Entacapone is a specific, potent, peripherally acting catechol-O-methyltransferase (COMT) inhibitor with IC50 of 151 nM for PD treatment. IC50 Value: 151 nM Target: COMT in vitro: Entacapone inhibits catechol-O-methyltransferase(COMT) with similar IC50 in different tissues including live, duodenum, kidney and lung, but entacapone is more active than tolcapone in those tissues. Entacapone (< 100 μM) is a potent inhibitor of α-syn and β-amyloid (Aβ) oligomerization and fibrillogenesis, and also protects against extracellular toxicity induced by the aggregation of both proteins in PC12 cells. in vivo: Levodopa/carbidopa/entacapone has been shown to improve the pharmacokinetic profile of levodopa and provide superior symptomatic control compared with conventional levodopa/dopa decarboxylase inhibitor therapy. We report four case histories describing clinical experience of using levodopa/carbidopa/entacapone 200/50/200 mg, one of the latest doses of this formulation, in a range of patients with Parkinson's disease. These cases illustrate that levodopa/carbidopa/entacapone 200/50/200 mg provides improvements in symptomatic control. Clinical trial: The combination product carbidopa/levodopa/entacapone (CLE) was approved in 2003 for the treatment of PD patients.