Intrinsic difference in cellular response between full-length and B-domain deleted FVIII HEK293 secreting cells: implication for gene therapy

Introduction Hemophilia A treatment relied on replacement of FVIII, but recently new treatment approaches aimed at overcoming the shortcomings of factor replacement. AAV-based gene therapy have achieved good results, but are still far from universal applicability as they still face many challenges. A major problem is the lack of sustainability of FVIII levels; we also still have no idea on ​​the status of the transfected cells in the liver. Most of these protocols target hepatocytes and use a BDD-FVIII, implying two non-natural phenomena linked in one way or another to the deterioration of FVIII blood levels over 2-3 years.This gradual decrease in FVIII levels over time strongly demand a thorough investigation of the suspected mechanisms at the cellular level of transfected cells.The latter include abnormal control/levels of expression and abnormal cellular trafficking leading to cytotoxicity in the cells.The phenomenon could be dose-dependent and could be related to different intra-cellular pathways of BDD-FVIII.Understanding the reasons behind this phenomenon is the first step to avoiding its side effects.This will be directly beneficial for the patient, since better optimization of gene therapy protocols could be achieved. The aim of this study to compare the cellular response to different forms (FL vs BDD) and levels of FVIII in HEK293 cells