Rebalancing Coagulation Pathways and Human Factor 9 Gene Knock-In Strategy Identified for Hemophilia B

Researchers developed a strategy for treating hemophilia B by combining rebalancing coagulation pathways and human factor 9 (hF9) gene knock-in (KI) using a lipid nanoparticle (LNP) and adeno-associated virus (AAV), according to a report published in Molecular Therapy Nucleic Acids.

“Various types of coagulation disorders can be treated by rebalancing against antithrombin (AT) through weekly or monthly subcutaneous injections. However… rebalancing might be insufficient to control acute bleeding,” the authors explained. “Therefore, it needs to be combined with another therapeutic method. To this end, therapeutic gene KI is considered a next generation strategy for restoring synthesis ability.”

The selected target anticoagulation pathway for gene KI in the study was AT Serpin family C member 1 (Serpinc1). The researchers selected F9 as the target locus because it is a small gene encoding coagulation factor IX in hepatocytes and it is easy to pack with AAV. Following this selection, hF9 was knocked into the locus in vivo using a hybrid system of clustered regularly interspaced short palindromic repeats (CRISPR) packed with LPN and hF9 donor templates packed with AAV.

Overall, the study found that the hF9 coding sequences restored coagulation activity to a normal level in mice. The sequences were integrated into approximately 3% of the target locus and yielded approximately 1,000 ng/mL human factor IX. Serpinc1 had 20% insertions or deletions and there was a 67% reduction of blood mouse AT concentration. In addition, the combined LNP and CRISPR injection caused sustained AT downregulation and hFIX production up to 63 weeks. The researchers note that in the case of partial hepatectomy, AT inhibition and the ability of hFIX to produce protein could be maintained through increased production of genetically edited hepatocytes.

“The most significant advantage of the rebalancing approach is its applicability in treating all types of hemophilia, with or without inhibitors,” said the authors.  “[The results] support the positive effect of combining rebalancing and therapeutic gene KI. Moreover, the AAV and LNP combination approach used in this study resulted in a high KI efficiency, thus showing its high potential for use.”

Reference

Lee JH, Han JP, Song SW, et al. In vivo genome editing for hemophilia B therapy by the combination of rebalancing and therapeutic gene knockin using a viral and non-viral vector. Mol Ther Nucleic Acids. 2023;32:161-172. doi:10.1016/j.omtn.2023.03.008