Inotersen for the Treatment of Hereditary Transthyretin Amyloidosis

Hereditary transthyretin amyloidosis (hATTR) is a rare autosomal dominant condition in which mutations in the transthyretin gene cause amyloid fibrils to develop and deposit into tissues, affecting primarily the nerves and heart causing polyneuropathy and cardiomyopathy respectively. Standard treatment has been liver transplants to try and eliminate the mutated transthyretin products as the liver is the main source of transthyretin production. A new drug named inotersen (brand name Tagsedi), also known as IONIS-TTRRX, has been approved by the United States Food and Drug Agency, Health Canada, and European Commission in 2018, and introduced to the market for patients in stage 1 and stage 2 hATTR polyneuropathy. Inotersen is a second-generation antisense oligonucleotide with 2'-O-methoxyethyl modification designed to bind to the 3' untranslated region of the transthyretin mRNA in the nucleus of the liver cells. By doing so, it prevents the production of the mutant and wild-type forms of transthyretin, impeding the progression of the disease. In this article, the mechanism of action and safety profile of inotersen will be discussed along with some future directions following its approval.