Synthesis and mechanistic evaluation of novel N'-benzylidene-carbohydrazide-1H-pyrazolo[3,4-b]pyridine derivatives as non-anionic antiplatelet agents

A further pocket or conformational plasticity by mapping COX-1 catalytic site through modified-mofezolac structure-inhibitory activity relationships and their antiplatelet behavior

Cyclooxygenase enzymes have distinct roles in cardiovascular, neurological, and neurodegenerative disease. They are differently expressed in different type of cancers. Specific and selective COXs inhibitors are needed to be used alone or in combo-therapies. Fully understand the differences at the catalytic site of the two cyclooxygenase (COX) isoforms is still opened to investigation. Thus, two series of novel compounds were designed and synthesized in fair to good yields using the highly selective COX-1 inhibitor mofezolac as the lead compound to explore a COX-1 zone formed by the polar residues Q192, S353, H90 and Y355, as well as hydrophobic amino acids I523, F518 and L352. According to the structure of the COX-1:mofezolac complex, hydrophobic amino acids appear to have free volume eventually accessible to the more sterically hindering groups than the methoxy linked to the phenyl groups of mofezolac, in particular the methoxyphenyl at C4-mofezolac isoxazole. Mofezolac bears two methoxyphenyl groups linked to C3 and C4 of the isoxazole core ring. Thus, in the novel compounds, one or both methoxy groups were replaced by the higher homologous ethoxy, normal and isopropyl, normal and tertiary butyl, and phenyl and benzyl. Furthermore, a major difference between the two sets of compounds is the presence of either a methyl or acetic moiety at the C5 of the isoxazole. Among the C5-methyl series, 12 (direct precursor of mofezolac) (COX-1 IC50 = 0.076 μM and COX-2 IC50 = 0.35 μM) and 15a (ethoxy replacing the two methoxy groups in 12; COX-1 IC50 = 0.23 μM and COX-2 IC50 > 50 μM) were still active and with a Selectivity Index (SI = COX-2 IC50/COX-1 IC50) = 5 and 217, respectively. The other symmetrically substituted alkoxyphenyl moietis were inactive at 50 μM final concentration. Among the asymmetrically substituted, only the 16a (methoxyphenyl on C3-isoxazole and ethoxyphenyl on C4-isoxazole) and 16b (methoxyphenyl on C3-isoxazole and n-propoxyphenyl on C4-isoxazole) were active with SI = 1087 and 38, respectively. Among the set of compounds with the acetic moiety, structurally more similar to mofezolac (SI = 6329), SI ranged between 1.4 and 943. It is noteworthy that 17b (n-propoxyphenyl on both C3- and C4-isoxazole) were found to be a COX-2 slightly selective inhibitor with SI = 0.072 (COX-1 IC50 > 50 μM and COX-2 IC50 = 3.6 μM). Platelet aggregation induced by arachidonic acid (AA) can be in vitro suppressed by the synthesized compounds, without affecting of the secondary hemostasia, confirming the biological effect provided by the selective inhibition of COX-1. A positive profile of hemocompatibility in relation to erythrocyte and platelet toxicity was observed. Additionally, these compounds exhibited a positive profile of hemocompatibility and reduced cytotoxicity. Quantitative structure activity relationship (QSAR) models and molecular modelling (Ligand and Structure based virtual screening procedures) provide key information on the physicochemical and pharmacokinetic properties of the COX-1 inhibitors as well as new insights into the mechanisms of inhibition that will be used to guide the development of more effective and selective compounds. X-ray analysis was used to confirm the chemical structure of 14 (MSA17).

Microwave assisted one-pot access to pyrazolo quinolinone and tetrahydroisoxazolo quinolinone derivatives via T3P®-DMSO catalysed tandem oxidative-condensation reaction

A new approach for the synthesis of two important annulated pyrazolo quinolinone and tetrahydroisoxazolo quinolinone derivatives from multicomponent reactions was achieved by using T3P®-DMSO-catalysed reactions of stable alcohols, cyclic 1,3-dicarbonyl compounds and amino derivatives of phenyl pyrazoles and isoxazole and has been reported for the first time. This reaction occurred via a tandem oxidative-condensation reaction under microwave irradiation and notable characteristics of this protocol are MCR reactions, shorter reaction time, less waste creation, ease of workup, stable precursors, broad substrate scope and functional group tolerance.

