Inhibition of catechol-O-methyltransferase (COMT) is an established strategy for treating end-of-dose motor fluctuations (wearing-off) in patients with Parkinson’s disease (PD) treated with levodopa (L-dopa) and a DOPA decarboxylase inhibitor (DCI) (Fox et al. 2018). Here, COMT is linked to Parkinson disease.