, the bespoke manufacturing of autologous CAR T cells is complex and expensive. The development of methods for in vivo engineering of T cells will enable generation of CAR T cells directly within the patient, bypassing the need for ex vivo manufacturing thereby enabling greater access for patients. Here we describe development of an improved retargeted Nipah envelope system paired with a 4th generation lentiviral vector capable of specifically targeting T cells with increased efficiency, which generates high levels of functional CAR T cells in vivo. The retargeted vectors exhibited greater specificity to T cells compared to the VSV-G-pseudotyped vector. Vectors targeted to either CD3 or CD8 similarly generated high levels of CAR T cells which rapidly eradicated B cells suggesting that TCR engagement is not required for lentiviral vectors to efficiently transduce T cells in vivo. Furthermore, the 4th generation lentiviral vector platform (referred to as TetraVecta™ system) employs the TRiP system™ to prevent incorporation of CAR protein into the vector particles, minimizing the risk of inadvertent transduction of tumour cells.