mNIS+7 and lower limb function in inotersen treatment of hereditary transthyretin-mediated amyloidosis

Anti-MAG neuropathy: historical aspects, clinical-pathological correlations, and considerations for future therapeutical trials

BACKGROUND

 Patients with anti-MAG neuropathy present with distal demyelinating polyneuropathy, IgM monoclonal gammopathy, and elevated titers of anti-MAG antibodies.

OBJECTIVE

 This paper reviews what is known about the clinical presentation, course, pathophysiology, and treatment of anti-MAG neuropathy, with considerations for the design of therapeutic trials.

METHODS

 A literature review of the medical and scientific literature related to anti-MAG neuropathy, and the design of therapeutic clinical trials in peripheral neuropathy.

RESULTS

 Anti-MAG neuropathy can remain indolent for many years but then enter a progressive phase. Highly elevated antibody titers are diagnostic, but intermediate titers can also occur in chronic inflammatory demyelinating polyneuropathy (CIDP). The peripheral nerves can become inexcitable, thereby masking the demyelinating abnormalities. There is good evidence that the anti-MAG antibodies cause neuropathy. Reduction of the autoantibody concentration by agents that target B-cells was reported to result in clinical improvement in case series and uncontrolled trials, but not in controlled clinical trials, probably due to inadequate trial design.

CONCLUSION

 We propose that therapeutic trials for anti-MAG neuropathy include patients with the typical presentation, some degree of weakness, highly elevated anti-MAG antibody titers, and at least one nerve exhibiting demyelinating range abnormalities. Treatment with one or a combination of anti-B-cell agents would aim at reducing the autoantibody concentration by at least 60%. A trial duration of 2 years may be required to show efficacy. The neuropathy impairment score of the lower extremities (NIS-LL) plus the Lower Limb Function (LLF) score would be a suitable primary outcome measure.

Peripheral Nervous, Hepatic, and Gastrointestinal Endpoints for AL Amyloidosis Clinical Trials: Report from the Amyloidosis Forum Multi-organ System Working Group

Systemic immunoglobulin light chain (AL) amyloidosis is a heterogeneous rare disease driven by a destructive monoclonal gammopathy and typified by misfolded immunoglobulin light and/or heavy chains which aggregate and deposit in organs as insoluble amyloid fibrils. Disease heterogeneity is driven by the degree of multi-systemic involvement; cardiac, renal, neurological, and gastrointestinal (GI) systems are affected to varying degrees in different patients. While prognosis is primarily driven by hematologic response to treatment and outcomes associated with cardiac events and overall survival, the involvement of the peripheral nervous, hepatic, and GI systems can also have a significant impact on patients. The Amyloidosis Forum ( https://amyloidosisforum.org ) is a public-private partnership between the nonprofit Amyloidosis Research Consortium ( www.arci.org ) and the US Food and Drug Administration (FDA) Center for Drug Evaluation and Research formed to advance drug development for the treatment of systemic amyloid disorders. A series of virtual workshops focused on the development of novel, patient-relevant endpoint components and analytical strategies for clinical trials in AL amyloidosis. This review summarizes the proceedings and recommendations of the Multi-Systemic Working Group which identified, reviewed, and prioritized endpoints relevant to the impacts of AL amyloidosis on the peripheral nervous, hepatic, and GI systems. The Working Group comprised amyloidosis experts, patient representatives, statisticians, and representatives from the FDA, Medicines and Healthcare products Regulatory Agency (MHRA), and pharmaceutical companies. Prioritized neuropathy/autonomic endpoints included a modified form of the Neuropathy Impairment Score (NIS + 7) and the Composite Autonomic Symptom Score (COMPASS-31), respectively. Alkaline phosphatase was identified as the most relevant indicator of liver involvement and disease progression. Following extensive review of potential GI endpoints, the Working Group identified multiple exploratory endpoints. These recommended components will be further explored through evaluation of clinical trial datasets and possible integration into composite endpoint analysis.

Novel Therapeutic Approaches in Inherited Neuropathies: A Systematic Review

The management of inherited neuropathies relies mostly on the treatment of symptoms. In recent years, a better understanding of the pathogenic mechanisms that underlie neuropathies has allowed for the development of disease-modifying therapies. Here, we systematically review the therapies that have emerged in this field over the last five years. An updated list of diseases with peripheral neuropathy as a clinical feature was created based on panels of genes used clinically to diagnose inherited neuropathy. This list was extended by an analysis of published data by the authors and verified by two experts. A comprehensive search for studies of human patients suffering from one of the diseases in our list yielded 28 studies that assessed neuropathy as a primary or secondary outcome. Although the use of various scales and scoring systems made comparisons difficult, this analysis identified diseases associated with neuropathy for which approved therapies exist. An important finding is that the symptoms and/or biomarkers of neuropathies were assessed only in a minority of cases. Therefore, further investigation of treatment efficacy on neuropathies in future trials must employ objective, consistent methods such as wearable technologies, motor unit indexes, MRI or sonography imaging, or the use of blood biomarkers associated with consistent nerve conduction studies.

