CNS involvement in V30M transthyretin amyloidosis: clinical, neuropathological and biochemical findings

Hereditary transthyretin-related amyloidosis

Hereditary transthyretin(TTR)-related amyloidosis (ATTRm amyloidosis) is an endemic/non-endemic, autosomal-dominant, early- and late-onset, rare, progressive disorder, predominantly manifesting as length-dependent, small fiber dominant, axonal polyneuropathy and frequently associated with cardiac disorders and other multisystem diseases. ATTRm amyloidosis is due to variants in the TTR gene, with the substitution Val30Met as the most frequent mutation. TTR mutations lead to destabilization and dissociation of TTR tetramers into variant TTR monomers, and formation of amyloid fibrils, which are consecutively deposited extracellularly in various tissues, such as nerves, heart, brain, eyes, intestines, kidneys, or the skin. Neuropathy may not only include large nerve fibers but also small fibers, and not only sensory and motor fibers but also autonomic fibers. Types of TTR variants, age at onset, penetrance, and clinical presentation vary between geographical areas. Suggestive of a ATTRm amyloidosis are a sensorimotor polyneuropathy, positive family history, autonomic dysfunction, cardiomyopathy, carpal tunnel syndrome, unexplained weight loss, and resistance to immunotherapy. If only sensory A-delta or C fibers are affected, small fiber neuropathy ensues. Diagnostic tests for small fiber neuropathy include determination of intraepidermal nerve fiber density, laser-evoked potentials, heat- and cold-detection thresholds, and measurement of the electrochemical skin conductance. Therapy currently relies on liver transplantation and TTR-stabilizers (tafamidis, diflunisal).

Patisiran for the treatment of hereditary transthyretin-mediated amyloidosis

INTRODUCTION

Hereditary transthyretin-mediated amyloidosis is caused by a mutation in transthyretin (TTR) gene resulting in misfolded TTR protein accumulating as amyloid fibrils. Patisiran is a lipid nanoparticle formulation of ribonucleic acid interference (RNAi), which can reduce the production of TTR. Areas covered: In this review, the chemical property, mechanism of action, pharmacokinetics, clinical efficacy, and safety of patisiran were introduced. Expert Commentary: Patisiran offers a new treatment option for patients with hereditary transthyretin-mediated amyloidosis. Patisiran can significantly reduce the TTR level and improve patient's neuropathy and quality of life. The common adverse reactions were upper respiratory tract infections and infusion-related reactions.

Clinical Presentation, Diagnosis and Treatment of TTR Amyloidosis

Systemic amyloidosis can be hereditary or acquired with autosomal dominant mutations in the transthyretin gene (TTR) being the most common cause of hereditary amyloidosis. ATTRm amyloidosis is a multi-system disorder with cardiovascular, peripheral and autonomic nerve involvement that can be difficult to diagnose due to phenotypic heterogeneity. This review will focus on the neuropathic manifestations of ATTRm, the genotype-phenotype variability, the diagnostic approach and the recent therapeutic advances in this disabling condition.

Diagnosis of amyloid neuropathy

Systemic amyloidosis can be hereditary or acquired. The autosomal dominant hereditary transthyretin amyloidosis and the acquired light-chain amyloidosis, the result of a plasma cell dyscrasia, are multisystem disorders with cardiovascular, autonomic and peripheral nerve involvement. There are numerous investigational modalities available to diagnose systemic amyloidosis and to assess the extent of organ involvement, but it is frequently misdiagnosed due to its heterogeneous clinical presentations and misleading investigation findings. An accurate and timely diagnosis of amyloid neuropathy can greatly impact on the outcomes for patients, especially as there will soon be new gene-silencing treatments for hereditary transthyretin amyloidosis.

[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.

The identification of a transthyretin variant p.D38G in a Chinese family with early-onset leptomeningeal amyloidosis

Familial amyloid polyneuropathies (FAPs) are life-threatening, autosomal dominant diseases resulting, in most instances, from transthyretin gene (TTR) variants. A small number of TTR variants lead to leptomeningeal amyloidosis (LA), which is a rare FAP subtype with late-onset central nervous system (CNS) impairment symptoms. Previous studies suggest that LA's CNS selectivity was due to complete endoplasmic reticulum-associated degradation of highly destabilized mutants in peripheral tissues. LA's later age at onset (AAO) was due to lower choroid plexus secretory efficacy. This study reports on a family with LA, including six symptomatic and three presymptomatic members. The LA diagnosis was confirmed by leptomeningeal enhancement on contrast MRI, elevated cerebrospinal fluid protein levels, and positive Congo red staining. The predominant symptoms included headaches, dizziness, vomiting, hallucinations, and cognitive impairments which associated with obstructive hydrocephalus. The TTR p.D38G variant with the lowest secretory efficacy was identified as the genetic cause by whole exome sequencing. The family had a statistically significantly earlier mean AAO of 31.3 ± 7.4 (p = 0.001). These uncommon phenotypes indicate unknown factors influencing the progress of CNS impairment via TTR mutants. Medical imaging examinations suggest the potential early diagnosis value of contrast MRI and the importance of ependyma involvement in LA. LA genetic and clinical data were reviewed and summarized. These findings expand the FAPs' phenotypic spectrum and are valuable in FAP diagnosis, treatment, and further research.

