Responder analysis for neuropathic impairment and quality-of-life assessment in patients with hereditary transthyretin amyloidosis with polyneuropathy in the NEURO-TTR study

OBJECTIVE: Hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN) is a rare disease characterized by rapid neuropathic progression. In pivotal studies of gene-silencing treatments, the modified Neuropathy Impairment Score + 7 tests (mNIS + 7) and Norfolk-Quality of Life (QOL)-Diabetic Neuropathy (DN) questionnaire assessed treatment impact on neuropathic progression. Establishing responder definition (RD) thresholds for these measures would enable evaluation of clinically meaningful treatment benefit. METHODS: mNIS + 7 and Norfolk-QOL-DN were administered at baseline and week 65 to 165 adults with ATTRv-PN receiving inotersen (n = 106) or placebo (n = 59) in the NEURO-TTR study. Anchor-based approaches for estimating RD thresholds were used for Norfolk QOL-DN, while distribution-based approaches were used for both measures. Responders were patients with a score change < RD, indicating improvement or stabilization (i.e., no clinically meaningful progression). Odds ratios (ORs) and Fisher’s exact tests compared proportions of responders by treatment. RESULTS: The mean RD estimates were 12.2 points and 8.8 points for mNIS + 7 and Norfolk QOL-DN, respectively. The proportions of patients whose change in score indicated improvement or stabilization were statistically significantly larger for inotersen than placebo for all estimated RD thresholds for mNIS + 7 (64–86% responders for inotersen vs. 27–46% for placebo, ORs = 3.8–7.2, ps < 0.001) and Norfolk QOL-DN (66–81% vs. 35–56%, ORs = 2.4–3.6, ps < 0.05). DISCUSSION: Establishing RD thresholds for these instruments enables evaluation of clinically relevant and individual-level treatment benefit on neuropathic progression. Across RDs estimated using multiple methods, a higher proportion of patients receiving inotersen than placebo showed improved or stabilized neuropathic progression at week 65. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01737398; Date of registration: November 29, 2012.