The impact of inotersen on Neuropathy Impairment Score in patients with hereditary transthyretin amyloidosis with polyneuropathy

BACKGROUND

Patients with hereditary transthyretin amyloidosis (ATTRv) frequently experience symptoms of polyneuropathy (PN) that worsen over time and impair daily functioning. Previous analyses supported efficacy of inotersen, an antisense oligonucleotide, to slow neuropathic progression in patients with ATTRv-PN, as indicated by larger mean changes, relative to placebo, in total score and several subscales of the Neuropathy Impairment Score (NIS), and for the subset of NIS items specific to lower limbs (NIS-LL) for the overall study sample. A key objective of the current study was to evaluate efficacy of inotersen for slowing neuropathic progression in NIS/NIS-LL within key clinical subgroups of patients with ATTRv-PN. Additionally, for this study, responder definition (RD) thresholds were estimated for NIS/NIS-LL total and subscale scores, for the purpose of evaluating clinically meaningful benefit of inotersen at the individual patient-level.

METHODS

Post hoc analyses used data from the NEURO-TTR phase 3 trial of inotersen in patients with ATTRv-PN (NCT01737398). Treatment differences in mean changes on NIS/NIS-LL total and subscale scores from baseline to week 65 were examined within patient subgroups defined by clinical characteristics. Anchor- and distribution-based approaches estimated RDs for NIS/NIS-LL scores, with responders defined as patients who did not experience clinically meaningful neuropathic progression. Responder analyses compared the proportion of patients classified as responders for each NIS/NIS-LL score between treatment arms.

RESULTS

Within each patient subgroup, mean increases in NIS/NIS-LL total and muscle weakness subscales were significantly smaller after 65 weeks of treatment with inotersen compared to placebo. Similar patterns were observed for some, but not all, subgroups on NIS/NIS-LL reflex subscale scores. Recommended RDs were 8.1 points for NIS total and 4.7 points for NIS-LL total. Patients receiving inotersen for 65 weeks were significantly less likely than those receiving placebo to exhibit clinically meaningful increases on NIS/NIS-LL total, muscle weakness, and sensation subscales.

CONCLUSIONS

This study supports previous evidence for efficacy of inotersen in this patient population and provides interpretation guidelines for clinically meaningful changes in NIS/NIS-LL scores.

Long-Term Treatment Effects of Inotersen on Health-Related Quality of Life in Patients with hATTR Amyloidosis with Polyneuropathy: Analysis of the Open-Label Extension of the NEURO-TTR Trial

INTRODUCTION/AIMS

Hereditary transthyretin-mediated amyloidosis with polyneuropathy (hATTR-PN) progressively affects patients' functionality and compromises health-related quality of life (HRQL). The aim of this study was to quantify the projected long-term treatment effects of inotersen versus placebo on HRQL measures.

METHODS

The inotersen phase 2/3 randomized, double-blind, placebo-controlled trial NEURO-TTR (NCT01737398, 66 weeks) and subsequent open-label extension (OLE; NCT02175004, 104 weeks) included 172 patients (inotersen = 112; placebo = 60). Placebo double-blind period and overall inotersen-inotersen (double-blind/OLE) treatment period (170 weeks) data were used to extrapolate long-term placebo-placebo effect using mixed-effects models with repeated measures. Changes from baseline in the Norfolk Quality of Life-Diabetic Neuropathy (QoL-DN) and Short-Form 36 Health Survey (SF-36v2) in hATTR-PN were estimated. Differences in changes were compared between the inotersen/inotersen and extrapolated placebo/placebo arms.

RESULTS

Inotersen-inotersen patients maintained their HRQL with an observed change ranging from 10.3% improvement (Norfolk QoL-DN item "Pain Kept You Awake at Night") to 11.6% deterioration (SF-36v2 Activities of Daily Living subdomain). The extrapolated placebo-placebo results suggest greater deterioration over time compared to inotersen-inotersen treatment on Norfolk QoL-DN total score (23.6, [95% CI: 8.9-38.3], p < 0.01), Activities of Daily Living (4.6, [2.0-7.3], p < 0.001), and item "Pain Kept You Awake at Night" (1.2, [0.4-1.9], p < 0.01). Similarly, greater deterioration was expected for SF-36v2 Physical Component Summary (8.0, [3.2-12.8], p < 0.01), Bodily Pain (7.8, [2.0-13.5], p < 0.01), and Physical Functioning domain (10.6, [5.5-15.6], p < 0.0001).

