Changes in pathological and biochemical findings of systemic tissue sites in familial amyloid polyneuropathy more than 10 years after liver transplantation

Disease-Modifying Drugs Extend Survival in Hereditary Transthyretin Amyloid Polyneuropathy

Hereditary transthyretin (ATTRv) amyloidosis is a rare, fatal systemic disease, associated with polyneuropathy and cardiomyopathy, that is caused by mutant transthyretin (TTR). In addition to liver transplantation, several groundbreaking disease-modifying drugs (DMDs) such as tetrameric TTR stabilizers and TTR gene-silencing therapies have been developed for ATTRv amyloid polyneuropathy. They were based on a working hypothesis of the mechanisms of ATTRv amyloid formation. In this retrospective cohort study, we investigated survival of all 201 consecutive patients with ATTRv amyloidosis in our center. The effects of DMDs on survival improvements were significant not only in early-onset patients but also in late-onset patients. ANN NEUROL 2024;95:230-236.

Nerve pathology of microangiopathy and thromboinflammation in hereditary transthyretin amyloidosis

OBJECTIVE

Despite amyloid deposition as a hallmark of hereditary transthyretin amyloidosis (ATTRv) with polyneuropathy, this pathology could not completely account for nerve degeneration. ATTRv patients frequently have vasomotor symptoms, but microangiopathy hypothesis in ATTRv was not systemically clarified.

METHODS

This study examined the vascular pathology of sural nerves in ATTRv patients with transthyretin (TTR) mutation of p.Ala117Ser (TTR-A97S), focusing on morphometry and patterns of molecular expression in relation to nerve degeneration. We further applied human microvascular endothelial cell (HMEC-1) culture to examine the direct effect of TTR-A97S protein on endothelial cells.

RESULTS

In ATTRv nerves, there was characteristic microangiopathy compared to controls: increased vessel wall thickness and decreased luminal area; both were correlated with the reduction of myelinated fiber density. Among the components of vascular wall, the area of collagen IV in ATTRv nerves was larger than that of controls. This finding was validated in a cell model of HMEC-1 culture in which the expression of collagen IV was upregulated after exposure to TTR-A97S. Apoptosis contributed to the endothelial cell degeneration of microvasculatures in ATTRv endoneurium. ATTRv showed prothrombotic status with intravascular fibrin deposition, which was correlated with (1) increased tissue factor and coagulation factor XIIIA and (2) reduced tissue plasminogen activator. This cascade led to intravascular thrombin deposition, which was colocalized with upregulated p-selectin and thrombomodulin, accompanied by complement deposition and macrophages infiltration, indicating thromboinflammation in ATTRv.

INTERPRETATION

Microangiopathy with thromboinflammation is characteristic of advanced-stage ATTRv nerves, which provides an add-on mechanism and therapeutic target for nerve degeneration.

3-O-Methyltolcapone and Its Lipophilic Analogues Are Potent Inhibitors of Transthyretin Amyloidogenesis with High Permeability and Low Toxicity

Transthyretin (TTR) is an amyloidogenic homotetramer involved in the transport of thyroxine in blood and cerebrospinal fluid. To date, more than 130 TTR point mutations are known to destabilise the TTR tetramer, leading to its extracellular pathological aggregation accumulating in several organs, such as heart, peripheral and autonomic nerves, and leptomeninges. Tolcapone is an FDA-approved drug for Parkinson's disease that has been repurposed as a TTR stabiliser. We characterised 3-O-methyltolcapone and two newly synthesized lipophilic analogues, which are expected to be protected from the metabolic glucuronidation that is responsible for the lability of tolcapone in the organism. Immunoblotting assays indicated the high degree of TTR stabilisation, coupled with binding selectivity towards TTR in diluted plasma of 3-O-methyltolcapone and its lipophilic analogues. Furthermore, in vitro toxicity data showed their several-fold improved neuronal and hepatic safety compared to tolcapone. Calorimetric and structural data showed that both T4 binding sites of TTR are occupied by 3-O-methyltolcapone and its lipophilic analogs, consistent with an effective TTR tetramer stabilisation. Moreover, in vitro permeability studies showed that the three compounds can effectively cross the blood-brain barrier, which is a prerequisite for the inhibition of TTR amyloidogenesis in the cerebrospinal fluid. Our data demonstrate the relevance of 3-O-methyltolcapone and its lipophilic analogs as potent inhibitors of TTR amyloidogenesis.