Anterior Chamber Flare as an Objective and Quantitative Noninvasive Method for Oculopathy in Transthyretin V30M Amyloidosis Patients

Purpose

Assess the aqueous humor flare in transthyretin V30M amyloidosis patients (ATTRV30M).

Materials and Methods

This is a retrospective, cross-sectional, noninterventional comparative study including 28 ATTRV30M patients with a unilateral scalloped iris. For comparative analysis, the fellow eye, the nonscalloped iris eye, from each patient was used as control. All patients underwent aqueous humor flare meter and intraocular pressure (IOP) measurements.

Results

Mean aqueous humor flare was significantly higher in the eyes with the scalloped iris than the control group with the nonscalloped iris (14.1 ± 2.2 versus 6.5 ± 0.9 pc/ms, respectively). No significant differences in IOP were found in the scalloped iris eyes than those in the nonscalloped iris control group (17.1 ± 0.8 versus 16.8 ± 0.7 mmHg, respectively). No significant correlation was not found between the flare and the IOP value within groups.

Conclusions

In this study, aqueous humor flare values in the scalloped iris eyes may be a valid marker for controlling the stage of the oculopathy in ATTRV30M patients.

Atrial Fibrillation and Central Nervous Complications in Liver Transplanted Hereditary Transthyretin Amyloidosis Patients

Background

Central nervous system (CNS) complications are increasingly noted in liver transplanted (LTx) hereditary transthyretin amyloid (ATTRm) amyloidosis patients; this suggests that the increased survival allows for intracranial ATTRm formation from brain synthesized mutant TTR. However, atrial fibrillation (AF), a recognised risk factor for ischemic CNS complications, is also observed after LTx. The aim of the study was to investigate the occurrence of CNS complications and AF in LTx ATTRm amyloidosis patients.

Methods

The medical records of all LTx ATTRm amyloidosis patients in the county of Västerbotten, Sweden, were investigated for information on CNS complications, AF, anticoagulation (AC) therapy, hypertension, cardiac ischemic disease, hypertrophy, and neurological status.

Results

Sixty-three patients that had survived for 3 years or longer after LTx were included in the analysis. Twenty-five patients had developed 1 or more CNS complications at a median of 21 years after onset of disease. AF was noted in 21 patients (median time to diagnosis 24 years). Cerebrovascular events (CVE) developed in 17 (median time to event 21 years). CVEs occurred significantly more often in patients with AF (P < 0.002). AC therapy significantly reduced CVEs, including bleeding in patients with AF (P = 0.04). Multivariate analysis identified AF as the only remaining regressor with a significant impact on CVE (hazard ratio, 3.8; 95% confidence interval 1.1-9.5; P = 0.029).

Conclusions

AF is an important risk factor for CVE in LTx ATTRm amyloidosis patients, and AC therapy should be considered. However, the increased bleeding risk with AC therapy in patients with intracranial amyloidosis should be acknowledged.

The authors of this retrospective study investigated the occurrence of central nervous system complications, such as cerebrovascular events and their potential association with atrial fibrillation in liver transplanted ATTRm Val30Met amyloidosis patients.

Progression of transthyretin (TTR) amyloidosis in donors and recipients after domino liver transplantation-a prospective single-center cohort study

Liver transplantation (LT) is the first-line therapy in patients with transthyretin (TTR) amyloidosis and progressive familial amyloid polyneuropathy (FAP). Explanted organs from these patients can be used for domino liver transplantation (DLT). After DLT, de novo amyloidosis may develop in domino recipients (DR). Data were collected prospectively in a transplant database. Electroneurography by nerve conduction velocity (NCV), quantitative sensory testing, heart rate variability (HRV), sympathetic skin response, orthostatic reaction (tilt table test), transthoracic echocardiography, cardiac MRI and organ biopsy results were evaluated. The cohort included 24 FAP- (11 Val30Met, 13 nonVal30Met) and 23 DR-patients. DR symptoms referred to post-DLT only, while those of FAP patients were both pre- and post-transplantation. Symptoms of TTR-amyloidosis in Val30Met and Non-Val30Met patients pre- and post-LT were similarly distributed. Biopsy-proven de novo amyloidosis occurred in 4/23 DR after a mean observation of 10 years. Analysis for manifestations of amyloidosis only included patients with available 5-year follow-up data (n = 13 FAP, n = 12 DR). Compared to Val30Met FAP patients pre-LT, Val30Met DR patients had better NCV (P = 0.04) and HRV (P = 0.015). In the Non-Val30Met group no differences were found between DR and FAP patients pre-LT. TTR-amyloidosis symptoms showed no differences in FAP patients pre- and 5 years post-LT, irrespective of Val30Met status. In DR patients, de novo amyloidosis occurred earlier than expected. Therefore, recipients for DLT need to be carefully selected and followed.