Pyrazolopyridine: An efficient pharmacophore in recent drug design and development

Among the various heterocyclic molecules employed for drug design and discovery, pyrazolopyridine is one of the promising pharmacophores. Pyrazolopyridine is a result of fusion of pyrazole and pyridine rings. The potent pharmacology of pyrazolopyridine may be the synergistic effect of pyrazole and pyridine moieties in a single framework. It has been used in drug design of a wide range of diseases such as anticancer, antimicrobial, anti-inflammatory, and neuroprotection. Cancer has become a common disease among elderly people now a days that might be because of genetic inheritance to some extent, carcinogens, pollution, and some infectious diseases. Whatever may be the reason, cancer is one of the major causes of deaths worldwide. In addition, over-usage and improper usage of antibiotics have led to drug resistance of microbes. Further, inflammation is a cause of various diseases such as arthritis, and other diseases. Thus, proinflammatory kinases are considered as primary target for inhibition of inflammation. In view of this, a work that compiles potent pharmacology of recently reported pyrazolopyridine analogs has been planned. The review is aimed to discuss pharmacology in brief along with structure-activity relationship (SAR). The review would emphasize importance of pyrazolopyridines in future drug design and discovery and may help in design of potent pharmacological agents.

Evaluation of Neurotropic Activity and Molecular Docking Study of New Derivatives of pyrano[4″,3″:4',5']pyrido[3',2':4,5]thieno[3,2-d]pyrimidines on the Basis of pyrano[3,4-c]pyridines

Background: Heterocyclic compounds and their fused analogs, which contain pharmacophore fragments such as pyridine, thiophene and pyrimidine rings, are of great interest due to their broad spectrum of biological activity. Chemical compounds containing two or more pharmacophore groups due to additional interactions with active receptor centers usually enhance biological activity and can even lead to a new type of activity. The search for new effective neurotropic drugs in the series of derivatives of heterocycles containing pharmacophore groups in organic, bioorganic and medical chemistry is a serious problem. Methods: Modern methodology of drugs involves synthesis, physicochemical study, molecular modeling and selection of active compounds through virtual screening and experimental evaluation of the biological activity of new chimeric compounds with pharmacophore fragments. For the synthesis of new compounds, classical organic methods were used and developed. For the evaluation of neurotropic activity of new synthesized compounds, some biological methods were used according to indicators characterizing anticonvulsant, sedative and antianxiety activity as well as side effects. For docking analysis, various soft ware packages and methods were used. Results: As a result of multistep reactions, 11 new, tri- and tetracyclic heterocyclic systems were obtained. The studied compounds exhibit protection against pentylenetetrazole (PTZ) seizures as well as some psychotropic effects. The biological assays evidenced that nine of the eleven studied compounds showed a high anticonvulsant activity by antagonism with pentylenetetrazole. The toxicity of the compounds is low, and they do not induce muscle relaxation in the studied doses. According to the study of psychotropic activity, it was found that the selected compounds have an activating behavior and anxiolytic effects on the “open field” and “elevated plus maze” (EPM) models. The data obtained indicate the anxiolytic (antianxiety) activity of the derivatives of tricyclic thieno[2,3-b]pyridines and tetracyclic pyridothieno[3,2-d]pyrimidin-8-ones, especially pronounced in compounds 3b–f and 4e. The studied compounds increase the latent time of first immobilization on the “forced swimming” (FS) model and exhibit antidepressant effects; compounds 3e and 3f especially exhibit these effects, similarly to diazepam. Docking studies revealed that compounds 3c and 4b bound tightly in the active site of γ-aminobutyric acid type A (GABA_A) receptors with a value of the scoring function that estimates free energy of binding (∆G) at −10.0 ± 5 kcal/mol. Compound 4e showed the best affinity ((∆G) at −11.0 ± 0.54 kcal/mol) and seems to be an inhibitor of serotonin (SERT) transporter. Compounds 3c–f and 4e practically bound with the groove of T4L of 5HT_1A and blocked it completely, while the best affinity observed was in compound 3f ((∆G) at −9.3 ± 0.46 kcal/mol). Conclusions: The selected compounds have an anticonvulsant, activating behavior and anxiolytic effects and at the same time exhibit antidepressant effects.

