Bespoke Base and Prime Editing Approaches for STING-Associated Vasculopathy with Onset in Infancy (SAVI)

Introduction STING-associated vasculopathy with onset in infancy (SAVI) is a rare, severe type I interferonopathy caused by gain-of-function mutations in STING1, leading to early-onset systemic inflammation, cutaneous vasculopathy, and life-threatening interstitial lung disease. Current treatments attenuate downstream inflammation without fully addressing the pathogenic driver and carry significant adverse effects. Recently, gene editing has emerged as a paradigm-shifting approach for IEI, with substantial potential for gain-of-function disorders that require allele-specific correction. We present a highly efficient and specific base- and prime-editing strategy that supports both ex vivo and in vivo therapeutic applications. Results K562 were transduced to generate stable STING1-WT and STING1-V155M lines (K562wt, K562mut). 8 sgRNAs were screened for base editing across PAM-flexible nucleases (SpCas9-NG, SpRY) in K562mut, and sgRNA2 and sgRNA5 were selected based on on-target editing. Given the high bystander activity observed with sgRNA5, we leveraged a previously developed library-derived in silico TadA design tool to identify >15 variants for testing. The TadA variant prioritized after experimental screening (var_17) reduced bystander editing (p