PE3bmax

PE3bmax is a prime editing gene therapy system delivered via a helper-dependent adenoviral (HDAd) vector, specifically designed to treat sickle cell disease by correcting the mutation in the hemoglobin subunit beta (HBB) gene. The system is an optimized iteration of the prime editing technology, incorporating the "max" architecture which includes codon optimization and improved nuclear localization signals to enhance editing efficiency. It consists of three primary components: a prime editing guide RNA (pegRNA) that targets the sickle mutation site and provides the repair template, a nicking single guide RNA (sgRNA) that nicks the non-edited DNA strand to stimulate repair, and a fusion protein comprising a Cas9 nickase (nCas9) and an M-MLV reverse transcriptase (RT). The mechanism involves the pegRNA-guided nCas9 creating a single-strand break at the target site, followed by the RT-mediated synthesis of corrected DNA using the pegRNA template. PE3bmax is particularly noted for its use of the "b" nicking strategy, which differs from the PE3max system in the specific configuration of the nicking sgRNA to further optimize genomic correction in hematopoietic stem cells (HSCs).