Epigenetic control of multiple genes with a single lentiviral vector encoding transcriptional repressors fused to compact zinc finger arrays

Gene silencing without gene editing holds great potential for the development of safe therapeutic applications. Here, we describe a novel strategy to concomitantly repress multiple genes using zinc finger proteins fused to Krüppel-Associated Box repression domains (ZF-Rs). This was achieved via the optimization of a lentiviral system tailored for the delivery of ZF-Rs in hematopoietic cells. We showed that an optimal design of the lentiviral backbone is crucial to multiplex up to three ZF-Rs or two ZF-Rs and a chimeric antigen receptor. ZF-R expression had no impact on the integrity and functionality of transduced cells. Furthermore, gene repression in ZF-R-expressing T cells was highly efficient in vitro and in vivo during the entire monitoring period (up to ten weeks), and it was accompanied by epigenetic remodeling events. Finally, we described an approach to improve ZF-R specificity to illustrate the path towards the generation of ZF-Rs with a safe clinical profile. In conclusion, we successfully developed an epigenetic-based cell engineering approach for concomitant modulation of multiple gene expressions that bypass the risks associated with DNA editing. ### Competing Interest Statement All the authors are current or former Sangamo Therapeutics employees. Sangamo Therapeutics has filed a patent application covering the technology described in this paper.