A Dose Ranging Study to Evaluate Dermatan Sulphate in Preventing Deep Vein Thrombosis following Total Hip Arthroplasty

Recombinant dermatan sulfate is a potent activator of heparin cofactor II-dependent inhibition of thrombin

The glycosaminoglycan dermatan sulfate (DS) is a well-known activator of heparin cofactor II-dependent inactivation of thrombin. In contrast to heparin, dermatan sulfate has never been prepared recombinantly from material of non-animal origin. Here we report on the enzymatic synthesis of structurally well-defined DS with high anticoagulant activity. Using a microbial K4 polysaccharide and the recombinant enzymes DS-epimerase 1, dermatan 4-O-sulfotransferase 1, uronyl 2-O-sulfotransferase and N-acetylgalactosamine 4-sulfate 6-O-sulfotransferase, several new glycostructures have been prepared, such as a homogenously sulfated IdoA-GalNAc-4S polymer and its 2-O-, 6-O- and 2,6-O-sulfated derivatives. Importantly, the recombinant highly 2,4-O-sulfated DS inhibits thrombin via heparin cofactor II, approximately 20 times better than heparin, enabling manipulation of vascular and extravascular coagulation. The potential of this method can be extended to preparation of specific structures that are of importance for binding and activation of cytokines, and control of inflammation and metastasis, involving extravasation and migration.

Pharmacokinetics and pharmacodynamics of intramuscular dermatan sulfate revisited : a single- and repeated-dose study in healthy volunteers

OBJECTIVE

To assess the pharmacokinetics and effects on blood coagulation of dermatan sulfate (DS), a glycosaminoglycan with antithrombotic properties, following intravenous and single and repeated intramuscular administrations. The mean molecular weight of DS is currently 22kD, i.e. 5kD lower than batches used in the early development of the compound.

SUBJECTS AND METHODS

Each of 14 male healthy volunteers received DS 300mg as an 8-hour intravenous infusion and as single and repeated (once daily for 9 days) intramuscular injections. Nine of the same subjects were also given DS 100mg and 200mg as single intramuscular doses. Plasma DS concentrations were measured with a specific chromogenic assay. Activated partial thromboplastin time (aPTT) and thrombin clotting time (TCT) responses were also determined.

RESULTS

The mean +/- SD volume of distribution and terminal half-life of DS were 6.0 +/- 1.4L and 0.9 +/- 0.2h after intravenous infusion. Maximum plasma concentration (C(max)) and area under the plasma concentration-time curve after single intramuscular injections were dose-proportional. After repeated intramuscular administration, steady state was reached by day 3. On day 9, plasma DS fluctuated between 4.3 +/- 1.5 (C(max)) and 0.9 +/- 0.4 (minimum plasma concentration at steady state) mg/L, time to C(max) was 3.4 +/- 0.8h, terminal half-life was 12.2 +/- 4.1h and the accumulation factor was 2.0 +/- 0.5. Geometric mean bioavailability of intramuscular DS was 54% and 79% after single and repeated 300mg administration, respectively. aPTT and TCT responses were both linearly related to plasma DS concentrations, with TCT showing greater responsivity.

CONCLUSION

As compared with earlier DS studies, the present data showed a greater extent of DS absorption after single intramuscular administration and a faster absorption rate after repeated dosing, and provided evidence of dose-response predictability. These findings may explain the improved antithrombotic efficacy of DS observed in a recent clinical trial.

Prolonged bleeding time induced by anticoagulant glycosaminoglycans in dogs is associated with the inhibition of thrombin-induced platelet aggregation

INTRODUCTION

The clinical use of unfractionated heparin (UFH) is complicated by hemorrhage. This has led to a search for safer alternatives, one of which, the recently identified depolymerized holothurian glycosaminoglycan (DHG), causes less bleeding and exhibits a better antithrombotic-hemorrhagic ratio in rats and dogs than UFH and low-molecular-weight heparin (LMWH). In contrast to UFH and LMWH, which exert their anticoagulant effects by inhibiting thrombin in the presence of antithrombin III (AT), DHG exerts its anticoagulant effect by inhibiting the intrinsic factor Xase complex and thrombin in the presence of heparin cofactor II (HCII).

