Fluorinated Analog NMR s of Organosulfur Compounds from Garlic (Allium sativum): Synthesis, Chemistry and Anti-Angiogenesis and Antithrombotic Studies.

We describe the synthesis, reactivity, and antithrombotic and anti-angiogenesis activity of difluoroallicin (S-(2-fluoroallyl) 2-fluoroprop-2-ene-1-sulfinothioate) and S-2-fluoro-2-propenyl-l-cysteine, both easily prepared from commercially available 3-chloro-2-fluoroprop-1-ene, as well as the synthesis of 1,2-bis(2-fluoroallyl)disulfane, 5-fluoro-3-(1-fluorovinyl)-3,4-dihydro-1,2-dithiin, trifluoroajoene ((E,Z)-1-(2-fluoro-3-((2-fluoroallyl)sulfinyl)prop-1-en-1-yl)-2-(2-fluoroallyl)disulfane), and a bis(2-fluoroallyl)polysulfane mixture. All tested organosulfur compounds demonstrated effective inhibition of either FGF or VEG-mediated angiogenesis (anti-angiogenesis activity) in the chick chorioallantoic membrane (CAM) or the mouse Matrigel® models. No embryo mortality was observed. Difluoroallicin demonstrated greater inhibition (p < 0.01) versus organosulfur compounds tested. Difluoroallicin demonstrated dose-dependent inhibition of angiogenesis in the mouse Matrigel® model, with maximal inhibition at 0.01 mg/implant. Allicin and difluoroallicin showed an effective antiplatelet effect in suppressing platelet aggregation compared to other organosulfur compounds tested. In platelet/fibrin clotting (anti-coagulant activity), difluoroallicin showed concentration-dependent inhibition of clot strength compared to allicin and the other organosulfur compounds tested.

Discovery of diarylurea P2Y(1) antagonists with improved aqueous solubility.

Preclinical data suggests that P2Y1 antagonists, such as diarylurea compound 1, may provide antithrombotic efficacy similar to P2Y12 antagonists and may have the potential of providing reduced bleeding liabilities. This manuscript describes a series of diarylureas bearing solublizing amine side chains as potent P2Y1 antagonists. Among them, compounds 2l and 3h had improved aqueous solubility and maintained antiplatelet activity compared with compound 1. Compound 2l was moderately efficacious in both rat and rabbit thrombosis models and had a moderate prolongation of bleeding time in rats similar to that of compound 1.

The discovery and development of rivaroxaban.

Thromboembolic conditions present a considerable challenge to healthcare services because they are associated with substantial morbidity and mortality. The mainstays of prevention and treatment are anticoagulants and antiplatelet agents. Established anticoagulants have drawbacks that make their use difficult to manage and sustain. This has stimulated the search for new oral anticoagulants that are more convenient and yet still effective. This paper describes the development and future potential of rivaroxaban (Xarelto; Bayer Schering Pharma AG, Berlin, Germany)-the first oral, direct Factor Xa inhibitor to be approved for clinical use in the prevention of venous thromboembolism in adult patients undergoing elective hip or knee replacement surgery.

[Advancement on thrombolytic characteristic, function and clinical application of different fibrinolytic enzymes].

Cardio-cerebral vascular diseases endanger people's health very seriously. Thrombolytic therapy is effective in curing thrombotic diseases at present. Microorganism is an important source of thrombolytic drug. Plasminogen activators are widely used as thrombolytic drugs clinically, while they are still exists some defects. This article analyzed research and development status of kinds of thrombolytic drugs from microorganisms, and evaluated their clinical efficacy and safety, aiming at showing the direction to search new and effective thrombolytic drugs and prevent and treat thromboembolic disease.

ARC-1779, a PEGylated aptamer antagonist of von Willebrand factor for potential use as an anticoagulant or antithrombotic agent.

