Antithrombotic Compounds Research Articles

Evaluation of novel factor Xa inhibitors from Oxya chinensis sinuosa with anti-platelet aggregation activity

The edible grasshopper Oxya chinensis sinuosa is consumed worldwide for its various medicinal effects. The purpose of this study was to investigate potential bioactive antithrombotic and antiplatelet compounds from O. chinensis sinuosa. Five N-acetyldopamine dimers (1–5) were isolated from O. chinensis sinuosa and compounds 1 and 2 were identified as new chemicals with chiral centers at H-2 and H-3 of the benzo-1,4-dioxane structure. Compounds 1–4 were found to have both FXa and platelet aggregation inhibitory activities. These compounds inhibited the catalytic activity of FXa toward its synthetic substrate, S-2222, by noncompetitive inhibition, and inhibited platelet aggregation induced by ADP and U46619. Furthermore, compounds 1–4 showed enhanced antithrombotic effects, which were assessed using in vivo models of pulmonary embolism and arterial thrombosis. The isolated compounds also showed anticoagulant effects in mice. However, compounds 1–4 did not prolong bleeding time in mice, as shown by tail clipping. N-Acetyldopamine dimers, including two new stereoisomers 1 and 2, are novel antithrombotic compounds showing both FXa inhibition and antiplatelet aggregation activity with a low bleeding risk. Collectively, these results suggest that compounds 1–4 could serve as candidates and provide scaffolds for development of new antithrombotic drugs.

Anti-factor Xa activities of zingerone with anti-platelet aggregation activity

Zingerone (ZGR), a phenolic alkanone found in Zingiber officinale, has been reported to have various pharmacological activities such as anti-inflammatory, anti-apoptotic, and protecting myocardial infarction and irritable bowel disorder. The aim was to identify the unreported bioactive anti-factor Xa (FXa) and anti-platelet activities of ZGR. ZGR was evaluated for their anti-FXa and anti-platelet aggregation properties by monitoring clotting time, platelet aggregation, FXa activity and production, and thrombus formation. ZGR reduced activated partial thromboplastin time and it inhibited the catalytic activity of FXa toward its substrate S-2222 in a noncompetitive inhibition model and inhibited platelet aggregation induced by adenosine diphosphate (ADP) and U46619 (not thrombin). However, ZGR did not prolong bleeding time in mice, as shown by tail clipping. ZGR also inhibited ADP- and U46619- induced phosphorylation of myristolated alanine-rich C-kinase substrate (MARCKS) and the expressions of P-selectin and PAC-1 in platelets. In an animal model of arterial and pulmonary thrombosis, ZGR showed enhanced antithrombotic effects. ZGR also elicited anticoagulant effects in mice. Our results reveal that ZGR is an antithrombotic compound with both FXa inhibitory and anti-platelet aggregation activities. Collectively, these results show that ZGR could serve as candidates and provide scaffolds for the development of new anti-FXa and anti-platelet drugs.

Thromboprophylaxis With Apixaban in Patients Undergoing Major Orthopedic Surgery: Meta-Analysis and Trial-Sequential Analysis.

