Plasma-derived C1 esterase inhibitor pharmacokinetics and safety in patients with hereditary angioedema

Background

Over 40 years of use demonstrates that complement 1 esterase inhibitor (C1-INH) concentrate is effective and well tolerated for acute edema attacks and prophylaxis in patients with hereditary angioedema. OCTA-C1-INH is a new stable, virus-inactivated, nanofiltrated concentrate of C1-INH derived from human plasma.

Objective

We investigated the pharmacokinetics and safety profile of new C1-INH in people with hereditary angioedema during an attack-free period.

Methods

In this prospective, multicenter, open-label, single-arm study, adults with hereditary angioedema type I/II received a single intravenous dose of 20 IU/kg C1-INH. Blood samples were taken ≤30 minutes before infusion, and 0, 0.25, 1, 2, 6, 12, 24, 48, 72, 120, 144, and 168 hours after infusion. The primary end point was assessing the pharmacokinetic parameters of C1-INH measured by C1-INH activity. Safety end points were also examined.

Results

Twenty patients received a single dose of 20 IU/kg new C1-INH with a mean (standard deviation) total dose of 1457.3 (356.51) IU. Mean (standard deviation) area under the curve normalized by dose was 51.6 (17.9) h∙IU/mL/IU, maximum blood concentration was 1.14 (0.989) IU/mL, incremental recovery was 0.0466 (0.051) (IU∙kg)/(IU∙mL), half-life was 0.598 (0.716) hours, and time to maximum concentration was 0.598 (0.716) hours. No thromboembolic events were recorded. No treatment-emergent adverse events were rated as severe/serious.

Conclusion

PK parameters of new C1-INH were in line with those reported for other C1-INH concentrates. New C1-INH demonstrated a favorable safety profile in patients with C1-INH deficiency. Further studies are warranted to determine the effectiveness and longer-term safety of new C1-INH.

Cloning and expression of gene fragment IgA-binding protein of group B streptococci

Different fragments of the bac gene coding for the IgA-binding protein were cloned, sequenced and expressed in E. coli. Cloning was accomplished after amplification of different parts of the gene by PCR. The 1.5-kb fragment of the gene was cloned using plasmid pBluescript. This fragment coded for the 45-kDa protein with the stable expression of IgA binding. In order to verify the exact location of the IgA-binding domain two smaller plasmids were constructed. Both plasmids were prepared using pQE30 (31, 32) expression vectors from Qiagen. The plasmids carried 245 and 123 bp bac gene fragments encoding 14- and 7-kDa proteins. These proteins together with the 20-amino-acid oligopeptide ITNEDKDSMLKKIEDINRQA were tested for IgA binding. Only the 14-kDa protein was able to bind IgA. This protein was used for rabbit immunization and found to be immunogenic. The data obtained lead to the conclusion that there is a lower limit in the size of recombinant IgA-binding proteins that can be utilized for anti-GBS vaccination.

Characterization of clinical isolates of group C and G streptococci on the basis of protein G gene

Treatment of human group C and G streptococci with cyanogen bromide results in solubilization of surface protein G molecules. Strain-to-strain variation in the quantity, molar mass and functional activity of protein G extracted from representative group C and G isolates led to the identification of three structurally and functionally distinct forms of the protein. Using different molecular biological approaches it was possible to determine the group of streptococci (C or G), or the quantity of IgG and HSA domains.

Protein G expressed by human group C and G streptococci: cloning of gene and binding properties

PCR generated fragments of the protein G gene from three GCS and GGS strains belonging to different G types had been cloned. The resulting PCR products were cloned into E. coli using expression vector pQE31. The clones, producing IgG-binding peptides were selected. Recombinant plasmids carried different inserts and encoded proteins of different size and with different binding properties.

Comparative genetic study of group B streptococcal strains of human and bovine origin

The presence and restriction fragment length polymorphism (RFLP) of DNA fragments hybridizing with virulence and "house keeping" gene probes were analyzed for 87 group B streptococcal (GBS) strains of human and bovine origin. Most characteristics obtained for bovine strains were similar when compared with those for human strains. The most significant degree of RFLP was discovered for the sizes of HindIII fragments containing bca gene. Human GBS strains with bac gene, encoding beta antigen with IgA binding capacity, were characterized by almost identical complex hybridization patterns with multiple gene probes. At the same time bac gene was not found among bovine GBS strains. Gene scpB that encodes C5a peptidase in all human GBS strains was detected only in 9 of 39 strains of bovine origin. These two characteristics effectively distinguished bovine GBS strains from GBS strains of human origin.