Electrocardiographic heterogeneity of patients with variant transthyretin amyloid cardiomyopathy: Genotype-phenotype correlations

BACKGORUND

Hereditary transthyretin(vATTR) cardiac amyloidosis has extremely different features according to the type of transthyretin(TTR) mutation. Data about electrocardiographic findings(ECG) in vATTR are limited and not informative of genotype correlation. Aim of this study is to analyze ECG characteristics and their correlation to clinical and echocardiographic aspects in patients with vATTR, focusing on different TTR mutations.

METHODS AND RESULTS

This is a multicentric, retrospective, observational study performed in six Italian referral centres. We divided patients in two groups, according to the previously described phenotypic manifestations of the TTR mutation. Of 64 patients with vATTR, 23(36%) had prevalent cardiac(PC) TTR mutations and 41(64%) patients had a prevalent neurological(PN) TTR mutations. Patients with PC mutations were more frequently males and older, with advanced NAC staging. At baseline ECG, atrial fibrillation was more common in patients with PC, while pacemaker induced rhythm in PN mutations. PQ and QRS durations were longer and voltage to mass ratio was lower in PC mutations. Different TTR mutations tend to have distinctive ECG features.

CONCLUSIONS

ECG in vATTR is extremely heterogeneous and the specific mutations are associated with distinct instrumental and clinical features. The differences between PN and PC vATTR are only partially explained by the different degree of cardiac infiltration.

Human transthyretin gene expression is markedly increased in repair Schwann cells in an in vitro model of hereditary transthyretin amyloidosis

Hereditary transthyretin (TTR) amyloidosis (ATTRv) is characterized by TTR amyloid deposition in the peripheral nervous system. It remains unknown why variant TTR preferentially deposits in the peripheral nerves and dorsal root ganglia. We previously detected low levels of TTR expression in Schwann cells and established an immortalized Schwann cell line, TgS1, derived from a mouse model of ATTRv amyloidosis expressing the variant TTR gene. In the present study, the expression of TTR and Schwann cell marker genes was investigated in TgS1 cells by quantitative RT-PCR. TTR gene expression was markedly upregulated in TgS1 cells incubated in non-growth medium-Dulbecco's modified Eagle's medium supplemented with 10% fetal bovine serum. The expression levels of c-Jun, Gdnf and Sox2 were increased, while Mpz was downregulated, suggesting that TgS1 cells exhibit a repair Schwann cell-like phenotype in the non-growth medium. Western blot analysis revealed that TTR protein was produced and secreted by the TgS1 cells. Furthermore, downregulation of Hsf1 with siRNA induced TTR aggregates in the TgS1 cells. These findings indicate that TTR expression is markedly increased in repair Schwann cells, likely to promote axonal regeneration. Therefore, aged dysfunctional repair Schwann cells may cause the deposition of variant TTR aggregates in the nerves of patients with ATTRv.

[ATTRv amyloidosis with early improvement demonstrated by the 6-minute walk test following Patisiran therapy: a case report]

We report the case of a 65-year-old man who gradually developed numbness in both hands, lower limb muscle weakness and atrophy, and orthostatic hypotension over two and a half years. These symptoms indicated hereditary ATTR amyloidosis (ATTRv amyloidosis), and the final diagnosis was established through proof of TTR gene mutation (V30M). We initiated patisiran therapy, and a continuous 6-minute walking test performed 3 weeks from the start of therapy demonstrated improvement in the walking distance. This is a single case report showing the improvement in the motor and sensory function on administration of patisiran monotherapy from an early stage.

Amyloid fibril composition type is consistent over time in patients with Val30Met (p.Val50Met) transthyretin amyloidosis

Background

We have previously shown that transthyretin (TTR) amyloidosis patients have amyloid fibrils of either of two compositions; type A fibrils consisting of large amounts of C-terminal TTR fragments in addition to full-length TTR, or type B fibrils consisting of only full-length TTR. Since type A fibrils are associated with an older age in ATTRVal30Met (p.Val50Met) amyloidosis patients, it has been discussed if the TTR fragments are derived from degradation of the amyloid deposits as the patients are aging. The present study aimed to investigate if the fibril composition type changes over time, especially if type B fibrils can shift to type A fibrils as the disease progresses.

