Clinically Relevant Gene Editing in Hematopoietic Stem Cells for the Treatment of Pyruvate Kinase Deficiency Hemolytic Anemia

Abstract

Pyruvate Kinase Deficiency (PKD) is an autosomal recessive disorder caused by mutations in the PKLR gene, which constitutes the main cause of chronic non-spherocytic hemolytic anemia. PKD incidence is estimated in 1 in 20,000 people worldwide. The PKLR gene encodes for the erythroid pyruvate kinase protein (RPK) implicated in the last step of the anaerobic glycolysis in red blood cells. The defective enzyme fails to maintain normal erythrocyte ATP levels, producing severe hemolytic anemia, and can be fatal in severe patients. The only curative treatment for PKD is allogeneic hematopoietic stem and progenitor cells (HSPC) transplantation, so far. However, HSPC transplant is associated with a significant morbidity and mortality, especially in PKD patients. Here, we address the correction of PKD through precise gene editing at the PKLR endogenous locus to keep the tight regulation of RPK enzyme during erythropoiesis. We combined CRISPR/Cas9 system and rAAVs for donor matrix delivery to build an efficient and safe system to knock-in a therapeutic donor at the translation start site of the RPK isoform in human hematopoietic progenitors. Edited human hematopoietic progenitors efficiently reconstituted human hematopoiesis in primary and secondary immunodeficient recipient mice. Moreover, erythroid cells derived from edited PKD-HSPCs restored normal levels of ATP, demonstrating the restoration of RPK function in PKD erythropoiesis after gene editing. Our gene editing strategy may represent a lifelong therapy to restore RPK functionality in RBCs of patients and correct PKD. Single Sentence SummaryClinically relevant gene editing in hematopoietic stem cells for the treatment of Pyruvate Kinase Deficiency.