Transthyretin familial amyloid polyneuropathy

Clinical spectrum of Transthyretin amyloidogenic mutations among diverse population origins

PURPOSE

Coding mutations in the Transthyretin (TTR) gene cause a hereditary form of amyloidosis characterized by a complex genotype-phenotype correlation with limited information regarding differences among worldwide populations.

METHODS

We compared 676 diverse individuals carrying TTR amyloidogenic mutations (rs138065384, Phe44Leu; rs730881165, Ala81Thr; rs121918074, His90Asn; rs76992529, Val122Ile) to 12,430 non-carriers matched by age, sex, and genetically-inferred ancestry to assess their clinical presentations across 1,693 outcomes derived from electronic health records in UK biobank.

RESULTS

In individuals of African descent (AFR), Val122Ile mutation was linked to multiple outcomes related to the circulatory system (fold-enrichment = 2.96, p = 0.002) with the strongest associations being cardiac congenital anomalies (phecode 747.1, p = 0.003), endocarditis (phecode 420.3, p = 0.006), and cardiomyopathy (phecode 425, p = 0.007). In individuals of Central-South Asian descent (CSA), His90Asn mutation was associated with dermatologic outcomes (fold-enrichment = 28, p = 0.001). The same TTR mutation was linked to neoplasms in European-descent individuals (EUR, fold-enrichment = 3.09, p = 0.003). In EUR, Ala81Thr showed multiple associations with respiratory outcomes related (fold-enrichment = 3.61, p = 0.002), but the strongest association was with atrioventricular block (phecode 426.2, p = 2.81 × 10- 4). Additionally, the same mutation in East Asians (EAS) showed associations with endocrine-metabolic traits (fold-enrichment = 4.47, p = 0.003). In the cross-ancestry meta-analysis, Val122Ile mutation was associated with peripheral nerve disorders (phecode 351, p = 0.004) in addition to cardiac congenital anomalies (fold-enrichment = 6.94, p = 0.003).

CONCLUSIONS

Overall, these findings highlight that TTR amyloidogenic mutations present ancestry-specific and ancestry-convergent associations related to a range of health domains. This supports the need to increase awareness regarding the range of outcomes associated with TTR mutations across worldwide populations to reduce misdiagnosis and delayed diagnosis of TTR-related amyloidosis.

Eplontersen for Hereditary Transthyretin Amyloidosis With Polyneuropathy

Importance

Transthyretin gene silencing is an emerging treatment strategy for hereditary transthyretin (ATTRv) amyloidosis.

Objective

To evaluate eplontersen, an investigational ligand-conjugated antisense oligonucleotide, in ATTRv polyneuropathy.

Design, Setting, and Participants

NEURO-TTRansform was an open-label, single-group, phase 3 trial conducted at 40 sites across 15 countries (December 2019-April 2023) in 168 adults with Coutinho stage 1 or 2 ATTRv polyneuropathy, Neuropathy Impairment Score 10-130, and a documented TTR variant. Patients treated with placebo from NEURO-TTR (NCT01737398; March 2013-November 2017), an inotersen trial with similar eligibility criteria and end points, served as a historical placebo ("placebo") group.

Interventions

Subcutaneous eplontersen (45 mg every 4 weeks; n = 144); a small reference group received subcutaneous inotersen (300 mg weekly; n = 24); subcutaneous placebo weekly (in NEURO-TTR; n = 60).

Main Outcomes and Measures

Primary efficacy end points at week 65/66 were changes from baseline in serum transthyretin concentration, modified Neuropathy Impairment Score +7 (mNIS+7) composite score (scoring range, -22.3 to 346.3; higher scores indicate poorer function), and Norfolk Quality of Life Questionnaire-Diabetic Neuropathy (Norfolk QoL-DN) total score (scoring range, -4 to 136; higher scores indicate poorer quality of life). Analyses of efficacy end points were based on a mixed-effects model with repeated measures adjusted by propensity score weights.

Results

Among 144 eplontersen-treated patients (mean age, 53.0 years; 69% male), 136 (94.4%) completed week-66 follow-up; among 60 placebo patients (mean age, 59.5 years; 68% male), 52 (86.7%) completed week-66 follow-up. At week 65, adjusted mean percentage reduction in serum transthyretin was -81.7% with eplontersen and -11.2% with placebo (difference, -70.4% [95% CI, -75.2% to -65.7%]; P < .001). Adjusted mean change from baseline to week 66 was lower (better) with eplontersen vs placebo for mNIS+7 composite score (0.3 vs 25.1; difference, -24.8 [95% CI, -31.0 to -18.6; P < .001) and for Norfolk QoL-DN (-5.5 vs 14.2; difference, -19.7 [95% CI, -25.6 to -13.8]; P < .001). Adverse events by week 66 that led to study drug discontinuation occurred in 6 patients (4%) in the eplontersen group vs 2 (3%) in the placebo group. Through week 66, there were 2 deaths in the eplontersen group consistent with known disease-related sequelae (cardiac arrhythmia; intracerebral hemorrhage); there were no deaths in the placebo group.

Conclusions and Relevance

In patients with ATTRv polyneuropathy, the eplontersen treatment group demonstrated changes consistent with significantly lowered serum transthyretin concentration, less neuropathy impairment, and better quality of life compared with a historical placebo.

Trial Registration

ClinicalTrials.gov Identifier: NCT04136184; EU Clinical Trials Register: EudraCT 2019-001698-10.