Cerebrospinal fluid and vitreous body exposure to orally administered tafamidis in hereditary ATTRV30M (p.TTRV50M) amyloidosis patients

Hereditary transthyretin (TTR) amyloidosis associated with the TTRV30M (p.TTRV50M) mutation presents predominantly as an axonal polyneuropathy, with variable involvement of other organs. Serious central nervous system (CNS) and eye manifestations, including stroke, dementia, vitreous opacities and glaucoma, have been reported in untreated V30M TTR amyloidosis patients, and in these patients after treatment with liver transplantation (LT). Distinct therapies for V30M TTR amyloidosis developed during the last decade exhibit promising results in slowing the peripheral and autonomic nervous system pathology. However, the effect of these therapies on the CNS and eye manifestations of V30M TTR amyloidosis is not known. Herein, we show that in a small cohort of patients taking tafamidis orally (20 mg tafamidis meglumine daily) we could detect this small molecule in the cerebrospinal fluid (CSF) and the vitreous body. In the CSF, the ratio of TTR tetramer to tafamidis was ≈2:1, leading to a moderate kinetic stabilization of TTR in the CSF of these patients. Our data suggest that tafamidis can cross the CSF-blood and eye-blood barriers. Future studies comparing CNS and eye manifestations in patients treated with LT, kinetic stabilizers or TTR lowering drugs are essential to understand the clinical effect of our observations.

Diagnosis and management of transthyretin familial amyloid polyneuropathy in Japan: red-flag symptom clusters and treatment algorithm

Hereditary ATTR (ATTRm) amyloidosis (also called transthyretin-type familial amyloid polyneuropathy [ATTR-FAP]) is an autosomal-dominant, adult-onset, rare systemic disorder predominantly characterized by irreversible, progressive, and persistent peripheral nerve damage. TTR gene mutations (e.g. replacement of valine with methionine at position 30 [Val30Met (p.Val50Met)]) lead to destabilization and dissociation of TTR tetramers into variant TTR monomers, which form amyloid fibrils that deposit in peripheral nerves and various organs, giving rise to peripheral and autonomic neuropathy and several non-disease specific symptoms.

Phenotypic and genetic variability and non–disease-specific symptoms often delay diagnosis and lead to misdiagnosis. Red-flag symptom clusters simplify diagnosis globally. However, in Japan, types of TTR variants, age of onset, penetrance, and clinical symptoms of Val30Met are more varied than in other countries. Hence, development of a Japan-specific red-flag symptom cluster is warranted. Presence of progressive peripheral sensory-motor polyneuropathy and ≥1 red-flag sign/symptom (e.g. family history, autonomic dysfunction, cardiac involvement, carpal tunnel syndrome, gastrointestinal disturbances, unexplained weight loss, and immunotherapy resistance) suggests ATTR-FAP. Outside of Japan, pharmacotherapeutic options are first-line therapy. However, because of positive outcomes (better life expectancy and higher survival rates) with living donor transplant in Japan, liver transplantation remains first-line treatment, necessitating a Japan-specific treatment algorithm.

Herein, we present a consolidated review of the ATTR-FAP Val30Met landscape in Japan and summarize findings from a medical advisory board meeting held in Tokyo on 18th August 2016, at which a Japan-specific ATTR-FAP red-flag symptom cluster and treatment algorithm was developed. Beside liver transplantation, a TTR-stabilizing agent (e.g. tafamidis) is a treatment option. Early diagnosis and timely treatment using the Japan-specific red-flag symptom cluster and treatment algorithm might help guide clinicians regarding apt and judicious use of available treatment modalities.

Transthyretin familial amyloid polyneuropathy: an update

Transthyretin familial amyloid polyneuropathy (TTR-FAP) is a progressive, fatal, inherited disorder first identified in Portugal and now recognized in all continents. Over the past decade, thanks to the availability of the genetic test, our knowledge on the range of clinical expressions of this disorder has expanded, including different patterns and progression rates of the neuropathy, as well as aspects of the cardiomyopathy, which can be prominent. In the mean time, new tools are being developed to detect earlier TTR amyloid deposition such as cardiac scintigraphy with technetium-labelled pyrophosphate tracers or small nerve fiber alterations from skin biopsies, or using neurophysiological approaches as well as magnetic resonance neurography (MRN). Such refinements, along with an increased awareness of the disease, should reduce the diagnostic delay and facilitate early treatment. In this regard, thanks to a better understanding of the TTR amyloid formation, major advances have been made, allowing for therapeutic developments which are less invasive than liver transplantation (LT). TTR stabilizer drugs are safe and seem to delay the disease progression in some groups of patients. Indeed, positive results have just been released from 2 phase III trials on TTR gene modifiers, namely silencing RNA and antisense oligonucleotide therapies. These recent advances open a new area in the field with the hope that we can safely bring about long-term stabilization of the disease. Furthermore, immunotherapies targeting the amyloid deposits are being explored.

Psychopathological Dimensions in Portuguese Subjects with Transthyretin Familial Amyloid Polyneuropathy

Background

Transthyretin familial amyloid polyneuropathy (TTR-FAP) is a fatal, chronic, progressive disease. It is a rare hereditary amyloidosis, which manifests as a sensorimotor neuropathy and autonomic dysfunction. It begins during adulthood.

