Multiplex engineering using microRNA-mediated gene silencing in CAR T cells.

Background: Multiplex gene-edited chimeric antigen receptor (CAR) T-cell therapies face significant challenges, including potential oncogenic risks associated with double-strand DNA breaks. Targeted microRNAs (miRNAs) may provide a safer, functional, and tunable alternative for gene silencing without the need for DNA editing.

Methods: As a proof of concept for multiplex gene silencing, we employed an optimized miRNA backbone and gene architecture to silence T-cell receptor (TCR) and major histocompatibility complex class I (MHC-I) in mesothelin-directed CAR (M5CAR) T cells. The efficacy of this approach was compared to CD3ζ and β2-microglobulin (β2M) CRISPR/Cas9 knockout (KO) cells. miRNA-expressing cassettes were incorporated into M5CAR lentiviral vectors, enabling combined gene silencing and CAR expression. Antitumor activity was evaluated using assays and pancreatic ductal adenocarcinoma models.

Results: Silenced (S) M5CAR T cells retained antitumor functionality comparable to, and in some cases exceeding, that of KO cells. , S M5CAR T cells achieved tumor control with higher persistence and superior metastasis prevention. assays demonstrated enhanced resistance to alloreactive natural killer (NK) cells and peripheral blood mononuclear cells (PBMCs).

Conclusions: Titratable multiplex gene silencing via targeted miRNAs offers an alternative to gene editing for CAR T cells, with potential advantages in potency, persistence, metastasis prevention, and immune evasion for allogeneic products. This strategy may overcome tumor-induced immunosuppression while avoiding the risks associated with DNA double-strand breaks.