The patient pathway in ATTR-CM in Greece and how to improve it: A multidisciplinary perspective

Transthyretin amyloid cardiomyopathy (ATTR-CM) is an underdiagnosed disease associated with high mortality rates and the patient journey is characterized by increased complexities. Accurate and timely diagnosis and prompt initiation of disease-modifying treatment constitute the contemporary unmet need in ATTR-CM. ATTR-CM diagnosis is characterized by considerable delays and high rates of misdiagnosis. The majority of patients present themselves to primary care physicians, internists, and cardiologists, and many have undergone repeated medical evaluations before an accurate diagnosis has been made. The disease is diagnosed mainly after the development of heart failure symptoms, reflecting a long course of missed opportunities before diagnosis and disease-modifying treatment initiation. Early referral to experienced centers ensures prompt diagnosis and therapy. Early diagnosis, better care coordination, acceleration of digital transformation and reference networks, encouragement of patient engagement, and implementation of rare disease registries are the key pillars to improve the ATTR-CM patient pathway and achieve important benefits in ATTR-CM outcomes.

Modified Technique of Ex-PRESS® Filtration Device Combined with a Scleral Pocket for Hereditary Transthyretin Amyloidosis (hATTR) Secondary Open-Angle Glaucoma

Purpose

To evaluate the effectiveness and safety of a modified approach using the Ex-PRESS^® implant combined with a scleral pocket in the management of secondary open-angle glaucoma in hereditary transthyretin amyloidosis (hATTR) at our department.

Methods

This was a retrospective analysis. The primary endpoints included Intraocular pressure (IOP) evaluation (baseline, 1st day, 1st week, 1, 3, 6, 12 months and at last follow-up) and number of hypotensive drugs (baseline, 6th, 12th months and at last follow-up). As secondary endpoints surgical complications, the need for additional glaucoma surgery and LogMAR BCVA were evaluated. Qualified and complete success were defined as ≥ 30% IOP decrease from baseline, with or without additional medications, respectively. The minimum follow-up was 12 months.

Results

A total of 32 eyes were included with a mean follow-up of 2.4±2.9 years. IOP decreased significantly from baseline (27.4±4.4 mmHg) to 1st day (5.00±2.9 mmHg), 1st week (6.9±4.1 mmHg), 1st month (11.7±7.8 mmHg), 3rd month (11.6±6.1 mmHg), 6th month (13.1±6.8 mmHg), 12th month (12.0±3.5 mmHg) and last visit (11.8±2.4 mmHg), p<0.001. There was also a significant reduction in the number of antiglaucoma medications from baseline (3.8±0.6) and last follow-up (0.4±0.8), p<0.001. LogMAR BCVA remained stable (0.25±0.26 at baseline and 0.25±0.24 at last follow-up), p=0.767. Transient hypotony occurred in 17 eyes (53.1%), but only 11 (34.4%) exhibited anterior chamber shallowing and needed additional care, namely cycloplegic drops and viscoelastic injection. Complete surgical success was achieved in 22 eyes (68.8%) and qualified success in 6 eyes (18.8%). Four eyes (12.5%) needed additional glaucoma surgery.

Conclusion

The modified ExPRESS^® technique appears to be effective, especially when low levels of IOP are required. Additionally, fewer anti-glaucoma drugs were necessary. In the other hand, hypotony was a common side effect with this procedure, although all patients were properly handled, preserving the surgical outcomes.

Red flags in patients with hereditary transthyretin amyloidosis at diagnosis in a non-endemic area of Spain

INTRODUCTION

Hereditary transthyretin (hATTR) amyloidosis with polyneuropathy is a rare multisystemic disease characterised by onset during adulthood and associated with poor prognosis if untreated. A set of signs and symptoms, commonly known as "red flags," have been proposed to assist in early detection of the disease; presence of red flags may suggest underlying hATTR amyloidosis in patients with progressive sensorimotor polyneuropathy.

MATERIAL AND METHODS

We analysed the frequency of red flags at the time of diagnosis in 30 patients with hATTR amyloidosis in a non-endemic area of Spain; onset was late in the majority of patients.

RESULTS

The frequencies of the red flags were as follows: bilateral carpal tunnel syndrome in 15 patients (50%), early autonomic dysfunction in 17 (56%), gastrointestinal problems in 14 (46.6%), unexplained weight loss in 8 (26.6%), heart disease in 12 (40%), asymptomatic cardiac findings in 13 (43.3%), kidney disease in one (3.3%), vitreous opacities in none, family history of neuropathy in 21 (70%), family history of heart disease in 15 (50%), and family history of gastrointestinal problems in 3 (10%). All patients presented at least one red flag at diagnosis, with a median of 4 red flags.

CONCLUSION

Red flags were common at the time of diagnosis, even in patients with late-onset hATTR amyloidosis. Presence of red flags in a patient with symmetrical sensorimotor polyneuropathy should serve as a warning sign, and lead to targeted diagnosis to rule out hATTR amyloidosis, independently of age of onset.

High Hereditary Transthyretin-Related Amyloidosis Prevalence in Crete

Background and Objectives

Our goal was to study hereditary transthyretin-related amyloidosis (hATTR) in Crete, Greece.

Methods

We aimed at ascertaining all hATTR cases in Crete, an island of 0.62 million people. For this, we evaluated patients with polyneuropathy, autonomic involvement, cardiomyopathy, and/or ophthalmopathy suggestive of hATTR, who presented to the physicians of this study or were referred to them by other physicians. Genetic analyses were performed on all patients suspected of suffering from hATTR. We included in our observational longitudinal cohort study all individuals, residents of Crete, who, during the study period (1993–2019), were found to carry a pathogenic TTR variant.

