The low molecular weight heparin, tinzaparin, in thrombosis and beyond

Quality control, safety assessment and preparation approaches of low molecular weight heparin

Low Molecular Weight Heparins (LMWHs) are well-established for use in the prevention and treatment of thrombotic diseases, and as a substitute for unfractionated heparin (UFH) due to their predictable pharmacokinetics and subcutaneous bioavailability. LMWHs are produced by various depolymerization methods from UFH, resulting in heterogeneous compounds with similar biochemical and pharmacological properties. However, the delicate supply chain of UFH and potential contamination from animal sources require new manufacturing approaches for LMWHs. Various LMWH preparation methods are emerging, such as chemical synthesis, enzymatic or chemical depolymerization and chemoenzymatic synthesis. To establish the sameness of active ingredients in both innovator and generic LMWH products, the Food and Drug Administration has implemented a stringent scientific method of equivalence based on physicochemical properties, heparin source material and depolymerization techniques, disaccharide composition and oligosaccharide mapping, biological and biochemical properties, and in vivo pharmacodynamic profiles. In this review, we discuss currently available LMWHs, potential manufacturing methods, and recent progress for manufacturing quality control of these LMWHs.

Intensive-Dose Tinzaparin in Hospitalized COVID-19 Patients: The INTERACT Study

(1) Background: It is well-established that coronavirus disease-2019 (COVID-19) is highly pro-inflammatory, leading to activation of the coagulation cascade. COVID-19-induced hypercoagulability is associated with adverse outcomes and mortality. Current guidelines recommend that hospitalized COVID-19 patients should receive pharmacological prophylaxis against venous thromboembolism (VTE). (2) INTERACT is a retrospective, phase IV, observational cohort study aiming to evaluate the overall clinical effectiveness and safety of a higher than conventionally used prophylactic dose of anticoagulation with tinzaparin administered for VTE prevention in non-critically ill COVID-19 patients with moderate disease severity. (3) Results: A total of 705 patients from 13 hospitals in Greece participated in the study (55% men, median age 62 years). Anticoagulation with tinzaparin was initiated immediately after admission. A full therapeutic dose was received by 36.3% of the participants (mean ± SD 166 ± 33 IU/Kgr/day) and the remaining patients (63.9%) received an intermediate dose (mean ± SD 114 ± 22 IU/Kgr/day). The median treatment duration was 13 days (Q1−Q3: 8−20 days). During the study (April 2020 to November 2021), 14 thrombotic events (2.0%) were diagnosed (i.e., three cases of pulmonary embolism (PE) and 11 cases of deep venous thrombosis, DVT). Four bleeding events were recorded (0.6%). In-hospital death occurred in 12 patients (1.7%). Thrombosis was associated with increasing age (median: 74.5 years, Q1−Q3: 62−79, for patients with thrombosis vs. 61.9 years, Q1−Q3: 49−72, p = 0.0149), increased D-dimer levels for all three evaluation time points (at admission: 2490, Q1−Q3: 1580−6480 vs. 700, Q1−Q3: 400−1475, p < 0.0001), one week ± two days after admission (3510, Q1−Q3: 1458−9500 vs. 619, Q1−Q3: 352−1054.5, p < 0.0001), as well as upon discharge (1618.5, Q1−Q3: 1010−2255 vs. 500, Q1−Q3: 294−918, p < 0.0001). Clinical and laboratory improvement was affirmed by decreasing D-dimer and CRP levels, increasing platelet numbers and oxygen saturation measurements, and a drop in the World Health Organization (WHO) progression scale. (4) Conclusions: The findings of our study are in favor of prophylactic anticoagulation with an intermediate to full therapeutic dose of tinzaparin among non-critically ill patients hospitalized with COVID-19.

Enoxaparin-induced reactive thrombocytosis: a case report

Background

Enoxaparin is an anticoagulant that falls in the class of medications called low molecular weight heparins (LMWHs), and is used to prevent or treat patients with deep vein thrombosis (DVT) and pulmonary embolism. Enoxaparin is the most widely used LMWH for DVT prophylaxis following knee or hip replacement surgery. Common side effects of enoxaparin include bleeding, petechiae at the injection site, and thrombocytopenia. However, reactive thrombocytosis is a rarely reported adverse reaction. We managed a patient who developed enoxaparin-associated thrombocytosis, which was completely resolved after treatment cessation.

