Short-term Effects of TOLCAPONE on Transthyretin Stability in Subjects With Leptomeningeal TTR Amyloidosis (ATTR)

This study is designed as a clinical proof-of-concept evaluating whether TOLCAPONE is capable of stabilizing tetrameric TTR (Transthyretin) in the plasma and CSF of symptomatic or asymptomatic patients with leptomeningeal ATTR. Additionally the study will determine the plasma and CSF concentrations of TOLCAPONE needed to induce maximal stabilization of TTR across different TTR variants (TTR mutations). The study will be carried out in two different populations of subjects, defined by the TTR variant expressed: * Mutant TTR (up to 10 subjects): symptomatic leptomeningeal TTR patient with any documented leptomeningeal mutations in the TTR gene. * Mutant TTR (remaining subjects up to 10): asymptomatic leptomeningeal TTR patient with any documented leptomeningeal mutation in the TTR gene. TTR tetramers stability in plasma and CSF samples will be determined by urea-induced denaturation methodology.