Aims and Methods

Our aim is to evaluate psychopathological dimensions in a population attending a consultation center for TTR-FAP. Two hundred and nine subjects (symptomatic and asymptomatic carriers), 84 men and 127, women participated in the study. Most subjects were married (67.1%) and most of them were still working; 33% were retired from work or on a sick leave. A sociodemographic questionnaire and The Brief Symptom Inventory (BSI) were applied. Statistical analysis was performed (descriptive analysis, Mann-Whitney, Wilcoxon, and Spearman tests).

Results

The Global Symptom Index (GSI) was significantly higher in patients (p = 0.001). Considering GSI, 32.7% of total subjects were above the median for general population. When subgroups were evaluated, 25.6% of symptomatic carriers, 26.3% of subjects without established diagnosis, and 39.1% of patients were above median. GSI was significantly higher in patients (p = 0.001). Some BSI dimensions were also significantly higher in the patient group (somatization, depression, anxiety, and psychoticism) when compared with carriers. Women scored higher than men. Sick women scored higher for all dimensions except somatization. Asymptomatic carriers scored statistically higher for phobic anxiety (p = 0.01), interpersonal sensitivity, anxiety, and depression. In patients, most dimensions and GSI (rho = 0.33, p = 0.002) had positive correlations with years of disease.

Conclusions

TTR-FAP patients and carriers are a very vulnerable group for psychological distress and psychopathological problems. Women and patients are at higher risk.

Life paths of patients with transthyretin-related familial amyloid polyneuropathy Val30Met: a descriptive study

Transthyretin-related familial amyloid polyneuropathy Val30Met is a fatal progressive disease. It is a rare hereditary amyloidosis, manifesting as a sensorimotor neuropathy and autonomic dysfunction. It begins during adulthood and is a disabling disease, posing a great psychological burden to patients and their families. Our aim was to describe and characterize life events related to the disease and discuss its psychosocial implications. Social and demographic data and a questionnaire on history of family and personal disease, and biographic events, were applied to 209 subjects attending an outpatient specialized clinic. Descriptive and statistical analyses were performed. They were 84 men and 127 women belonging to three groups: pre-symptomatic carriers, patients, and subjects with no established diagnosis. Most subjects were married/lived with a partner and had children (mean of 4). Most (96.3%) had contact with the disease before having a diagnosis; the affected or at-risk parent was the mother in 53.8% and the father in 43.3%; 71.8% of these had deceased. At their parent's death, many subjects were aged under 10 (9.9%), 10-14 (15.5%), or 15-24 years (31.7%). Most were under age 14 (44.9%) at their parent's disease onset; 37.2% referred this brought life changes with psychological and familial impact; most had been parent's caregivers; 7.5% had not been raised by the parents. Some (8.4%) declined to know their genetic tests results for over 1 year. Parent's disease and death are very common early in these patient's lives. During childhood or youth, many subjects became caregivers, implying changes in family roles. This disease and its life implications pose a significant psychosocial burden since childhood. TTR-FAP patients and their relatives are highly vulnerable to emotional stress and psychopathology during their lifetime. Psychological and psychiatric support, implying a multidisciplinary group, must thus be available for all of them.

Evidence that glial cells attenuate G47R transthyretin accumulation in the central nervous system

Amyloidogenic protein forms amyloid aggregations at membranes leading to dysfunction of amyloid clearance and amyloidosis. Glial cells function in the clearance and degradation of amyloid β (Aβ) in the brain. This study aimed to clarify the reason why amyloid transthyretin (ATTR) rarely accumulates in the CNS. We pathologically analyzed the relationship between amyloid deposition with basement membranes or glial cells in a rare case of ATTR leptomeningeal amyloidosis. In addition, we compared the cytotoxicity of ATTR G47R, the amyloidosis-causing mutation in the case studied (n = 1), and Aβ in brains from patients with cerebral amyloid angiopathy (n = 6). In the subarachnoid space of the ATTR G47R case, most amyloids accumulated at the components of basement membranes. On the CNS surface, ATTR accumulations were retained by astrocytic end feet. In areas where glial end feet enveloped ATTR, ubiquitination and micro-vacuolation of ATTR was evident. The colocalization of GFAP and ubiquitin was also evident. The accumulation of ATTR G47R in the CNS was negatively correlated with the prevalence of astrocytes. Quantitatively, amyloid deposits along the vessels were mostly partial in cerebral Aβ angiopathy cases and nearly complete along the basement membrane in the ATTR G47R case. The vascular expressions of type IV collagen and smooth muscle actin were severely reduced in areas with ATTR G47R deposition, but not in areas with Aβ deposition. The vascular protein level recovered in the ATTR G47R case when vessels entered into areas of parenchyma that were rich in astrocytes. In addition, the strong interactions between the transthyretin variant and basement membranes may have led to dysfunction of transthyretin clearance and leptomeningeal amyloidosis. The present study was the first to show that glial cells may attenuate G47R transthyretin accumulation in the CNS.

