During our review of the amyloid inhibitors in the literature in our previous study (Lump et al., 2015; Xun et al., 2015; Ren et al., 2018; Zhang et al., 2018; Li et al., 2019; Tan et al., 2019), we noticed that tolcapone, an active catechol-O-methyltransferase (COMT) inhibitor clinically used as an adjunct to levodopa/carbidopa for Parkinson’s disease (Olanow and Watkins, 2007; Müller, 2015), possessed inhibitory activity against transthyretin (TTR) amyloidosis, which is a plasma homotetrameric protein associated with fatal systemic amyloidoses. This evidence concerns the gene COMT and Parkinson disease.