MATERIALS AND METHODS

The hemorrhagic effect of DHG was compared with those of UFH and LMWH in healthy dogs, and the mechanism responsible for prolonging bleeding time was examined both in dogs and with human platelets.

RESULTS

DHG prolonged template-bleeding time in dogs less than UFH and LMWH do. Although the maximum noneffective concentrations of each glycosaminoglycan (GAG) that prolong the bleeding time are almost the same as the concentrations that inhibit thrombin-induced platelet aggregation, they are not related to those that inhibit ADP-induced platelet aggregation. Results of experiments on gel-filtered platelets from humans indicate that the inhibition of thrombin-induced platelet aggregation caused by UFH and LMWH in the presence of AT is more prominent than that caused by DHG with HCII.

CONCLUSIONS

These results suggest that the prolongation of bleeding time caused by GAGs are associated with the inhibition of thrombin-induced platelet aggregation, and DHG may cause less bleeding than UFH and LMWH because of its different thrombin inhibition mechanism in platelet-rich plasma (PRP).

Effect of covalent serpin-heparinoid complexes on plasma thrombin generation on fetal distal lung epithelium

Extravascular coagulation within the lung airspace is a hallmark of respiratory distress syndrome (RDS) in premature infants. We previously showed that covalent antithrombin-heparin complex (ATH) is superior to noncovalent antithrombin (AT) + heparin (H) mixtures at inhibiting plasma thrombin generation on rat fetal distal lung epithelium (FDLE) in vitro. However, heparin cofactor II (HC) has been shown to selectively inhibit thrombin, which may be advantageous if other enzyme activities are present in the airspace. We compared the abilities of ATH, covalent HC-heparin complex (HCH), and covalent HC-dermatan sulfate (HCD) to inhibit thrombin generation on FDLE in plasmas from either adults or newborns. In the presence of ATH, peak free thrombin generation in adult plasma on the cell surface was reduced by 92% compared with controls (no anticoagulant). However, whereas HCH reduced peak free thrombin generation in adult plasma by 81%, HCD was only able to reduce activity by 33%. All covalent complexes caused a greater decrease in thrombin activity compared with that with the corresponding noncovalent serpin + heparinoid mixtures. Experiments in plasma from newborns resulted in peak free thrombin that was less than or equal to that in adult plasma when covalent conjugates were added. Relative peak free thrombin was proportional to rate of prothrombin consumption and amount of thrombin-inhibitor complexes formed. In vivo, experiments in newborn rats showed that a greater percentage of intratracheally instilled ATH and HCH could be recovered in lung lavage fluid compared withwith that for HCD. In summary, ATH, HCH, and HCD are inhibitors of thrombin generation on FDLE superior to the corresponding noncovalent mixtures, with ATH and HCH being more potent than HCD. Covalent conjugates of AT or HC with H may be preferred in treatment of extravascular coagulation.

Dermatan sulfate versus unfractionated heparin for the prevention of venous thromboembolism in patients undergoing surgery for cancer. A cost-effectiveness analysis

BACKGROUND

In a recent clinical trial, dermatan sulfate was found to be more effective than unfractionated heparin (UFH), but equally well tolerated, for the prevention of deep vein thrombosis (DVT) after major surgery for cancer.

OBJECTIVE

To perform a cost-effectiveness analysis of dermatan sulfate versus UFH in this clinical setting.

DESIGN AND SETTING

This was a retrospective economic analysis using data from a randomised clinical trial, and was performed from the hospital perspective.

METHODS

Clinical event rates were extrapolated from the observed venographic DVT rates, using appropriate assumptions from the scientific literature. The economic effects of switching DVT prophylaxis from UFH to dermatan sulfate and the potential lives saved were assessed by a predictive decision model.