Transthyretin amyloidosis: an under-recognized neuropathy and cardiomyopathy

Transthyretin (TTR) amyloidosis (ATTR amyloidosis) is an underdiagnosed and important type of cardiomyopathy and/or polyneuropathy that requires increased awareness within the medical community. Raising awareness among clinicians about this type of neuropathy and lethal form of heart disease is critical for improving earlier diagnosis and the identification of patients for treatment. The following review summarizes current criteria used to diagnose both hereditary and wild-type ATTR (ATTRwt) amyloidosis, tools available to clinicians to improve diagnostic accuracy, available and newly developing therapeutics, as well as a brief biochemical and biophysical background of TTR amyloidogenesis.

Cognitive impairment in liver transplanted patients with transthyretin-related hereditary amyloid polyneuropathy

INTRODUCTION AND AIM

Hereditary transthyretin-related amyloidosis (ATTR-FAP) is characterized by a progressive neuropathy, cardiomyopathy, nephropathy and ocular disease. More than 90% of amyloidogenic transthyretin is produced by the liver; however, this protein is also synthesized in the choroid plexus. Although some patients have transitory neurologic events, the impact on cognition is still unknown. The aim was to study the cognitive performance of ATTR-FAP V30M patients with long disease course.

METHODS

A prospective observational study of a consecutive sample of patients with 10 or more years of disease duration was conducted. All patients underwent an extensive neuropsychological evaluation.

RESULTS

Sixteen patients were included, with a mean age of 53 years and mean duration of disease of 18 years. All had been submitted to liver transplantation. The functional status was not incapacitating in the majority, with 75% needing at most a stick to walk and 38% still actively working. The neuropsychological evaluation disclosed episodic memory impairments in 31% and executive dysfunction in 25% of patients.

CONCLUSIONS

These novel findings suggest that cognitive dysfunction can be a delayed manifestation of hereditary transthyretin-related amyloidosis. The putative relation of cognitive dysfunction with transthyretin-amyloid deposition can provide another model to study the amyloid hypothesis of cognitive impairment.

Semi-quantitative models for identifying potent and selective transthyretin amyloidogenesis inhibitors

Rate-limiting dissociation of the tetrameric protein transthyretin (TTR), followed by monomer misfolding and misassembly, appears to cause degenerative diseases in humans known as the transthyretin amyloidoses, based on human genetic, biochemical and pharmacologic evidence. Small molecules that bind to the generally unoccupied thyroxine binding pockets in the native TTR tetramer kinetically stabilize the tetramer, slowing subunit dissociation proportional to the extent that the molecules stabilize the native state over the dissociative transition state-thereby inhibiting amyloidogenesis. Herein, we use previously reported structure-activity relationship data to develop two semi-quantitative algorithms for identifying the structures of potent and selective transthyretin kinetic stabilizers/amyloidogenesis inhibitors. The viability of these prediction algorithms, in particular the more robust in silico docking model, is perhaps best validated by the clinical success of tafamidis, the first-in-class drug approved in Europe, Japan, South America, and elsewhere for treating transthyretin aggregation-associated familial amyloid polyneuropathy. Tafamidis is also being evaluated in a fully-enrolled placebo-controlled clinical trial for its efficacy against TTR cardiomyopathy. These prediction algorithms will be useful for identifying second generation TTR kinetic stabilizers, should these be needed to ameliorate the central nervous system or ophthalmologic pathology caused by TTR aggregation in organs not accessed by oral tafamidis administration.

Efficiency of silencing RNA for removal of transthyretin V30M in a TTR leptomeningeal animal model

Some TTR mutants target the central nervous system (CNS). Familial amyloid polyneuropathy (FAP) with leptomeningeal involvement has been described in 9% of transthyretin (TTR) mutations and in valine for methionine at position 30 (V30M) patients. These individuals present dementia, ataxia, brain hemorrhages and focal neurological episodes (FNEs). FNEs occurred also in V30M FAP patients with longer disease duration, who have undergone liver transplant to remove the source of plasma mutant TTR as a form of treatment. It is thus to expect that as better treatments for FAP emerge and prolong survival, meningeal-vascular CNS deposition will increase and need special therapies. Recently, we detected TTR meningeal-vascular deposition in a V30M TTR transgenic mouse model, opening new avenues of research to investigate selective treatments of this condition. Since pre-clinical studies with TTR siRNA therapeutics were shown to promote clearance of TTR non-fibrillar deposits in several organs and tissues, we investigated its effect on TTR meningeal-vascular deposition. We show that systemically administered TTR siRNA promoted TTR clearance in the extracellular matrix of meninges and brain blood vessels. Surprisingly, despite the striking decline of blood TTR, cerebrospinal fluid TTR levels were unaffected. Though this is reassuring because siRNA will not interfere with the neuroprotective role of TTR in the CNS, it raises new questions on therapeutical approaches for CNS ATTR.

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.

First European consensus for diagnosis, management, and treatment of transthyretin familial amyloid polyneuropathy

Purpose of review

Early and accurate diagnosis of transthyretin familial amyloid polyneuropathy (TTR-FAP) represents one of the major challenges faced by physicians when caring for patients with idiopathic progressive neuropathy. There is little consensus in diagnostic and management approaches across Europe.

