ABSTRACT
In this study, we have demonstrated that the critical hydrogen bonding motif of the established 3-aminopyrazinone thrombin inhibitors can be effectively mimicked by a 2-aminopyridine N-oxide. As this peptidomimetic core is more resistant toward oxidative metabolism, it also overcomes the metabolic liability associated with the pyrazinones. An optimization study of the P(1) benzylamide delivered the potent thrombin inhibitor 21 (K(i) = 3.2 nM, 2xaPTT = 360 nM), which exhibited good plasma levels and half-life after oral dosing in the dog (C(max) = 2.6 microM, t(1/2) = 4.5 h).
Subject(s)
Antithrombins/chemistry , Pyrimidines/chemistry , Hydrogen Bonding , Models, Molecular , Molecular MimicryABSTRACT
In an effort to discover potent, clinically useful thrombin inhibitors, a rapid analogue synthetic approach was used to explore the P(1) region. Various benzylamines were coupled to a pyridine/pyrazinone P(2)-P(3) template. One compound with an o-thiadiazole benzylic substitution was found to have a thrombin K(i) of 0.84 nM. A study of ortho-substituted five-membered-ring heterocycles was undertaken and subsequently demonstrated that the o-triazole and tetrazole rings were optimal. Combination of these potent P(1) aryl heterocycles with a variety of P(2)-P(3) groups produced a compound with an extraordinary thrombin inhibitory activity of 1.4 pM. It is hoped that this potency enhancement in P(1) will allow for more diversification in the P(2)-P(3) region to ultimately address additional pharmacological concerns.
Subject(s)
Heterocyclic Compounds/chemical synthesis , Thrombin/antagonists & inhibitors , Benzylamines/chemical synthesis , Benzylamines/chemistry , Binding Sites , Heterocyclic Compounds/chemistry , Models, Molecular , Pyrazines/chemical synthesis , Pyrazines/chemistry , Pyridines/chemical synthesis , Pyridines/chemistry , Structure-Activity Relationship , Tetrazoles/chemical synthesis , Tetrazoles/chemistry , Thiadiazoles/chemical synthesis , Thiadiazoles/chemistry , Thrombin/chemistry , Triazoles/chemical synthesis , Triazoles/chemistryABSTRACT
A series of potent and selective proline- and pyrazinone-based macrocyclic thrombin inhibitors is described. Detailed SAR studies led to the incorporation of specific functional groups in the tether that enhanced functional activity against thrombin and provided exquisite selectivity against trypsin and tPA. X-ray crystallography and molecular modeling studies revealed the inhibitor-enzyme interactions responsible for this selectivity.
Subject(s)
Antithrombins/chemical synthesis , Antithrombins/pharmacology , Binding Sites , Crystallography, X-Ray , Drug Design , Models, Molecular , Proline/chemistry , Pyrazines/chemistry , Structure-Activity Relationship , Thrombin/chemistry , Trypsin/chemistryABSTRACT
In this manuscript we demonstrate that a modification principally directed toward the improvement of the aqueous solubility (i.e., introduction a P3 pyridine N-oxide) of the previous lead compound afforded a new series of potent orally bioavailable P1 N-benzylamide thrombin inhibitors. An expedited investigation of the P1 SAR with respect to oral bioavailability, plasma half-life, and human liver microsome stability revealed 5 as the best candidate for advanced evaluation.
Subject(s)
Acetamides/chemical synthesis , Acetamides/pharmacology , Pyrazines/chemical synthesis , Pyrazines/pharmacology , Pyridines/chemistry , Thrombin/antagonists & inhibitors , Animals , Biological Availability , Chemical Phenomena , Chemistry, Physical , Crystallography, X-Ray , Dogs , Half-Life , Humans , In Vitro Techniques , Injections, Intravenous , Macaca mulatta , Microsomes, Liver/metabolism , Models, Molecular , Oxides/chemistry , Rats , Solubility , Structure-Activity Relationship , Thrombosis/chemically induced , Thrombosis/drug therapyABSTRACT
The synthesis and biological evaluation of a series of nonpeptidic small molecule antagonists of the human platelet thrombin receptor (PAR-1) are described. Optimization of the 5-amino-3-arylisoxazole lead resulted in an approximate 100-fold increase in potency. The most potent of these compounds (54) inhibits platelet activation with IC(50)s of 90 nM against the thrombin receptor agonist peptide (TRAP) and 510 nM against thrombin as the agonist. Further, antagonist 54 fully blocks platelet aggregation stimulated by 1 nM thrombin for 10 min.