Case presentation

A 78-year-old female was hospitalized for post-hip replacement rehabilitation. Low molecular weight heparin 40 mg/day was administered subcutaneously to prevent deep venous thrombosis (DVT). At admission, her platelet count was normal (228 × 10⁹/L) and her white blood cell count was slightly elevated (12.91 × 10⁹/L). Seven days after admission, the patient developed thrombocytosis, which peaked on the 14th day (836 × 10⁹/L), while her white blood cell count had returned to normal (8.86 × 10⁹/L). Her therapeutic regimen was reviewed, and enoxaparin was identified as a potentially reversible cause of reactive thrombocytosis. Switching from enoxaparin to rivaroxaban lead to a gradual decrease in the patient’s platelet count, which eventually returned to normal levels 16 days after enoxaparin was discontinued. No complications secondary to thrombocytosis was observed, and no conclusion was reached on the use of small doses of aspirin for antithrombotic therapy under these circumstances.

Conclusion

Enoxaparin-induced reactive thrombocytosis should be suspected in patients with thrombocytosis following enoxaparin administration as an anticoagulant to prevent certain complications.

Recent Developments in the Separation of Low Molecular Weight Heparin Anticoagulants

The general function of anticoagulants is to prevent blood clotting and growing of the existing clots in blood vessels. In recent years, there has been a significant improvement in developing methods of prevention as well as pharmacologic and surgical treatment of thrombosis. For over the last two decades, low molecular weight heparins (LMWHs) have found their application in the antithrombotic diseases treatment. These types of drugs are widely used in clinical therapy. Despite the biological and medical importance of LMWHs, they have not been completely characterized in terms of their chemical structure. Due to both, the structural complexity of these anticoagulants and the presence of impurities, their structural characterization requires the employment of advanced analytical techniques. Since separation techniques play the key role in these endeavors, this review will focus on the presentation of recent developments in the separation of LMWH anticoagulants.

Prevention and treatment of the post-thrombotic syndrome

Post thrombotic syndrome (PTS) is a common chronic complication of deep vein thrombosis of the leg (DVT). Treatment options are limited therefore emphasis is placed on its prevention. Several risk factors have been recognized, but were so far not used for risk stratification or translation into prediction models. Early interventions did not yet result in more successful preventive treatment strategies; for the acute phase of DVT there is equipoise on the value of elastic compression, as well as on catheter directed thrombolysis. There are no drugs specifically targeted at PTS prevention. The use of anticoagulant medication such as direct oral anticoagulants (DOACs) might decrease PTS incidence, but this needs to be corroborated. Both research into more effective treatment options as well as future PTS management may benefit from a uniform diagnostic strategy and the use of prediction rules to better allocate treatment and thereby increase treatment efficacy.

Ultrasonic-assisted preparation of a low molecular weight heparin (LMWH) with anticoagulant activity

Low molecular weight heparin (LMWH) is currently used as an anticoagulant agent and constitutes an alternative to unfractionated heparin, which is the cause of serious adverse drug reaction such as heparin-induced thrombocytopenia (HIT). Commercially available LMWH is produced by enzymatic depolymerization that is costly or by chemical methods that are generally carried out under conditions that could imply side reactions that reduce final product efficiency and yields. In this work, we present the use of a physicochemical method for the production of LMWH. This method consists in the use of hydrogen peroxide-catalyzed radical hydrolysis assisted by ultrasonic waves. LMWH that are produced using this physicochemical method have an average molecular weight and anticoagulant properties (Anti-Xa and Anti-IIa) that are comparable to some of commercial LMWH that are currently used. Ultrasonic-assisted radical depolymerization of heparin leads to products with a remarkably low polydispersity index. Moreover, in comparison to other LMWH such as those produced by enzymatic β-elimination, this physicochemical depolymerization of heparin induces fewer oligosaccharides with less than five monosaccharide units. This contributes to the better preservation of the ATIII pentasaccharide binding sequence, which results in a high Anti-Xa/Anti-IIa ratio (1.86). However, LMWH obtained using this physicochemical method have a lower degree of sulfation than other LMWH, which seems to be the cause of a lower Anti-Xa and Anti-IIa activity (143.62±5.42 and 77.07±4.4, respectively).