BACKGROUNDVenous thromboembolism (VTE) is a potentially fatal complication of orthopedic surgery, and until recently, few antithrombotic compounds were available for postoperative thromboprophylaxis. The introduction of the non–vitamin K antagonists oral anticoagulants (NOAC), including apixaban, has extended the therapeutic armamentarium in this field. Therefore, estimation of NOAC net clinical benefit in comparison with the established treatment is needed to inform clinical decision making.OBJECTIVESSystematic review to assess the efficacy and safety of apixaban 2.5 mg twice a day versus low-molecular-weight heparins (LMWH) for thromboprophylaxis in patients undergoing knee or hip replacement.DATA SOURCESMEDLINE, Embase, and CENTRAL were searched from inception to September 2016, other systematic reviews, reference lists, and experts were consulted.STUDY ELIGIBILITY CRITERIA, PARTICIPANTS, AND INTERVENTIONAll major orthopedic surgery randomized controlled trials comparing apixaban 2.5 mg twice daily with LMWH, reporting thrombotic and bleeding events.DATA EXTRACTIONTwo independent reviewers, using a predetermined form.STUDY APPRAISAL AND SYNTHESIS METHODSThe Cochrane tool to assess risk bias was used by two independent authors. RevMan software was used to estimate pooled risk ratio (RR) and 95% confidence intervals (95% CI) using random-effects meta-analysis. Trial sequential analysis (TSA) was performed in statistical significant results to evaluate whether cumulative sample size was powered for the obtained effect. Overall confidence in cumulative evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group methodology.RESULTSFour studies comparing apixaban 2.5 mg twice daily with LMWH were included, with a total of 11.828 patients (55% undergoing knee and 45% hip replacement). The overall risk of bias across studies was low. In comparison with LMWH (all regimens), apixaban showed a significantly lower risk of VTE events and overall mortality combined (RR: 0.63, 95% CI: 0.42–0.95, I2 = 84%, n = 8346), but not of major VTE events (RR: 0.62, 95% CI: 0.32–1.19, I2 = 63%, n = 9493), or of symptomatic VTE events and VTE-related mortality combined (RR: 1.14, 95% CI: 0.68–1.90, I2 = 0%, n = 11 879). Trial sequential analysis showed that the risk reduction obtained for VTE and mortality was based on underpowered cumulative sample size and effect dimension. Subgroup analysis according to LMWH regimens showed that apixaban reduced the risk of VTE events and overall mortality, and major VTE events, when compared with LMWH once daily, without differences between apixaban and LMWH twice daily.CONCLUSIONSThere is low to moderate evidence that in patients undergoing knee or hip replacement, apixaban seems equally effective and safe to LMWH twice a day. When compared with LMWH once a day, apixaban seems a superior thromboprophylaxis option. However, the results are underpowered which precludes definite answers regarding the true net clinical benefit of apixaban versus LMWH in this clinical context.

Prophylaxis and treatment of venous thromboembolism based on Japanese clinical guides.

Venous thromboembolism (VTE) has recently increased owing to the westernization of our food habits and an aging society in Japan. The Japanese Guidelines for VTE Prophylaxis were formulated and issued in 2004 and then revised in 2009. The incidence rates of symptomatic perioperative pulmonary thromboembolism (PTE) in Japan are being investigated by the Japanese Society of Anesthesiologists since 2002. The average rate of perioperative PTE was estimated to be 3.1 per 10,000 operations between 2002 and 2011. However, this rate significantly declined after the guidelines for thromboprophylaxis were issued and the management fee for PTE prophylaxis was covered by a health insurance in 2004. The average mortality rate was 17.9%, but it significantly decreased after new anticoagulants were approved in 2008. An anticoagulant, which is effective for both acute and long-term VTE treatment, is clearly beneficial and avoids the need for any form of overlapping therapy. The emerging oral antithrombotic compounds such as direct oral anticoagulants (DOACs), which have the potential to inhibit factor Xa, do not require laboratory monitoring. The oral administration of DOACs results in a benefit-to-risk ratio that is at least comparable with that provided by a conventional treatment with heparin followed by vitamin K antagonists.

First in man study of EP217609, a new long-acting, neutralisable parenteral antithrombotic with a dual mechanism of action.

EP217609 is a parenteral antithrombotic compound combining in one molecule an indirect anti-factor Xa inhibitor, a direct thrombin active site inhibitor and a biotin moiety. The aim of the study is to investigate the safety, pharmacokinetics and pharmacodynamics of single ascending intravenous doses of EP217609. In this randomised double-blind placebo-controlled study, healthy male subjects were administered intravenously single ascending doses (1, 3 or 10mg) of EP217609 or placebo. Each treatment group consisted of 10 subjects of whom 8 received EP217609 and 2 received placebo. All doses of EP217609 were well tolerated. A total of five treatment-emergent adverse events were reported, all considered unrelated, but no bleedings or other significant adverse events occurred during this study. In both plasma and urine, there was a strong correlation between EP217609 concentrations as measured by anti-factor IIa and Xa specific bioassays indicating that the two pharmacological activities of EP217609 did not dissociate in vivo. EP217609 pharmacokinetics were dose proportional and characterised by a low clearance, a small volume of distribution and a terminal half-life of 20.4h. The long half-life was reflected in long-lasting, dose-dependent effects on activated and ecarin clotting time, thrombin and prothrombin time, activated partial thromboplastin time, thrombin generation time and anti-factor Xa activity. Pharmacokinetic/pharmacodynamic modelling indicated that the concentration of EP217609 producing 50% of the pharmacodynamic effect was 3400 and 2210ng/mL for activated clotting time and anti-factor Xa activity, respectively. These results warranted further clinical development of EP217609. • There is a limited number of neutralisable anticoagulants, particularly when rapid neutralisation is required. • Synthetic anti-Xa compounds have predictable pharmacokinetic profiles. However, problems with thrombin rebound remain because of the inability to inhibit clot-bound thrombin. • This manuscript provides a comprehensive investigation of the pharmacokinetics, pharmacodynamics and safety of EP217609, and the results were the basis of future clinical studies in both healthy subjects and patients. • The pharmacokinetic/pharmacodynamic modelling provided information for dose selection in such future studies.