DISCUSSION

Long-term (>3 years) inotersen treatment was associated with slowing, and in some domains halting, of deterioration in key HRQL outcomes, particularly physical functioning and pain measures. This article is protected by copyright. All rights reserved.

Novel approaches to diagnosis and management of hereditary transthyretin amyloidosis

Hereditary transthyretin amyloidosis (ATTRv) is a severe, adult-onset autosomal dominant inherited systemic disease predominantly affecting the peripheral and autonomic nervous system, heart, kidney and the eyes. ATTRv is caused by mutations of the transthyretin (TTR) gene, leading to extracellular deposition of amyloid fibrils in multiple organs including the peripheral nervous system. Typically, the neuropathy associated with ATTRv is characterised by a rapidly progressive and disabling sensorimotor axonal neuropathy with early small-fibre involvement. Carpal tunnel syndrome and cardiac dysfunction frequently coexist as part of the ATTRv phenotype. Although awareness of ATTRv polyneuropathy among neurologists has increased, the rate of misdiagnosis remains high, resulting in significant diagnostic delays and accrued disability. A timely and definitive diagnosis is important, given the emergence of effective therapies which have revolutionised the management of transthyretin amyloidosis. TTR protein stabilisers diflunisal and tafamidis can delay the progression of the disease, if treated early in the course. Additionally, TTR gene silencing medications, patisiran and inotersen, have resulted in up to 80% reduction in TTR production, leading to stabilisation or slight improvement of peripheral neuropathy and cardiac dysfunction, as well as improvement in quality of life and functional outcomes. The considerable therapeutic advances have raised additional challenges, including optimisation of diagnostic techniques and management approaches in ATTRv neuropathy. This review highlights the key advances in the diagnostic techniques, current and emerging management strategies, and biomarker development for disease progression in ATTRv.

Variable differences of nerve conduction amplitudes versus velocities and distal latencies of healthy subjects assessed in ethnic cohorts

Variable differences of nerve conduction amplitudes vs velocities and distal latencies (DLs) of healthy subjects assessed in ethnic cohorts.

INTRODUCTION/AIMS

The variables affecting reference compound muscle (CMAP) and sensory nerve action potential (SNAP) amplitudes as compared to ones affecting conduction velocities and DLs have not been adequately evaluated in previous studies. In this report, this subject is studied in healthy subject cohorts mainly of Northern European extraction, Northern Plains Indians, and Latinos.

METHODS

Nineteen variables and 18 attributes of nerve conductions (NCs) were assessed using highly standard testing conditions and techniques. Classification and Regression Tree analyses were used to assess variable differences among amplitudes, conduction velocities, and DLs.

RESULTS

The most important variable affecting CMAP and SNAP amplitudes was age. For conduction velocities (CVs) and DLs, the variables were height, ethnic cohort, and age.

DISCUSSION

The variables affecting attributes of NCs were similar for the three ethnic cohorts evaluated. The differences of variables affecting amplitudes compared to CVs and DLs need to be taken into account in interpretation of NC results and in setting reference limits for use in medical practice, epidemiology surveys, and therapeutic trials. Scores of CMAP and SNAP amplitudes are suitable measures of sensorimotor polyneuropathy severity, whereas conduction velocities and DLs reflect physiologic/pathologic abnormality of nerve fibers.

mNIS+7 and lower limb function in inotersen treatment of hereditary transthyretin-mediated amyloidosis

Introduction

Inotersen, an antisense oligonucleotide inhibitor of transthyretin (TTR) protein production, demonstrated significant benefit versus placebo in the modified Neuropathy Impairment Score (NIS) +7 neurophysiologic tests (mNIS+7) in patients with hereditary TTR‐mediated amyloidosis (hATTR) with polyneuropathy. This analysis assessed the mNIS+7 components by anatomic location and the lower limb function (LLF) test.

Methods

Adults with hATTR in the NEURO‐TTR trial (NCT01737398) were randomly assigned to receive weekly doses of subcutaneous inotersen 300 mg or placebo for 65 weeks. The mNIS+7 and LLF were assessed at 35 and 66 weeks.

Results

All major mNIS+7 components (muscle weakness, muscle stretch reflexes, sensation) and the LLF showed significant efficacy in patients receiving inotersen versus placebo; however, NIS‐reflexes (upper limb), touch pressure (upper and lower limbs), and heart rate during deep breathing did not show significant effects.

Discussion

The results of this analysis reinforce the beneficial effect of inotersen on slowing neuropathy progression in patients with hATTR polyneuropathy.

See article on pages 509–515 in this issue.