Piperazinyl-glutamate-pyridines as potent orally bioavailable P2Y12 antagonists for inhibition of platelet aggregation

Polymer-assisted solution-phase (PASP) parallel library synthesis was used to discover a piperazinyl-glutamate-pyridine as a P2Y₁₂ antagonist. Exploitation of this lead provided compounds with excellent inhibition of platelet aggregation as measured in a human platelet rich plasma (PRP) assay. Pharmacokinetic and physiochemical properties were optimized leading to compound (4S)-4-[({4-[4-(methoxymethyl)piperidin-1-yl]-6-phenylpyridin-2-yl}carbonyl)amino]-5-oxo-5-{4-[(pentyloxy)carbonyl]piperazin-1-yl}pentanoic acid 22J with good human PRP potency, selectivity, in vivo efficacy and oral bioavailability.     

Part II: Piperazinyl-glutamate-pyridines as potent orally bioavailable P2Y12 antagonists for inhibition of platelet aggregation

Efforts to refine the SAR of the piperazinyl-glutamate-pyridines for more potent analogs with improved pharmacokinetic profiles are described. Exploring substituted piperidines and other ring systems at the 4-pyridyl position led to compounds with improved potency and pharmacokinetic properties over candidate I. In particular, compounds 4t and 5t were discovered with a 10-fold improvement over potency and improved pharmacokinetic profiles in both the rat and dog.     

Optimization of 2-phenyl-pyrimidine-4-carboxamides towards potent,orally bioavailable and selective P2Y12 antagonists for inhibition of platelet aggregation

2-Phenyl-pyrimidine-4-carboxamide analogs were identified as P2Y₁₂ antagonists. Optimization of the carbon-linked or nitrogen-linked substituent at the 6-position of the pyrimidine ring provided compounds with excellent ex vivo potency in the platelet aggregation assay in human plasma. Compound 23u met the objectives for activity, selectivity and ADMET properties.     

Thienopyrimidine-based P2Y12 platelet aggregation inhibitors

Herein we describe the design and synthesis of a novel series of potent thienopyrimidine P2Y₁₂ inhibitors and the negative impact protein binding has on the inhibition of platelet aggregation.     

Adenosine analogues as inhibitors of P2Y12 receptor mediated platelet aggregation

Modified adenosine derivatives may lead to the development of P2Y(12) antagonists that are potent, selective, and bind reversibly to the receptor. Analogues of 2',3'-trans-styryl acetal-N6-ureido-adenosine monophosphate were prepared by modification of the 5'-position. The resulting analogues were tested for P2Y(12) antagonism in a platelet aggregation assay.     

Molecular mechanism of action for reversible P2Y12 antagonists

Recently, reversible antagonists of the P2Y(12) receptor have been reported. However, the mechanisms of binding have not been elucidated. To this end, a number of homology models were built by means of three programs from four templates. A consensus model was derived from those initial models. The final model was created by refining the consensus model with molecular dynamics simulations. The agonist and antagonists of P2Y(12) have been docked in the final model. For the agonist, the Arg256, Lys280, and Phe252 are "hot" residues. For the antagonists, the Lys280 and Phe252 are "hot" residues that have hydrogen bonding contacts and π-π interactions, respectively. These results can explain the observations of mutation experiments and can guide the design of new inhibitors.     

Novel nucleotide triphosphates as potent P2Y2 agonists

The synthesis and P2Y2 activities of a novel series of nucleoside triphosphates are described. Many of these compounds were potent agonists of the P2Y2 receptor.     

Docking-based virtual screening of potential human P2Y12 receptor antagonists

Platelet plays essential roles in hemostasis and its dysregulation can lead to arterial thrombosis. P2Y12 is an important platelet membrane adenosine diphosphate receptor, and its antagonists have been widely developed as anti-coagulation agents. The current P2Y12 inhibitors available in clinical practice have not fully achieved satisfactory anti-thrombotic effects, leaving room for further improvement. To identify new chemical compounds as potential anti-coagulation inhibitors, we constructed a three-dimensional structure model of human P2Y12 by homology modeling based on the recently reported G-protein coupled receptor Meleagris gallopavo β1 adrenergic receptor. Virtual screening of the modeled P2Y12 against three subsets of small molecules from the ZINC database, namely lead-like, fragment-like, and drug-like, identified a number of compounds that might have high binding affinity to P2Y12. Detailed analyses of the top three compounds from each subset with the highest scores indicated that all of these compounds beard a hydrophobic bulk supplemented with a few polar atoms which bound at the ligand binding site via largely hydrophobic interactions with the receptor. This study not only provides a structure model of P2Y12 for rational design of anti-platelet inhibitors, but also identifies some potential chemicals for further development.     

