In summary, we have shown that tolcapone, a FDA-approved drug, is a potent inhibitor of TTR amyloidogenesis, prevents early events of WT and mutant TTR-induced cytotoxicity, binds to and stabilizes TTR in human plasma ex-vivo, to human V30M TTR in transgenic mice plasma in vivo and importantly, to human plasma TTR in vivo after oral administration at the therapeutic doses used for Parkinson's disease treatment. Here, TTR is linked to Parkinson disease.