Structural Characterization of a Human/Porcine Chimeric FVIII Construct and an Improved Human Factor VIII Model and Progress Towards Determination of the FVIII C1 Domain In Complex With Inhibitory Antibodies

Blood coagulation factor VIII (FVIII) is a non-enzymatic protein cofactor, which plays a crucial role in the formation of a stable blood clot. Absence or deficiency of FVIII results in the blood disorder hemophilia A, with symptoms including internal hemorrhaging and the inability to stop bleeding from open wounds. Treatment of hemophilia A relies on replacement of FVIII with blood, plasma, or protein concentrate infusions. Unfortunately, approximately 30% of patients receiving replacement FVIII generate pathologic anti-FVIII inhibitory antibodies, which both reduce the effectiveness of the FVIII therapeutic and increase the severity of hemophilia A symptoms. This thesis reports the determination of the molecular structure for “Et3i”, a next-generation human/porcine chimeric FVIII protein for hemophilia A therapy. At 3.2 Å resolution with a Rwork of 0.2146 and Rfree of 0.2879, this will be the highest resolution structure of FVIII to date and will be of substantial interest to the hematological community. Furthermore, an improved model of human FVIII with more robust geometry and amino acid register assignment, and a Rwork of 0.2655, and Rfree of 0.2895 based on previous 3.7 Å data has been constructed. Lastly, progress has been made towards the structural determination of the inhibitory antibodies M6143, 2A9, and B136 in complex with the C1 domain of human FVIII. Details of these interactions could inform the development of future hemophilia A protein therapeutics with reduced immunogenicity