Results

Over the past 27 years, 30 individuals (15 female patients, 15 male patients), from 12 apparently unrelated families, were diagnosed with hATTR, whereas evaluation of their offspring identified 5 asymptomatic TTR pathogenic variant carriers. The most prevalent TTR variant detected was p.Val50Met, affecting 19 patients (11 female patients, 8 male patients) and causing a rather consistent phenotype characterized by predominant polyneuropathy of early adult onset (median age of symptom onset: 30 years; range: 18–37 years). Specifically, patients affected by the p.Val50Met TTR variant experienced progressive sensorimotor disturbances, involving mainly the lower extremities, associated with autonomic and/or gastrointestinal dysfunction. The second most frequent TTR variant was p.Val114Ala, found in 10 patients (4 female patients, 6 male patients) who were affected at an older age (median age of symptom onset: 70 years; range: 54–78 years). This variant caused a predominantly cardiomyopathic phenotype, manifested by congestive heart failure and associated with peripheral neuropathy, carpal tunnel syndrome, and/or autonomic involvement. In these patients, cardiac amyloid deposition was detected on 99m-technetium pyrophosphate scintigraphy and/or heart biopsy. The third TTR variant (p.Arg54Gly) was found in a 50-year-old male patient with ophthalmopathy due to vitreous opacities and positive family history for visual loss. As 22 patients were alive at the end of the study, we calculated the hATTR prevalence in Crete to be 35 cases per 1 million inhabitants.

Discussion

Our study revealed that the prevalence of hATTR in Crete is one of the world's highest. Three different pathogenic TTR variants causing distinct clinical phenotypes were identified in this relatively small population pool.

CHOROIDAL INVOLVEMENT IN HEREDITARY TRANSTHYRETIN AMYLOIDOSIS PATIENTS

PURPOSE

To compare the choroidal characteristics between the eyes of patients with and without hereditary transthyretin amyloidosis.

METHODS

Case-control observational study with choroidal thickness and vasculature evaluation by optical coherence tomography with enhanced depth imaging protocol of the macula.

RESULTS

The study included 332 eyes: 166 eyes of hereditary transthyretin amyloidosis patients and 166 eyes of healthy patients. Mean age was similar between groups (P = 0.979). For hereditary transthyretin amyloidosis patients, on average, in all sectors analyzed (in the full 5 mm-width image [G] and also in 1-mm-width central [C], nasal [N], and temporal [T] sectors), there was a higher stromal area, a lower choroidal thickness, and a lower choroidal vascularity index, compared with the control group. The linear mixed models revealed no differences according to the systemic treatment groups.

CONCLUSION

Hereditary transthyretin amyloidosis patients showed statistically significant differences in choroidal characteristics, compared with eyes without pathology. These age-related and statistically significant changes compared with the healthy eyes may help in the future to better monitor the systemic hereditary transthyretin amyloidosis disease and complement other systemic evaluations, including on clinical trials to analyze more objectively, the results of new therapies.

Ahmed valve for secondary glaucoma in patients with hereditary transthyretin amyloidosis

OBJECTIVE

To evaluate the surgical outcomes of patients with hereditary transthyretin amyloidosis (TTR-FAP) who underwent Ahmed glaucoma valve (AGV) implantation.

METHODS

A retrospective cohort study was performed on patients with a diagnosis of TTR-FAP secondary glaucoma, who underwent AGV implantation in our department, between November 2010 and July 2019. The cumulative probability of treatment success was measured with Kaplan-Meier survival analysis. The primary outcome was success, defined as intraocular pressure (IOP) ≥ 6 mmHg and ≤21 mmHg with or without medication, with no need for further glaucoma surgery and without loss of light perception at last follow-up. Secondary outcomes were postoperative IOP, number of IOP-lowering medications, and rates of complications.

RESULTS

The study included 114 eyes of 87 patients. The mean follow-up duration was 3.81 ± 2.11 years (y) [range, 1.00-8.28 y]. Compared to the preoperative values, the mean IOP was reduced from 28.20 ± 7.01 to 12.87 ± 3.76 mmHg at the final visit (p < 0.001), with a reduction in the number of medications from 3.89 ± 0.66 to 1.86 ± 1.43 (p < 0.001). Early and late postoperative complications occurred in 20 (17.09%) and 9 (7.89%) eyes, respectively. Kaplan-Meier analysis indicated probabilities of success of 0.98 at 1 y, 0.97 at 2 y, 0.95 at 3 y, 0.89 at 4 y, 0.77 at 5 y and 0.72 at 6 y. The linear correlation analysis showed a correlation between some characteristics of the natural history of TTR-FAP patients and AGV implantation success.

CONCLUSION

Although glaucoma in TTR-FAP patients is very difficult to manage, AGV implantation is an effective and relatively safe procedure.

Low Prevalence of Clinically Apparent Cardiac Amyloidosis Among Carriers of Transthyretin V122I Variant in a Large Electronic Medical Record

BACKGROUND

Transthyretin (TTR) gene mutations are the most common cause of hereditary amyloidosis. Valine replaced by isoleucine in position 122 (V122I) variant is common, particularly in the black population. Carriers of V122I have increased risk for developing cardiac amyloidosis. Despite a relatively high prevalence, the penetrance of V122I is not firmly established. This study sought to determine the prevalence of clinically apparent cardiac amyloidosis among carriers of the TTR V122I variant.

METHODS

BioVU, a Vanderbilt University resource linking DNA samples and pre-existing genetic data to de-identified electronic medical records was used to identify TTR V122I mutation carriers. Automated billing code queries (International Classification of Diseases, 9th revision codes), problem list searches, and manual chart reviews were used to identify subjects with clinically diagnosed cardiac amyloidosis.

RESULTS

Among 28,429 subjects with available genotype data, 129 were V122I carriers. Carriers had a median age of 42 years (interquartile range 16-64). Noncarriers had a median age of 62 years, (interquartile range 41-77). The carrier rate was 3.7% in blacks and 0.02% in whites. Overall, the prevalence of clinically apparent cardiac amyloidosis was 0.8% in carriers and 0.04% in noncarriers (P = .05). Above age 60, the prevalence of cardiac amyloidosis was 2.6% in carriers and 0.06% in noncarriers (P = .03).

