Structure−Activity Relationships of Bisphosphate Nucleotide Derivatives as P2Y₁ Receptor Antagonists and Partial Agonists

Abstract

The P2Y1 receptor is present in the heart, in skeletal and various smooth muscles, and in platelets, where its activation is linked to aggregation. Adenosine 3',5'- and 2',5'-bisphosphates have been identified as selective antagonists at the P2Y1 receptor (Boyer et al. Mol. Pharmacol. 1996, 50, 1323-1329) and have been modified structurally to increase receptor affinity (Camaioni et al. J. Med. Chem. 1998, 41, 183-190). We have extended the structure-activity relationships to a new series of deoxyadenosine bisphosphates with substitutions in the adenine base, ribose moiety, and phosphate groups. The activity of each analogue at P2Y1 receptors was determined by measuring its capacity to stimulate phospholipase C in turkey erythrocyte membranes (agonist effect) and to inhibit phospholipase C stimulation elicited by 10 nM 2-(methylthio)adenosine 5'-diphosphate (antagonist effect). 2'-Deoxyadenosine bisphosphate analogues containing halo, amino, and thioether groups at the 2-position of the adenine ring were more potent P2Y1 receptor antagonists than analogues containing various heteroatom substitutions at the 8-position. An N6-methyl-2-chloro analogue, 6, was a full antagonist and displayed an IC50 of 206 nM. Similarly, N6-methyl-2-alkylthio derivatives 10, 14, and 15 were nearly full antagonists of IC50 < 0.5 microM. On the ribose moiety, 2'-hydroxy, 4'-thio, carbocyclic, and six-membered anhydrohexitol ring modifications have been prepared and resulted in enhanced agonist properties. The 1,5-anhydrohexitol analogue 36 was a pure agonist with an EC50 of 3 microM, i.e., similar in potency to ATP. 5'-Phosphate groups have been modified in the form of triphosphate, methyl phosphate, and cyclic 3',5'-diphosphate derivatives. The carbocyclic analogue had enhanced agonist efficacy, and the 5'-O-phosphonylmethyl modification was tolerated, suggesting that deviations from the nucleotide structure may result in improved utility as pharmacological probes. The N6-methoxy modification eliminated receptor affinity. Pyrimidine nucleoside 3', 5'-bisphosphate derivatives were inactive as agonists or antagonists at P2Y receptor subtypes.

Purinergic receptors and synaptic transmission in enteric neurons

“…5) that are blocked by the selective P2Y 1 antagonist MRS 2179 [19,104,105]. Interestingly, a single-stimulus-evoked EPSP with a time course between that of a fast and a slow EPSP (an intermediate EPSP) was shown to be blocked by PPADS, suramin, and the selective P2Y 1 receptor antagonist MRS 2179 [19].…”

Structurally related nucleotides as selective agonists and antagonists at P2Y1 receptors

“…Antagonism was defined as the ability to reverse completely the stimulation of PLC elicted by 30 nM 2-methylthioadenosine-5′-diphosphate, an agonist of nanomolar potency. In some cases the related nucleotides could be interconverted between agonists (or partial agonists) and antagonists with small structural changes [17][18][19]. SAR analysis indicated that the 2-position accommodated Cl or thioethers, while the N 6 -position was limited to Me or Et.…”

“…Methods utilized in these recent investigations include: conformationally constraining the ribose, or ribose-like, moiety of nucleosides and nucleotides to freeze a conformation that may provide favorable affinity and/or selectivity at P1 and P2 receptors [3,4]; modifying known receptor antagonists [5][6][7]; use of a template approach based on the pyridine family for the design of novel adenosine antagonists [8]; and the screening of chemical libraries in conjunction with molecular modeling [9].…”

Design and synthesis of new bicyclic diketopiperazines as scaffolds for receptor probes of structurally diverse functionality

“…Exploration of selective agonists and antagonists modulators is most advanced at the P2Y 1 and P2Y 12 receptors, but at most of the P2Y receptors selective pharmacological probes are lacking. [22][23][24][25][26][27][28][29][30][31][32] Compound 20 was shown to antagonize signaling of the P2Y 1 receptor selectively and with moderate potency. At the P2Y 1 receptor, the previously described high affinity antagonists are nucleotide derivatives and therefore highly charged, which is highly limiting in pharmacological studies due to low bioavailability and stability.…”

“…For example, antagonists of the P2Y 1 and P2Y 12 receptors are of interest as antithrombotic agents. [22][23][24][25][26][27][28][29][30][31][32] Agonists of the P2Y 2 receptor are of interest in the treatment of pulmonary diseases, including cystic fibrosis. The P2Y 6 receptor has recently been implicated in protection against apoptosis induced by TNFα.…”