Description
Imidafenacin, an M3/M1 muscarinic receptor antagonist, was introduced in
Japan for the oral treatment of OAB. The majority of OAB symptoms are
thought to result from overactivity of the detrusor muscle, which is primarily
mediated by acetylcholine-induced stimulation of muscarinic M3 receptors in the
bladder. Previously marketed muscarinic antagonists for OAB include propiverine,
tolterodine, oxybutynin, trospium, darifenacin, and solifenacin. In vitro,
imidafenacin is equally active against M1 and M3 receptors (Kb＝0.32 and
0.55nM, respectively), and approximately 10-fold less active against M2 receptors
(Kb＝4.13nM).
Imidafenacin is chemically synthesized in three steps starting with alkylation of diphenylacetonitrile with dibromoethane, followed by condensation with 2-methylimidazole, and hydrolysis of the cyano group to a carboxamide group with 70% sulfuric acid.
Chemical Properties
White Solid
Originator
Kyorin (Japan)
Uses
A novel therapeutic agent for overactive bladder with antimuscarinic activity, on mediator release from urothelium and detrusor overactivity induced by cerebral infarction. A muscarinic antagonist.
Definition
ChEBI: Imidafenacin is a diarylmethane.
Mechanism of action
Imidafenacin binds to and antagonizes muscarinic M1 and M3 receptors with high affinity. It also antagonizes muscarinic M2 receptors but with lower affinity. M3 receptors stimulate the contraction of the detrusor muscle in the bladder via the release of calcium from the sarcoplasmic reticulum. M2 receptors are also present in the detrusor muscle but inhibit adenylate cyclase, which reduces the relaxation mediated by β adrenergic receptors. Finally, M1 receptors are present in the parasympathetic neurons, which release acetylcholine in the bladder. They act as an autocrine positive feedback loop and further increase the release of acetylcholine. Antagonism of these receptors by imidafenacin prevents contraction of the bladder's detrusor muscle, prevents inhibition of the relation produced by sympathetic tone, and reduces acetylcholine release. Together, these reduce the frequency of urination.
Side effects
Like all medicines, imidafenacin can cause side effects, but not everybody will experience them. This drug can cause sleepiness, blurred vision, stomach upset, constipation, and increased triglyceride levels.
Synthesis
Diphenylacetonitrile
(53) was alkylated with dibromoethane in the presence
of NaNH2 in toluene to give bromide compound 54. The bromide 54 was condensed with 2-methylimidazole
in the presence of Et3N in hot DMF to afford 2-methylimidazole
derivative 55. Hydrolysis of the cyano group of 55
with 70% sulfuric acid provided imidafenacin (VII).
