Scarless circular mRNA-based CAR-T cell therapy elicits superior anti-tumor efficacy

Messenger RNA (mRNA)-based transient expression of CAR shows optimal safety profiles and provides promising opportunities to address existing challenges of viral vector-based CAR-T therapies and to meet emerging medical needs in noncancerous indications. However, linear mRNAs are intrinsically unstable and thus just achieve compromised efficacy. Here, we engineered a permuted intron exon (PIE) platform to synthesize scarless circular mRNA (cmRNA) for potent CAR expression and long-lasting efficacy. cmRNA significantly increased amount and duration of anti-CD19 CAR expression on human T cells. cmRNA-based anti-CD19 CAR-T cells elicit superior anti-tumor efficacy over linear mRNA counterparts, demonstrated by parallel lines of evidence including in vitro specific cell-killing, cytokine release, transcriptomics patterns, and in vivo tumor elimination and survival benefit. We found that cmRNA-based anti-CD19 CAR-T efficiently eliminated target cells in vivo and provide long-lasting antitumor efficacy. These results suggested that cmRNA could be a potent platform for unleashing full potential of mRNA technologies in cell therapies.