Material and methods

Abdominal adipose tissue biopsies from 29 Swedish ATTRVal30Met amyloidosis patients were investigated. The fibril type in the patients´ initial biopsy taken for diagnostic purposes was compared to a biopsy taken several years later (ranging between 2 and 13 years). The fibril composition type was determined by western blot.

Results

All 29 patients had the same fibril composition type in both the initial and the follow-up biopsy (8 type A and 21 type B). Even patients with a disease duration of more than 12 years and an age over 75 years at the time of the follow-up biopsy had type B fibrils in both biopsies.

Discussion

The result clearly shows that the amyloid fibril composition containing large amounts of C-terminal fragments (fibril type A) is a consequence of other factors than a slow degradation process occurring over time.

Plasmin activity promotes amyloid deposition in a transgenic model of human transthyretin amyloidosis

Cardiac ATTR amyloidosis, a serious but much under-diagnosed form of cardiomyopathy, is caused by deposition of amyloid fibrils derived from the plasma protein transthyretin (TTR), but its pathogenesis is poorly understood and informative in vivo models have proved elusive. Here we report the generation of a mouse model of cardiac ATTR amyloidosis with transgenic expression of human TTR^S52P. The model is characterised by substantial ATTR amyloid deposits in the heart and tongue. The amyloid fibrils contain both full-length human TTR protomers and the residue 49-127 cleavage fragment which are present in ATTR amyloidosis patients. Urokinase-type plasminogen activator (uPA) and plasmin are abundant within the cardiac and lingual amyloid deposits, which contain marked serine protease activity; knockout of α₂-antiplasmin, the physiological inhibitor of plasmin, enhances amyloid formation. Together, these findings indicate that cardiac ATTR amyloid deposition involves local uPA-mediated generation of plasmin and cleavage of TTR, consistent with the previously described mechano-enzymatic hypothesis for cardiac ATTR amyloid formation. This experimental model of ATTR cardiomyopathy has potential to allow further investigations of the factors that influence human ATTR amyloid deposition and the development of new treatments.

ATTR amyloidosis causes heart failure through the accumulation of misfolded transthyretin in cardiac muscle. Here the authors report a mouse model of ATTR amyloidosis and demonstrate the involvement of protease activity in ATTR amyloid deposition.

In Vitro and In Vivo Effects of SerpinA1 on the Modulation of Transthyretin Proteolysis

Transthyretin (TTR) proteolysis has been recognized as a complementary mechanism contributing to transthyretin-related amyloidosis (ATTR amyloidosis). Accordingly, amyloid deposits can be composed mainly of full-length TTR or contain a mixture of both cleaved and full-length TTR, particularly in the heart. The fragmentation pattern at Lys48 suggests the involvement of a serine protease, such as plasmin. The most common TTR variant, TTR V30M, is susceptible to plasmin-mediated proteolysis, and the presence of TTR fragments facilitates TTR amyloidogenesis. Recent studies revealed that the serine protease inhibitor, SerpinA1, was differentially expressed in hepatocyte-like cells (HLCs) from ATTR patients. In this work, we evaluated the effects of SerpinA1 on in vitro and in vivo modulation of TTR V30M proteolysis, aggregation, and deposition. We found that plasmin-mediated TTR proteolysis and aggregation are partially inhibited by SerpinA1. Furthermore, in vivo downregulation of SerpinA1 increased TTR levels in mice plasma and deposition in the cardiac tissue of older animals. The presence of TTR fragments was observed in the heart of young and old mice but not in other tissues following SerpinA1 knockdown. Increased proteolytic activity, particularly plasmin activity, was detected in mice plasmas. Overall, our results indicate that SerpinA1 modulates TTR proteolysis and aggregation in vitro and in vivo.

