title: Intracellular allosteric antagonism of the CCR9 receptor.
abstract: Chemokines and their G-protein-coupled receptors play a diverse role in immune defence by controlling the migration, activation and survival of immune cells. They are also involved in viral entry, tumour growth and metastasis and hence are important drug targets in a wide range of diseases. Despite very significant efforts by the pharmaceutical industry to develop drugs, with over 50 small-molecule drugs directed at the family entering clinical development, only two compounds have reached the market: maraviroc (CCR5) for HIV infection and plerixafor (CXCR4) for stem-cell mobilization. The high failure rate may in part be due to limited understanding of the mechanism of action of chemokine antagonists and an inability to optimize compounds in the absence of structural information. CC chemokine receptor type 9 (CCR9) activation by CCL25 plays a key role in leukocyte recruitment to the gut and represents a therapeutic target in inflammatory bowel disease. The selective CCR9 antagonist vercirnon progressed to phase 3 clinical trials in Crohn's disease but efficacy was limited, with the need for very high doses to block receptor activation. Here we report the crystal structure of the CCR9 receptor in complex with vercirnon at 2.8 Å resolution. Remarkably, vercirnon binds to the intracellular side of the receptor, exerting allosteric antagonism and preventing G-protein coupling. This binding site explains the need for relatively lipophilic ligands and describes another example of an allosteric site on G-protein-coupled receptors that can be targeted for drug design, not only at CCR9, but potentially extending to other chemokine receptors.
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: Christine
authors.initials: C
authors.lastname: Oswald
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Rappas
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: James
authors.initials: J
authors.lastname: Kean
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Doré
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: James C
authors.initials: JC
authors.lastname: Errey
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: Kirstie
authors.initials: K
authors.lastname: Bennett
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: Francesca
authors.initials: F
authors.lastname: Deflorian
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: John A
authors.initials: JA
authors.lastname: Christopher
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: Ali
authors.initials: A
authors.lastname: Jazayeri
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Mason
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: Miles
authors.initials: M
authors.lastname: Congreve
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Cooke
authors.affiliation: Heptares Therapeutics Ltd, BioPark, Broadwater Road, Welwyn Garden City, Hertfordshire AL7 3AX, UK.
authors.forename: Fiona H
authors.initials: FH
authors.lastname: Marshall
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects; D000495:Allosteric Site / Q000187:drug effects / Q000235:genetics; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D003593:Cytoplasm / Q000378:metabolism; D015195:Drug Design; D020962:Heterotrimeric GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D016296:Mutagenesis; D054388:Receptors, CCR / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics; D019713:Receptors, CCR5 / Q000737:chemistry; D019718:Receptors, CXCR4 / Q000737:chemistry; D013449:Sulfonamides / Q000737:chemistry* / Q000494:pharmacology*
chemical_list: C119309:CC chemokine receptor 9; C584933:CCR5 protein, human; C583420:CCX282-B; C527276:CXCR4 protein, human; D008024:Ligands; D054388:Receptors, CCR; D019713:Receptors, CCR5; D019718:Receptors, CXCR4; D013449:Sulfonamides; D020962:Heterotrimeric GTP-Binding Proteins