[New therapeutic directions on hemophilia]

Hemophilia is a congenital bleeding disorder that occurs due to quantitative and functional abnormalities of FVIII or FIX. It has a long history, dating as far back as the Babylonian era, with many high profile reports, including the British royal family and the last prince of the Romanov dynasty. The treatment used to be blood transfusion, consisting of plasma derived products from the 1970s onwards and recombinant products introduced later in the 1990s. In the 2000s, due to various modifications of factor protein, extended half-life (EHL) products have appeared and replaced conventional products. In EHL research, new products are also being developed that further the extension of the half-life and are more convenient. In 2018, an antibody-based medicine arrived, exhibiting a mechanism different from factor replacement therapy. Some other therapeutic agents used to suppress bleeding, called nonfactor agents, are currently under development. Recently, gene therapy has finally come into the clinical trial space in Japan and can be expected to be a treatment which aims at "cure," as it can be used with no exposure to bleedings for several years with one injection. This article outlines the future of hemophilia treatment.