Exploration of Alternative Scaffolds for P2Y₁₄ Receptor Antagonists Containing a Biaryl Core

Various heteroaryl and bicyclo-aliphatic analogues of zwitterionic biaryl P2Y₁₄ receptor (P2Y₁₄R) antagonists were synthesized, and affinity was measured in P2Y₁₄R-expressing Chinese hamster ovary cells by flow cytometry. Given this series' low water solubility, various polyethylene glycol derivatives of the distally binding piperidin-4-yl moiety of moderate affinity were synthesized. Rotation of previously identified 1,2,3-triazole attached to the central m-benzoic acid core (25) provided moderate affinity but not indole and benzimidazole substitution of the aryl-triazole. The corresponding P2Y₁₄R region is predicted by homology modeling as a deep, sterically limited hydrophobic pocket, with the outward pointing piperidine moiety being the most flexible. Bicyclic-substituted piperidine ring derivatives of naphthalene antagonist 1, e.g., quinuclidine 17 (MRS4608, IC₅₀ ≈ 20 nM at hP2Y₁₄R/mP2Y₁₄R), or of triazole 2, preserved affinity. Potent antagonists 1, 7a, 17, and 23 (10 mg/kg) protected in an ovalbumin/Aspergillus mouse asthma model, and PEG conjugate 12 reduced chronic pain. Thus, we expanded P2Y₁₄R antagonist structure-activity relationship, introducing diverse physical-chemical properties.