The bivalent ligand approach leads to highly potent and selective acylguanidine-type histamine H₂ receptor agonists.
Bivalent histamine H(2) receptor (H(2)R) agonists were synthesized by connecting pharmacophoric 3-(2-amino-4-methylthiazol-5-yl)-, 3-(2-aminothiazol-5-yl)-, 3-(imidazol-4-yl)-, or 3-(1,2,4-triazol-5-yl)propylguanidine moieties by N(G)-acylation with alkanedioic acids of various chain lengths. The compounds were investigated for H(2)R agonism in GTPase and [(35)S]GTPγS binding assays at guinea pig (gp) and human (h) H(2)R-Gsα(S) fusion proteins including various H(2)R mutants, at the isolated gp right atrium, and in GTPase assays for activity on recombinant H(1), H(3), and H(4) receptors. The bivalent ligands are H(2)R partial or full agonists, up to 2 orders of magnitude more potent than monovalent acylguanidines and, with octanedioyl or decanedioyl spacers, up to 4000 times more potent than histamine at the gpH(2)R. In contrast to their imidazole analogues, the aminothiazoles are highly selective for H(2)R vs other HR subtypes. Compounds with (theoretically) sufficient spacer length (20 CH(2) groups) to simultaneously occupy two orthosteric binding sites in H(2)R dimers are nearly inactive, whereas the highest potency resides in compounds with considerably shorter spacers. Thus, there is no evidence for interaction with H(2)R dimers. The high agonistic potency may result from interaction with an accessory binding site at the same receptor protomer.
Department of Pharmaceutical/Medicinal Chemistry, Faculty of Chemistry and Pharmacy, University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany.
Tobias
T
Birnkammer
Anja
A
Spickenreither
Irena
I
Brunskole
Miroslaw
M
Lopuch
Nicole
N
Kagermeier
Günther
G
Bernhardt
Stefan
S
Dove
Roland
R
Seifert
Sigurd
S
Elz
Armin
A
Buschauer
D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics; D006146:Guanidines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects / Q000502:physiology; D017442:Histamine Agonists / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D008024:Ligands; D009154:Mutation; D011401:Promoter Regions, Genetic; D055503:Protein Multimerization; D011970:Receptors, Histamine H2 / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000819:agonists / Q000235:genetics; D013329:Structure-Activity Relationship
D006146:Guanidines; D017442:Histamine Agonists; D008024:Ligands; D011970:Receptors, Histamine H2; D011993:Recombinant Fusion Proteins; D019205:GTP-Binding Protein alpha Subunits, Gs