Abstract 342: Analysis of Mechanism of a Novel Drug Candidate using an Organ-level Functional Microdevice that Reconstitutes Human Pulmonary Thrombosis

Pulmonary microvascular thrombosis is a catastrophic medical condition and yet, it is very difficult to predict response and study mechanism of action of potential drug candidates to humans. This is partly so because currently available in vitro assays do not recapitulate physiologically-relevant forces and animal models can also be very complex, making it impossible to analyze intercellular signaling within the lung that occurs under coagulation or drug administration. We designed a model of lung thrombosis in which human primary alveolar and endothelial cells are co-cultured and maintained up to 2 weeks. The device consists of a top chamber seeded with human alveolar epithelial cells (AE) and a lower chamber seeded with endothelial cells, separated by a porous matrix-coated membrane. Whole blood was perfused at a physiological shear stress through the vascular channel and clots were visualized in real-time. When healthy cells were cultured, no intravascular blood clotting was observed, even when lipopolysaccharide (LPS) endotoxin was administered. In contrast, when LPS was added to the AE channel, it caused a significant increase in platelet adhesion at the endothelium, demonstrating that the presence of alveolar epithelium is critical to LPS-induced intravascular thrombosis in vitro . We evaluated this device by analyzing a novel protease activator receptor-1 (PAR1) antithrombotic compound, termed parmodulin 2 (PM2). When the endothelium was cultured along with PM2 under the condition of LPS stimulated AE, we found inhibition of clotting, demonstrating the therapeutic effect of PM2 in the presence of epithelial-endothelial-blood cell signaling. Finally, to test if PM2 performs the therapeutic function of Activated Protein C (APC) that has been reported to stimulate its cytosolic effects via the β-arrestin pathway, we knocked down β-arrestin in the endothelium and analyzed clot formation again. We found that clotting reoccurred in vascular channel, thus showing that PM2 acts like an APC-like drug candidate. In conclusion, the lung alveolus-on-a-chip reconstitutes organ-level responses to blood clotting and may offer a valuable platform for drug development by allowing to dissect contributions of various cells in their mechanism of action.

Antithrombosis activity of protocatechuic and shikimic acids from functional plant Pinus densiflora Sieb. et Zucc needles.

Pine needle extract (PE) and fermented pine needle extract (FPE) have been reported to show various biological and pharmacological activities such as antioxidant, anti-inflammatory, anti-bacterial, anti-cholesterol, gastrointestinal motility control, and fibrinolytic effect. The aims of our research were to isolate fibrinolytic compounds from PE and FPE and evaluate their antithrombotic activity in vitro and in vivo. Protocatechuic (1) and shikimic (2) acids were isolated and identified from FPE.1 and 2 not only have fibrinolysis activity but also inhibit fibrin formation similar to aspirin. Lysis of fibrin clots by 1 and 2 occurred completely at pH 2-4. Results of SDS-PAGE showed that fibrin polypeptide chains (Aα, Bβ, γ) lysed by 1 and 2 were intact. The antithrombotic effects of 1 and 2 were confirmed by models of carrageenan-induced tail thrombosis, collagen and epinephrine-induced pulmonary thromboembolism in mice, and FeCl3-induced carotid arterial thrombus. Moreover, 1 and 2 did not induce hemorrhage in the tail veins of mice, unlike common antithrombotic compounds. We also measured changes in the quantities of 1 and 2 obtained from FPE. As fermentation progressed, we demonstrated that the quantity of 1 steadily increased, while the quantity of 2 did not significantly change. We therefore demonstrated that FPE is an excellent resource for 1 and 2 and can be produced inexpensively in sufficient quantities for industrial-scale extraction.