CONCLUSION

Carriers of the TTR V122I variant are at a higher risk for development of cardiac amyloidosis, particularly at age>60 years. However, clinically apparent cardiac amyloidosis in this population was uncommon. These results support that the penetrance of TTR V122I is age dependent and suggest it may be significantly lower than previously reported.

Red flags in patients with hereditary transthyretin amyloidosis at diagnosis in a non-endemic area of Spain

INTRODUCTION

Hereditary transthyretin (hATTR) amyloidosis with polyneuropathy is a rare multisystemic disease characterised by onset during adulthood and associated with poor prognosis if untreated. A set of signs and symptoms, commonly known as "red flags," have been proposed to assist in early detection of the disease; presence of red flags may suggest underlying hATTR amyloidosis in patients with progressive sensorimotor polyneuropathy.

MATERIAL AND METHODS

We analysed the frequency of red flags at the time of diagnosis in 30 patients with hATTR amyloidosis in a non-endemic area of Spain; onset was late in the majority of patients.

RESULTS

The frequencies of the red flags were as follows: bilateral carpal tunnel syndrome in 15 patients (50%), early autonomic dysfunction in 17 (56%), gastrointestinal problems in 14 (46.6%), unexplained weight loss in 8 (26.6%), heart disease in 12 (40%), asymptomatic cardiac findings in 13 (43.3%), kidney disease in one (3.3%), vitreous opacities in none, family history of neuropathy in 21 (70%), family history of heart disease in 15 (50%), and family history of gastrointestinal problems in 3 (10%). All patients presented at least one red flag at diagnosis, with a median of 4 red flags.

CONCLUSION

Red flags were common at the time of diagnosis, even in patients with late-onset hATTR amyloidosis. Presence of red flags in a patient with symmetrical sensorimotor polyneuropathy should serve as a warning sign, and lead to targeted diagnosis to rule out hATTR amyloidosis, independently of age of onset.

Societal costs and burden of hereditary transthyretin amyloidosis polyneuropathy

Background: Hereditary transthyretin amyloidosis polyneuropathy (ATTRv-PN) is a rare life-threatening disease that imposes considerable mortality and morbidity associated with increased costs, high social support and productivity losses. This study aims to estimate the societal costs and burden of ATTRv-PN.Methods: A cost-of-illness (COI) and burden of disease model were specified from a societal perspective, using a prevalence-based approach. Direct and indirect costs were included. Healthcare resource use was retrieved from public databases, previous Portuguese studies and the literature. The burden of disease was expressed in terms of disability-adjusted life years (DALYs), as defined by the World Health Organisation.Results: In 2016, the total annual COI of ATTRv-PN in Portugal was 52,502,796€ and the mean cost per patient was 28,152€ (79% direct; 21% indirect costs). Treatments accounted for 52% of total costs, while 0.18% were devoted to disease prevention. A total of 2056 DALYs were lost, 26% due to disability and 74% due to death.Conclusions: Annual costs and burden of ATTRv-PN were considerable but within the range of other rare diseases. Policies and public interventions to prevent and reduce the burden of disease should be prioritised, since patients experience excess morbidity, mortality and total costs will likely increase in the future.

Evaluation of Mortality During Long-Term Treatment with Tafamidis for Transthyretin Amyloidosis with Polyneuropathy: Clinical Trial Results up to 8.5 Years

Introduction

The effects of tafamidis on mortality in Val30Met and non-Val30Met patients with transthyretin amyloidosis with polyneuropathy (ATTR-PN) were evaluated.

Methods

The analyses were based on cumulative data from the Val30Met patients in the 18-month double-blind registration study and its 12-month open-label extension study, the non-Val30Met patients of the 12-month open-label study, and both patient groups in the ongoing 10-year extension study. Kaplan–Meier analyses of time to death from first treatment dose were performed. For the Val30Met group, two treatment groups were analyzed: those who received tafamidis in both the parent and extension studies (T–T) and those who received placebo in the parent study and switched to tafamidis in the extension studies (P–T).

Results

Kaplan–Meier estimates (95% confidence interval [CI]) were available up to 9 years for the Val30Met group, at which time 85.9% (53.1–96.4) and 91.1% (77.9–96.6) of the patients in the T–T and P–T groups, respectively, were alive. For the non-Val30Met group, estimates were available up to 8 years from the first dose, and the percentage of patients alive was 75.9% (47.7–90.2).

Conclusion

Long-term tafamidis treatment may confer survival benefit in patients with ATTR-PN.

Trial registration

ClinicalTrials.gov identifier: NCT00409175, NCT00791492, NCT00630864, and NCT00925002.

Drivers of α-Sheet Formation in Transthyretin under Amyloidogenic Conditions

Amyloid diseases make up a set of fatal disorders in which proteins aggregate to form fibrils that deposit in tissues throughout the body. Amyloid-associated diseases are challenging to study because amyloid formation occurs on time scales that span several orders of magnitude and involve heterogeneous, interconverting protein conformations. The development of more effective technologies to diagnose and treat amyloid disease requires both a map of the conformations sampled during amyloidogenesis and an understanding of the molecular mechanisms that drive this process. In prior molecular dynamics simulations of amyloid proteins, we observed the formation of a nonstandard type of secondary structure, called α-sheet, that we proposed is associated with the pathogenic conformers in amyloid disease, the soluble oligomers. However, the detailed molecular interactions that drive the conversion to α-sheet remain elusive. Here we use molecular dynamics simulations to interrogate a critical event in transthyretin aggregation, the formation of aggregation-competent, monomeric species. We show that conformational changes in one of the two β-sheets in transthyretin enable solvent molecules and polar side chains to form electrostatic interactions with main-chain peptide groups to facilitate and modulate conversion to α-sheet secondary structure. Our results shed light on the early conformational changes that drive transthyretin toward the α-sheet structure associated with toxicity. Delineation of the molecular events that lead to aggregation at atomic resolution can aid strategies to target the early, critical toxic soluble oligomers.

