F9 Human

Factor IX is a serine protease that belongs to the peptidase family S1 . The protein is synthesized in the liver and circulates in the bloodstream in an inactive form. Upon activation, it undergoes a series of proteolytic cleavages to become activated factor IX (factor IXa). Factor IXa then interacts with factor VIIIa to form the factor X-activating complex at the site of injury, which is essential for the formation of a stable blood clot .

Deficiency or dysfunction of factor IX leads to hemophilia B, a genetic disorder characterized by excessive bleeding . Hemophilia B is caused by mutations in the F9 gene, which encodes the factor IX protein. These mutations can result in either a lack of circulating factor IX or the production of a dysfunctional protein with reduced activity .

Treatment for hemophilia B involves the replacement of the missing or defective factor IX. This can be achieved through the administration of plasma-derived factor IX, recombinant factor IX, or gene therapy . Advances in understanding the structure and function of factor IX have led to the development of modified forms of the protein with increased stability, higher functional activity, and protection from inhibitors .

Ongoing research aims to improve the therapeutic efficacy of factor IX by enhancing its residence time in circulation and its activity in the absence of factor VIIIa . These advancements hold the potential to significantly improve the quality of life for patients with hemophilia B.