Archemix Corp's ARC-1779 is an optimized, second-generation, PEGylated aptamer that exerts a novel antithrombotic action through targeting the A1 domain of activated von Willebrand factor (vWF) and inhibiting the binding of platelet receptor glycoprotein Ib, thus reducing platelet adhesion, aggregation and thrombus growth in arterial beds. By inhibiting vWF-dependent arterial thrombogenesis, ARC-1779 has potential therapeutic benefit in acute coronary syndromes and von Willebrand's disease, as well as in vWF-related platelet disorders such as thrombotic thrombocytopenic purpura (TTP) and other thrombotic microangiopathies. As an aptamer, the actions of ARC-1779, unlike other antiplatelet agents, can be readily reversed by binding to a complementary sequence of oligonucleotides; this ability offers potential therapeutic benefit in surgery. In phase I and II clinical trials, ARC-1779 has exhibited favorable pharmacokinetic, pharmacodynamic and safety properties in healthy individuals and patients with TTP. At the time of publication, phase II trials in patients with TTP and thrombosis were ongoing or recruiting patients. Further phase II and III trials are necessary and highly anticipated to establish the therapeutic potential of ARC-1779 as an antithrombotic agent.

Drug evaluation: alfimeprase, a plasminogen-independent thrombolytic.

Alfimeprase is an analog of a fibrolase that disrupts formed thrombi through the hydrolysis of fibrin, rather than by activation of plasminogen. Nuvelo Inc, under license from Amgen Inc and together with Bayer AG, is developing this thrombolytic for the potential intravenous treatment of peripheral arterial occlusions and for other cardiovascular indications. Pharmacokinetic studies showed that alfimeprase was rapidly absorbed and achieved therapeutic concentrations at relatively low doses. Preclinical studies showed that adjunctive therapy with antiplatelet agents was necessary to maintain luminal patency. In phase I and II clinical trials alfimeprase effectively thombolysed clots with no drug-related adverse events. However, phase III clinical trials of alfimeprase did not meet their primary endpoints and enrollment in ongoing trials has been suspended pending further analyses and discussion with outside experts and regulatory agencies. In spite of this, the authors conclude that alfimeprase seems to be a lytic agent with much potential. Refinement in its use and dosing needs to be addressed, and further investigation into its pharmacokinetic properties may be worthwhile. Alfimeprase is a drug that is a 'work in progress'.

Synthesis of new class dipeptide analogues with improved permeability and antithrombotic activity.

3-(S)-1,2,3,4-Tetrahydro-beta-carboline-3-carboxylic acid isolated from A. Chinese G. Don was found to possess moderate anti-aggregation activity, but with poor bioavailability. To improve its pharmacological property, we designed and synthesized a series of novel dipeptide analogues by incorporating tetrahydro-beta-carboline-3-carboxylic acid skeleton as an amino acid surrogate (*Trp). It turned out these dipeptide analogues exhibited good membrane permeability based on in vitro Caco-2 cell monolayers permeability assay. As a result, the overall biological properties of these molecules were significantly improved depending on the nature of the amino acid residues introduced onto the 3-position of the tetrahydro-beta-carboline moiety. It was very interesting to notice that these dipeptide analogues (5b,c,h,i,n,o,p,q) displayed a remarkable dual antiaggregatory activity in both of ADP- and PAF-induced platelet aggregation assay, and their aggregation response was significantly higher than that of aspirin (p<0.01). In addition, these dipeptide analogues were observed for the dose-dependent antithrombotic effect using in vivo rat arterial thrombosis model. The potency of antithrombotic activity of 5h,i,n,p was significantly higher than that of aspirin (n=12, p<0.01) at equal dose (5 micromol/kg).

Development of 3,4-dihydro-2H-benzo[1,4]oxazine derivatives as dual thromboxane A2 receptor antagonists and prostacyclin receptor agonists.

We discovered a novel series of 3,4-dihydro-2H-benzo[1,4]oxazin-8-yloxyacetic acid derivatives as potent dual-acting agents to block the TXA2 receptor and to activate the PGI2 receptor. We report the synthesis, structure-activity relationship, and in vitro, ex vivo, and in vivo pharmacology of this series of compounds. 4-[2-(1,1-Diphenylethylsulfanyl)ethyl]-3,4-dihydro-2H-benzo[1,4]oxazin-8-yloxyacetic acid N-methyl-D-glucamine salt (7) is a promising candidate for a novel treatment in the anti-thrombotic and the cardiovascular fields avoiding hypotensive side effects.