Therapeutic implementation in arterial thrombosis with pulmonary administration of fucoidan microparticles containing acetylsalicylic acid

Several antithrombotic drugs are available to treat cardiovascular diseases due to its high mortality and morbidity worldwide. Despite these, severe adverse effects that can lead to treatment withdrawal have been described, highlighting the importance of new therapies. Thus, this work describes the development of fucoidan microparticles containing acetylsalicylic acid (MP/F4M) for pulmonary delivery and in vitro, ex vivo, and in vivo evaluation. Microparticles were prepared via spray-drying and characterized in vitro (mucoadhesive properties, coagulation time, platelet aggregation, adhesion, and hemolysis) followed by ex vivo platelet aggregation, in vivo arterial thrombosis, and hemorrhagic profile. The formulation physicochemical characterization showed suitable characteristics along with delayed drug release, increased breathable particle fraction, and high washability resistance as well as antiplatelet activity and enhanced platelet adhesion in vitro. In in vivo assays, MP/F4M protected against arterial thrombosis, without changes in the hemorrhagic profile. Finally, no lung changes were observed after prolonged pulmonary administration, whereas isolated ASA led to an inflammatory response. In conclusion, pulmonary administration of fucoidan microparticles with an antiplatelet drug may be an alternative therapy to treat cardiovascular diseases, opening the field for different formulations.

One-pot three-component synthesis of novel pyrazolo[3,4-b]pyridines as potent antileukemic agents

In the current study, we report on the development of novel series of pyrazolo[3,4-b]pyridine derivatives (8a-u, 11a-n, and 14a,b) as potential anticancer agents. The prepared pyrazolo[3,4-b]pyridines have been screened for their antitumor activity in vitro at NCI-DTP. Thereafter, compound 8a was qualified by NCI for full panel five-dose assay to assess its GI₅₀, TGI and LC₅₀ values. Compound 8a showed broad-spectrum anti-proliferative activities over the whole NCI panel, with outstanding growth inhibition full panel GI₅₀ (MG-MID) value equals 2.16 μM and subpanel GI₅₀ (MG-MID) range: 1.92-2.86 μM. Furthermore, pyrazolo[3,4-b]pyridines 8a, 8e-h, 8o, 8u, 11a, 11e, 11h, 11l and 14a-b were assayed for their antiproliferative effect against a panel of leukemia cell lines (K562, MV4-11, CEM, RS4;11, ML-2 and KOPN-8) where they possessed moderate to excellent anti-leukemic activity. Moreover, pyrazolo[3,4-b]pyridines 8o, 8u, 14a and 14b were further explored for their effect on cell cycle on RS4;11 cells, in which they dose-dependently increased populations of cells in G2/M phases. Finally we analyzed the changes of selected proteins (HOXA9, MEIS1, PARP, BcL-2 and McL-1) related to cell death and viability in RS4;11 cells via Western blotting. Collectively, the obtained results suggested pyrazolo[3,4-b]pyridines 8o, 8u, 14a and 14b as promising lead molecules for further optimization to develop more potent and efficient anticancer candidates.

Synthesis of 3,3-dimethyl-6-oxopyrano[3,4-c]pyridines and their antiplatelet and vasodilatory activity

OBJECTIVES

Both pyridine and pyrano derivatives have been previously shown to possess biologically relevant activity. In this study, we report the incorporation of these two scaffolds into one molecule.

METHODS

The designed 3,3-dimethyl-6-oxopyrano[3,4-c]pyridines were synthesized by the acylation of enamine under Stork conditions followed by condensation of formed β-diketones with 2-cyanoacetamide. The structures of these compounds were confirmed by using a wide spectrum of physico-chemical methods. Their antiplatelet, anticoagulant and vasodilatory activity together with toxicity were evaluated.

KEY FINDINGS

A series of 6-oxopyrano[3,4-c]pyridines 3a-j was obtained. Four of these compounds were reported for the first time. None of the tested compounds demonstrated anticoagulant effect but 8-methyl derivative (3a) was a potent antiplatelet compound with IC50 numerically twice as low as the clinically used acetylsalicylic acid. A series of further mechanistic tests showed that 3a interferes with calcium signaling. The compound is also not toxic and in addition possesses vasodilatory activity as well.

CONCLUSIONS

Compound 3a is a promising inhibitor of platelet aggregation, whose mechanism of action should be studied in detail.

