Entacapone, a nitrocatechol compound, is a selective and reversible inhibitor of catechol-O-methyltransferase (COMT), a Mg2+-dependent enzyme involved in the metabolism of catecholamines and catechol compounds, with the half maximal inhibition concentration IC50 and inhibition constant Ki values of 20.1 nM and 10.7 nM respectively [1 & 2].
The nitro group at the position ortho to the hydroxyl group in the chemical structure of entacapone has been identified as a critical component for its potency and ability to inhibit COMT [2].
Entacapone is an FDA-approved COMT inhibitor for use as an adjunct to levodopa therapy in patients’ with Parkinson’s disease, where it increases both the peripheral and central availability of levodopa [2].
Reference
References:
[1] Forsberg M, Lehtonen M, Heikkinen M, Savolainen J, Järvinen T, Männistö PT. Pharmacokinetics and pharmacodynamics of entacapone and tolcapone after acute and repeated administration: a comparative study in the rat. J Pharmacol Exp Ther. 2003 Feb;304(2):498-506.
[2] Najib J. Entacapone: a catechol-O-methyltransferase inhibitor for the adjunctive treatment of Parkinson's disease. Clin Ther. 2001 Jun;23(6):802-32; discussion 771.