Antithrombotic potential of new direct thrombin inhibitors built on the azaphenylalanine scaffold in two rat venous thrombosis models.

The antithrombotic potential of new direct thrombin inhibitors built on the azaphenylalanine scaffold (LK-732, LK-639 and LK-731) and their amidoxime prodrugs (LK-658, LK-633 and LK-730) was studied in comparison to argatroban and nadroparin in two rat models of venous thrombosis, induced either by complete stasis combined with hypercoagulability (model 1) or by partial stasis combined with vessel injury (model 2). In initial experiments LK-732 was established as the most promising antithrombotic of the LK inhibitors and as such was further tested. In model 1, intravenous bolus administration of LK-732 produced a dose-dependent inhibition of thrombus formation with an ID50 value of 1.3 mg/kg. This ID50 value was approximately four times higher than the ID50 value of argatroban (0.3 mg/kg; p=0.011). However, in model 2, LK-732 and argatroban decreased thrombus weight by 50% at similar ID50 values (3.8 mg/kg vs 3.0 mg/kg, respectively; p=0.726). The ex vivo anticoagulant effect of LK-732 was substantially weaker compared to argatroban at doses that produced comparable antithrombotic effects. After subcutaneous administration, in vivo thrombus weight reduction of LK inhibitors (10 mg/kg) ranged between 22 to 48%. However, their oral antithrombotic effect at a dose of 30 mg/kg was rather low. LK amidoxime prodrugs failed to produce a substantial antithrombotic effect after subcutaneous (10 mg/kg) as well as after oral administration (30 mg/kg). In conclusion, thrombin inhibitors built on the azaphenylalanine scaffold represent a new group of intravenously effective antithrombotics. However, optimisation of the oral antithrombotic effect of amidoxime prodrug LK-658 of the lead inhibitor LK-732 is required for justifying further development of these inhibitors.

Improving upon the in vitro biological activity of antithrombotic disulfides.

Several sulfur-containing compounds, isolated from garlic, have been implicated as highly active antithrombotic agents. We have prepared 10 new aromatic disulfides and an aromatic thiosulfonate in order to determine the in vitro response of human platelets to dosages of these compounds. The poor biological activity of PhSSCH3 was enhanced by the introduction of, inter alia, a nitro group onto the aromatic ring. The nitro group increased potency by activating the disulfide linkage. Anti-platelet aggregation activity was also enhanced by increasing the lipophilicity of one test compound. The ability of an aromatic disulfide to inhibit platelet aggregation can be enhanced by appending an electron-withdrawing group to the aromatic ring. The results presented establish that the aromatic thiosulfonate is a very effective inhibitor of platelet aggregation.

Combinatorial synthesis and biological evaluation of isoxazole-based libraries as antithrombotic agents.

The 3-substituted phenyl-5-isoxazolecarboxaldehydes have been identified as activated aldehydes for the generation of isoxazole-based combinatorial libraries on solid phase through automation. Three highly functionalized isoxazole-based libraries comprising of 32, 96 and 45 compounds each have been synthesized in parallel format using Baylis Hillman reaction, Michael addition, reductive amination and alkylation reactions. With an objective of lead generation all the three libraries were evaluated for their antithrombin activity in vivo.

Structure-based design of novel potent nonpeptide thrombin inhibitors.

The clinical syndromes of thromboembolism are evoked by an excessive stimulation of the coagulation cascade. In this context, the serine protease thrombin plays a key role. Considerable efforts have therefore been devoted to the discovery of safe, orally active inhibitors of this enzyme. On the basis of the X-ray crystal structure of the peptide-like thrombin inhibitor NAPAP complexed with bovine thrombin, we have designed a new structural class of nonpeptidic inhibitors employing a 1,2,5-trisubstituted benzimidazole as the central scaffold. Supported by a series of X-ray structure analyses, we optimized the activity of these compounds. Thrombin inhibition in the lower nanomolar range could be achieved although the binding energy mainly results from nonpolar, hydrophobic interactions. To improve in vivo potency, we increased the overall hydrophilicity of the molecules by introducing carboxylate groups. The very polar compound 24 (BIBR 953) exhibited the most favorable activity profile in vivo. This zwitterionic molecule was converted into the double-prodrug 31 (BIBR 1048), which showed strong oral activity in different animal species. On the basis of these results, 31 was chosen for clinical development.