Orthostatic hypotension in hereditary transthyretin amyloidosis: epidemiology, diagnosis and management

Purpose

Neurogenic orthostatic hypotension is a prominent and disabling manifestation of autonomic dysfunction in patients with hereditary transthyretin (TTR) amyloidosis affecting an estimated 40–60% of patients, and reducing their quality of life. We reviewed the epidemiology and pathophysiology of neurogenic orthostatic hypotension in patients with hereditary TTR amyloidosis, summarize non-pharmacologic and pharmacological treatment strategies and discuss the impact of novel disease-modifying treatments such as transthyretin stabilizers (diflunisal, tafamidis) and RNA interference agents (patisiran, inotersen).

Methods

Literature review.

Results

Orthostatic hypotension in patients with hereditary transthyretin amyloidosis can be a consequence of heart failure due to amyloid cardiomyopathy or volume depletion due to diarrhea or drug effects. When none of these circumstances are apparent, orthostatic hypotension is usually neurogenic, i.e., caused by impaired norepinephrine release from sympathetic postganglionic neurons, because of neuronal amyloid fibril deposition.

Conclusions

When recognized, neurogenic orthostatic hypotension can be treated. Discontinuation of potentially aggravating medications, patient education and non-pharmacologic approaches should be applied first. Droxidopa (Northera^®), a synthetic norepinephrine precursor, has shown efficacy in controlled trials of neurogenic orthostatic hypotension in patients with hereditary TTR amyloidosis and is now approved in the US and Asia. Although they may be useful to ameliorate autonomic dysfunction in hereditary TTR amyloidosis, the impact of disease-modifying treatments on neurogenic orthostatic hypotension is still uninvestigated.

Uncovering the Neuroprotective Mechanisms of Curcumin on Transthyretin Amyloidosis

Transthyretin (TTR) amyloidoses (ATTR amyloidosis) are diseases associated with transthyretin (TTR) misfolding, aggregation and extracellular deposition in tissues as amyloid. Clinical manifestations of the disease are variable and include mainly polyneuropathy and/or cardiomyopathy. The reasons why TTR forms aggregates and amyloid are related with amino acid substitutions in the protein due to mutations, or with environmental alterations associated with aging, that make the protein more unstable and prone to aggregation. According to this model, several therapeutic approaches have been proposed for the diseases that range from stabilization of TTR, using chemical chaperones, to clearance of the aggregated protein deposited in tissues in the form of oligomers or small aggregates, by the action of disruptors or by activation of the immune system. Interestingly, different studies revealed that curcumin presents anti-amyloid properties, targeting multiple steps in the ATTR amyloidogenic cascade. The effects of curcumin on ATTR amyloidosis will be reviewed and discussed in the current work in order to contribute to knowledge of the molecular mechanisms involved in TTR amyloidosis and propose more efficient drugs for therapy.

Demyelinating Neuropathy in a Patient Treated With Revusiran for Transthyretin (Thr60Ala) Amyloidosis

Transthyretin amyloidosis patients develop length-dependent peripheral neuropathy, autonomic dysfunction, and restrictive cardiomyopathy associated with deposition of amyloid fibrils in these tissues. Despite advances in management over the past decade, this disorder causes profound debilitation and ultimately proves fatal. In this report, we describe a man with late-onset cardiac amyloidosis due to a transthyretin Thr60Ala mutation who was treated with an investigational RNAi therapeutic, revusiran, which targets hepatic transthyretin production. Sixteen months into treatment, he developed bilateral lower-extremity weakness and numbness, worsening balance, difficulty manipulating objects with his hands, and finger numbness. Nerve conduction studies were consistent with multifocal demyelinating neuropathy. Intravenous immunoglobulin therapy improved sensation in his hands and feet, and improved hand dexterity. A sural nerve biopsy demonstrated demyelination with substantial axonal loss in the absence of histologically detectable endoneurial amyloid deposition. This case expands the clinicopathologic spectrum of transthyretin amyloidosis and may represent complex disease and treatment effects.

Baseline disease characteristics in Brazilian patients enrolled in Transthyretin Amyloidosis Outcome Survey (THAOS)

Transthyretin amyloidosis (ATTR) is characterized by the deposit of mutant or wild-type transthyretin that forms amyloid fibrils, which are extracellularly deposited within tissues and organs. Clinical manifestations of familial amyloid polyneuropathy vary according to the mutation, age at onset and geographical location. This study aimed to describe baseline disease characteristics of Brazilian patients with transthyretin familial amyloid polyneuropathy (ATTR-FAP) enrolled in the Transthyretin Amyloidosis Outcome Survey (THAOS).

METHODS

The THAOS is an international, noninterventional, longitudinal, observational, web-based registry designed to characterize ATTR. The outcome measures included demographics (age at symptom onset, gender, time from onset of symptoms to diagnosis, family history), genotype, and clinical characteristics (presence of amyloid deposit, frequency of misdiagnosis, presenting symptomatology). The analysis was conducted in a dataset from Brazilian patients (from November 2008 to January 2016).

RESULTS

One hundred and sixty participants (52.5% male) were included in the analysis. The majority of participants (90.6%) reported a positive family history of ATTR-FAP Median age at symptom onset was 32.5 years. Val30Met mutation was found in 91.9%. Misdiagnosis was observed in 26.6% of symptomatic patients. Over one-third (35.3%) of the misdiagnosed patients experienced a delay of more than one year before receiving a correct diagnosis. At presentation, 79.7% of the patients had motor, 87.5% sensory and 93.8% autonomic symptoms.