Post-thrombotic syndrome: a clinical review

Up to half of patients with proximal deep vein thrombosis (DVT) will develop post-thrombotic syndrome (PTS) despite optimal anticoagulant therapy. PTS significantly impacts upon quality of life and has major health-economic implications. This narrative review describes the pathophysiology, risk factors, and diagnosis, prevention and treatment of PTS, to improve our understanding of the disease and guide treatment. Relevant articles were identified through systematic searches of the PubMed, EMBASE and Cochrane databases between 1966 and November 2011. Studies were included for detailed assessment if they met the following criteria: published in English, human study participants, study population aged > 18 years, and lower limb post-thrombotic syndrome. All non-systematic reviews and single patient case reports were excluded. Recurrent thrombosis, thrombus location and obesity are major risk factors, whereas the importance of gender and age remain uncertain. The diagnosis of PTS is based on clinical findings in patients with a known history of DVT. Several clinical scales have been described, with the Villalta Score gaining increasing popularity. Adequate anticoagulation and use of elastic compression stockings (ECS) following DVT can reduce the incidence of PTS. Catheter-directed thrombolysis and mechanical thrombectomy of acute DVT may preserve valvular function. Studies to date of these techniques are encouraging, and have reported improved hemodynamics and a reduced incidence of PTS. The management of established PTS is challenging. Compression therapy, aimed at reducing the underling venous hypertension, remains the mainstay of treatment. This is despite a paucity of high-quality evidence to support its use. Pharmacologic and surgical treatments have also been described, with a number of studies citing symptomatic improvement.

The antineoplastic effect of low-molecular-weight heparins - a literature review

There is some evidence for the antitumor effect of heparins, especially the low-molecular-weight ones. The authors discuss the potential mechanism of this antineoplastic effect and present results from several in vitro and in vivo experiments. The clinical trials concerning the impact of low-molecular-weight heparins on the tumor and on the patients' survival are described. The objective was to find out if heparins could be administered as an antitumor drug, independently of their anticoagulatory properties. The antitumor role of tissue factor, heparinase, chemokines, stromal proteins, cellular interactions as well as angiogenesis and immunology seems certain. The results of the available studies seem promising but large clinical trials are necessary in order to confirm the antineoplastic effect of the low-molecular-weight heparins and to approve them for standard anticancer treatment. It could be a breakthrough in modern oncology.

Review: Management of Painful Vaso-Occlusive Crisis of Sickle-Cell Anemia: Consensus Opinion

Sickle-cell disease (SCD) is a wide-spread inherited hemolytic anemia that is due to a point mutation, leading to the substitution of valine for glutamic acid, causing a spectrum of clinical manifestations in addition to hemolysis and anemia. Acute painful crisis is a common sequela that can cause significant morbidity and negatively impact the patient’s quality of life. Remarkable improvements in the understanding of the pathogenesis of this clinical syndrome and the role of cell adhesion, inflammation, and coagulation in acute painful crisis have led to changes in the management of pain. Due to the endemic nature of SCD in various parts of the Middle East, a group of physicians and scientists from the United States and Middle East recently met to draw up a set of suggested guidelines for the management of acute painful crisis that are reflective of local and international experience. This review brings together a detailed etiology, the pathophysiology, and clinical presentation of SCD, including the differential diagnoses of pain associated with the disease, with evidence-based recommendations for pain management and the potential impact of low-molecular-weight heparin (LMWH), from the perspective of physicians and scientists with long-term experience in the management of a large number of patients with SCD.

