Screening of molecules under clinical development or already in use in humans led to the discovery that tolcapone, a drug used to treat patients with Parkinson’s disease, is a potent TTR tetramer binder, which can bind TTR in human plasma, stabilize TTR tetramers in vivo and inhibit TTR cytotoxicity (Sant’Anna et al., 2016; Gamez et al., 2019). Here, TTR is linked to Parkinson disease.