CONCLUSION

ATTR-FAP in Brazil starts early, has a strong family history and the majority has Val30Met mutation. Misdiagnosis is common and the most common presentation is of a sensorimotor and autonomic neuropathy.

[Transthyretin familial amyloid polyneuropathy]

Transthyretin family amyloid polyneuropathy (TTR-FAP) is a progressive, ultimately fatal disease. It manifests itself primarily with sensory, motor and autonomic polyneuropathy and/or cardiomyopathy and is caused by extracellular deposition of insoluble amyloid fibrils in the endoneurium. The cause of TTR-FAP is the mutation in the gene encoding transthyretin, more than 100 types of mutations are known. Given the phenotypic diversity of TTR-FAP, it is difficult for clinicians to make this diagnosis. An erroneous diagnosis is a frequent occurrence, risking the onset of an organ pathology. The paper addresses the issues of the pathogenesis, diagnosis and treatment of TTR-FAP.

Insights into the pharmaceuticals and mechanisms of neurological orphan diseases: Current Status and future expectations

Several rare or orphan diseases have been characterized that singly affect low numbers of people, but cumulatively reach ∼6%-10% of the population in Europe and in the United States. Human genetics has shown to be broadly effective when evaluating subjacent genetic defects such as orphan genetic diseases, but on the other hand, a modest progress has been achieved toward comprehending the molecular pathologies and designing new therapies. Chemical genetics, placed at the interface of chemistry and genetics, could be employed to understand the molecular mechanisms of subjacent illnesses and for the discovery of new remediation processes. This review debates current progress in chemical genetics, and how a variety of compounds and reaction mechanisms can be used to study and ultimately treat rare genetic diseases. We focus here on a study involving Amyotrophic lateral sclerosis (ALS), Duchenne Muscular Dystrophy (DMD), Spinal muscular atrophy (SMA) and Familial Amyloid Polyneuropathy (FAP), approaching different treatment methods and the reaction mechanisms of several compounds, trying to elucidate new routes capable of assisting in the treatment profile.

Recent advances in the noninvasive strategies of cardiac amyloidosis

The heart, like any organ in the body, is susceptible to amyloid deposition. Although more than 30 types of protein can cause amyloidosis, only two types commonly deposit in the ventricular myocardium: amyloid light chain and amyloid transthyretin. Amyloid cardiomyopathy is usually a major determinant of patient outcomes, and the diagnosis of heart involvement can be often relatively under-diagnosed, owing to nonspecific presenting symptoms and signs at a subclinical stage. The diagnosis of cardiac amyloidosis is usually performed by endomyocardial biopsy; however, the invasive nature and related high-risk complications restrict its wide use in clinical settings. Recently, with the advent of innovative techniques used for evaluating cardiac amyloidosis, noninvasive methods become increasingly important, especially in earlier diagnosis, distinguishing typing, risk prediction and response to treatment. Here, we will review recent developments in the noninvasive methods used in the assessment of cardiac amyloidosis, focused on the laboratory biomarkers and imaging modalities.

Causally treatable, hereditary neuropathies in Fabry's disease, transthyretin-related familial amyloidosis, and Pompe's disease

OBJECTIVES

Most acquired neuropathies are treatable, whereas genetic neuropathies respond to treatment in Fabry's disease (FD), transthyretin-related familial amyloidosis (TTR-FA), and Pompe's disease (PD). This review summarizes and discusses recent findings and future perspectives concerning etiology, pathophysiology, clinical presentation, diagnosis, treatment, and outcome of neuropathy in FD, TTR-FA, and PD.

METHODS

Literature review.

RESULTS

Neuropathy in FD concerns particularly small, unmyelinated, or myelinated sensory fibers (small fiber neuropathy [SFN]) and autonomic fibers, manifesting as acroparesthesias, Fabry's crises, or autonomous disturbances. FD neuropathy benefits from agalsidase alpha (0.2 mg/kg every second week intravenously) or from beta (1.0 mg/kg every second week intravenously). Neuropathy in TTR-FA is axonal and affects large and small sensory, motor, and autonomous fibers. Neuropathy in TTR-FA profits from liver transplantation and the TTR kinetic stabilizer tafamidis (20 mg/d). Neuropathy in PD particularly occurs in late-onset PD and manifests as mononeuropathy, polyneuropathy, or SFN. PD neuropathy presumably responds to alglucosidase-alpha (20 mg/kg every second week intravenously).

CONCLUSIONS

Neuropathy in FD, TTR-FA, and PD is predominantly a SFN and can be the dominant feature in FD and TTR-FA. SFN in FD, TTR-FA, and PD needs to be recognized and benefits from enzyme replacement treatment or TT-kinetic stabilizers.

Current and Future Treatment Approaches in Transthyretin Familial Amyloid Polyneuropathy

