Recombinant Factor IX Fc Fusion Protein Maintains Full Procoagulant Properties and Exhibits Prolonged Efficacy in Hemophilia B Mice.

Introduction: Hemophilia B is an inherited X chromosome-linked disorder characterized by impaired blood clotting owing to the absence of functional coagulation factor IX. Due to the relatively short half-life of factor IX, patients with hemophilia B require frequent factor IX infusions to maintain prophylaxis. We have developed a recombinant factor IX (rFIX) fused to the Fc region of IgG (rFIXFc) with an extended half-life in animals and humans.

Fully human monoclonal antibody inhibitors of the neonatal fc receptor reduce circulating IgG in non-human primates.

The therapeutic management of antibody-mediated autoimmune disease typically involves immunosuppressant and immunomodulatory strategies. However, perturbing the fundamental role of the neonatal Fc receptor (FcRn) in salvaging IgG from lysosomal degradation provides a novel approach - depleting the body of pathogenic immunoglobulin by preventing IgG binding to FcRn and thereby increasing the rate of IgG catabolism. Herein, we describe the discovery and preclinical evaluation of fully human monoclonal IgG antibody inhibitors of FcRn.

Atrial natriuretic peptide-Fc, ANP-Fc, fusion proteins: semisynthesis, in vitro activity and pharmacokinetics in rats.

Atrial natriuretic peptide (ANP) may be a useful molecule for the treatment of cardiovascular diseases due to its potent natriuretic effects. In an effort to prolong the short in vivo half-life of ANP, fusions of the peptide to the Fc domain of IgG were generated using a semisynthetic methodology. Synthetic ANP peptides were synthesized with thioesters at either the N- or C-termini of the peptide and subsequently linked to the N-terminus of recombinantly expressed Fc using native chemical ligation.

Prolonged activity of a recombinant factor VIII-Fc fusion protein in hemophilia A mice and dogs.

Despite proven benefits, prophylactic treatment for hemophilia A is hampered by the short half-life of factor VIII. A recombinant factor VIII-Fc fusion protein (rFVIIIFc) was constructed to determine the potential for reduced frequency of dosing. rFVIIIFc has an ∼ 2-fold longer half-life than rFVIII in hemophilia A (HemA) mice and dogs.

Pulmonary administration of interferon Beta-1a-fc fusion protein in non-human primates using an immunoglobulin transport pathway.

Currently, products containing interferon beta (IFNβ) are injected either intramuscularly or subcutaneously. To avoid the necessity of injection, we developed a novel monomeric Fc fusion protein of IFNβ (IFNβFc) that is absorbed via an immunoglobulin transport system present in the upper and central airways upon administration of the drug as an inhaled aerosol. The systemic absorption of IFNβFc through the lung in non-human primates, at deposited doses of 1, 3, and 10 μg/kg, was compared to the absorption of a single 3 μg/kg dose of IFNβ-1a (Avonex®) subcutaneously administered.

Recombinant factor IX-Fc fusion protein (rFIXFc) demonstrates safety and prolonged activity in a phase 1/2a study in hemophilia B patients.

Current factor IX (FIX) products display a half-life (t(1/2)) of ∼ 18 hours, requiring frequent intravenous infusions for prophylaxis and treatment in patients with hemophilia B. This open-label, dose-escalation trial in previously treated adult subjects with hemophilia B examined the safety and pharmacokinetics of rFIXFc. rFIXFc is a recombinant fusion protein composed of FIX and the Fc domain of human IgG(1), to extend circulating time.

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.

Reduction of IgG in nonhuman primates by a peptide antagonist of the neonatal Fc receptor FcRn.

The neonatal Fc receptor FcRn provides IgG molecules with their characteristically long half-lives in vivo by protecting them from intracellular catabolism and then returning them to the extracellular space. Other investigators have demonstrated that mice lacking FcRn are protected from induction of various autoimmune diseases, presumably because of the accelerated catabolism of pathogenic IgGs in the animals. Therefore, targeting FcRn with a specific inhibitor may represent a unique approach for the treatment of autoimmune disease or other diseases where the reduction of pathogenic IgG will have a therapeutic benefit.

Amelioration of experimental autoimmune myasthenia gravis in rats by neonatal FcR blockade.

The neonatal FcR (FcRn) plays a critical role in IgG homeostasis by protecting it from a lysosomal degradation pathway. It has been shown that IgG has an abnormally short half-life in FcRn-deficient mice and that FcRn blockade significantly increases the catabolism of serum IgG in mice. Therefore, reduction of serum IgG half-life may have therapeutic benefits in Ab-mediated autoimmune diseases.

Pulmonary administration of therapeutic proteins using an immunoglobulin transport pathway.

We have applied a "physiologic" approach to the pulmonary delivery of therapeutic proteins, utilizing an immunoglobulin (antibody) transport pathway recently shown to be present predominantly in the conducting airways of the human respiratory tract. Therapeutic proteins are fused to the Fc-domain of an IgG1, allowing them to bind with high affinity to the antibody transport receptor, FcRn. Liquid aerosols are administered into the lung using normal breathing maneuvers and efficient delivery of several different Fc-fusion proteins has been achieved with retention of biological activity and an increase in circulating half-life.

Monomeric Fc fusions: impact on pharmacokinetic and biological activity of protein therapeutics.

The delivery of therapeutic proteins by noninvasive routes of administration has been a challenging goal, hence current modes of delivery generally require injections. However, we have recently shown that a naturally occurring receptor, the neonatal Fc receptor (FcRn) can be utilized to carry aerosolized therapeutic proteins conjugated to a portion of its respective ligand (Fc domain of immunoglobulin G) across epithelial cells of the lung to effectively deliver biologically active molecules to the bloodstream. First-generation dimeric Fc fusion molecules were successfully transported by the pulmonary route and biologic activity was demonstrated in both non-human primates and human volunteers.

Delivery of an erythropoietin-Fc fusion protein by inhalation in humans through an immunoglobulin transport pathway.

A novel drug delivery platform has been developed that utilizes a naturally occurring receptor known as the neonatal Fc receptor (FcRn). The receptor is specific for the Fc fragment of IgG and is expressed in epithelial cells where it functions to transport immunoglobulins across these cell barriers. It has been shown that FcRn is expressed in both the upper and central airways in non-human primates as well as in humans.

Pulmonary delivery of an erythropoietin Fc fusion protein in non-human primates through an immunoglobulin transport pathway.

Administration of therapeutic proteins by methods other than injection is limited, in part, by inefficient penetration of epithelial barriers. Therefore, unique approaches to breaching these barriers are needed. The neonatal constant region fragment (Fc) receptor (FcRn), which is responsible for IgG transport across the intestinal epithelium in newborn rodents, is expressed in epithelial cells in adult humans and non-human primates.