M344

Recombinant adeno‐associated viruses (rAAV) are one of the most popular gene therapy vectors. To date, low‐product yields are limiting a broader clinical application. To identify targets for improving productivity, two human embryonic kidney cell lines (HEK293) with varying productive profiles were transiently transfected for rAAV2 production and transcriptomes were compared at 18 h after transfection. As expected, high‐producing cell lines exhibited elevated levels of plasmid‐derived viral gene expression. Gene set enrichment analysis indicated that these cells demonstrated increased transcriptional activity and upregulation of mRNA‐processing mechanisms. Furthermore, transcriptomic analysis suggested increased transcription of histone‐coding genes and a modulated cell cycle under the influence of viral gene expression, with differences being more prominent in the high‐producer cell line. Aiming to increase rAAV yield, cyclin‐dependent kinases and histone deacetylases were targeted by treatment with the small molecule inhibitors Flavopiridol and M344, respectively. Without compromising biological activity, Flavopiridol increased rAAV titer by 2‐fold, and M344 increased it up to 8‐fold in a cell line‐independent manner, while also enhancing the percentage of filled capsids. A DoE‐based approach also revealed the potential for combining both molecules to enhance rAAV production, exhibiting an additive effect across three different HEK293 derivatives. Consequently, novel functions of M344 and Flavopiridol as enhancers of rAAV production were unraveled, which can be employed to enhance the accessibility of in vivo gene therapy applications.

Epigenetic modification shapes differentiation trajectory and regulates the exhaustion state of chimeric antigen receptor T (CAR-T) cells. Limited efficacy induced by terminal exhaustion closely ties with intrinsic transcriptional regulation. However, the comprehensive regulatory mechanisms remain largely elusive. Here, we identify class I histone deacetylase inhibitors (HDACi) as boosters of CAR-T cell function by high-throughput screening of chromatin-modifying drugs, in which M344 and chidamide enhance memory maintenance and resistance to exhaustion of CAR-T cells that induce sustained antitumor efficacy both in vitro and in vivo. Mechanistically, HDACi decrease HDAC1 expression and enhance H3K27ac activity. Multi-omics analyses from RNA-seq, ATAC-seq, and H3K27ac CUT&Tag-seq show that HDACi upregulate expression of TCF4, LEF1, and CTNNB1, which subsequently activate the canonical Wnt/β-catenin pathway. Collectively, our findings elucidate the functional roles of class I HDACi in enhancing CAR-T cell function, which provides the basis and therapeutic targets for synergic combination of CAR-T cell therapy and HDACi treatment.