Genome editing for treatment of JAK2 V617F-driven myeloproliferative neoplasms

JAK2 V617F is a common haematological driver mutation and underlies most cases of myeloproliferative neoplasms (MPNs). Reducing variant allele frequency (VAF) is an important treatment goal, but no current treatment modalities fully and specifically inhibit mutant signalling. Thus, the consequences of V617F inactivation are unclear, including whether selective inhibition of V617F signalling will eradicate mutant cells due to oncogene addiction. Here, we describe an allele-selective CRISPR-Cas genome editing strategy that achieves selective and efficient JAK2 V617F inactivation in patient stem and progenitor cells. We show that JAK2 V617F heterozygous cells are not oncogene addicted and maintain viability and differentiation potential upon loss of their mutant allele. In contrast, homozygous mutant cells are eradicated upon deletion of both mutant alleles. Across in vitro, organoid, xenotransplantation and single-cell assays, selective deletion of V617F alleles reverts MPN hallmarks including erythroid clonogenicity, inflammatory gene expression signatures, as well as myelofibrosis and splenomegaly phenotypes in an in vivo xenograft model. Collectively, our results show that is it possible to revert heterozygous JAK2 V617F mutant cells to a normal phenotype and suggest that ex vivo genome editing of stem and progenitor cells may be a viable treatment option to achieve rapid and deep reductions in VAF.