Recent findings

The low prevalence of TTR-FAP across Europe and the high variation in both genotype and phenotypic expression of the disease means that recognizing symptoms can be difficult outside of a specialized diagnostic environment. The resulting delay in diagnosis and the possibility of misdiagnosis can misguide clinical decision-making and negatively impact subsequent treatment approaches and outcomes.

Summary

This review summarizes the findings from two meetings of the European Network for TTR-FAP (ATTReuNET). This is an emerging group comprising representatives from 10 European countries with expertise in the diagnosis and management of TTR-FAP, including nine National Reference Centres. The current review presents management strategies and a consensus on the gold standard for diagnosis of TTR-FAP as well as a structured approach to ongoing multidisciplinary care for the patient. Greater communication, not just between members of an individual patient's treatment team, but also between regional and national centres of expertise, is the key to the effective management of TTR-FAP.

Liver transplantation in transthyretin amyloidosis: Characteristics and management related to kidney disease

Orthotopic liver transplantation (LT) was implemented as the inaugural disease-modifying therapy for hereditary transthyretin (ATTR) amyloidosis, a systemic amyloidosis mainly affecting the peripheral nervous system and heart. The first approach to pharmacologic therapy was focused on the stabilization of the TTR tetramer; following that new advent LT was assumed as the second step of treatment, for those patients whose neuropathy becomes worse after a course of pharmacologic therapy. The renal disease has been ignored in hereditary ATTR amyloidosis. The low level of proteinuria or slight renal impairment does not suppose such a heavy glomerular and vascular amyloid deposition. Moreover, severity of renal deposits does not consistently parallel that of myelinated nerve fiber loss. These are pitfalls that limit the success of LT and suggest troublesome criteria for pharmacological therapy or LT. An algorithm of evaluation concerning renal disease and treatment options is presented and some bridges-to-decision are exposed. In stage 4 or 5 kidney disease, the approach remains to deliver combined or sequential liver-kidney transplantation in eligible patients. However, in the majority, hemodialysis is the only option even in the presence of a well-functioning liver graft. In this review, we highlight useful information to aid the transplant hepatologist in the clinical practice.

Current and future treatment of amyloid diseases

There are more than 30 human proteins whose aggregation appears to cause degenerative maladies referred to as amyloid diseases or amyloidoses. These disorders are named after the characteristic cross-β-sheet amyloid fibrils that accumulate systemically or are localized to specific organs. In most cases, current treatment is limited to symptomatic approaches and thus disease-modifying therapies are needed. Alzheimer's disease is a neurodegenerative disorder with extracellular amyloid β-peptide (Aβ) fibrils and intracellular tau neurofibrillary tangles as pathological hallmarks. Numerous clinical trials have been conducted with passive and active immunotherapy, and small molecules to inhibit Aβ formation and aggregation or to enhance Aβ clearance; so far such clinical trials have been unsuccessful. Novel strategies are therefore required and here we will discuss the possibility of utilizing the chaperone BRICHOS to prevent Aβ aggregation and toxicity. Type 2 diabetes mellitus is symptomatically treated with insulin. However, the underlying pathology is linked to the aggregation and progressive accumulation of islet amyloid polypeptide as fibrils and oligomers, which are cytotoxic. Several compounds have been shown to inhibit islet amyloid aggregation and cytotoxicity in vitro. Future animal studies and clinical trials have to be conducted to determine their efficacy in vivo. The transthyretin (TTR) amyloidoses are a group of systemic degenerative diseases compromising multiple organ systems, caused by TTR aggregation. Liver transplantation decreases the generation of misfolded TTR and improves the quality of life for a subgroup of this patient population. Compounds that stabilize the natively folded, nonamyloidogenic, tetrameric conformation of TTR have been developed and the drug tafamidis is available as a promising treatment.

Cerebral amyloid angiopathy in posttransplant patients with hereditary ATTR amyloidosis

OBJECTIVE

To investigate the prevalence and clinical features of posttransplant CNS symptoms in patients with hereditary ATTR amyloidosis and their Pittsburgh compound B (PiB)-PET imaging correlates.

METHODS

We monitored prevalence and type of CNS symptoms in 53 consecutive posttransplant patients with hereditary ATTR amyloidosis. (11)C-PiB-PET was performed in 15 patients with various disease durations. We also analyzed pathologic and biochemical characteristics of ATTR amyloid deposition in the brain of a posttransplant patient.

RESULTS

Transient focal neurologic episodes (TFNEs) attributed to ATTR-type cerebral amyloid angiopathy (CAA) were found in 11.3% of posttransplant hereditary ATTR amyloidosis patients. TFNE occurred on average 16.8 years after onset of the disease. Patients with longer duration of illness (≥10 years) showed increased (11)C-PiB retention in the brain. The (11)C-PiB accumulation pattern in hereditary ATTR amyloidosis was unique and different from those in Alzheimer disease or Aβ-type CAA. In the autopsy case, ATTR amyloid deposition was mainly localized to leptomeningeal vessels and leptomeninges of the brain. Amyloid fibrils in the brain were almost completely composed of variant transthyretin (TTR).