Effect of new synthetic heparin mimetics on whole blood thrombin generation in vivo and in vitro in rats.

The effect of new heparin mimetics (synthetic oligosaccharides) was studied in vitro with regard to thrombin generation (TG) in rat platelet rich plasma (PRP) and whole blood (WB) and in vivo on stasis-induced venous thrombosis in the rat. TG in PRP and in WB was highly dependent on platelet count and strongly influenced by the haematocrit. The peak of TG appeared to be significantly higher in WB than in PRP whereas the endogenous thrombin potential (ETP) was not significantly different under either condition. The effect of hirudin, the synthetic pentasaccharide SR90107/Org31540 (SP) and heparin were measured on TG in PRP and WB. We then compared the effect of two new synthetic heparin mimetics (SR121903A and SanOrg123781) with potent and comparable antithrombin (AT) mediated activity against factor Xa and thrombin. These two compounds were made of a pentasaccharide with a high affinity to AT, prolonged at the non-reducing end by an oligosaccharide chain recognised by thrombin. In SR121903A, the charge density and charge distribution was analogous to that of heparin whereas in SanOrg123781 the charges were only located on the last 5 saccharides of the non-reducing end of the molecule. In PRP and in WB, SR121903A acted on the lag time and on the AUC whereas SanOrg123781 inhibited thrombin formation with no effect on the lag time. SanOrg123781 was more potent in inhibiting TG than SR121903A. This difference was due to the structures of the compounds that differed in their ability to be neutralised by platelet factor 4. The antithrombotic effect of the two compounds was examined in a venous thrombosis model in rats. We observed that SanOrg123781 was more active than SR121903A and heparin. Taken together, these results indicate that the activity of oligosaccharides is greatly influenced by the global charge density of the molecule and show that SanOrg123781 is a potent and promising antithrombotic drug candidate.

Synthesis and SAR of N-substituted dibenzazepinone derivatives as novel potent and selective alpha(V)beta(3) antagonists.

Synthesis and SARs of new integrin alpha(V)beta(3) antagonists based on an N-substituted dibenzazepinone scaffold are described. Variation of spacer and guanidine mimetic led to potent compounds exhibiting an IC(50) towards alpha(V)beta(3) in the nanomolar range, high selectivity versus integrin alpha(IIb)beta(3) and efficacy in functional cellular assays.

Thrombin active site inhibitors: chemical synthesis, in vitro and in vivo pharmacological profile of a novel and selective agent BMS-189090 and analogues.

A series of structurally novel small molecule inhibitors of human alpha-thrombin was prepared to elucidate their structure- activity relationships (SAR), selectivity and activity in vivo. BMS-189090 (5) is identified as a potent, selective, and reversible inhibitor of human alpha-thrombin that is efficacious in vivo in a mice lethality model, and in inhibiting both arterial and venous thrombosis in a rat model.

Potent dibasic GPIIb/IIIa antagonists with reduced prolongation of bleeding time: synthesis and pharmacological evaluation of 2-oxopiperazine derivatives.

A series of 2-oxopiperazine derivatives, possessing basic moieties at the 3- and the 4-positions, were synthesized and evaluated for their abilities to inhibit platelet aggregation and for their effects on bleeding time. Among the compounds, 2-[(3S)-4-[2-[(4-guanidinobenzoyl)amino]acetyl]-3-[3-[(4-guanidinobenzoyl)amino]propyl]-2-oxopiperazinyl]acetic acid (12c) showed a potent inhibitory effect on platelet aggregation and good dissociation between the efficacy and the bleeding side effect. Intravenous infusion of compound 12c at 1.6 microg/mL/min completely prevented arterial thrombus formation induced by endothelial injury in guinea pigs. The dose of 12c that prolonged the bleeding time to three times the control value was 5.8 microg/mL/min. These results suggest that compound 12c might be useful in the clinical treatment of thrombotic diseases, and we selected 12c (TAK-024) as a candidate for the clinical trials.

