title: Discovery of a Novel Class of Negative Allosteric Modulator of the Dopamine D2 Receptor Through Fragmentation of a Bitopic Ligand.
abstract: Recently, we have demonstrated that N-((trans)-4-(2-(7-cyano-3,4-dihydroisoquinolin-2(1H)-yl)ethyl)cyclohexyl)-1H-indole-2-carboxamide (SB269652) (1) adopts a bitopic pose at one protomer of a dopamine D2 receptor (D2R) dimer to negatively modulate the binding of dopamine at the other protomer. The 1H-indole-2-carboxamide moiety of 1 extends into a secondary pocket between the extracellular ends of TM2 and TM7 within the D2R protomer. To target this putative allosteric site, we generated and characterized fragments that include and extend from the 1H-indole-2-carboxamide moiety of 1. N-Isopropyl-1H-indole-2-carboxamide (3) displayed allosteric pharmacology and sensitivity to mutations of the same residues at the top of TM2 as was observed for 1. Using 3 as an "allosteric lead", we designed and synthesized an extensive fragment library to generate novel SAR and identify N-butyl-1H-indole-2-carboxamide (11d), which displayed both increased negative cooperativity and affinity for the D2R. These data illustrate that fragmentation of extended compounds can expose fragments with purely allosteric pharmacology.
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville 3052, Victoria Australia.
authors.forename: Shailesh N
authors.initials: SN
authors.lastname: Mistry
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville 3052, Victoria Australia.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Shonberg
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville 3052, Victoria Australia.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Draper-Joyce
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville 3052, Victoria Australia.
authors.forename: Carmen
authors.initials: C
authors.lastname: Klein Herenbrink
authors.affiliation: Computational Chemistry and Molecular Biophysics Unit, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health , Baltimore, Maryland 21224, United States.
authors.forename: Mayako
authors.initials: M
authors.lastname: Michino
authors.affiliation: Computational Chemistry and Molecular Biophysics Unit, National Institute on Drug Abuse-Intramural Research Program, National Institutes of Health , Baltimore, Maryland 21224, United States.|Department of Physiology and Biophysics, Weill Medical College of Cornell University , New York, New York 10065, United States.|Institute for Computational Biomedicine, Weill Medical College of Cornell University , New York, New York 10021, United States.
authors.forename: Lei
authors.initials: L
authors.lastname: Shi
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville 3052, Victoria Australia.
authors.forename: Arthur
authors.initials: A
authors.lastname: Christopoulos
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville 3052, Victoria Australia.
authors.forename: Ben
authors.initials: B
authors.lastname: Capuano
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville 3052, Victoria Australia.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Scammells
authors.affiliation: Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University , 381 Royal Parade, Parkville 3052, Victoria Australia.
authors.forename: J Robert
authors.initials: JR
authors.lastname: Lane
mesh_terms: D000494:Allosteric Regulation; D000577:Amides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D000818:Animals; D019390:Arrestins / Q000378:metabolism; D016466:CHO Cells; D003342:Corpus Striatum / Q000378:metabolism; D003412:Cricetulus; D015259:Dopamine Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D007546:Isoquinolines / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D011869:Radioligand Assay; D051381:Rats; D017448:Receptors, Dopamine D2 / Q000235:genetics / Q000378:metabolism*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D000071557:beta-Arrestins
chemical_list: C553924:1H-indole-2-carboxylic acid (4-(2-(cyano-3,4-dihydro-1H-isoquinolin-2-yl)ethyl)cyclohexyl)amide; D000577:Amides; D019390:Arrestins; D015259:Dopamine Agents; D007211:Indoles; D007546:Isoquinolines; C000603347:N-butyl-1H-indole-2-carboxamide; D017448:Receptors, Dopamine D2; D000071557:beta-Arrestins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D019204:GTP-Binding Proteins