CONCLUSIONS

TFNE due to ATTR-type CAA occurred frequently in posttransplant patients with long disease durations. (11)C-PiB-PET is a useful diagnostic tool for ATTR-type CAA. ATTR amyloid deposition in the CNS, as measured by PiB-PET, was detected approximately 10 years before onset of TFNE.

[Familial amyloid polyneuropathy involving a homozygous Val30Met mutation in the amyloidogenic transthyretin gene presenting with superficial siderosis: a case report]

A 76-year-old woman was admitted to our hospital because of transthyretin-related familial amyloid polyneuropathy (TTR-FAP). She had developed bilateral vitreous opacity at the age of 58 and paroxysmal atrial fibrillation at the age of 62. She suffered gait disturbance and dysesthesia of the limbs at the age of 68 and was diagnosed with FAP involving a homozygous Val30Met mutation in the amyloidogenic transthyretin (ATTR) gene after a genetic test. Her parents were cousins, and her aunt's medical history included pacemaker implantation and polyneuropathy. At the age of 74, the patient developed gait disturbance and dysesthesia of her extremities. A neurological examination revealed visual loss, hearing impairment, distal muscle weakness, dysesthesia, and decreased sensation in all modalities in her extremities. She could neither walk nor remain standing without support. Brain magnetic resonance imaging (MRI) revealed a low intensity lesion on the surface of the cerebellum on T2*-weighted images and susceptibility-weighted images. A low intensity pattern that was indicative of the classical type of superficial siderosis was detected. At the age of 76, when she was admitted to our hospital because of the deterioration of her gait disturbance and dysesthesia, brain MRI showed that the patient's cerebellar atrophy and hemosiderin deposition had worsened. Some reports suggest that FAP patients that are homozygous for the ATTR Val30Met mutation are more likely to develop central nervous involvement than those that are heterozygous for the mutation. Superficial siderosis may be responsible for the central nervous involvement.

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.

Diagnosis, Prognosis, and Therapy of Transthyretin Amyloidosis

Transthyretin amyloidosis is a fatal disorder that is characterized primarily by progressive neuropathy and cardiomyopathy. It occurs in both a mutant form (with autosomal dominant inheritance) and a wild-type form (with predominant cardiac involvement). This article guides clinicians as to when the disease should be suspected, describes the appropriate diagnostic evaluation for those with known or suspected amyloidosis, and reviews the interventions currently available for affected patients.

TTR kinetic stabilizers and TTR gene silencing: a new era in therapy for familial amyloidotic polyneuropathies

INTRODUCTION

Transthyretin Familial Amyloid Polyneuropathy (TTR-FAP) is a rare disease with autosomal dominant transmission due to a point mutation of the TTR gene. By removing the main source of systemic mutant TTR, liver transplantation (LT) has become the reference therapy of this severe and fatal polyneuropathy of adult-onset, stopping disease progression in subgroup of patients. Recently, new therapeutic strategies have emerged, which intend to stabilize TTR or to silence the TTR gene. Amongst them, the TTR kinetic stabilizer tafamidis is the first drug approved in the EU.

AREAS COVERED

We shall review the natural history of TTR-FAP and the best indications for LT. Data on the efficacy, safety and tolerability of the TTR kinetic stabilizers, tafamidis and diflunisal, have been reviewed, from the pivotal Phase III clinical trials published in PubMed medical journals or presented at international meetings. We will review the ongoing phase III clinical trials of TTR gene silencing with RNAi therapeutics and ASO published in clinicaltrialgov.

EXPERT OPINION

Due to the data on efficacy, tolerability, safety, tafamidis and diflunisal became the first line anti-amyloid treatment in stage 1 TTR-FAP. Both drugs slow progression of the disease. Only tafamidis got marketing authorization. We are waiting for results of the 2 phase III clinical trials of TTR gene silencing in varied stages of the disease.

A novel bis-furan scaffold for transthyretin stabilization and amyloid inhibition

The design and synthesis of a novel bis-furan scaffold tailored for high efficiency at inhibiting transthyretin amyloid formation is reported. In vitro results show that the discovered compounds are more efficient inhibitors of amyloid formation than tafamidis, a drug currently used in the treatment of familial amyloid polyneuropathy (FAP), despite their lower molecular weight and lipophilicity. Moreover, ex vivo experiments with the strongest inhibitor in the series, conducted in human blood plasma from normal and FAP Val30Met-transthyretin carriers, disclose remarkable affinity and selectivity profiles. The promises and challenges facing further development of this compound are discussed under the light of increasing evidence implicating transthyretin stability as a key factor not only in transthyretin amyloidoses and several associated co-morbidities, but also in Alzheimer's disease.

Long-term outcome of patients with hereditary transthyretin V30M amyloidosis with polyneuropathy after liver transplantation

BACKGROUND

Liver transplantation halts production of mutated transthyretin (TTR), and thus it is an accepted treatment, with improved survival, in patients with hereditary (familial) amyloidosis with polyneuropathy (FAP). However, the effects of transplantation on the clinical manifestations of FAP have not yet been adequately clarified. This study aimed to investigate whether liver transplantation would improve the long-term clinical manifestations in FAP patients who had undergone transplantations.

PATIENTS AND METHODS

We assessed 29 non-transplant and 36 transplant FAP V30M patients using an FAP clinical scoring system.