RESULTS

The per patient cost, including the burden of residual thromboembolic events and major bleeding complications, was estimated to be 154 euros (EUR) for dermatan sulfate and EUR185 for UFH (1998 values). With reference to a potential target population of 60,000 patients/year undergoing surgery for cancer in Italy, the total prophylaxis-associated cost was EUR9,258,000 for dermatan sulfate and EUR11,096,000 for UFH, whereas the potential deaths from prophylaxis failure were 204 and 392, respectively. This represented a saving of EUR1,838,000 and 188 potential lives per year with the dermatan sulfate option. The final costs and effects were mainly sensitive to variations in the rates of DVT and pulmonary embolism, and to the possible need for 1 extra day of hospitalisation because of the earlier preoperative initiation of dermatan sulfate prophylaxis.

CONCLUSION

Dermatan sulfate is more cost effective than UFH for the prevention of postoperative venous thromboembolism in patients with cancer. If the hospital stay needs to be prolonged, then the dermatan sulfate option may involve a small additional cost (EUR47) per potential life saved.

Dermatan sulphate in patients with heparin-induced thrombocytopenia

Patients with thromboembolic diseases who develop heparin-induced thrombocytopenia (HIT) type II require an alternative anticoagulation strategy. Dermatan sulphate (DS) was administered to five patients with thromboembolic diseases who developed HIT type II and showed an in vitro cross-reactivity with low molecular weight heparins. The platelet count and the extension of thrombosis were monitored during DS administration. In four of the five patients the platelet count rapidly increased after heparin was discontinued and DS started. A low platelet count persisted in the single patient with cross-reactivity to DS, up to 4 d after its discontinuation. None of the patients experienced thrombus extension, haemorrhagic side-effects or other adverse events.

Covalent heparin cofactor II-heparin and heparin cofactor II-dermatan sulfate complexes. Characterization of novel anticoagulants

Heparin cofactor II is a naturally occurring anticoagulant that acts by specifically inhibiting thrombin and is facilitated by the binding of glycosaminoglycans such as heparin and dermatan sulfate. In vivo, heparin cofactor II-glycosaminoglycan complexes dissociate, leaving the inhibitor less active in its ability to function as a component of the anticoagulation pathway. We have produced permanently activated heparin cofactor II molecules by covalent linkage to either heparin or dermatan sulfate. Covalent heparin cofactor II-heparin and heparin cofactor II-dermatan sulfate complexes had catalytic antithrombin activities similar to those of the corresponding starting heparin and dermatan sulfate (86% and 110% of standard heparin and dermatan sulfate activity, respectively). Both heparin cofactor II-heparin and heparin cofactor II-dermatan sulfate had fast bimolecular rate constants of 1.4 x 10(7) M-1 s-1 and 1.3 x 10(7) M-1 s-1, respectively, for reaction with thrombin. The intravenous half-life of the covalent complexes in rabbits was significantly longer than that of free heparin or dermatan sulfate (4.4, 3.4, 0.33, and 0.50 h for heparin cofactor II-heparin, heparin cofactor II-dermatan sulfate, heparin, and dermatan sulfate, respectively). Given their unique properties, these conjugates may have a clinical application for long term, selective inhibition of thrombin.

DHG, a new depolymerized holothurian glycosaminoglycan, exerts an antithrombotic effect with less bleeding than unfractionated or low molecular weight heparin, in rats

We characterized the antithrombotic, haemorrhagic, and ex vivo anticoagulant effects of a recently identified depolymerized holothurian glycosaminoglycan (DHG), and compared these effects with those of unfractionated heparin (UFH), low molecular weight heparin (LMWH), and dermatan sulfate (DS). In thrombin-induced venous thrombus formation in rats, DHG had a significant preventive effect at 0.3 mg/kg or more at 5 min after i.v., administration. UFH, LMWH, and DS also showed a significant antithrombotic effect at 0.3, 0.3, and 1 mg/kg, respectively, under the same experimental conditions. After rat tail transection, DHG, UFH, LMWH, and DS prolonged the bleeding time significantly at 10, 1, 1, and 10 mg/kg, respectively, at 5 min after i.v., injection. Therefore, DHG exerts its antithrombotic effect with less bleeding than UFH and LMWH in experimental animals. DHG prolonged the activated partial thromboplastin time in a dose-dependent manner at 0.3-3 mg/kg, at which dose an antithrombotic effect was exhibited without any significant haemorrhagic effect. All of these glycosaminoglycans prolonged thrombin clotting time markedly at their haemorrhagic doses.