In Vivo CAR-T Generation via T Cell–Activating mRNA Vehicle

The clinical success of chimeric antigen receptor (CAR) T-cell therapy highlights the need for scalable, non-invasive strategies to engineer T cells directly in vivo. Although mRNA delivery offers a promising alternative, lipid nanoparticle-based carriers generally exhibit limited T-cell transfection efficiency in vivo and often require antibody conjugation.

Recently, researchers published a study in Nature Materials entitled “An Inherent T Cell-Activating mRNA Delivery Carrier for In Vivo CAR T Generation.” The study describes an antibody-free, inherently T cell-activating polymer–lipid nanoparticle platform, termed ERTLNPs, that enables the direct generation of functional CAR-T cells in vivo through systemic mRNA delivery. The platform demonstrated significant therapeutic efficacy in models of pulmonary fibrosis, liver fibrosis, and pancreatic cancer, providing a new approach to off-the-shelf and controllable in vivo CAR-T therapy.

Figure 1. ERTLNP-mediated T-cell activation and transfection in vivo. (Cao Q, et al., 2026)

T cell-based immunotherapies have attracted considerable attention because of their promising potential in cancer treatment, particularly following the approval of CAR-T cell therapies by the U.S. Food and Drug Administration. Their clinical success has also encouraged the exploration of CAR-T therapies beyond oncology. However, despite major advances in treating hematological malignancies, ex vivo-engineered CAR-T cell therapies remain constrained by complex manufacturing procedures and high costs.

mRNA technology is rapidly advancing for the treatment and prevention of diseases such as infectious diseases and cancer. Direct delivery of mRNA encoding CAR constructs into host T cells offers a promising alternative by eliminating the need for ex vivo cell manipulation. However, most existing lipid nanoparticle-based mRNA delivery systems predominantly target the liver. Moreover, monoclonal antibody-conjugated LNPs have been shown to induce T-cell exhaustion following treatment, raising concerns about their use in in vivo CAR-T therapy.

In this study, the researchers developed an inherently T cell-activating polymer–lipid nanoparticle capable of efficient, ligand-free mRNA transfection and activation of T cells in vivo. The mRNA carrier consists of oligoethylenimine-based lipid nanoparticles modified with tosyl arginine (RT), referred to as ERTLNPs. Following systemic administration, ERTLNPs preferentially mediated mRNA transfection in the spleen. Even in the absence of exogenous stimulation, the nanoparticles activated T cells and induced robust mRNA expression and cellular proliferation.

Mechanistically, ERTLNPs engage the PI3K/AKT/mTOR signaling axis to reprogram T-cell metabolism, thereby promoting T-cell expansion while suppressing exhaustion. Systemic delivery of mRNA encoding a fibroblast activation protein-targeting CAR (FAP CAR) using ERTLNPs enabled the in situ generation of functional CAR-T cells. These cells effectively eliminated pathological fibroblasts in cancer and fibrosis models while producing minimal off-target effects. This ligand-free, metabolically reprogramming mRNA delivery system therefore provides a clinically translatable strategy for generating CAR-T cells directly in vivo.