Method of identifying an inhibitor of the prostanoid EP4 receptor
The present invention provides for the treatment of primary headache disorders, particularly migraine, using antagonists of the EP 4 receptor for prostaglandin E2. Particular EP 4 receptor antagonists include azole compounds of formula (I): wherein R 1 is a group such as lower alkyl substituted with carboxy; R 2 is hydrogen or lower alkyl, R 3 and R 4 are aryl optionally substituted with halogen, Q is in which -A 1 - is a single bond or lower alkylene, is a cyclo group, -A 3 - is a single bond or lower alkylene, and X is O, NH or S; or a salt or its solvate thereof.
1. A method for identifying an EP 4 receptor antagonist, which antagonist inhibits prostaglandin-induced relaxation of cerebral blood vessels having a diameter of less than 1 mm by selectively preventing the relaxation of cerebral vessels of less than 1 mm diameter, wherein said method comprises:
(a) providing an EP 4 receptor together with at least one other receptor selected from the group of EP 1 , EP 2 and EP 3 receptors;
(b) bringing a potential antagonist into contact with said receptors;
(c) determining whether said potential antagonist is an EP 4 receptor antagonist having a binding affinity for the EP 4 receptor at least 10-fold higher than for said EP 1 , EP 2 and/or EP 3 receptors; and
(d) selecting the EP 4 receptor antagonist which so binds as an agent for the treatment of primary headache disorder or drug-induced headache;
wherein said EP 4 receptor is provided in the form of isolated vasculature from a cerebral artery.
2. The method of claim 1 wherein said other receptor is an EP 3 receptor.
3. The method of claim 1 which further comprises one or more of the following steps:
(e′) testing the EP 4 receptor antagonist so selected for safety and/or toxicity in a human or animal subject;
(e″) testing the EP 4 receptor antagonist so selected in a human patient for efficacy in treating a primary headache disorder; and
(e′″) formulating the EP 4 receptor antagonist with one or more carriers, diluents or second agents for the treatment of primary headache disorders.
4. The method of claim 1 wherein step (c) comprises determining whether said potential antagonist is an EP 4 receptor antagonist having a binding affinity for the EP 4 receptor at least 10-fold higher than for said EP 1 , EP 2 and EP 3 receptors.
5. The method of claim 4 which further comprises one or more of the following steps:
(e′) testing the EP 4 receptor antagonist so selected for safety and/or toxicity in a human or animal subject;
(e″) testing the EP 4 receptor antagonist so selected in a human patient for efficacy in treating a primary headache disorder; and
(e′″) formulating the EP 4 receptor antagonist with one or more carriers, diluents or second agents for the treatment of primary headache disorders.
6. A method for identifying an EP 4 receptor antagonist, which antagonist inhibits prostaglandin induced relaxation of cerebral blood vessels having a diameter of less than 1 mm by selectively preventing the relaxation of cerebral vessels of less than 1 mm diameter, wherein said method comprises:
(a) providing an EP 4 receptor in the form of isolated vasculature from a cerebral artery;
(b) bringing a potential antagonist into contact with said receptor;
(c) determining whether said potential antagonist is an EP 4 receptor antagonist which binds the EP 4 receptor; and
(d) selecting the EP 4 receptor antagonist which so binds as an agent for the treatment of primary headache disorder or drug-induced headache.
7. The method of claim 6 wherein step (c) comprises determining whether the potential antagonist is an EP 4 receptor antagonist having a binding affinity for the EP 4 receptor at least 10-fold higher than for said EP 1 , EP 2 and/or EP 3 receptors.
8. The method of claim 6 which further comprises one or more of the following steps:
(e′) testing the EP 4 receptor antagonist so selected for safety and/or toxicity in a human or animal subject;
(e″) testing the EP 4 receptor antagonist so selected in a human patient for efficacy in treating a primary headache disorder; and
(e′″) formulating the EP 4 receptor antagonist with one or more carriers, diluents or second agents for the treatment of primary headache disorders.