OPINION STATEMENT

Treatment of transthyretin familial amyloid polyneuropathy (TTR FAP) must be tailored to disease stage. Patients with early stage disease (i.e., without major impairment in walking ability), especially younger patients, should be referred as soon as possible for liver transplantation (LT) in the absence of major comorbid conditions. LT remains the most effective treatment option to date and should be offered to these patients as early as possible. Bridging therapy with an oral TTR stabilizer (tafamidis or diflunisal, according to local access to these treatments) should be started as soon as the diagnosis of TTR FAP is established. Early stage patients who do not wish to or have contraindications to LT should be treated with an oral TTR stabilizer or get access to the newly developed therapeutic options (IONIS TTR-Rx, patisiran, doxycycline/TUDCA). Late stage patients (presenting with significant walking impairment) are usually older and notoriously difficult to treat. They should be offered an oral TTR stabilizer but are not candidates for LT due to a significant rate of perioperative complications and increased risk of progressive neurological and especially cardiac disease despite LT. Access to the different therapies in development should also be considered depending on respective inclusion and exclusion criteria. The abovementioned treatment options were mostly validated in Val30Met mutation patients, but should also be offered to non-Val30Met patients, although mortality rates after LT are higher in these patients. Treatment decisions should be made on an individual basis. Screening for heart, eye, and renal involvement is mandatory for every patient at disease diagnosis and regularly thereafter, even in transplanted patients. Symptomatic treatment should be offered as needed, as well as genetic counseling to at-risk family members. Asymptomatic mutation carriers should benefit from regular screening for early symptoms of disease. Current therapeutic management of TTR FAP will hopefully be changed in the near future with data from the ongoing phase 2/3 studies testing the TTR gene silencing agents. In the longer term, it is likely that combined therapeutic approaches will be necessary to reverse the disease process.

Familial amyloidosis with polyneuropathy type 1 caused by transthyretin mutation Val50Met (Val30Met): 4 cases in a non-endemic area

INTRODUCTION

Transthyretin-related familial amyloid polyneuropathy (TTR-FAP) typically arises as an autonomic neuropathy primarily affecting small fibres and it occurs in adult patients in their second or third decades of life. It progresses rapidly and can lead to death in approximately 10 years. Other phenotypes have been described in non-endemic areas.

OBJECTIVES AND METHODS

We described 4 cases from the Spanish province of Guipuzcoa, a non-endemic area, to highlight the clinical variability of this disease.

PATIENTS AND RESULTS

Three patients presented a late-onset form manifesting after the age of 50, featuring a predominantly motor polyneuropathy initially causing distal impairment of the lower limbs followed by the upper limbs. One patient suffered severe neuropathic pain. None showed signs of autonomic involvement. The fourth patient, of Portuguese descent, presented a typical form with onset in her thirties, neuropathic pain and dysautonomia. All patients carry the Val50Met mutation in the TTR gene.

CONCLUSION

FAP is a pleomorphic disease even in patients carrying the same mutation. In non-endemic areas, its main form of presentation may resemble a predominantly motor polyneuropathy developing in the sixth decade of life with no signs of dysautonomia. Given this non-specific presentation and the widely available technical means of studying the TTR gene, we believe that the protocol for the aetiological diagnosis of any polyneuropathy should include genetic sequencing of TTR.

Evaluation of Therapeutic Oligonucleotides for Familial Amyloid Polyneuropathy in Patient-Derived Hepatocyte-Like Cells

Familial amyloid polyneuropathy (FAP) is caused by mutations of the transthyretin (TTR) gene, predominantly expressed in the liver. Two compounds that knockdown TTR, comprising a small interfering RNA (siRNA; ALN-TTR-02) and an antisense oligonucleotide (ASO; IONIS-TTRRx), are currently being evaluated in clinical trials. Since primary hepatocytes from FAP patients are rarely available for molecular analysis and commercial tissue culture cells or animal models lack the patient-specific genetic background, this study uses primary cells derived from urine of FAP patients. Urine-derived cells were reprogrammed to induced pluripotent stem cells (iPSCs) with high efficiency. Hepatocyte-like cells (HLCs) showing typical hepatic marker expression were obtained from iPSCs of the FAP patients. TTR mRNA expression of FAP HLCs almost reached levels measured in human hepatocytes. To assess TTR knockdown, siTTR1 and TTR-ASO were introduced to HLCs. A significant downregulation (>80%) of TTR mRNA was induced in the HLCs by both oligonucleotides. TTR protein present in the cell culture supernatant of HLCs was similarly downregulated. Gene expression of other hepatic markers was not affected by the therapeutic oligonucleotides. Our data indicate that urine cells (UCs) after reprogramming and hepatic differentiation represent excellent primary human target cells to assess the efficacy and specificity of novel compounds.

Rare Variants in MME, Encoding Metalloprotease Neprilysin, Are Linked to Late-Onset Autosomal-Dominant Axonal Polyneuropathies

Axonal polyneuropathies are a frequent cause of progressive disability in the elderly. Common etiologies comprise diabetes mellitus, paraproteinaemia, and inflammatory disorders, but often the underlying causes remain elusive. Late-onset axonal Charcot-Marie-Tooth neuropathy (CMT2) is an autosomal-dominantly inherited condition that manifests in the second half of life and is genetically largely unexplained. We assumed age-dependent penetrance of mutations in a so far unknown gene causing late-onset CMT2. We screened 51 index case subjects with late-onset CMT2 for mutations by whole-exome (WES) and Sanger sequencing and subsequently queried WES repositories for further case subjects carrying mutations in the identified candidate gene. We studied nerve pathology and tissue levels and function of the abnormal protein in order to explore consequences of the mutations. Altogether, we observed heterozygous rare loss-of-function and missense mutations in MME encoding the metalloprotease neprilysin in 19 index case subjects diagnosed with axonal polyneuropathies or neurodegenerative conditions involving the peripheral nervous system. MME mutations segregated in an autosomal-dominant fashion with age-related incomplete penetrance and some affected individuals were isolated case subjects. We also found that MME mutations resulted in strongly decreased tissue availability of neprilysin and impaired enzymatic activity. Although neprilysin is known to degrade β-amyloid, we observed no increased amyloid deposition or increased incidence of dementia in individuals with MME mutations. Detection of MME mutations is expected to increase the diagnostic yield in late-onset polyneuropathies, and it will be tempting to explore whether substances that can elevate neprilysin activity could be a rational option for treatment.

Recent advances in familial amyloid polyneuropathy

PURPOSE OF REVIEW

To highlight the advances in the knowledge of the clinical features, diagnostic techniques, clinimetrics, and therapeutics of transthyretin familial amyloid polyneuropathy.