A novel series of piperazinyl-pyridine ureas as antagonists of the purinergic P2Y12 receptor

A novel series of P2Y₁₂ antagonists for development of drugs within the antiplatelet area is presented. The synthesis of the piperazinyl-pyridine urea derivatives and their structure-activity relationships (SAR) are described. Several compounds showed P2Y₁₂ antagonistic activities in the sub-micromolar range.     

2-Amino-1,3,4-thiadiazoles in the 7-hydroxy-N-neopentyl spiropiperidine indolinyl series as potent P2Y1 receptor antagonists

Blockade of the P2Y₁ receptor is important to the treatment of thrombosis with potentially improved safety margins compared with P2Y₁₂ receptor antagonists. Investigation of a series of urea surrogates of the diaryl urea lead 3 led to the discovery of 2-amino-1,3,4-thiadiazoles in the 7-hydroxy-N-neopentyl spiropiperidine indolinyl series as potent P2Y₁ receptor antagonists, among which compound 5a was the most potent and the first non-urea analog with platelet aggregation (PA) IC₅₀ less than 0.5 μM with 10 μM ADP. Several 2-amino-1,3,4-thiadiazole analogs such as 5b and 5f had a more favorable pharmacokinetic profile, such as higher C_trough, lower Cl, smaller Vdss, and similar bioavailability compared with 3.     

P2Y1 receptor antagonists as novel antithrombotic agents

The P2Y(1) and P2Y(12) purinergic receptors are responsible for mediating adenosine diphosphate (ADP) dependent platelet aggregation. Evidence from P2Y(1) knockout studies as well as from nucleotide-based small molecule P2Y(1) antagonists has suggested that the antagonism of this receptor may offer a novel and effective method for the treatment of thrombotic disorders. Herein, we report the identification and optimization of a series of non-nucleotide P2Y(1) antagonists that are potent and orally bioavailable.     

Inhibition of ADP-induced intracellular Ca2+ responses and platelet aggregation by the P2Y12 receptor antagonists AR-C69931MX and clopidogrel is enhanced by prostaglandin E1

P2Y(12) antagonists such as clopidogrel and AR-C69931MX inhibit aggregation by antagonizing the effects of ADP at P2Y(12) receptors on platelets. Agents such as PGE(1) also inhibit aggregation by stimulating adenylate cyclase to produce cAMP, which interferes with Ca(2+) mobilization within the cell. Since one facet of P2Y(12) receptors is that they mediate inhibition of adenylate cyclase by ADP, it might be expected that P2Y(12) antagonists would interact with PGE(1). We have explored the effects of PGE(1) and AR-C69931MX singly and in combination on ADP-induced intracellular Ca(2+) ([Ca(2+)](i)) responses and aggregation. PGE(1) alone caused parallel dose-dependent inhibition of [Ca(2+)](i) and aggregation responses. AR-C66931MX alone caused only partial inhibition of [Ca(2+)](i) despite a marked inhibitory effect on aggregation. Combinations of PGE(1) with AR-C66931MX were found to act in synergy to reduce both [Ca(2+)](i) and aggregation. This effect was confirmed in patients with acute coronary syndromes by studying the inhibitory effects of PGE(1) on [Ca(2+)](i) and aggregation before and after clopidogrel. In summary, we have shown that P2Y(12) antagonists interact with natural agents such as PGE(1) to provide more effective inhibition of [Ca(2+)](i) and platelet aggregation. This would contribute to the effectiveness of P2Y(12) antagonists as antithrombotic agents in man.     

The discovery of potent selective NPY Y2 antagonists

A series of small molecules with a piperidinyl core were synthesized and tested for binding affinity (IC₅₀) at human Neuropeptide Y Y₂ receptor. Various amide related analogs (ureas, reversed amides, and sulfonamides) were evaluated. Several potent and selective NPY Y₂ antagonists were identified.     

