 SEATTLE, WA ACCESSWIRE January 30, 2020 Aptevo Therapeutics Inc. APVO, a biotechnology company focused on developing novel oncology and hematology therapeutics, today announced that the company has begun dosing patients in a Phase 4 clinical trial to evaluate the safety and efficacy of IXINITY Coagulation Factor IX Recombinant in previously treated patients under 12 years of age with hemophilia B. Launched in the United States in 2015 and wholly-owned by Aptevo, IXINITY is an intravenous recombinant factor IX therapeutic for use in people 12 years of age or older with hemophilia B, a hereditary bleeding disorder characterized by a deficiency of clotting factor IX in the blood. 