A tryptophan derivative TD-26 attenuates thrombus formation by inhibiting both PI3K/Akt signaling and binding of fibrinogen to integrin αIIbβ3

The incidence and mortality of thrombotic disorders are rapidly increasing worldwide. The existing antithrombotic drugs, however, are associated with side effects, especially bleeding complications. Therefore, there remains a need for the development of more effective and safer antithrombotic agents. In this study, we discovered a new synthetic tryptophan derivative TD-26, producing potent inhibitory effect on platelet aggregation while without causing obvious bleeding risk. It has been shown that TD-26 inhibited platelet aggregation induced by ADP, thrombin, U46619 and collagen in vitro and suppressed the platelet aggregation induced by ADP ex vivo. Mechanism studies indicated that TD-26 inhibited platelet adhesion to fibrinogen-coated surfaces, blocked the binding of fibrinogen to integrin αIIbβ3 and reduced AktSer473 phosphorylation in platelet phosphatidylinositol 3-kinase (PI3K) signaling. Furthermore, TD-26 exhibited potent antithrombotic activity in vivo. In animal models, it decreased death of mice with acute pulmonary thrombosis by 90% and attenuated thrombosis weight by 60.3%, both at a dose of 3 mg/kg. Additionally, TD-26 did not obviously prolong bleeding time in mice. Taken together, our results reveal that TD-26 is a novel antithrombotic compound exhibiting both integrin αIIbβ3 inhibition and PI3K signaling blockage, with a low bleeding risk.

The treatment of venous thromboembolism with novel oral anticoagulants: warnings and limitations.

The treatment of venous thromboembolism with novel oral anticoagulants: warnings and limitations.

Purified polysaccharides of Geoffroea spinosa barks have anticoagulant and antithrombotic activities devoid of hemorrhagic risks

Polysaccharides were extracted from the barks of Geoffroea spinosa, purified using anion exchange chromatography and characterized by chemical and methylation analysis, complemented by infrared and NMR spectroscopies. These polysaccharides were tested for their anticoagulant, antithrombotic and antiplatelet activities and also for their effects on bleeding. Unfractionated polysaccharide contains low levels of protein and high levels of carbohydrate (including hexuronic acid). The purified polysaccharides (fractions FII and FIII) are composed of arabinose (Ara), rhamnose (Rha), hexuronic acid, small amounts of galactose, but no sulfate ester. They have highly complex structure, which was partially characterized. NMR and methylation analysis indicate that the polysaccharides have a core of α-Rhap and branches of 5-linked α-Araf. Residues of 4-linked α-GalpA are also found in the structure. The unfractionated (TPL) and fraction FIII, but not fractions FI and FII, prolonged the activated partial thromboplastin time (aPTT). TPL, FII and FIII inhibited the platelet aggregation induced by ADP. More significantly, both unfractionated and purified fractions exhibited potent antithrombotic effect (31–60%) and the fractions did not modify the bleeding tendency. These plant polysaccharides could be alternative source of new anticoagulant, antiplatelet and antithrombotic compounds devoid of the undesirable risk of hemorrhage.

C1-Inhibitor protects from focal brain trauma in a cortical cryolesion mice model by reducing thrombo-inflammation.

Traumatic brain injury (TBI) induces a strong inflammatory response which includes blood-brain barrier damage, edema formation and infiltration of different immune cell subsets. More recently, microvascular thrombosis has been identified as another pathophysiological feature of TBI. The contact-kinin system represents an interface between inflammatory and thrombotic circuits and is activated in different neurological diseases. C1-Inhibitor counteracts activation of the contact-kinin system at multiple levels. We investigated the therapeutic potential of C1-Inhibitor in a model of TBI. Male and female C57BL/6 mice were subjected to cortical cryolesion and treated with C1-Inhibitor after 1 h. Lesion volumes were assessed between day 1 and day 5 and blood-brain barrier damage, thrombus formation as well as the local inflammatory response were determined post TBI. Treatment of male mice with 15.0 IU C1-Inhibitor, but not 7.5 IU, 1 h after cryolesion reduced lesion volumes by ~75% on day 1. This protective effect was preserved in female mice and at later stages of trauma. Mechanistically, C1-Inhibitor stabilized the blood-brain barrier and decreased the invasion of immune cells into the brain parenchyma. Moreover, C1-Inhibitor had strong antithrombotic effects. C1-Inhibitor represents a multifaceted anti-inflammatory and antithrombotic compound that prevents traumatic neurodegeneration in clinically meaningful settings.