Synthesis of 4-substituted phenyl 3,6-anhydro-1,3-dithio-D-glucofuranosides and -pyranosides as well as 2,6-anhydro-1,2-dithio-alpha-D-altrofuranosides possessing antithrombotic activity.

1,2,5-Tri-O-acetyl-3,6-anhydro-3-thio-D-glucofuranose was synthesised starting from D-glucose and was used as a donor for the glycosidation of 4-cyano- and 4-nitrobenzenethiol. In the latter reaction, besides an anomeric mixture of the 4-nitrophenyl 2,5-di-O-acetyl-3,6-anhydro-1,3-dithio-D-glucofuranosides, the corresponding 2,6-anhydro-1,2-dithio-D-altrofuranosides were also obtained, formed via a rearrangement of the sugar moiety. A similar rearrangement could be observed during the hydrolysis of the glycosidic bond of methyl 3,6-anhydro-2,4-di-O-(4-nitrobenzoyl)-3-thio-alpha-D-glucopyranoside with aqueous trifluoroacetic acid, affording after acetylation besides 1-O-acetyl-3,6-anhydro-2,4-di-O-(4-nitrobenzoyl)-3-thio-alpha-D-glucopyranose (32alpha), 1,1,5-tri-O-acetyl-3,6-anhydro-2,4-di-O-(4-nitrobenzoyl)-3-thio-D-glucose, methyl 3,6-anhydro-2,4-di-O-(4-nitrobenzoyl)-3-thio-beta-D-glucopyranoside and 1,5-di-O-acetyl-2,6-anhydro-3-O-(4-nitrobenzoyl)-2-thio-alpha-D-altrofuranose (40). Glycosidation of 4-cyanobenzethiol with 32alpha in the presence of trimethylsilyl triflate as promoter afforded 4-cyanophenyl 3,6-anhydro-2,4-di-O-(4-nitrobenzoyl)-1,3-dithio-beta-D-glucopyranoside as a minor component only, besides 4-cyanophenyl 3,6-anhydro-2-S-(4-cyanophenyl)-4-O-(4-nitrobenzoyl)-1,2,3-trithio-beta-D-glucopyranoside. When boron trifluoride etherate was used as promoter in the reaction of 32alpha with 4-cyano- and 4-nitrobenzenethiol, the corresponding beta-thioglycosides were obtained, while 40 gave under identical conditions the alpha anomers exclusively. All thioglycosides obtained after deacylation were submitted to biological evaluation. Among these glycosides, the 4-cyanophenyl 3,6-thioanhydro-1,3-dithio-D-glucofuranoside possessed the strongest oral antithrombotic effect.

[Experimental study on effect of antagonizing platelet-activating factor and histamine of synthetic ginkgolide F in guinea-pigs].

OBJECTIVE: To investigate the antagonizing effect of synthetic Ginkgolide F (SGF) on platelet-activating factor (PAF) and histamine (HA) in guinea-pigs. METHODS: The contraction rate of isolated lung tissue of guinea-pig and the change of pulmonary function of sensitized guinea-pig after SGF treatment were examined. RESULTS: (1) The contraction rate of guinea-pigs' isolated trachea and lung strip induced by HA reduced from (50.97 +/- 16.00)% and (54.24 +/- 12.17)% to (21.69 +/- 3.85)% and (22.97 +/- 17.78)% after SGF treatment (P < 0.05). (2) PAF induced relative contraction of isolated guinea-pig lung strip was reduced from (89.49 +/- 16.00)% to (46.21 +/- 14.23)% in presence of SGF (P < 0.05). (3) The pulmonary function of sensitized animal had a tendency of being improved by SGF. CONCLUSION: SGF can antagonize the contraction of isolated lung tissue induced by HA or PAF in vitro, and has a tendency to improve the pulmonary function of sensitized guinea-pig, therefore, it may be a promising drug in treatment of bronchial asthma.