In vivo HSC prime editing rescues Sickle Cell Disease in a mouse model

We tested HDAd5/35++-vector based ex vivo and in vivo approaches for prime editing in hematopoietic stem cells (HSCs) with the goal to correct the mutation that causes Sickle Cell Disease (SCD) in a mouse model (CD46/Townes mice). The in vivo gene therapy setting involved a single intravenous injection of a non-integrating, prime editor-expressing HDAd5/35++ vector into mobilized CD46/Townes mice and minimal in vivo selection. This procedure resulted in the correction of ~40% of _S alleles in HSCs. On average 43% of HbS was replaced by HbA thereby greatly improving the SCD phenotype. Studies in secondary recipients indicated that long-term repopulating HSCs were edited. Highly efficient target site editing was achieved with minimal generation of indels, no detectable off-target editing, and alterations in the transcriptome. Because of its simplicity and portability, our in vivo prime editing approach has the potential for application in resource-poor countries where SCD is prevalent.