RESULTS

The total clinical score of the non-transplant group increased and was significantly correlated with FAP duration; that of the transplant group increased slowly after transplantation. In patients 5 years or more after FAP onset, the total clinical scores of the transplant group were significantly lower than those of the non-transplant group. In the same patients, scores for sensory, motor, autonomic and organ impairments of the transplant group were significantly lower than those of the non-transplant group.

CONCLUSIONS

Liver transplantation had beneficial effects on FAP clinical manifestations in patients with FAP TTR V30M. Liver transplantation should therefore be considered as an effective treatment in the clinical management of patients with FAP TTR V30M.

A Review of Tafamidis for the Treatment of Transthyretin-Related Amyloidosis

Transthyretin (TTR)-related amyloidosis (ATTR) is a devastating disease which affects a combination of organs including the heart and the peripheral nerves, and which has a fatal outcome if not treated within a average of 10 years. Tafamidis, or 2-(3,5-dichloro-phenyl)-benzoxazole-6-carboxylic acid, selectively binds to TTR with negative cooperativity and kinetically stabilizes wild-type native TTR and mutant TTR; tafamidis therefore has the potential to halt the amyloidogenic cascade initiated by TTR tetramer dissociation, monomer misfolding, and aggregation. The first tafamidis trial, Fx-005, evaluated the effect of 18 months of tafamidis treatment (20 mg once daily) on disease progression, as well as assessing its safety in TTR-FAP Val30Met patients. The secondary objective of this trial was to study the pharmacodynamic stabilization of mutated TTR. Tafamidis proved effective in reducing the progress of neuropathy, and in maintaining the nutritional status and quality of life of stage 1 (able to walk without support) Val3OMet TTR-FAP patients. Furthermore, TTR stabilization was achieved in more than 90% of patients. An extension study, Fx-006, was conducted to determine the long-term safety and tolerability of tafamidis and to assess the efficacy of the drug on slowing disease progression. No significant safety or tolerability issues were noticed. Taken together, the results from both trials indicated that the beneficial effects of tafamidis were sustained over a 30-month period and that starting treatment early is desirable. Results are expected from an extended open-label study but data that have already been presented show that long-term use of tafamidis in Val30Met patients is associated with reduced progression in polyneuropathy. Tafamidis was initially approved for commercial use in Europe in 2011 and has since been approved for use in Japan, Mexico, and Argentina where it is used as a first-line treatment option for patients with early-stage TTR-FAP. Patients should be carefully followed at referral centers to ascertain the individual response to treatment. In cases of discontinuation, liver transplantation and enrollment in clinical trials of novel drugs aimed mostly toward suppression of TTR production are options.

Targeting protein aggregation for the treatment of degenerative diseases

The aggregation of specific proteins is hypothesized to underlie several degenerative diseases, which are collectively known as amyloid disorders. However, the mechanistic connection between the process of protein aggregation and tissue degeneration is not yet fully understood. Here, we review current and emerging strategies to ameliorate aggregation-associated degenerative disorders, with a focus on disease-modifying strategies that prevent the formation of and/or eliminate protein aggregates. Persuasive pharmacological and genetic evidence now supports protein aggregation as the cause of postmitotic tissue dysfunction or loss. However, a more detailed understanding of the factors that trigger and sustain aggregate formation and of the structure-activity relationships underlying proteotoxicity is needed to develop future disease-modifying therapies.

Neuropathologic analysis of Tyr69His TTR variant meningovascular amyloidosis with dementia

Transthyretin/TTR gene mutations usually cause systemic amyloidotic diseases. Few TTR variants preferentially affect the central nervous system, manifesting as oculoleptomeningeal amyloidosis. Patients with TTR meningovascular amyloidosis often show dementia, however the neuropathologic features of dementia in these cases have not been elucidated. We report the neuropathologic findings from a brain autopsy of a 72-year-old man with the rare Tyr69His (Y69H) TTR gene variant, dementia and ataxia. Severe amyloid deposits were observed in the leptomeninges and in a subpial and subependymal distribution. Mass spectrometry analysis demonstrated that the amyloid deposits were comprised of over 80 % of the variant TTR. TTR was undetectable by mass spectrometry in the neocortex subjacent to the subpial amyloid deposits. Subpial TTR amyloid deposits were associated with brisk superficial reactive gliosis and siderosis in the neocortex and cerebellar cortex. Subependymal TTR amyloid deposits were associated with subjacent myelin pallor in the hippocampal outflow tract structures including the alveus, fimbria and fornix. Phospho-tau immunostains demonstrated transentorhinal-stage neurofibrillary degeneration (Braak stage II) which, in the absence of neocortical amyloid-beta and neuritic plaques, was indicative of primary age-related tauopathy (PART). However, distinctive phospho-tau aggregates were observed subjacent to the subpial TTR amyloid deposits in all regions of the neocortex, including the primary motor and striate cortices, suggesting a potential link between TTR amyloid and neocortical tauopathy. Our report reveals novel insights into the potential neuropathologic substrates of dementia in variant TTR amyloidosis that need to be investigated in larger autopsy series.