The value of inhibitors of factor Xa for the treatment of pulmonary embolism.

The introduction of factor Xa inhibitors advocated the initiation of clinical trials that addressed the value of anticoagulation in patients with hemodynamically stable primary pulmonary embolism (PE). In the Matisse trial in patients with PE, fondaparinux administered at therapeutic doses followed by vitamin K antagonists (VKA) has shown a comparable efficacy and safety profile to that seen with intravenous adjusted-dose unfractionated heparin/VKA. A long-acting derivative of fondaparinux, idraparinux, failed to achieve similar results. On the other hand, the Cassiopea study revealed that once weekly injections of idrabiotaparinux, a slightly modified form of idraparinux, have similar efficacy and better safety profile compared to VKAs in the long-term treatment of patients with PE. However, the inconvenient parenteral administration of both fondaparinux and idrabiotaparinux limits their routine clinical use. The availability of antithrombotic compounds that can be administered orally in fixed dose, owing to their predictable pharmacokinetics and pharmacodynamics, and have a lower potential for drug and food interactions has opened new horizons for the treatment of patients with PE. The Einstein PE, Amplify and Hokusai studies, conducted with rivaroxaban, apixaban and edoxaban, respectively, showed that for the treatment of PE they possess a more favorable benefit-to-risk profile than the conventional antithrombotic drugs. In addition, rivaroxaban and apixaban make it possible to treat uncomplicated PE patients from the beginning, without the need for the parenteral administration of heparins or fondaparinux, and edoxaban allows the treatment of fragile patients with lower doses. All of them cover a wide spectrum of clinical presentations, including PE patients at intermediate risk.

The P2Y receptors and thrombosis

Blood platelets play a key role in arterial thrombosis which is one of the leading causes of mortality in western countries. They may also be involved in the pathogenesis of deep vein thrombosis. Adenosine 5′‐diphosphate (ADP) is one of the most important mediators of platelet activation. Two G protein‐coupled ADP receptors, P2Y1 and P2Y12, selectively contribute to platelet aggregation and formation of a thrombus. Playing a central role in platelet activation and in growth and stabilization of a thrombus, the P2Y12 receptor is an established target of antithrombotic drugs like the thienopyridines clopidogrel or prasugrel, or direct reversible antagonists such as ticagrelor or cangrelor. Each of these drugs has proven efficacy in large clinical trials. At a preclinical stage, studies in P2Y1 deficient mice and using selective P2Y1 antagonists in experimental models of thrombosis and inflammation have shown that this receptor is also an attractive target for new antithrombotic compounds. WIREs Membr Transp Signal 2013. doi: 10.1002/wmts.97Conflict of interest: The authors have declared no conflicts of interest for this article.For further resources related to this article, please visit the WIREs website.

Treatment of venous thromboembolism: the single-drug approach

SUMMARY An anticoagulant that is effective for both acute and long-term treatment of venous thromboembolism is clearly beneficial and avoids the need for any form of overlapping therapy. Among the emerging oral antithrombotic compounds that have the potential to inhibit either factor Xa (rivaroxaban, apixaban and edoxaban) or factor IIa (dabigatran etexilate), and do not require laboratory monitoring, rivaroxaban and apixaban are the only ones to date for which there is persuasive evidence coming from randomized clinical trials in support of the ‘single-drug’ approach for the treatment of both patients with deep vein thrombosis and those with hemodynamically stable pulmonary embolism. The oral administration of rivaroxaban (15 mg twice a day for the first 3 weeks, followed by 20 mg once daily for 3–12 months) or apixaban (10 mg twice a day for 7 days, followed by 5 mg twice a day for 6 months) results in a benefit-to-risk ratio that is at least comparable with that provided by conventional treatment with ...