Diagnosis and management of sickle cell disorders

Sickle cell disease (SCD) is a wide-spread inherited hemolytic anemia that is due to a point mutation leading to a valine/glutamic acid substitution in the beta-globin chain, causing a spectrum of clinical manifestations in addition to hemolysis and anemia. Acute painful crisis is a common sequela that can cause significant morbidity and negatively impact the patient's quality of life. Remarkable improvements in our understanding of the pathogenesis of this clinical syndrome and the role of cell adhesion, inflammation, and coagulation in acute painful crisis have led to changes in the management of pain. Due to the endemic nature of SCD in various parts of the Middle East, a group of physicians and scientists from the United States and Middle East recently met to draw up a set of suggested guidelines for the management of acute painful crisis that are reflective of local and international experience. This chapter brings together a detailed etiology, pathophysiology, and clinical presentation of SCD, including the differential diagnoses of pain associated with the disease, with evidence-based recommendations for pain management and the potential impact of low-molecular weight heparin (LMWH), from the perspective of physicians and scientists with long-term experience in the management of a large number of SCD patients.

FRAGMATIC: a randomised phase III clinical trial investigating the effect of fragmin added to standard therapy in patients with lung cancer

Background

Venous thromboembolism (VTE) occurs when blood clots in the leg, pelvic or other deep vein (deep vein thrombosis) with or without transport of the thrombus into the pulmonary arterial circulation (pulmonary embolus). VTE is common in patients with cancer and is increased by surgery, chemotherapy, radiotherapy and disease progression. Low molecular weight heparin (LMWH) is routinely used to treat VTE and some evidence suggests that LMWH may also have an anticancer effect, by reduction in the incidence of metastases. The FRAGMATIC trial will assess the effect of adding dalteparin (FRAGMIN), a type of LMWH, to standard treatment for patients with lung cancer.

Methods/Design

The study design is a randomised multicentre phase III trial comparing standard treatment and standard treatment plus daily LMWH for 24 weeks in patients with lung cancer. Patients eligible for this study must have histopathological or cytological diagnosis of primary bronchial carcinoma (small cell or non-small cell) within 6 weeks of randomisation, be 18 or older, and must be willing and able to self-administer 5000 IU dalteparin by daily subcutaneous injection or have it administered to themselves or by a carer for 24 weeks. A total of 2200 patients will be recruited from all over the UK over a 3 year period and followed up for a minimum of 1 year after randomisation. Patients will be randomised to one of the two treatment groups in a 1:1 ratio, standard treatment or standard treatment plus dalteparin. The primary outcome measure of the trial is overall survival. The secondary outcome measures include venous thrombotic event (VTE) free survival, serious adverse events (SAEs), metastasis-free survival, toxicity, quality of life (QoL), levels of breathlessness, anxiety and depression, cost effectiveness and cost utility.

Trial registration

Current Controlled Trials ISRCTN80812769

Anticoagulation therapy for prevention and treatment of venous thromboembolic events in cancer patients: a review of current guidelines

Cancer patients in general have a high risk of venous thromboembolic events (VTE) driven not only by patient-related risk factors, but also risk factors related to the disease and anti-cancer therapies. Cancer patients with documented VTE have a notably worse outcome than non-cancer VTE patients. Since VTE is a highly preventable condition, it is striking that large surveys have shown significant underuse of VTE prophylaxis in surgical cancer patients and in medical cancer patients in particular. Recently, guidelines have been issued from European and American medical oncology societies and organizations for identification of cancer patients at risk, and the guidelines give recommendations for treatment of individual groups of cancer patients. This review summarizes the recommendations for VTE prophylaxis and treatment from the recent guidelines and reviews some outstanding issues in VTE prophylaxis and treatment of cancer patients.

Home therapy of venous thrombosis with long-term LMWH versus usual care: patient satisfaction and post-thrombotic syndrome

PURPOSE

Home-LITE compared long-term treatment at home with tinzaparin or usual care in terms of efficacy, safety, patients' treatment satisfaction, incidence of post-thrombotic syndrome, and associated venous leg ulcers.

METHODS

This multicenter, randomized, controlled trial enrolled 480 patients with documented, acute, proximal deep vein thrombosis. Patients received tinzaparin 175 IU/kg subcutaneously once daily for 12 weeks, or tinzaparin for >or=5 days plus oral warfarin, commenced on day 1, international normalized ratio-adjusted, and continued for >or=12 weeks ("usual care"). Patients received 1 in-clinic injection, then home treatment.

