Preclinical evaluation of a next-generation, subcutaneously administered, coagulation factor IX variant, dalcinonacog alfa.

INTRODUCTION: The rapid clearance of factor IX necessitates frequent intravenous administrations to achieve effective prophylaxis for patients with hemophilia B. Subcutaneous administration has historically been limited by low bioavailability and potency. Dalcinonacog alfa was developed using a rational design approach to be a subcutaneously administered, next-generation coagulation prophylactic factor IX therapy. AIM: This study aimed to investigate the pharmacokinetic, pharmacodynamic, and safety profile of dalcinonacog alfa administered subcutaneously in hemophilia B dogs. METHODS: Two hemophilia B dogs received single-dose daily subcutaneous dalcinonacog alfa injections for six days. Factor IX antigen and activity, whole blood clotting time, and activated partial thromboplastin time were measured at various time points. Additionally, safety assessments for clinical adverse events and evaluations of laboratory test results were conducted. RESULTS: There was an increase in plasma factor IX antigen with daily subcutaneous dalcinonacog alfa. Bioavailability of subcutaneous dalcinonacog alfa was 10.3% in hemophilia B dogs. Daily subcutaneous dosing of dalcinonacog alfa demonstrated the effects of bioavailability, time to maximal concentration, and half-life by reaching a steady-state activity sufficient to correct severe hemophilia to normal, after four days. CONCLUSION: The increased potency of dalcinonacog alfa facilitated the initiation and completion of the Phase 1/2 subcutaneous dosing study in individuals with hemophilia B.

Prolonged activity of factor IX as a monomeric Fc fusion protein.

Treatment of hemophilia B requires frequent infusions of factor IX (FIX) to prophylax against bleeding episodes. Hemophilia B management would benefit from a FIX protein with an extended half-life. A recombinant fusion protein (rFIXFc) containing a single FIX molecule attached to the Fc region of immunoglobulin G was administered intravenously and found to have an extended half-life, compared with recombinant FIX (rFIX) in normal mice, rats, monkeys, and FIX-deficient mice and dogs. Recombinant FIXFc protein concentration was determined in all species, and rFIXFc activity was measured in FIX-deficient animals. The half-life of rFIXFc was approximately 3- to 4-fold longer than that of rFIX in all species. In contrast, in mice in which the neonatal Fc receptor (FcRn) was deleted, the half-life of rFIXFc was similar to rFIX, confirming the increased circulatory time was due to protection of the rFIXFc via the Fc/FcRn interaction. Whole blood clotting time in FIX-deficient mice was corrected through 144 hours for rFIXFc, compared with 72 hours for rFIX; similar results were observed in FIX-deficient dogs. Taken together, these studies show the enhanced pharmacodynamic and pharmacokinetic properties of the rFIXFc fusion protein and provide the basis for evaluating rFIXFc in patients with hemophilia B.

Comparative response of plasma VWF in dogs to up-regulation of VWF mRNA by interleukin-11 versus Weibel-Palade body release by desmopressin (DDAVP).

Recombinant human interleukin-11 (rhIL-11), a glycoprotein 130 (gp130)-signaling cytokine approved for treatment of thrombocytopenia, also raises von Willebrand factor (VWF) and factor VIII (FVIII) by an unknown mechanism. Desmopressin (1-deamino-8-d-arginine vasopressin [DDAVP]) releases stored VWF and FVIII and is used for treatment of VWF and FVIII deficiencies. To compare the effect of these 2 agents, heterozygous von Willebrand disease (VWD) and normal dogs were treated with either rhIL-11 (50 microg/kg/d subcutaneously x 7 days) or DDAVP (5 microg/kg/d intravenously x 7 days). The rhIL-11 produced a gradual and sustained elevation of VWF and FVIII levels in both heterozygous VWD and normal dogs while DDAVP produced a rapid and unsustained increase. Importantly, rhIL-11 treatment produced a 2.5- to 11-fold increase in VWF mRNA in normal canine heart, aorta, and spleen but not in homozygous VWD dogs, thus identifying a mechanism for elevation of plasma VWF in vivo. Moreover, dogs pretreated with rhIL-11 retain a DDAVP-releasable pool of VWF and FVIII, suggesting that rhIL-11 does not significantly alter trafficking of these proteins to or from storage pools. The half-life of infused VWF is unchanged by rhIL-11 in homozygous VWD dogs. These results show that rhIL-11 and DDAVP raise plasma VWF by different mechanisms. Treatment with rhIL-11 with or without DDAVP may provide an alternative to plasma-derived products for some VWD and hemophilia A patients if it is shown safe in clinical trials.