title: Binding properties of the novel, non-peptide CGRP receptor antagonist radioligand, [(3)H]BIBN4096BS.
abstract: BIBN4096BS [[R-(R,(R*,S*)]-N-[2-[[5-amino-1-[[4-(4-pyridinyl)-1-piperazinyl]carbonyl] pentyl]amino]-1-[(3,5-dibromo-4-hydroxyphenyl)methyl]-2-oxoethyl]-4-(1,4-dihydro-2-oxo-3(2H)-quinazolinyl)-,1-Piperidinecarboxamide] is a selective calcitonin gene-related peptide (CGRP) receptor antagonist with a picomolar affinity to the CGRP receptor in human neuroblastoma SK-N-MC cells. Here, we describe the characterisation of the binding properties of the tritiated radioanalogue of BIBN4096BS in SK-N-MC cells as well as in marmoset tissue. [(3)H]BIBN4096BS showed reversible and saturable binding to SK-N-MC cells with a K(D) of 0.045 nM. In competition experiments, [3(H)]BIBN4096BS is concentration-dependently displaced from SK-N-MC cell membranes by BIBN4096BS as well as by the endogenous ligand CGRP and its analogues with the rank order of affinity BIBN4096BS>human alpha-CGRP=human beta-CGRP>[Cys(Et)(2,7)]human alpha-CGRP>adrenomedullin (high affinity site)=human alpha-CGRP-(8-37)=human beta-CGRP-(8-37)>calcitonin=amylin. In the marmoset cortex, saturable [(3)H]BIBN4096BS binding was observed with a K(D) of 0.077 nM. CGRP showed biphasic competition of [(3)H]BIBN4096BS binding, whilst BIBN4096BS monophasically displaced its radioanalogue with a K(i) of 0.099 nM. These data, using [(3)H]BIBN4096BS, confirm the high affinity of this novel antagonist for the primate CGRP receptor and demonstrate furthermore that this radioligand is a useful tool to study CGRP receptor pharmacology.
authors.affiliation: Department of Cardiovascular Research I, Boehringer Ingelheim Pharma KG, Birkendorfer Strasse 65, 88397 Biberach, Germany. marcus.schindler@bc.boehringer-ingelheim.de
authors.forename: Marcus
authors.initials: M
authors.lastname: Schindler
authors.forename: Henri N
authors.initials: HN
authors.lastname: Doods
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D002144:Callithrix; D002540:Cerebral Cortex / Q000378:metabolism; D004388:Dura Mater / Q000378:metabolism; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007457:Iodine Radioisotopes; D007700:Kinetics; D008297:Male; D010879:Piperazines; D010880:Piperidines / Q000378:metabolism* / Q000494:pharmacology; D011799:Quinazolines / Q000378:metabolism* / Q000494:pharmacology; D011869:Radioligand Assay; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000378:metabolism*; D013154:Spleen / Q000378:metabolism; D014316:Tritium; D014407:Tumor Cells, Cultured / Q000378:metabolism
chemical_list: D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D007457:Iodine Radioisotopes; D010879:Piperazines; D010880:Piperidines; D011799:Quinazolines; D018015:Receptors, Calcitonin Gene-Related Peptide; D014316:Tritium; D015740:Calcitonin Gene-Related Peptide; C406305:olcegepant