2-Aminothiazole based P2Y1 antagonists as novel antiplatelet agents

ADP receptors, P2Y₁ and P2Y₁₂ have been recognized as potential targets for antithrombotic drugs. A series of P2Y₁ antagonists that contain 2-aminothiazoles as urea surrogates were discovered. Extensive SAR of the thiazole ring is described. The most potent compound 7j showed good P2Y₁ binding (K_i = 12 nM), moderate antagonism of platelet aggregation (PA IC₅₀ = 5.2 μM) and acceptable PK in rats.     

Benzofuran-substituted urea derivatives as novel P2Y1 receptor antagonists

Benzofuran-substituted urea analogs have been identified as novel P2Y₁ receptor antagonists. Structure–activity relationship studies around the urea and the benzofuran moieties resulted in compounds having improved potency. Several analogs were shown to inhibit ADP-mediated platelet activation.     

Novel tricyclic benzothiazolo[2,3-c]thiadiazine antagonists of the platelet ADP receptor (P2Y(12)).

Novel non-nucleoside tricyclic platelet ADP receptor (P2Y(12)) antagonists have been discovered that bind reversibly and with high affinity to the platelet receptor. Condensation of various 2-aminobenzothiazoles with chlorosulfonylacetyl chloride affords these novel tricyclic heterocycles, which are novel and unpredicted products of this reaction.     

Optimization of ketone-based P2Y12 receptor antagonists as antithrombotic agents: Pharmacodynamics and receptor kinetics considerations

Modification of a series of P2Y₁₂ receptor antagonists by replacement of the ester functionality was aimed at minimizing the risk of in vivo metabolic instability and pharmacokinetic variability. The resulting ketones were then optimized for their P2Y₁₂ antagonistic and anticoagulation effects in combination with their physicochemical and absorption profiles. The most promising compound showed very potent antiplatelet action in vivo. However, pharmacodynamic–pharmacokinetic analysis did not reveal a significant separation between its anti-platelet and bleeding effects. The relevance of receptor binding kinetics to the in vivo profile is described.     

Azaindoles as potent CRTH2 receptor antagonists

A new class of 7-azaindole analogs of MK-7246 as potent and selective CRTH2 antagonists is reported. The SAR leading to the identification of the optimal azaindole regioisomer as well as the pharmacokinetics and off-target activities of the most potent antagonists are disclosed.     

Carbacyclin — A potent stable prost acyclin analogue for the inhibition of platelet aggregation

Carbacyclin is a chemically stable analogue of prostacyclin. As an inhibitor of platelet aggregation induced by ADP or collagen in vitro, carbacyclin is 0.03 times as active as prostacyclin in human, dog or rabbit plasma. Carbacyclin, like prostacyclin, reduces systemic arterial blood pressure (BP) in dogs, rabbits and rats and is not inactivated during passage through the pulmonary circulation. Further actions were investigated using a new ex vivo technique which allows rapid preparation of platelet-rich plasma and determination of platelet aggregation. In the dog, intravenous infusion of carbacyclin or prostacyclin inhibits platelet aggregation ex vivo with minimal effects on BP or heart rate. In the anaesthetised or conscious rabbit, carbacyclin and prostacyclin produces similar cardiovascular changes in doses producing an equivalent degree of platelet inhibition. In both rabbit and dog, carbacyclin is 0.1 times as active as prostacyclin in inhibiting ex vivo platelet aggregation. Platelet inhibition is maintained throughout the period of infusion of either compound (up to 3 h) yet is no longer apparent 10 min after terminating the infusion. Carbacyclin is thus a chemically-stable but metabolically-unstable analogue with a biological profile closely similar to prostacyclin.     

Synthesis and biological evaluation of cyclopentyl-triazolol-pyrimidine (CPTP) based P2Y12 antagonists

In this Letter we describe SAR investigation on the cyclopentyl-triazolol-pyrimidine scaffold in pursuit of new oral P2Y₁₂ inhibitors. Different synthetic routes were developed for variations at the cyclopentyl core. Optimization finally led to compound 2d which was advanced into preclinical development based on better potency and safety profile in comparison to ticagrelor.