CDPPB [3-cyano-N-(1,3-diphenyl-1H-pyrazol-5-yl)benzamide] was recently described as the first centrally active, positive allosteric modulator of rat and human metabotropic glutamate receptor (mGluR) mGluR5 subtype. We explored the structural requirements for potentiation of glutamate-induced calcium release in naturally expressed mGluR5 in cultured rat astrocytes and increasing affinity for the allosteric antagonist binding site by evaluating 50 analogues of CDPPB. In the fluorometric calcium assay, CDPPB exhibited an EC50 value of 77 +/- 15 nM in potentiating mGluR5-mediated responses in cortical astrocytes and a Ki value of 3760 +/- 430 nM in displacing [3H]methoxyPEPy binding in membranes of cultured HEK-293 cells expressing rat mGluR5. The structure-activity relationships showed that electronegative aromatic substituents in the para-position of the benzamide moiety of CDPPB increase potency. Both binding and functional activities were further increased with a halogen atom in the ortho-position of the 1-phenyl ring. These effects of substitution do not match those of either aromatic ring of MPEP [2-methyl-6-(phenylethynyl)pyridine] for the antagonist allosteric binding site. Combination of the optimal substituents and aromatic positions resulted in 4-nitro-N-(1-(2-fluorophenyl)-3-phenyl-1H-pyrazol-5-yl)benzamide (VU-1545) showing Ki = 156 +/- 29 nM and EC50 = 9.6 +/- 1.9 nM in the binding and functional assays, respectively.

中文翻译：

---

N-（1,3-二苯基-1H-吡唑-5-基）苯甲酰胺对大鼠皮质星形胶质细胞代谢型谷氨酸5受体的正构构调节的取代作用。

CDPPB [3-氰基-N-（1,3-二苯基-1H-吡唑-5-基）苯甲酰胺]最近被描述为大鼠和人类代谢型谷氨酸受体（mGluR）mGluR5亚型的第一个中枢活性，正构构调节剂。我们通过评估CDPPB的50个类似物，探索了在培养的大鼠星形胶质细胞中自然表达的mGluR5中谷氨酸诱导的钙释放增强的结构要求，并提高了对变构拮抗剂结合位点的亲和力。在荧光钙测定中，CDPPB在皮质星形胶质细胞中增强mGluR5介导的反应中的EC50值显示为77 +/- 15 nM，在置换培养的HEK膜中的[3H]甲氧基PEPy结合方面显示出3760 +/- 430 nM的Ki值。 -293细胞表达大鼠mGluR5。结构-活性关系表明，CDPPB的苯甲酰胺部分对位的负电芳族取代基增加了效能。在1-苯基环的邻位上的卤素原子进一步提高了结合活性和功能活性。这些取代作用与拮抗剂变构结合位点的MPEP [2-甲基-6-（苯基乙炔基）吡啶]任一芳香环都不匹配。最佳取代基和芳族位置的组合产生4-硝基-N-（1-（2-氟苯基）-3-苯基-1H-吡唑-5-基）苯甲酰胺（VU-1545），Ki = 156 +/-在结合和功能测定中分别为29 nM和EC50 = 9.6 +/- 1.9 nM。在1-苯基环的邻位上的卤素原子进一步提高了结合活性和功能活性。这些取代作用与拮抗剂变构结合位点的MPEP [2-甲基-6-（苯基乙炔基）吡啶]任一芳香环都不匹配。最佳取代基和芳族位置的组合产生4-硝基-N-（1-（2-氟苯基）-3-苯基-1H-吡唑-5-基）苯甲酰胺（VU-1545），Ki = 156 +/-在结合和功能测定中分别为29 nM和EC50 = 9.6 +/- 1.9 nM。在1-苯基环的邻位上的卤素原子进一步提高了结合活性和功能活性。这些取代作用与拮抗剂变构结合位点的MPEP [2-甲基-6-（苯基乙炔基）吡啶]任一芳香环都不匹配。最佳取代基和芳族位置的组合产生4-硝基-N-（1-（2-氟苯基）-3-苯基-1H-吡唑-5-基）苯甲酰胺（VU-1545），Ki = 156 +/-在结合和功能测定中分别为29 nM和EC50 = 9.6 +/- 1.9 nM。