RESULTS

The rate of recurrent venous thromboembolism at 12 weeks was 3.3% in both groups (absolute difference 0%; 95% confidence interval -3.2-3.2), and at 1 year was 10.4%/8.3% in the tinzaparin/usual-care groups, respectively (difference 2.1%; 95% confidence interval -3.1-7.3). There were no between-group differences in deaths at 12 weeks or 1 year, or bleeding at 12 weeks. Patients in the tinzaparin group expressed significantly greater treatment satisfaction (P = .0024), particularly regarding freedom from the inconvenience of blood monitoring; were less likely to report signs/symptoms of post-thrombotic syndrome (individual odds ratios 0.66 to 0.91, overall odds ratio 0.77, P = .001); and reported fewer leg ulcers at 12 weeks: 1 (0.5%) versus 8 (4.1%) (P = .02) with usual care.

CONCLUSIONS

Long-term home treatment with tinzaparin or usual care resulted in similar rates of recurrent venous thromboembolism, death, and bleeding. The significantly lower incidence of post-thrombotic syndrome and leg ulcers observed in the tinzaparin group is a potentially important benefit and deserves further study.

Quantitative PCR and Disaccharide Profiling to Characterize the Animal Origin of Low-Molecular-Weight Heparins

Low-molecular-weight heparins (LMWHs) are widely used in the management of thrombosis and acute coronary syndromes. They are obtained by the enzymatic or chemical depolymerization of porcine intestinal heparin. Enoxaparin sodium, a widely used LMWH, has a unique and reproducible oligosaccharide profile which is determined by the origin of the starting material and a tightly controlled manufacturing process. Although other enoxaparin-like LMWHs do exist, specific release criteria including the origin of the crude heparin utilized for their production, have not been established. A quantitative polymerase chain reaction method has been developed to ensure the purity of the porcine origin of crude heparin, with a DNA detection limit as low as 1 ppm for bovine, or 10 ppm for ovine contaminants. This method is routinely used as the release acceptance criterion during enoxaparin sodium manufacturing. Furthermore, when the process removes DNA, other analytical techniques can be used to assess any contamination. Disaccharide profiling after exhaustive depolymerization can determine the presence of at least 10% bovine or 20% ovine material; multivariate analysis is useful to perform the data analysis. Consistent with the availability of newer technology, these methods should be required as acceptance criteria for crude heparins used in the manufacture of LMWHs to ensure their safety, quality, and immunologic profile.

High yield, purity and activity of soluble recombinant Bacteroides thetaiotaomicron GST-heparinase I from Escherichia coli

Heparinase I from Flavobacterium heparinum, a source of diverse polysaccharidases, suffers from low yields, insufficient purity for structural studies and insolubility when expressed as a recombinant product in Escherichia coli that is devoid of glycosaminoglycan polysaccharidases. In this study, cDNA coding for the orthologue of F. heparinum heparinase I was constructed from genomic information from the mammalian gut symbiont Bacteroides thetaiotaomicron and expressed in E. coli as a fusion protein with GST at the N-terminus. This resulted in high yield (30 mg/g dry bacteria) of soluble product and facilitated one-step affinity purification to homogeneity. Purified heparinase I bearing the GST fusion exhibited a K(m) of 2.3 microM and V(max) of 42.7 micromol/min with a specific activity of 164 U/mg with heparin (average 12,000 Da) as substrate. The results indicate a 2-fold improvement in yield, specific activity and affinity for heparin as substrate over previous reports. The data suggest that the heparinase I from the gut symbiont exhibits a higher intrinsic affinity for heparin than that from F. heparinum. The purified GST fusion enzyme exhibited a requirement for Ca(2+) and a pH optimum between 6.7 and 7.3 that was similar to the enzyme freed of the N-terminal GST portion. Our study revealed that catalytic activity of heparinase I requires a reducing environment. The GST facilitated immobilization of heparinase I in solid phase either for clinical purposes or for structural studies in absence of interference by contaminating polysaccharidases.

