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Aprosulate sodium was the first representative of a new class of synthetic polyanions showing antithrombotic efficacy in different animal models. In several clinical trails (Phase I) in human volunteers aprosulate demonstrated anticoagulant properties, too. Searching for other active substances of similar structure, a series of bis-aldonic acid amides were synthesized. These compounds exhibited interesting antithrombotic and anticoagulant activities. The pharmacodynamic activities of the compounds LW 10121, LW 10125, LW 10114, 10244, and LW 10168 are summarized in this article. These substances prolonged the APTT to 150% of the blank values at concentrations of 1.5 to 13.5 micrograms/mL. The thrombin time and anti-Xa test were only slightly influenced by concentrations up to 100 micrograms/mL. All compounds were investigated in a jugular vein hemostasis model in rats to examine their antithrombotic potential. They all had an antithrombotic activity lower than aprosulate, except compound LW 10121, which seemed to be a little more active. The subcutaneous injection of 10 mg/kg LW 10121 resulted in a longer duration of action than aprosulate and heparin. On the basis of the chemical structure and the profile of action, it is assumed that the new compounds may possess the same mode of action as aprosulate, but the mechanism of action may be different from heparin and low molecular weight heparins.

Fifteen polyanionic bis-aldonic acid amides were synthesized by condensation of the corresponding aldonic acids and alpha,omega-diamines and by subsequent sulfation of the intermediates. The compounds were completely sulfated and exhibited molecular weights between 1450 and 2600 daltons. The antithrombotic activity of these synthetic heparin analogs was evaluated in a rat jugular vein clamping induced thrombosis model. Several compounds pounds were potent antithrombotic substances comparable in potency to the low molecular weight heparin Fraxiparin. Some structure activity relationships on their pharmacologic action could be deduced. The antithrombotic activity of a representative agent was confirmed using the Wessler stasis model in rabbits. In the in vitro tests the bis-aldonic acid amides exhibited moderate to low anticoagulant effects depending on the assay used. In the activated partial thromboplastin time assay, the anticoagulant potency of these compounds was between 2- and 30-fold lower than that of heparin. The anti-factor Xa activity of the experimental substances was at least 50 times lower than that of heparin, whereas the compounds were devoid of anti-factor IIa activity when measured in an amidolytic assay. The anticoagulant effects of these agents were dependent on the length of the spacing and on the type of aldonic acid moieties. These bisaldonic acid amides represent a novel class of potent antithrombotic substances without any anti-factor IIa activities and only very low anti-factor Xa activities, suggesting that these antiprotease actions are not a prerequisite for the antithrombotic action of polyanionic substances.

The dose- and time-dependent antithrombotic activity of recombinant hirudin (r-hirudin) was examined in a new animal model of venous thrombosis. For the evaluation of the antithrombotic activity of r-hirudin, an occluding thrombus was produced by repeated clamping of the rat jugular vein. The number of clampings necessary to induce thrombosis served as a measure of antithrombotic activity. The gradual reduction of blood flow was registered by Doppler sonography. In order to estimate the relative antithrombotic activity of r-hirudin, its potency in this model was compared with other antithrombotic substances. r-Hirudin proved to be less potent than heparin after intravenous administration. Its half-life after subcutaneous administration was relatively short; however, the antithrombotic potency after subcutaneous administration was comparable to that of heparin.

A series of sulfated bis-lactobionic acid amides was prepared. The compounds comprise highly charged poly-anions of very low molecular weight. Usually, the compounds contain 16 sulfate groups per molecule and are homogeneous, monodisperse substances. The molecular weights range from 2388 to 2514. The compounds were evaluated for anticoagulant activity using a number of standard tests. The compounds exhibited moderate to good APTT activity. Interestingly, the anti-Xa and anti-IIa activities were very low, particularly in amidolytic assays. Using prothrombin and Factor X activation assays, it was demonstrated that these compounds were more potent in these experimental settings than in standard anti-Xa or anti-IIa assays. Compared with heparin and LMW heparins, the bis-lactobionic acid amides were particularly active as inhibitors of the intrinsic system activation of Factor X. The bis-lactobionic acid amides exhibited potent anticomplement activity, being clearly superior to heparin and LMW heparins. For the most interesting substance, LW 10082, experimental results suggest that its anticoagulant activity is independent of antithrombin II. The anticoagulant activity of LW 10082 was readily neutralized by protamine sulfate. Platelet factor 4, however, did not reduce its anticoagulant activity. Because of these favorable properties, it is hoped that LW 10082 might prove to be an interesting alternative to heparin or LMW heparin in clinical use.

1. The introduced bis-lactobionic acid amides represent a new group of synthetic polyanions with a molecular weight of 2387 to 2514d. The compounds are homogeneous and chemically defined. 2. The in vitro blood coagulation parameters (APTT, Heptest, anti-Xa, thrombin time, and anti-IIa) are only marginally altered by these compounds. 3. In a rat model of venous thrombosis using endothelial damage as the thrombogenic stimulus, the antithrombotic activity of the bis-lactobionic acid amides was shown in a dose- and time-dependent manner. 4. LW 10082 and LW 10121 prolong the bleeding time at dosages about 10 times less than that of heparin. The safety/efficacy index appears to be wider for these compounds than for heparin. 5. In subchronic toxicologic studies in rats, LW 10082 was well tolerated up to a dosage of 100 mg/kg body weight. 6. The anticoagulant and antithrombotic activities of the bis-lactobionic acid amides decrease gradually with the increasing number of methylene groups in the alkylene chain.

Sulfated bis-lactobionic acid amides, a new class of polyanions with heparin-like properties, were synthesized and their antithrombotic and anticoagulant activities were determined. Compared to heparin and Fragmin, a low molecular weight heparin, the substances exhibited moderate to low anticoagulant activities in aPTT, thrombin clotting time and Heptest assays. In amidolytic assays no anti-IIa activity and only exceedingly low anti-Xa activity was observed. The antithrombotic activity of the bis-lactobionic acid amides was determined using two thrombosis models. In rabbit and rat models thrombi were induced by a combination of endothelial damage and reduction of blood flow or only by endothelial damage. At least one of the bis-lactobionic acid amides (LW 10082) exhibited a considerable antithrombotic activity which was similar to low molecular weight heparin.