RECENT FINDINGS

Expanding knowledge of the molecular underpinnings and therapeutics of transthyretin familial amyloid polyneuropathy have provided impetus to molecular-specific phenotype characterization, natural history studies, and target-based therapeutic interventions. These interventions have underscored the need for early, accurate diagnostic instruments and sensitive diagnostic and therapeutic biomarkers.

SUMMARY

Current and emerging target-based therapeutic interventions and novel diagnostic techniques may contribute to improved quality of life and survival in this disease.

Genotypic and phenotypic presentation of transthyretin-related familial amyloid polyneuropathy (TTR-FAP) in Turkey

Transthyretin-related familial amyloid polyneuropathy (TTR-FAP) is an autosomal dominant disorder caused by mutations of the transthyretin (TTR) gene. The mutant amyloidogenic transthyretin protein causes the systemic accumulation of amyloid fibrils that result in organ dysfunction. TTR-associated FAP is a progressive and fatal disease, if left untreated, and should be considered in the differential diagnosis of any person presenting with a progressive polyneuropathy, particularly with accompanying autonomic involvement. The clinical, electrophysiological, histopathological, and genetic characteristics of 17 patients from Turkey (5 female, 13 male) from nine families with polyneuropathy and mutations in TTR were evaluated. Sequence analysis of the TTR gene revealed five mutations (Val30Met, Glu89Gln, Gly53Glu, Glu54Gly and Gly47Glu). Mean age at disease onset was 40.4 ± 13.9 years (range 21-66 years). The most commonly reported initial complaint was paresthesia in the feet (asymmetric in three patients). Three patients (2 male) with the Glu89Gln mutation presented with carpal tunnel syndrome. Two patients with the Gly53Glu mutation showed episodes of dysarthria and hemiparesis, consistent with this genotype. Seven patients died during the period of follow-up as a result of systemic involvement. Our study suggests that a cohort of patients from Turkey with TTR-FAP exhibits clinical and genetic heterogeneity.

Systemic amyloidoses and proteomics: The state of the art

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Proteomics is an established approach for diagnostic amyloid typing.

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Mass spectrometry-based methods to analyze amyloid precursors have been developed.

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Proteomic studies are ongoing to identify novel biomarkers and clarify disease mechanisms.

Systemic amyloidoses are caused by misfolding-prone proteins that polymerize in tissues, causing organ dysfunction. Since proteins are etiological agents of these diseases, proteomics was soon recognized as a privileged instrument for their investigation. Mass spectrometry-based proteomics has acquired a fundamental role in management of systemic amyloidoses, being now considered a gold standard approach for amyloid typing. In parallel, approaches for analyzing circulating amyloid precursors have been developed. Moreover, differential and functional proteomics hold promise for identifying novel biomarkers and clarifying disease mechanisms. This review discusses recent proteomics achievements in systemic amyloidoses, providing a perspective on its present and future applications.

Ocular Manifestations and Therapeutic Options in Patients with Familial Amyloid Polyneuropathy: A Systematic Review

PURPOSE

This paper aims to review the morphological and functional characteristics of patients affected by familial amyloid polyneuropathy (FAP), with greater focus on type I and its progression after liver transplantation. We also analyse therapeutic options for the ophthalmic manifestations.

METHODS

The literature from 2002 through 2015 was reviewed, with a total of 45 articles studied, using the key terms related to amyloidosis and its therapeutic approaches. Information was collated, evaluated, critically assessed, and then summarised in its present form. PATHOPHYSIOLOGY AND TREATMENT: FAP results from mutation of the transthyretin gene, with Val30Met being the most frequent substitution. The symptoms are those typical of a sensorimotor autonomic neuropathy and can be halted with liver transplantation. Nowadays there are new medical therapies that delay the progression of the systemic neuropathy. However, there are still no options to avoid ocular disease.

CONCLUSION

The main ocular manifestations in patients with FAP type I are amyloid deposition in the vitreous, dry eye, and secondary glaucoma. Despite liver transplantation, eye synthesis of amyloid persists and is associated with progressive ocular manifestations, which require continued ophthalmologic follow-up. New therapeutic strategies are therefore needed, particularly to target the ocular synthesis of the abnormal protein.

Therapeutic Oligonucleotides Targeting Liver Disease: TTR Amyloidosis

The liver has become an increasingly interesting target for oligonucleotide therapy. Mutations of the gene encoding transthyretin (TTR), expressed in vast amounts by the liver, result in a complex degenerative disease, termed familial amyloid polyneuropathy (FAP). Misfolded variants of TTR are linked to the establishment of extracellular protein deposition in various tissues, including the heart and the peripheral nervous system. Recent progress in the chemistry and formulation of antisense (ASO) and small interfering RNA (siRNA) designed for a knockdown of TTR mRNA in the liver has allowed to address the issue of gene-specific molecular therapy in a clinical setting of FAP. The two therapeutic oligonucleotides bind to RNA in a sequence specific manner but exploit different mechanisms. Here we describe major developments that have led to the advent of therapeutic oligonucleotides for treatment of TTR-related disease.

Benzoxazoles and oxazolopyridines in medicinal chemistry studies

The benzoxazole heterocycle is often found in ligands targeting a plethora of receptors and enzymes. By analysis of published X-ray structures, this review aims at highlighting key interactions which the benzoxazole may engage in with its host protein. Furthermore, bioavailability, metabolism and the use of benzoxazole as a bioisostere are discussed. The review is extended to cover structure-activity relationship studies of 2-substituted benzoxazoles, 2-substituted oxazolopyridines, and in perspective, application of the recently published novel heterocycle oxazolopyrazine in medicinal chemistry studies.