Structure-activity relationships of privileged structures lead to the discovery of novel biased ligands at the dopamine D₂ receptor.
Biased agonism at GPCRs highlights the potential for the discovery and design of pathway-selective ligands and may confer therapeutic advantages to ligands targeting the dopamine D2 receptor (D2R). We investigated the determinants of efficacy, affinity, and bias for three privileged structures for the D2R, exploring changes to linker length and incorporation of a heterocyclic unit. Profiling the compounds in two signaling assays (cAMP and pERK1/2) allowed us to identify and quantify determinants of biased agonism at the D2R. Substitution on the phenylpiperazine privileged structures (2-methoxy vs 2,3-dichloro) influenced bias when the thienopyridine heterocycle was absent. Upon inclusion of the thienopyridine unit, the substitution pattern (4,6-dimethyl vs 5-chloro-6-methoxy-4-methyl) had a significant effect on bias that overruled the effect of the phenylpiperazine substitution pattern. This latter observation could be reconciled with an extended binding mode for these compounds, whereby the interaction of the heterocycle with a secondary binding pocket may engender bias.
Medicinal Chemistry and ‡Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University , Parkville 3052, Victoria, Australia.
Monika
M
Szabo
Carmen
C
Klein Herenbrink
Arthur
A
Christopoulos
J Robert
JR
Lane
Ben
B
Capuano
D000818:Animals; D016466:CHO Cells; D003412:Cricetulus; D000242:Cyclic AMP / Q000096:biosynthesis; D065127:Dopamine D2 Receptor Antagonists; D054333:Drug Partial Agonism; D008024:Ligands; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D010879:Piperazines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D010880:Piperidines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D011869:Radioligand Assay; D017448:Receptors, Dopamine D2 / Q000819:agonists* / Q000378:metabolism; D013329:Structure-Activity Relationship; D058924:Thienopyridines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology
D065127:Dopamine D2 Receptor Antagonists; D008024:Ligands; D010879:Piperazines; D010880:Piperidines; D017448:Receptors, Dopamine D2; D058924:Thienopyridines; D000242:Cyclic AMP; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3