Pergamon Thrombosis Research, Vol 81, No. 2 S, pp. SI-$27, 1996 Copyright © 1996 Elsevier Science Lid Printed in the USA. All rights reserved 0049-3848/96 $12.00 + .00 0049-3848(95)00226-X PRECLINICAL STUDIES ON A LOW MOLECULAR WEIGHT HEPARIN ~Jawed Fareed, ~Walter Jeske, 2Volker Eschenfelder, ~Omer lqbal, tDebra Hoppensteadt and ~Ahmad Ahsan ~Department of Pathology, Loyola University Medical Center, Maywood, IL, USA, and 2Research and Development, Knoll AG, Ludwigshafen, Germany ABSTRACT Some major developments in the area of antithrombotic therapy have occurred during the past decade. Of these, the concept of fractionation of heparin has resulted in the development of several products from this agent. The introduction of low molecular weight heparins (LMWHs) has added a new chapter to the prophylactic and therapeu- tic management of thromboembolic disorders. These agents are now globally accept- ed as drugs of choice tor post-surgical prophylaxis of deep vein thrombosis (DVT). Currently, the LMWHs are being developed for various therapeutic and cardiovascu- lar indications. Reviparin is an optimized LMWH prepared by controlled nitrous acid digestion of porcine mucosal heparin. This drug has been developed using validated procedures and exhibits a relatively narrow molecular weight distribution in contrast to most other commercially available LMWHs. The specific activity in anticoagulant assays is approximately 32 U/rag whereas the specific activity in terms of anti-Xa units is 120 anti-Xa U/mg. Reviparin is capable of producing a dose- and time- dependent antithrombotic effect in animal models of thrombosis. While the ex vivo effects initially occur at dosages that are antithrombotic, this agent has been found to produce sustained antithrombotic effects without any detectable ex viw) anticoagulant actions. This agent has also been found to release tissue factor pathway inhibitor (TFP1) after both intravenous and subcutaneous administration. Repeated admin- istration of reviparin produces progressively stronger antithrombotic effects. The cur- rent studies are designed to provide additional data on its molecular profile using new calibration methods and additional results on the pharmacological studies in a dose- dependent manner. In particular, the release of TFPI following i.v. and s.c. admin- istration in a primate model is described. The effect of repeated administration mimicking the post-surgical prophylaxis of DVT is also reported in terms of any in- crease in the antithrombotic or haemorrhagic effects of this agent. Comparative an- tithrombotic and pharmacological studies are also reported to compare the pharmaco- logical profiles of mviparin, nadroparin and enoxaparin. Key words: Low molecular weight heparin; Tissue filctor pathway inhibitor: Molecular profiling; Bleeding; Antitbrombotic actions Corresponding author: J. Fareed, Department of Pathology and Pharmacology Loyola University Medical Center, 2160 S. First Avenue, Maywood, IL 60153, USA. 81