Size-exclusion chromatography of heparin oligosaccharides at high and low pressure

Recent findings on specific and non-specific interactions of glycosaminoglycans (GAGs) accentuate their pivotal role in biology and the call for improved sequencing tools. The present study evaluates size-exclusion chromatography (SEC) of heparin oligosaccharides at high and low pressure, requiring amounts as low as 0.2 microgram, using conventional UV detection after depolymerization with heparin lyases. Because of their high charge at physiological pH, SEC elution volumes of heparin oligosaccharides depend on both molecular size and charge repulsion from the matrix. As a consequence, SEC elution volumes of GAGs are smaller than those of globular proteins of similar molecular weight, and this might be exploited. Accordingly, larger heparin oligosaccharides are best separated according to their size at high ionic strength of the mobile phase (>30 mM); in contrast, disaccharides are best separated according to their charge at low ionic strength, compatible with on-line coupling to mass spectrometry. Optimized SEC affords separation of characteristic heparin trisaccharides that contain uronic acid at the reducing end and suggest cellular storage of heparin as a free glycan.

Low-molecular-weight heparins and angiogenesis

The involvement of the vascular system in malignancy encompasses not only angiogenesis, but also systemic hypercoagulability and a pro-thrombotic state, and there is increasing evidence that pathways of blood coagulation and angiogenesis are reciprocally linked. In fact, cancer atients often display hypercoagulability resulting in markedly increased thromboembolism, which requires anti-coagulant treatment using heparins, for example. Clinical trials reveal that treatment with various low-molecular-weight heparins (LMWHs) improves the survival time in cancer patients receiving chemotherapy compared with those receiving unfractionated standard heparin (UFH) or no heparin treatment, as well as in cancer patients receiving LMWH as thrombosis prophylaxis during primary surgery. This anti-tumor effect of the heparins appears to be unrelated to their anti-coagulant activity, but the mechanisms involved are not fully understood. Tumor growth and spread are dependent on angiogenesis and it is noteworthy that the most potent endogenous pro- and anti-angiogenic factors are heparin-binding proteins that may be affected by systemic treatment with heparins. Heparin and other glycosaminoglycans play a role in vascular endothelial cell function, as they are able to modulate the activities of angiogenic growth factors by facilitating the interaction with their receptor and promoting receptor activation. To date, preclinical studies have demonstrated that only LMWH fragments produced by the heparinase digestion of UFH, i.e. tinzaparin, exert anti-angiogenic effects in any type of tissue in vivo. These effects are fragment-mass-specific and angiogenesis-type-specific. Data on the effect of various LMWHs and UFH on endothelial cell capillary tube formation and proliferation in vitro are also presented. We hope that this paper will stimulate and facilitate future research designed to elucidate whether the anti-angiogenic or anti-tumor effects of commercial LMWHs in their own right are agent specific and whether anti-angiogenic properties increase the anti-tumor properties of the LMWHs in the clinic.

Effect of low molecular weight heparin and different heparin molecular weight fractions on the activity of the matrix-degrading enzyme aggrecanase: Structure-function relationship

The matrix-degrading enzyme aggrecanase has been identified in cartilage and is largely responsible for cartilage breakdown. The present study determined the efficacy of different heparin molecular weight fractions (HMWFs) and low molecular weight heparins (LMWHs) on aggrecanase activity. Aggrecanase activity was determined using biotinylated peptide substrate, which was immobilized onto streptavidin-coated 96-well plates; aggrecanase enzyme was then added. Proteolysis of the substrate at the specific amide bond was detected using specific antibody for the neoepitope generated. HMWFs ranging from 1,700 to 12,000 Da demonstrated a concentration-dependent inhibitory efficacy of aggrecanase activity, with a Ki ranging from 5,000 nM down to 1 nM as a function of the molecular weight. The higher the molecular weight distribution, the greater the inhibitory efficacy of the heparin fragments toward aggrecanase activity. The absence or presence of antithrombin did not alter the affinity of heparin in inhibiting aggrecanase. Additionally, tissue factor pathway inhibitor at various levels did not alter the activity of aggrecanase. LMWHs demonstrated different levels of potency in inhibiting aggrecanase activity as a function of their average molecular weight distribution. Tinzaparin (average molecular weight = 6,500 Da) and enoxaparin (average molecular weight = 4,500 Da) demonstrated a Ki of 20 and 80 nM, respectively. The aggrecanase inhibitory effect of LMWH might contribute to blocking inflammation and tumor invasion by inhibiting aggrecanase activity and maintaining an intact extracellular matrix barrier.

