Pharmacokinetics of plasma-derived C1-esterase inhibitor after subcutaneous versus intravenous administration in subjects with mild or moderate hereditary angioedema: the PASSION study.

BACKGROUND: Hereditary angioedema (HAE) is a rare disease caused by C1-esterase inhibitor (C1-INH) deficiency, characterized by periodic attacks of acute edema affecting subcutaneous (SC) tissues and mucous membranes. Human C1-INH concentrate given intravenously (IV) is effective and safe, but venous access may be difficult. We compared SC and IV administration of human pasteurized C1-INH concentrate with respect to pharmacokinetics, pharmacodynamics, and safety. STUDY DESIGN AND METHODS: This was a prospective, randomized, open-label, crossover study. Twenty-four subjects with mild or moderate HAE were randomly assigned during an attack-free interval to receive 1000 units of human pasteurized C1-INH concentrate IV or SC. Plasma levels of C1-INH activity and antigen, C4 antigen, cleaved high-molecular-weight kininogen (clHK), and C1-INH antibodies were measured. RESULTS: The mean relative bioavailability of functional C1-INH after SC administration was 39.7%. Maximum C1-INH activity after SC administration occurred within 48 hours and persisted longer than after IV administration. C4 antigen levels increased and clHK levels decreased after IV and SC administration, indicating the pharmacodynamic action of C1-INH. The mean half-life of functional C1-INH was 62 hours after IV administration and 120 hours after SC administration (p=0.0595). C1-INH concentrate was safe and well tolerated when administered via both routes. As expected, SC administration resulted in a higher incidence of injection site reactions, all of which were mild. CONCLUSION: With a relative bioavailability of 39.7%, SC administration of human pasteurized C1-INH yields potentially clinically relevant and sustained plasma levels of C1-INH and is safe and well tolerated.

Intracerebral mass bleeding in a term neonate: manifestation of hereditary protein S deficiency with a new mutation in the PROS1 gene.

BACKGROUND: Vitamin K deficiency is the major cause of coagulopathy-induced intracranial bleeding in term neonates and is considered first in any term neonate with severe hemorrhage. The most common manifestation of hereditary prothrombotic disorders during the neonatal period is thrombosis of the A. cerebri media or sinus thrombosis. CASE REPORT: A 4-day-old newborn was admitted with seizures and hemorrhagic shock. Ultrasound revealed a left-sided intraparenchymatous bleeding. MRI findings supported a subarachnoidal and intracerebral mass bleeding. Vitamin K deficiency-related bleeding or hemophiliac diseases were excluded; however, homozygous protein S deficiency with a new mutation in the protein S (PROS1) gene (c.701A>G, p.Tyr234Cys) was found. The patient experienced an additional thrombosis of the A. abdominalis and expired. CONCLUSION: Congenital prothrombotic disorders have to be considered in the differential diagnosis of neonatal intracranial hemorrhage. This newly described mutation in the PROS1 gene (c.701A>G, p.Tyr234Cys) appears to be of clinical relevance.

Humoral immune responsiveness to a defined epitope on factor VIII before and after B cell ablation with rituximab.

In hemophilia A, up to 30% of patients develop neutralizing antibodies (inhibitors) to factor VIII (FVIII). Treatment of an inhibitor patient with anti-CD20 (rituximab) provided an opportunity to study the humoral immune response to the well defined and constantly administered antigen, FVIII, before therapy and after B cell repopulation. Levels of CD20(+) B cells, inhibitor titers as well as antibody titers to selected antigens and FVIII-specific IgG subclasses were monitored. Inhibitors were absent for 420 days after B cell depletion, whereas antibody titers to other monitored antigens remained constant. No changes of FVIII specific IgG subclass distribution were observed. In order to characterize specific epitopes phage displayed random peptide libraries were screened with plasma before treatment and after recurrence of inhibitors. A peptide corresponding to a dominant amino acid motif selected by phage display bound FVIII-specific IgG1 before and after anti-CD20 treatment and partially restored FVIII activity in vitro. This peptide mimics a conformational epitope in the A2 domain of factor VIII, which is still recognized after inhibitor relapse despite complete B cell depletion and long-term absence of inhibitors. Mapping of specific epitopes on a defined antigen gives further information on mechanisms underlying B cell repopulation after rituximab therapy.