Quantitative TFPI Antigen Release and Functionality After Intravenous Administration of Heparins Sourced From Various Species in Non‐human Primates
Authors: Jaradeh Mark , Baig Nausheen , Kouta Ahmed , Duff Richard , Cera Lee , Jeske Walter , Hoppensteadt Debra , Fareed Jawed 
Published: May 2022

Introduction

Tissue factor pathway inhibitor (TFPI) is a multi‐domain Kunitz‐type inhibitor that plays an important role in the regulation of the tissue factor pathway through its release from endothelial sites upon heparin administration. Currently, heparin is primarily sourced from porcine tissue, however, recent advancements have allowed for it to be re‐sources from bovine tissue. In this context, we elected to compare the relative abilities of porcine, bovine, and ovine heparins to release endogenous TFPI following intravenous administrations of gravimetric and USP potency‐adjusted heparin dosages.

Materials

Active pharmaceutical ingredient (API) forms of bovine, ovine, and porcine heparins of mucosal origin were obtained from Kinmaster, Brazil, Ronssi, China, and Medifill, USA, respectively. The active pharmaceutical ingredients were dissolved to obtain 10mg/mL solutions of each type. Individual groups of non‐human primates (n=6) were intravenously injected with 0.5mg/kg and 100U/kg dosages of each heparin type. Blood samples were subsequently drawn at 0, 15, 30, 60, and 120 minutes post‐administration. Citrated blood samples were centrifuged to obtain platelet‐poor plasma and stored at ‐ 80C until analysis. A sandwich ELISA method for TFPI antigen and a chromogenic substrate‐based functional method were used to quantify TFPI antigen release and functionality, respectively. All results were calculated in terms of group means ±SD. Applicable statistical methods were used to compare the heparins for their relative effects on TFPI release.

Results

Gravimetric dosages of ovine and porcine heparins produced comparable TFPI release in both the functional and immunologic assays while bovine heparin demonstrated slightly lower peak TFPI antigen release and slightly higher peak function, as shown in Figure 1a and 1b, respectively. When compared following administration of USP‐adjusted 100U/kg dosages, all three heparins consistently demonstrated essentially identical TFPI antigen release and functional profiles, as shown in Figure 1c and 1d, respectively. Overall, any potential differences in the gravimetric dosing regimens were adequately corrected following USP potency adjustment in both TFPI antigen release and functionality, as seen in Figure 1a and 1b and Figure 1c and 1d, respectively. Furthermore, all three heparins demonstrated comparable pharmacokinetic profiles in both TFPI antigen release and function levels, as shown in Table 1.

Conclusion

These results demonstrate that heparins from various sources are capable of comparatively releasing TFPI antigen. While the gravimetrically‐dosed studies demonstrated less consistent trajectories, potency‐based adjustments of the heparin dosages allowed for improved pharmacokinetic homogeneity. These studies underscore the potential for the development of alternative heparin sources as viable, pharmacokinetic equivalents.