Current approaches for treatment of hereditary transthyretin amyloidosis (ATTR)

Abstract

Rare, progressive, and fatal is a short description for autosomal dominant hereditary transthyretin (TTR) amyloidosis (ATTR). In the absence of a family background, delays in diagnosis are common. ATTR is often represented by a progressive, axonal fiber-length-dependent polyneuropathy (motor, autonomic, sensory). Cardiovascular, gastrointestinal, renal and ocular manifestations are frequently observed. ATTR is caused by mutated serum protein transthyretin (TTRm), which results in amyloid deposits.The three current concepts of ATTR treatment aim to replace, stabilize and reduce TTR synthesis. (i) The mutant TTRm is almost completely replaced in the peripheral blood after orthotopic liver transplantation by the synthesis of the wild-type (TTRwt) in the donor liver. (ii) Low molecular weight compounds stabilize the TTR tetramer and thereby minimize the formation of amyloid precursors. (iii) Gene silencers (mRNA-inhibiting oligonucleotides) reduce liver-secreted TTRm and TTRwt.Liver transplantation (LTx) is an established procedure in ATTR patients. LTx significantly prolongs survival, especially in early stage patients (< 50 years) with variant ATTRV30M. Some non-ATTRV30M variants show a higher mortality after LTx. The progression of the disease can be slowed down but not prevented by LTx. Diflunisal is a low-cost, off-label drug from the NSAID group. Similar to Tafamidis, it stabilizes the TTR tetramer. Tafamidis has been approved for the treatment of stage 1 ATTR since 2011. It is administered orally and used in patients with polyneuropathy and more recently with cardiomyopathy. Inotersen represents an antisense oligonucleotide that is administered subcutaneously (s. c.) once a week. Patisiran acts as a siRNA oligonucleotide administered intravenously (i. v.) every three weeks in combination with premedication. Both gene silencers were approved in 2018 for the treatment of ATTR stages 1 and 2. The new era of TTR gene silencers now affords an update of algorithms used for treatment of ATTR.