Lonizable Lipid Nanoparticles with Integrated Immune Checkpoint Inhibition for mRNA CAR T Cell Engineering.

The programmed cell death protein 1 (PD-1) signaling pathway is a major source of dampened T cell activity in the tumor microenvironment (TME). While clinical approaches to inhibiting the PD-1 pathway using antibody blockade have been broadly successful, these approaches lead to widespread PD-1 suppression, increasing the risk of autoimmune reactions. This work reports the development of an ionizable lipid nanoparticle (LNP) platform for simultaneous therapeutic mRNA expression and RNA interference (RNAi)-mediated transient gene knockdown in T cells. In developing this platform, interesting interactions were  observed between the two RNA cargoes when co-encapsulated, leading to improved expression and knockdown characteristics compared to delivering either cargo alone. This messenger RNA (mRNA)/small interfering RNA (siRNA) co-delivery platform was  adopted to deliver chimeric antigen receptor (CAR) mRNA and siRNA targeting PD-1 to primary human T cells ex vivo and strong CAR expression and PD-1 knockdown were  observed without apparent changes to overall T cell activation state. This delivery platform shows great promise for transient immune gene modulation for a number of immunoengineering applications, including in the development of improved cancer immunotherapies. This article is protected by copyright. All rights reserved.