New Evidence Supports Base Editing as Effective Toward FVIII Rescue in Hemophilia A

New proof-of-concept data, published in the Journal of Thrombosis and Haemostasis, support base and prime editing-mediated genetic corrections as leading to restored factor VIII (FVIII) production in hemophilia A.

These new data will “encourage studies in mouse models to develop a personalized cure for large cohorts of patients though a single intervention,” according to the investigators.

Comparing approaches in hemophilia A management, the investigators wrote that F8 gene correction with nucleases mediating homologous recombination has been clearly shown in animal models to restore FVIII production but has limited efficiency and translatability. Their study, meanwhile, was an examination of double-strand break/homologous recombination -independent base and prime editing approaches for correcting hemophilia A -producing mutations.

The investigators used transient assays with HEK293T cells expressing different FVIII variants. They identified which base or prime editing methods were most effective at rescuing FVIII expression. They measured the degree of rescue in engineered blood outgrowth endothelial cells (BOEC).

The highest degree of FVIII expression rescue the investigators observed was for p.R2166* and p.R2228Q mutations, with up to 25% of recombinant FVIII wild type. They found that in engineered BOEC with these two mutations, lentiviral-mediated delivery of base editing “led to an appreciable and dose-dependent rescue of secreted functional FVIII,” with a ~24% mutation reversion on DNA being associated with a 20% to 30% rescue of FVIII secretion and activity in stable clones.

Reference

Tonetto E, Cucci A, Follenzi A, Bernardi F, Pinotti M, Balestra D. DNA base editing corrects common Hemophilia A mutations and restores factor VIII expression in vitro and ex-vivo models. J Thromb Haemost. 2024. doi:10.1016/j.jtha.2024.04.020