In vitro metabolism of a novel antithrombotic compound, S002-333, and its enantiomers: quantitative cytochrome P450 phenotyping, metabolic profiling and enzyme kinetic studies

1. S002-333, (2-(4′-methoxy-benzenesulfonyl)-2,3,4,9-tetrahydro-1H-pyrido (3,4-b) indole-3-carboxylic acid amide) is a novel potent antithrombotic molecule currently under development phase. It is the racemic mixture of two enantiomers, namely S004-1032 (R-form) and S007-1558 (S-form).2. The contribution of five major isoenzymes, namely CYP2B6, 2C9, 2C19, 2D6 and 3A4 was quantified using recombinant P450s in the phase-I metabolism through relative activity factor approach. CYP2C19 was found to be the major contributor for S002-333 and S007-1558, while CYP3A4 showed greater involvement in S004-1032 metabolism. Chemical inhibition and immunoinhibition studies reconfirmed the results in human liver microsomes (HLM).3. Four major phase-I metabolites of S002-333; M-1 and M-3 (oxidative), M-2 (O-demethylated) and M-4 (dehydrogenated) were characterized in HLM. These metabolites constituted 11.2, 11.3 and 21.5% of the parent in comparison with the net phase-I metabolism of 29.9, 31.4 and 38.3% of S002-333, S004-1032 and S007-1558, respectively.4. Among CYP2C9, 2C19 and 3A4, the relative contribution of CYP2C9 was found to be maximum during M-1 through M-4 formation. Enzyme kinetic analysis for detected metabolites indicated that M-1 to M-3 followed classical hyperbolic kinetics, whereas M-4 showed evidence of autoactivation. In conclusion, the results suggest prominent role of CYP2C9, 2C19 and 3A4 isoforms for enantioselective disposition of S002-333 in vitro.

The phosphodiesterase-4 inhibitor rolipram protects from ischemic stroke in mice by reducing blood–brain-barrier damage, inflammation and thrombosis

Blood–brain-barrier (BBB) disruption, inflammation and thrombosis are important steps in the pathophysiology of acute ischemic stroke but are still inaccessible to therapeutic interventions. Rolipram specifically inhibits the enzyme phosphodiesterase (PDE) 4 thereby preventing the inactivation of the intracellular second messenger cyclic adenosine monophosphate (cAMP). Rolipram has been shown to relief inflammation and BBB damage in a variety of neurological disorders. We investigated the therapeutic potential of rolipram in a model of brain ischemia/reperfusion injury in mice. Treatment with 10mg/kg rolipram, but not 2mg/kg rolipram, 2h after 60min of transient middle cerebral artery occlusion (tMCAO) reduced infarct volumes by 50% and significantly improved clinical scores on day 1 compared with vehicle-treated controls. Rolipram maintained BBB function upon stroke as indicated by preserved expression of the tight junction proteins occludin and claudin-5. Accordingly, the formation of vascular brain edema was strongly attenuated in mice receiving rolipram. Moreover, rolipram reduced the invasion of neutrophils as well as the expression of the proinflammatory cytokines IL-1β and TNFα but increased the levels of TGFβ-1. Finally, rolipram exerted antithrombotic effects upon stroke and fewer neurons in the rolipram group underwent apoptosis. Rolipram is a multifaceted antiinflammatory and antithrombotic compound that protects from ischemic neurodegeneration in clinically meaningful settings.

Superoxide Anion Radical Sensor Using GC Electrode Modified with Heparin/PEDOT and Polymerized Iron Porphyrin

Blood coagulation on the electrode surface is a serious problem for a superoxide anion radical (O2−∙) sensor because it causes deterioration of the current signal especially in vivo. In order to solve this problem, we have developed iron porphyrin-based O2−∙ sensors immobilizing heparin, which is an anti-thrombotic compound, on the surface. In the present study, we immobilized heparin with a polyethylenedioxythiophene (PEDOT) matrix on poly[iron tetrakis(3-thienyl)porphyrin]-modified glassy carbon (GC) electrode, and the stability of the modified sensor to blood coagulation was investigated. The PEDOT matrix was found to be more effective for stable electrochemical detection of O2−∙ after immersion in a fibrinogen/thrombin solution for two weeks, while serious electrode fouling due to blood clot formation was occurred at a sensor using a polypyrrole matrix after immersion in the solution for one week.