Novel rivaroxaban-loaded poly(lactic-co-glycolic acid)/poloxamer nanoparticles: preparation, physicochemical characterization, in vitro evaluation of time-dependent anticoagulant activity and toxicological profile

Rivaroxaban (RXB), an oral direct factor Xa inhibitor, presents innovative therapeutic profile. However, RXB has shown adverse effects, mainly due to pharmacokinetic limitations, highlighting the importance of developing more effective formulations. Therefore, this work aims at the preparation, physicochemical characterization and in vitro evaluation of time-dependent anticoagulant activity and toxicology profile of RXB-loaded poly(lactic-co-glycolic acid) (PLGA)/poloxamer nanoparticles (RXBNps). RXBNp were produced by nanoprecipitation method and physicochemical characteristics were evaluated. In vitro analysis of time-dependent anticoagulant activity was performed by prothrombin time test and toxicological profile was assessed by hemolysis and MTT reduction assays. The developed RXBNp present spherical morphology with average diameter of 205.5 ± 16.95 nm (PdI 0.096 ± 0.04), negative zeta potential (-26.28 ± 0.77 mV), entrapment efficiency of 91.35 ± 2.40%, yield of 41.81 ± 1.68% and 3.72 ± 0.07% of drug loading. Drug release was characterized by an initial fast release followed by a sustained release with 28.34 ± 2.82% of RXB available in 72 h. RXBNp showed an expressive time-dependent anticoagulant activity in human and rat blood plasma and non-toxic profile. Based on the results presented, it is possible to consider that RXBNp may be able to assist in the development of promising new therapies for treatment of thrombotic disorders.

Antiviral Drug Discovery and Development for Mayaro Fever - What do we have so far?

Tropical infectious diseases cause millions of deaths every year in developing countries, with about half of the world population living at risk. Mayaro virus (MAYV) is an emerging arbovirus that causes Mayaro fever, which is characterized by fever, headache, diarrhea, arthralgia, and rash. These symptoms can be clinically indistinguishable from other arboviruses, such as Dengue, Zika, and Chikungunya, which makes the diagnosis and treatment of the disease more difficult. Though, the Mayaro virus is a potential candidate to cause large-scale epidemics on the scale of ZIKV and CHIKV. Despite this, there is no licensed vaccine or antiviral for the treatment of Mayaro fever and most arboviruses, so the design and development of candidates for antiviral drugs are urgently needed. In this context, this mini-review aims to provide an overview of studies of anti-MAYV derivatives and highlight the importance of the discovery and development of promising drug candidates for Mayaro fever.

Trypanocidal activity of new 1,6-diphenyl-1H-pyrazolo[3,4-b]pyridine derivatives: Synthesis, in vitro and in vivo studies

Despite the serious public health problems caused by Chagas disease in several countries, the available therapy remains with only two drugs that are poorly active during the chronic phase of the disease in addition to having severe side effects. In search of new trypanocidal agents, herein we describe the synthesis and biological evaluation of eleven new 1,6-diphenyl-1H-pyrazolo[3,4-b]pyridine compounds containing the carbohydrazide or the 2,3-dihydro-1,3,4-oxadiazole moieties. Two of them showed promising in vitro activity against amastigote forms of T. cruzi and were evaluated in vivo in male BALB/c mice infected with T. cruzi Y strain. Our results suggest that the substitution at the C-2 position of the phenyl group connected to the carbohydrazide or to the 2,3-dihydro-1,3,4-oxadiazole moieties plays an important role in the trypanocidal activity of this class of compounds. Moreover, the compound containing the 2,3-dihydro-1,3,4-oxadiazole moiety has demonstrated more favorable structural requirements for in vivo activity than its carbohydrazide analog.

An attempt to chemically state the cross-talk between monomers of COX homodimers by double/hybrid inhibitors mofezolac-spacer-mofezolac and mofezolac-spacer-arachidonic acid

