Gene therapy options for hereditary transthyretin-related amyloidosis

Abstract

Hereditary transthyretin-related amyloidosis (ATTRv) is arare autosomal dominant disease and is fatal if left untreated. It is caused by mutations in the transthyretin gene. All known mutations induce misfolding of the tetrameric transthyretin molecule and protein deposits in multiple organs. In peripheral nerves this result in sensorimotor and autonomic polyneuropathy and in cardiac muscle it causes cardiomyopathy. Untreated ATTRv is characterized by an irreversible and progressive course and death 7-11years after symptom onset. Treatment options consist of TTR stabilizing drugs, such as tafamidis and active agents that selectively interfere at the mRNA level, the so-called gene silencers patisiran and inotersen. All forms of treatment aim to prevent amyloid tissue deposition in tissues and organ dysfunction. Patisiran works by RNA interference on endogenous mechanisms of gene expression. It results in the cleavage of TTR-mRNA using the cytoplasmatic RNA-induced silencing complex. Inotersen, an antisense oligonucleotide, degrades TTR-mRNA via activation of nuclear RNaseH. Both mechanisms result in asignificant reduction of TTR protein serum levels. The efficacy could be demonstrated by slowing or improving neuropathy progression in the phase III study APOLLO (patisiran) or the NEURO-TTR study (inotersen). Furthermore, the use of both agents led to an improvement in the quality of life in patients with ATTRv. Both forms of treatment are approved in Germany since August 2018 for polyneuropathy stages1 and2 according to Coutinho. The choice of treatment should be carried out individually considering drug formulation, contraindications and the necessary safety monitoring controls.