Molecular and pharmacologic profile of tinzaparin and a comparable low-molecular-weight bacterial sulfaminoheparosan

Low-molecular-weight heparins (LMWH) represent depolymerized porcine mucosal heparin derivatives, which are commonly used for the management of thrombotic disorders. Because of their widespread usage, the supplies of the raw material namely unfractionated heparin are nearly exhausted. Porcine mucosal tissue is almost exclusively used for the preparation of these agents. Thus, there is a timely need for the production of heparin like drugs from other sources. Fermentation techniques have been used to produce carbohydrates such as dextran and innulin for therapeutic purposes. Bacterial cell wall polysaccharide mimics the linear hexose units, which constitute heparin. Utilizing Escherichia coli cell membranes produced by fermentation technology, chemical sulfation and enzymatic epimerization, sulfaminoheparosan type of polymer mimicking the structure of heparin has been produced. These semi-synthetic sulfaminoheparosans exhibit biologic actions comparable to that observed with heparin. The sulfaminoheparosan core can also be degraded to obtain low-molecular-weight (LMW) derivatives mimicking LMWHs. Using this technique, a novel LMW sulfaminoheparosan derivative (Q93C/239) was produced by Inalco, Milan, Italy. To compare this heparin analogue, a LMWH, namely tinzaparin, was used to determine the relative anticoagulant, antiprotease, and molecular profile. Additional studies were carried out to determine the susceptibility of this agent to heparinase-I. These comparative studies exhibited both antiprotease and anticoagulant properties similar to those of tinzaparin. However LMW sulfaminoheparosan resisted heparinase-I digestion at low heparinase-I concentrations. These studies demonstrate that the sulfaminoheparosan derived LMW components exhibit similar molecular and anticoagulant profile as tinzaparin and warrant additional preclinical and clinical development to determine their potential usefulness as antithrombotic agents.

Comparative study of the pharmacokinetic profiles of two LMWHs--bemiparin (3500 IU, anti-Xa) and tinzaparin (4500 IU, anti-Xa)--administered subcutaneously to healthy male volunteers

Pharmacokinetic profiles of bemiparin (3500 IU, anti-Xa) and tinzaparin (4500 IU, anti-Xa) administered subcutaneously to 12 healthy male volunteers were compared in a monocentric study. Each of the 12 subjects underwent successively the two low-molecular-weight heparin (LMWH) preparations in a randomised order and was considered as its own control. Anti-Xa activity, free and total tissue factor pathway inhibitor (TFPI), and thromboplastin-thrombomodulin-mediated time were determined as main variables. Activated partial thromboplastin time (APTT), thrombin clotting time, and anti-IIa activity were also determined. Bemiparin (3500 IU, anti-Xa) exerts a significantly more rapid, more potent, and more prolonged anti-Xa activity than tinzaparin (4500 IU, anti-Xa). The plasma level increase for free and total TFPI is significantly lower with bemiparin than with tinzaparin. Free and total TFPI peak levels occur earlier than anti-Xa activity peak levels for both LMWH preparations, but no statistical difference appeared between the two preparations for TFPI T(max). No significant effect was observed for both preparations for thromboplastin-thrombomodulin-mediated time. Subcutaneous injection of bemiparin exerts only minimal anti-IIa activity and does not prolong thrombin time, whereas tinzaparin elicits significant anti-IIa activity and prolongs thrombin clotting time. Bemiparin exerts a significantly lower prolongation of APTT than tinzaparin. No difference was observed for APTT prolongation T(max) between the two preparations. Globally, the overall tolerability of both formulations revealed no relevant adverse effects. In conclusion, bemiparin and tinzaparin are not bioequivalent. Bemiparin exerts an important and more prolonged anti-Xa activity in comparison with tinzaparin. An original finding of this study is the difference observed between the two formulations for free TFPI release.