 We have developed a novel base editing technique using a modified Cas9 protein with flexible PAM sequence to treat hemophilia B. This technique uses a single guide RNA, SGRNA, to target the mutant gene and a Nikkeis Cas9 variant to convert the mutation from C to T. This approach was successful in converting the mutation in both human-induced pluripotent stem cells, IPSCs, and knock-in mice, demonstrating the potential of this technique for treating genetic diseases. This article was authored by Tokafumi Hiramoto, Yutikashi Wakura, Morisada Hayakawa, and others.