Dyck, P. James B.

Background:Hereditary transthyretin amyloidosis (hATTR) is a rare protein misfolding disorder that causes progressive and debilitating polyneuropathy. A randomized, controlled phase 3 trial (NEURO‐TTR; NCT01737398) demonstrated efficacy and safety of inotersen in patients with hATTR polyneuropathy (Benson 2018 NEJM).Aims:To provide an update on the long‐term efficacy and safety of inotersen, an antisense oligonucleotide inhibitor of transthyretin protein production, in patients with hereditary transthyretin amyloidosis (hATTR) with polyneuropathy.Methods:Patients who completed NEURO‐TTR were eligible to enroll in an ongoing open‐label extension (OLE) study (NCT02175004). We report an update on the long‐term efficacy and safety of inotersen in patients with hATTR polyneuropathy after 24 months in the OLE. Assessments included modified Neuropathy Impairment Score +7 neurophysiologic tests composite score (mNIS+7), Norfolk Quality of Life–Diabetic Neuropathy questionnaire total score (Norfolk QoL‐DN), Short Form 36 Health Survey version 2 (SF‐36v2) physical component summary (PCS), and safety monitoring.Results:Of 139 patients who completed NEURO‐TTR, 135 (97.1%) enrolled in the OLE. As of 5/31/2018, some patients were ongoing but had not yet completed 24 months in the OLE, and longest inotersen exposure in both studies was 5.2 years. Patients who switched from placebo to inotersen in the OLE demonstrated slowing of neurologic disease progression by mNIS+7 and Norfolk QoL‐DN as early as 6 months after starting inotersen (mean change from OLE baseline to month 6/year 2: 6.22/5.08 for mNIS+7 and 0.54/2.26 for Norfolk QoL‐DN). Patients who received inotersen for 39 months (15 months NEURO‐TTR + 24 months OLE) continued to show benefit (mean change from OLE baseline to year 2: 11.18 for mNIS+7 and 5.22 for Norfolk QoL‐DN). Patients who continued inotersen also showed stabilization of health‐related quality of life measured by SF‐36v2 PCS. No evidence of increased risk for grade 4 thrombocytopenia or severe renal events has been observed with increased exposure duration; no new safety concerns have been identified.Summary/Conclusion:In the OLE, inotersen improved, halted, or slowed progression of hATTR polyneuropathy, with greater stabilization observed in patients who initiated inotersen earlier.

Abstract We report a 73-year-old man with Val142Ile transthyretin (TTR) amyloidosis and an atypical clinical presentation of upper-extremity–predominant neuropathy without significant autonomic or cardiac involvement. TTR familial amyloid polyneuropathy commonly presents as length-dependent sensorimotor polyneuropathy with marked and early autonomic involvement. Multiple pathogenic mutations in TTR gene have been identified, of which Val50Met is commonly associated with TTR familial amyloid polyneuropathy, and Val142Ile is commonly associated with familial amyloid cardiomyopathy. Our patient is from a nonendemic region, without family history for amyloidosis. Predominant upper-extremity neuropathy, without significant cardiac or autonomic involvement, distinguishes this case from previously reported Val142Ile-mutated TTR amyloidosis.

See article on pages 141–146 in this issue.

See article on pages 643–649 in this issue.

ABSTRACTIntroductionOnion‐bulbs (OB) are concentrically layered Schwann‐cell processes, surrounding nerve fibers, occurring in both inherited and acquired demyelinating polyneuropathies. We investigated whether OB patterns (generalized, mixed, or focal) correlate with acquired or inherited neuropathies.MethodsOne hundred thirty‐one OB‐rich nerve biopsies were graded for OB pattern and inflammation without knowledge of clinical history. We classified inherited (n = 49) or acquired (n = 82) neuropathies based solely on clinical history.ResultsFifty‐one biopsies had generalized (34 inherited vs. 17 acquired, P < 0.001), 54 mixed (48 acquired vs. 6 inherited, P < 0.001), and 26 focal/multifocal (inherited [n = 9], acquired [n = 17]) OB. Inflammation occurred more frequently in acquired (n = 54) than inherited (n = 14) neuropathy (P = 0.004).DiscussionGeneralized OB correlates with inherited neuropathy; mixed OB with acquired. Inflammation occurs more in acquired neuropathy cases. OB patterns are best explained by ubiquitous Schwann‐cell involvement in inherited and multifocal Schwann‐cell involvement in acquired neuropathies and predict the electrophysiology of uniform demyelination in inherited and unequal demyelination in acquired neuropathies. Muscle Nerve 59:665–670, 2019