Cardiovascular diseases (CVDs) account for over 17 million death globally each year, including arterial thrombosis. Platelets are key components in the pathogenesis of this disease and modulating their activity is an effective strategy to treat such thrombotic events. Cyclooxygenase-1 (COX-1) isoenzyme is involved in platelet activation and is the main target of non-steroidal anti-inflammatory drugs (NSAIDs) and new selective inhibitor research. Inhibitors of general formula mofezolac-spacer-mofezolac (mof-spacer-mof) and mofezolac-spacer-arachidonic acid (mof-spacer-AA) were projected to investigate the possible cross-talk between the two monomers (E_allo and E_cat) forming the COX-1 homodimer. Mofezolac was chosen as either one or two moieties of these molecules being the known most potent and selective COX-1 inhibitor and administrated to humans as Disopain™, then arachidonic acid (AA) was used to develop molecules bearing, in the same compound, in addition to the inhibitor moiety (mofezolac) also the natural COX substrate. Depending on the nature of the spacer, COX-1 and COX-2 activity was differently inhibited by mof-spacer-mof set with a preferential COX-1 inhibition. The highest COX-1 selectivity was exhibited by the compound in which the spacer was the benzidine [N,N'-(biphenyl-4,4'-di-yl)bis (2-[3,4-bis(4-methoxyphenyl)isoxazol-5-yl]acetamide) (15): COX-1 IC₅₀ = 0.08 μM, COX-2 IC₅₀ > 50 μM, Selectivity Index (SI) > 625]. In the case of mof-spacer-AA set, the COX inhibitory potency and also the isoform preference changed. (5Z, 8Z, 11Z, 14Z)-N-(4-{2-[3,4-Bis(4-methoxyphenyl)isoxazol-5-yl]acetamido}butyl)icosa-5,8,11,14-tetraenamide (19) and (5Z, 8Z, 11Z, 14Z)-N-(4'-{2-[3,4-bis(4-methoxyphenyl)isoxazol-5-yl]acetamido}-[1,1'-biphenyl]-4-yl)icosa-5,8,11,14-tetraenamide (21), in which the spacer is the 1,2-diaminobutane or benzidine, respectively, selectively inhibited the COX-2, whereas when the spacer is the 1,4-phenylendiamine [(5Z, 8Z, 11Z, 14Z)-N-(4-{2-[3,4-bis(4-methoxyphenyl)isoxazol-5-yl]acetamido}phenyl)icosa-5,8,11,14-tetraenamide) (20) the COX preference is COX-1 (COX-1 IC₅₀ = 0.05 μM, COX-2 IC₅₀ > 50 μM, with a COX-1 selectivity > 1000). Molecular modelling by using FLAP algorithm shows fundamental interactions of the novel compounds at the entry channel of COX and inside its catalytic cavity. The effect of these mof-spacer-mof and mof-spacer-AA in inhibiting in vitro free arachidonic acid-induced platelet aggregation was also determined. A positive profile of hemocompatibility in relation to their influence on the blood coagulation cascade and erythrocyte toxicity was observed. Cytotoxicity and genotoxicity safety were also found for these two novel sets of compounds.

Discovery of Novel Pyrazolo[3,4-b] Pyridine Derivatives with Dual Activities of Vascular Remodeling Inhibition and Vasodilation for the Treatment of Pulmonary Arterial Hypertension

Current pulmonary arterial hypertension (PAH) therapeutic strategies mainly focus on vascular relaxation with less emphasis on vascular remodeling, which results in poor prognosis. Hence, dual pathway regulators with vasodilation effect via soluble guanylate cyclase (sGC) stimulation and vascular remodeling regulation effect by AMP-activated protein kinase (AMPK) inhibition provide more advantages and potentialities. Herein, we designed and synthesized a series of novel pyrazolo[3,4-b] pyridine derivatives based on sGC stimulator and AMPK inhibitor scaffolds. In vitro, 2 exhibited moderate vasodilation activity and higher proliferation and migration suppressive effects compared to riociguat. In vivo, 2 significantly decreased right ventricular systolic pressure (RVSP), attenuated pulmonary artery medial thickness (PAMT), and right ventricular hypertrophy (RVH) in hypoxia-induced PAH rat models (i.g.). Given the unique advantages of significant vascular remodeling inhibition and moderate vascular relaxation based on the dual pathway regulation, we proposed 2 as a promising lead for anti-PAH drug discovery.

Synthesis of 4-Methoxy-1, 3-Benzenediolylhydrazones and Evaluation of Their Anti-Platelet Aggregation Activity

In our present investigation, a series of novel 4-methoxy-1,3-benzenediolyl-hydrazones were designed and synthesized, and their ability to inhibit platelet aggregation was evaluated by adenosine diphosphate (ADP) and arachidonic acid (AA). The structures of the synthesized compounds were confirmed by spectral data. Results demonstrated that the activities of all compounds excelled the positive drug Picotamide (25.1% inhibition rate) and seven compounds (PNN01, PNN03, PNN05, PNN07, PNN09, PNN12, and PNN14) have efficiently inhibited platelet aggregation even higher than Clopidogrel (37.6% inhibition rate) induced by AA. Among them, PNN07 (39.8% inhibition rate) was considered as the most potent analogue. Evaluation of cytotoxic activity of the compounds against L929 cell line revealed that none of the compounds have significant cytotoxicity. Thus, diolylhydrazones derives are potential to be antiplatelet aggregation inhibitors and maybe working in AA-induced selectively.

