Abstract
CRISPR-Cas9 offers unprecedented opportunities to modify genome sequences in primary human cells to study disease variants and reprogram cell functions for next-generation cellular therapies. CRISPR has several potential advantages over widely used retroviral vectors including: 1) site-specific transgene insertion via homology directed repair (HDR), and 2) reductions in the cost and complexity of genome modification. Despite rapid progress with ex vivo CRISPR genome engineering, many novel research and clinical applications would be enabled by methods to further improve knock-in efficiency and the absolute yield of live knock-in cells, especially with large HDR templates (HDRT). We recently reported that Cas9 target sequences (CTS) could be introduced into double-stranded DNA (dsDNA) HDRTs to improve knock-in, but yields and efficiencies were limited by toxicity at high HDRT concentrations. Here we developed a novel system that takes advantage of lower toxicity with single-stranded DNA (ssDNA). We designed hybrid ssDNA HDRTs that incorporate CTS sites and were able to boost knock-in percentages by >5-fold and live cell yields by >7-fold relative to dsDNA HDRTs with CTS. Knock-in efficiency and yield with ssCTS HDRTs were increased further with small molecule inhibitor combinations to improve HDR. We demonstrate application of these methods across a variety of target loci, knock-in constructs, and primary human cell types to reach ultra-high HDR efficiencies (>80-90%) which we use for pathogenic gene variant modeling and universal gene replacement strategies for IL2RA and CTLA4 mutations associated with mendelian immune disorders. Finally, we develop a GMP-compatible method for fully non-viral CAR-T cell manufacturing, demonstrating knock-in efficiencies of 46-62% and generating yields of >1.5 x 109 CAR+ T cells, well above current doses for adoptive cellular therapies. Taken together, we present a comprehensive non-viral approach to model disease associated mutations and re-write targeted genome sequences to program immune cell therapies at a scale compatible with future clinical application.
Competing Interest Statement
A.M. is a compensated co-founder, member of the boards of directors, and a member of the scientific advisory boards of Spotlight Therapeutics and Arsenal Biosciences. A.M. was a compensated member of the scientific advisory board at PACT Pharma and was a compensated advisor to Juno Therapeutics and Trizell. A.M. owns stock in Arsenal Biosciences, Spotlight Therapeutics, and PACT Pharma. A.M. has received fees from Merck and Vertex and is an investor in and informal advisor to Offline Ventures. The Marson lab has received research support from Juno Therapeutics, Epinomics, Sanofi, GlaxoSmithKline, Gilead, and Anthem. J.E. is a compensated co-founder at Mnemo Therapeutics. JE is a compensated scientific advisor to Cytovia Therapeutics. J.E own stocks in Mnemo Therapeutica and Cytovia Therapeutics. J.E. has received a consulting fee from Casdin Capital. The Eyquem lab has received research support from Cytovia Therapeutic and Takeda. J.E. is a holder of patents pertaining to but not resulting from this work. H.L and L.Y. are employees of Genscript Biotech Corporation. J.W. has received consulting fees from Teneobio and Adaptive Biotech. D.N.N receives consulting fees and sits on the scientific advisory board of Navan Technologies. T.L.R. is a co-founder, holds equity in, and is a member of the Scientific Advisory Board of Arsenal Bioscience. Discounted reagents were provided by Genscript. Patents have been filed based on the findings described here.
