Tissue Factor Pathway Inhibitor (TFPI) release by bovine, ovine and porcine unfractionated heparins in primates. Comparative studies at mass and potency adjusted intravenous dosing

Abstract

BackgroundUnfractionated heparin (UFH) is a highly sulfated glycosaminoglycan (GAG) that consists of repeating disaccharide units, containing iduronic acid (or glucuronic acid) and glucosamine, exhibiting variable degrees of sulfation. UFHs release tissue factor pathway inhibitor (TFPI) which inhibits extrinsic pathway of coagulation by rapidly inactivating of Factor Xa and the Factor VIIa/TF complex. Bovine mucosal heparins (BMH) and ovine mucosal heparin (OMH) are currently being developed for re‐introduction for both medical and surgical indications. In contrast to the porcine mucosal heparins (PMH), the active pharmaceutical ingredient (API) BMH exhibits a somewhat weaker anti‐coagulant activity as cross‐referenced against PMH. In this study, we determined the TFPI antigen release level by various dosages of UFHs using ELISA method. Also, we projected that potency adjusted BMH at equivalent dosage has the same TFPI release profile compared to OMH and PMH.Materials & MethodsBMH, OMH and PMH were obtained from various commercial sources. Potencies of each heparin were determined by an amidolytic anti‐Xa assay in relation to the USP heparin standard. Individual groups of primates (n=4) were administered 0.5 mg/kg or (50 or 100) U/kg dosage of bovine, ovine or porcine UFH via intravenous route. Blood samples were collected at baseline, 15, 30, 60 and 120 minutes post‐administration. Tissue Factor Pathway Inhibitor (TFPI) antigen levels were measured using a commercially available sandwich ELISA methods. All results were compiled as mean ± SD.ResultsAt a gravimetric level (0.5 mg/kg), BMH exhibited a lower TFPI level than OMH & PMH at all time points with a maximum value of (200 ng/ml) at 15 mins post drug administration. OMH and PMH showed comparable TFPI levels at all time points with maximum values of (250 ng/ml) and (265 ng/ml) respectively at 15 mins post drug administration. However, USP cross‐referenced anti‐Xa potency adjusted based dosing showed comparable TFPI antigen levels for all three UFHs at all time points with a maximum value of 250 ng/ml at 15 mins post drug administration. At 60 mins post drug administration, potency adjusted BMH showed slightly higher TFPI level of (200 ng/ml) compared to both OMH & PMH.ConclusionTissue factor pathway inhibitor (TFPI) levels at 15 minutes after IV administration of 0.5 mg/kg heparins to non‐human primates showed that both PMH and OMH release comparable TFPI antigen levels which were significantly higher than BMH. Potency equated dosing resulted in comparable TFPI release profiles for all three heparins. Therefore such dosing may provide uniform levels of anticoagulation for the parenteral indications for UFHs. These observations suggest that potency equated bovine heparin has comparable release of TFPI and therefore is biosimilar to the OMH and PMH.