Universal base editing for hemophilia B

Abstract

The repair of pathological gene variants is an ultimate aim for treating genetic diseases; however, it is not practical to develop different therapeutic reagents for each of the many variants that can occur in a gene. Here, we investigated whether base editing to induce a gain-of-function variant in blood coagulation factor IX (FIX) can increase FIX activity as a treatment strategy for hemophilia B. We engineered a G:C to A:T substitution at c.1151 of F9 by cytosine base editing to generate R338Q, known as the Shanghai F9 variant, which markedly potentiates coagulation factor activity. An adeno-associated virus vector harboring the base editor converted more than 60% of the target G:C to A:T and increased FIX activity in HEK293 cells harboring patient-derived F9 variants, as well as in knock-in mice harboring a human F9 cDNA. Furthermore, administration of lipid nanoparticles embedded with the base editor mRNA and gRNA increased FIX activity in mice. These data indicate that cytosine base editing to generate R338Q in FIX can become a universal genome editing strategy for hemophilia B.