Long-term treatment of transthyretin familial amyloid polyneuropathy with tafamidis: a clinical and neurophysiological study.

Tafamidis is a transthyretin (TTR) stabilizer recently approved to slow the neurologic impairment in TTR familial amyloid polyneuropathy (TTR-FAP). The pivotal studies on Tafamidis reported encouraging results on the short term, in the early onset Val30Met-TTR-FAP patients at an early stage of the neuropathy. However, the effect of the drug in the non-Val30Met patients, at a more advanced stage of the disease and on the long term, is less known. In this study, we report the effect of Tafamidis in 43 TTR-FAP patients with a variety of pathogenic mutations, including 53% of non-Val30Met variants, at different stages of neuropathy followed on the long term. General and neurological assessment was performed in a standardized protocol every 6-12 months along with neurophysiological variables, including testing of small nerve fibres. The mean follow-up under treatment was 2 years with a subset of 26 patients treated for 3 years. Overall, Tafamidis was well tolerated. A significant clinical deterioration of the neuropathy and the patient's general condition was observed across the 3 years follow-up, although neurophysiological parameters remained stable for the first 2 years. In contrast, patients had a significant increase of BMI under treatment. Deterioration of the neuropathy correlated to an older age at disease onset or treatment initiation and to poor clinical status at baseline. A higher BMI at baseline was associated with a lower progression of the neuropathy. About one-third of the patients who received 3 years of tafamidis had still preserved walking capacity or good clinical condition, suggesting that tafamidis slowed the disease progression in some patients. Overall, our work shows that tafamidis is well tolerated in TTR-FAP but does not prevent the steady progression of the neuropathy on the long term. Age, neurologic status, and general condition at baseline appear to be best predictors of tafamidis efficacy on the neurological function.