Towards dual antithrombotic compounds – Balancing thrombin inhibitory and fibrinogen GPIIb/IIIa binding inhibitory activities of 2,3-dihydro-1,4-benzodioxine derivatives through regio- and stereoisomerism

Enantiomers of 2,3-dihydro-1,4-benzodioxine derivatives possessing both thrombin and fibrinogen GPIIb/IIIa binding inhibitory activities were prepared from (R)- and (S)-glycidol as potential dual antithrombotic compounds. The influence of chirality and substitution pattern on thrombin inhibition and on inhibition of fibrinogen binding to GPIIb/IIIa was analyzed. Docking studies were used in an attempt to rationalize the results. The (S)-isomers of both 2,3-dihydro-1,4-benzodioxine regioisomers at positions 6 and 7 were found to be better thrombin inhibitors than the corresponding (R)-enantiomers, whereas we observed that stereochemistry does not display a consistent influence on fibrinogen GPIIb/IIIa binding inhibitory activity. Compound 11b, the (S)-isomer of the 6-substituted regioisomer, possessed the best balanced dual activity, with Ki(thrombin) = 1.67 ± 0.27 μM and IC50(GPIIb/IIIa) = 0.665 ± 0.26 μM, raising the hope that merging anticoagulant and platelet antiaggregatory activities in the same molecule could lead to successful multitarget antithrombotic agents.

Newer Anticoagulants in Cardiovascular Disease

Vitamin K antagonists (VKAs) such as warfarin have traditionally been the major therapeutic option for anticoagulation in clinical practice. VKAs are effective and extensively recommended for the prevention of venous and arterial thromboembolism in cardiovascular disease. Despite its effectiveness, warfarin is limited by factors such as a narrow therapeutic index, drug-drug interactions, food interactions, slow onset and offset of action, hemorrhage, and routine anticoagulation monitoring to maintain therapeutic international normalized ratio. During the last 2 decades, the approval of anticoagulants, such as low-molecular-weight heparins, indirect factor Xa inhibitors (eg, fondaparinux), and direct thrombin inhibitors (eg, argatroban, lepirudin, and desirudin), have expanded the number of available antithrombotic compounds with additional targets within the anticoagulation pathway. Although these medications offer several potential therapeutic advantages, they all require parenteral or subcutaneous administration and are substantially more expensive than VKAs. Thus, VKAs, despite several limitations, have remained the major option for most patients requiring chronic anticoagulation. These limitations have prompted interest in the development of newer oral anticoagulants. Novel anticoagulants targeting inhibition of factor Xa and thrombin (factor IIa) have now been incorporated into clinical practice based on the results of large randomized clinical trials, with the recent U.S. Food and Drug Administration approval of dabigatran for stroke prevention in atrial fibrillation and rivaroxaban for deep vein thrombosis and stroke prevention in atrial fibrillation, with multiple other agents in various stages of development for these and other indications. This review discusses the pharmacological properties, clinical results, and therapeutic applications of novel and new anticoagulants, thereby providing an outline for the future of anticoagulation in cardiovascular disease.

Exploration of the antiplatelet activity profile of betulinic acid on human platelets.

Betulinic acid, a natural pentacyclic triterpene acid, presents a diverse mode of biological actions including antiretroviral, antibacterial, antimalarial, and anti-inflammatory activities. The potency of betulinic acid as an inhibitor of human platelet activation was evaluated, and its antiplatelet profile against in vitro platelet aggregation, induced by several platelet agonists (adenosine diphosphate, thrombin receptor activator peptide-14, and arachidonic acid), was explored. Flow cytometric analysis was performed to examine the effect of betulinic acid on P-selectin membrane expression and PAC-1 binding to activated platelets. Betulinic acid potently inhibits platelet aggregation and also reduced PAC-1 binding and the membrane expression of P-selectin. Principal component analysis was used to screen, on the chemical property space, for potential common pharmacophores of betulinic acid with approved antithrombotic drugs. A common pharmacophore was defined between the NMR-derived structure of betulinic acid and prostacyclin agonists (PGI2), and the importance of its carboxylate group in its antiplatelet activity was determined. The present results indicate that betulinic acid has potential use as an antithrombotic compound and suggest that the mechanism underlying the antiplatelet effects of betulinic acid is similar to that of the PGI2 receptor agonists, a hypothesis that deserves further investigation.