A one-pot three-component strategy for highly diastereoselective synthesis of spirocycloalkane fused pyrazolo[3,4-b]pyridine derivatives using recyclable solid acid as a catalyst

An efficient and eco-friendly approach for highly diastereoselective synthesis of spirocycloalkane fused pyrazolo[3,4-b]pyridine derivatives has been developed.

3-Acyltetramic acids as a novel class of inhibitors for human kallikreins 5 and 7

Human kallikreins 5 and 7 (KLK5 and KLK7) exhibit trypsin- and chymotrypsin-like activities and are involved in pathologies related to skin desquamation process. A series of new 3-acyltetramic acids were developed as a novel class of inhibitors of KLK5, KLK7 and trypsin enzymes. The nature and length of the acyl chain is crucial to the KLK5, KLK7 and trypsin inhibition activities, and the most potent compounds (but not the most selective) 2b, 2c and 2g showed low micromolar IC₅₀ values. While very few of the compounds were selective for KLK5, the selective inhibition of trypsin against chymotrypsin was achieved. Our molecular modelling studies revealed that the double bond in 2g provided the best fit in the binding site of KLK5, while the hydrogen bonding interactions modulated the best fit of 2c in the binding site of KLK7 due to the hydrophobicity of the cavity.

A multicomponent, facile and catalyst-free microwave-assisted protocol for the synthesis of pyrazolo-[3,4-b]-quinolines under green conditions

A facile, swift and ecofriendly microwave-assisted multi-component/one-pot protocol is designed for the synthesis of novel pyrazolo-[3,4-b]-quinolines at ambient temperature in aqueous ethanol as a reaction medium. The 18 novel pyrazolo-[3,4-b]-quinoline derivatives were synthesized by fusion of chosen aryl aldehyde, dimedone and 5-amino-3-methyl-1-phenylpyrazole in excellent yields (91–98%). All the molecular structures were confirmed by ¹H-NMR, ¹⁵N-NMR, ¹³C-NMR, and HRMS data analysis. Operational simplicity, easy handling, one-step simple workup procedure, mild reaction conditions, short reaction time (≤10 min), high selectivity and no by-product formation are the striking features of the protocol.

A facile, swift and ecofriendly microwave-assisted multi-component/one-pot protocol is designed for the synthesis of novel pyrazolo-[3,4-b]-quinolines at ambient temperature in aqueous ethanol as a reaction medium.

Synthesis of Imine Congeners of Resveratrol and Evaluation of Their Anti-Platelet Activity

Resveratrol (3,5,4′-trihydroxy-trans-stilbene) is a cardioprotective phytochemical occurring in many plant products. In this study, a new series of imine congeners of resveratrol has been synthesized in which the imine moiety replaced the double bond in the structure of resveratrol. In addition, the in vitro antiplatelet activity of these resveratrol derivatives has been evaluated against adenosine diphosphate (ADP), arachidonic acid (AA), and collagen as platelet aggregation inducers. In general, the synthesized compounds were active as antiplatelet agents, and, therefore, the imine functional group may be considered as an effective replacement for a double bond in resveratrol for developing new and promising antiplatelet drugs.

Docking based design of diastereoisomeric MTCA as GPIIb/IIIa receptor inhibitor

In GPIIb/IIIa mediated arterial thrombosis platelet activation plays a central role. To discover platelet activation inhibitor the pharmacophores of GPIIb/IIIa receptor inhibitors and anti-thrombotic agents were analyzed. This led to the design of (1R,3S)- and (1S,3S)-1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acids as GPIIb/IIIa inhibitors. Comparing to (1S,3S)-isomer (1R,3S)-isomer had lower cdocker interaction energy. AFM image showed that the minimal effective concentration of (1S,3S)-isomer and (1R,3S)-isomer inhibiting platelet activation were 10^-5 M and 10^-6 M, respectively. In vivo 1 μmol/kg of oral (1S,3S)-isomer effectively inhibited the rats to form arterial thrombus and down regulated GPIIb/IIIa expression, but the activities were significantly lower than those of 1 μmol/kg of oral (1R,3S)-isomer. Both (1S,3S)-isomer and (1R,3S)-isomer can be safely used for structural modifications, but (1R,3S)-isomer should be superior to (1S,3S)-isomer.