Target-mediated clearance and bio-distribution of a monoclonal antibody against the Kunitz-type protease inhibitor 2 domain of Tissue Factor Pathway Inhibitor

Thromb Res. 2014 Mar;133(3):464-71. doi: 10.1016/j.thromres.2013.12.015. Epub 2013 Dec 17.

Abstract

Introduction: A humanised monoclonal antibody, concizumab, that binds with high affinity to the Kunitz-type protease inhibitor (KPI) 2 domain of human tissue factor pathway inhibitor (TFPI) is in clinical development. It promotes coagulation by neutralising the inhibitory function of TFPI and may provide a subcutaneous prophylaxis option for patients with haemophilia. We aimed to study biodistribution and pharmacokinetics (PK) of concizumab.

Materials and methods: Blockage of cellular TFPI by concizumab was measured by tissue factor/Factor VIIa-mediated Factor X activation on human EA.hy926 cells. Biodistribution of concizumab was analysed in rabbits by immunohistology, and the PK was measured in rabbits and rats.

Results and conclusions: Concizumab bound to cell surface TFPI on EA.hy926 cells and neutralised TFPI inhibition of Factor X activation. The antibody cross-reacted with rabbit TFPI, but not with rat TFPI, allowing for comparative PK studies. PK data in rats described a log-linear profile typical for a non-binding antibody, whereas PK data in rabbits revealed a non-linear, dose-dependent profile, consistent with a target-mediated clearance mechanism. Immunohistology in rabbits during target-saturation showed localisation of the antibody on the endothelium of the microvasculature in several organs. We observed a marked co-localisation with endogenous rabbit TFPI, but a negligible sub-endothelial build-up. Concizumab binds and neutralises the inhibitory effect of cell surface-bound TFPI. The PK profile observed in rabbits is consistent with a TFPI-mediated drug disposition. Double immunofluorescence shows co-localisation of the antibody with TFPI on the endothelium of the microvasculature and points to this TFPI as a putative target involved in the clearance mechanism.

Keywords: Antibody; Extrinsic pathway; Immunofluorescence; Pharmacokinetics; TFPI; Tissue factor pathway inhibitor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Monoclonal, Humanized / immunology
  • Antibodies, Monoclonal, Humanized / pharmacokinetics*
  • Blood Coagulation
  • Female
  • Humans
  • Lipoproteins / antagonists & inhibitors
  • Lipoproteins / immunology*
  • Mice
  • Protease Inhibitors / immunology
  • Protease Inhibitors / pharmacokinetics*
  • Protein Structure, Tertiary
  • Rabbits
  • Rats
  • Tissue Distribution
  • Trypsin Inhibitor, Kunitz Soybean / immunology

Substances

  • Antibodies, Monoclonal, Humanized
  • Lipoproteins
  • Protease Inhibitors
  • lipoprotein-associated coagulation inhibitor
  • concizumab
  • Trypsin Inhibitor, Kunitz Soybean