Neuromuscular amyloidosis: Unmasking the master of disguise

Amyloidosis refers to an etiologically heterogeneous group of protein misfolding diseases, pathologically characterized by extracellular amyloid fibrils producing congophillic amorphous deposits in organs and tissues, which may lead to severe organ dysfunction and mortality. Clinical presentations vary and are often nonspecific, depending on what organs or tissues are affected. In systemic amyloidosis, the peripheral nervous system is commonly affected, whereas the skeletal muscles are only rarely involved. Immunoglobulin light chain (AL) amyloidosis and hereditary transthyretin (ATTRv) amyloidosis are the most frequent types of systemic amyloidosis involving the neuromuscular system. Localized amyloidosis can occur in skeletal muscle, so-called isolated amyloid myopathy. Amyloid neuropathy typically involves small myelinated and unmyelinated sensory and autonomic nerve fibers early in the course of the disease, followed by large myelinated fiber sensory and motor deficits. The relentlessly progressive nature with motor, painful sensory and severe autonomic dysfunction, profound weight loss, and systemic features are distinct characteristics of amyloid neuropathy. Amyloid myopathy presentation differs between systemic amyloidosis and isolated amyloid myopathy. Long-standing symptoms, distal predominant myopathy, markedly elevated creatine kinase level, and lack of peripheral neuropathy or systemic features are highly suggestive of isolated amyloid myopathy. In ATTR and AL amyloidosis, early treatment correlates with favorable outcomes. Therefore, awareness of these disorders and active screening for amyloidosis in patients with neuropathy or myopathy are crucial in detecting these patients in the everyday practice of neuromuscular medicine. Herein, we review the clinical manifestations of neuromuscular amyloidosis and provide a diagnostic approach to this disorder.

Transthyretin amyloid cardiomyopathy in women: frequency, characteristics, and diagnostic challenges

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressive, life-threatening disease characterized by deposition of insoluble amyloid fibrils in the myocardium, resulting in cardiac structural and functional abnormalities and ultimately heart failure. Disease frequency is reportedly lower in women than men, but sex-related differences have not been well established. We conducted a systematic literature review (SLR), based on PRISMA-P guidelines and registered with PROSPERO, to assess whether the epidemiology and clinical presentation of ATTR-CM differ between women and men. MEDLINE, Embase, and Cochrane databases and selected conference proceedings were searched (August 16, 2019) to identify observational and clinical studies reporting sex-specific data for patients with wild-type or hereditary ATTR-CM. Of 193 publications satisfying final eligibility criteria, 69 studies were included in our pooled analysis. Among the 4669 patients with ATTR-CM analyzed, 791 (17%) were women, including 174 (9%), 366 (29%), and 251 (18%) in studies of wild-type, hereditary, and undefined ATTR-CM, respectively. Data available on disease characteristics were limited and very heterogeneous, but trends suggested some cardiac structural/functional differences, i.e., lower interventricular septal and posterior wall thickness and left ventricular (LV) end diastolic diameter, and higher LV ejection fractions, in women versus men across ATTR-CM subtypes. Because LV wall thickness > 12 mm is generally the suggested threshold for ATTR-CM diagnosis in both sexes, smaller cardiac anatomy in women with the disease may lead to underdiagnosis. Additional research and studies are needed to elucidate potential disparities between sexes in ATTR-CM frequency, clinical characteristics, and underlying biological mechanisms. This study was registered within the International Prospective Register of Systematic Reviews (PROSPERO) database of the University of York (CRD42019146995).

Hereditary transthyretin amyloidosis: a model of medical progress for a fatal disease

Hereditary amyloidogenic transthyretin (ATTRv) amyloidosis with polyneuropathy (also known as familial amyloid polyneuropathy) is a condition with adult onset caused by mutation of transthyretin (TTR) and characterized by extracellular deposition of amyloid and destruction of the somatic and autonomic PNS, leading to loss of autonomy and death. This disease represents a model of the scientific and medical progress of the past 30 years. ATTRv amyloidosis is a worldwide disease with broad genetic and phenotypic heterogeneity that presents a diagnostic challenge for neurologists. The pathophysiology of the neuropathy is increasingly understood and includes instability and proteolysis of mutant TTR leading to deposition of amyloid with variable lengths of fibrils, microangiopathy and involvement of Schwann cells. Wild-type TTR is amyloidogenic in older individuals. The main symptoms are neuropathic, but the disease is systemic; neurologists should be aware of cardiac, eye and kidney involvement that justify a multidisciplinary approach to management. Infiltrative cardiomyopathy is usually latent but present in half of patients. Disease-modifying therapeutics that have been developed include liver transplantation and TTR stabilizers, both of which can slow progression of the disease and increase survival in the early stages. Most recently, gene-silencing drugs have been used to control disease in the more advanced stages and produce some degree of improvement.

A cell-based high-throughput screening method to directly examine transthyretin amyloid fibril formation at neutral pH

Transthyretin (TTR) is a major amyloidogenic protein associated with hereditary (ATTRm) and nonhereditary (ATTRwt) intractable systemic transthyretin amyloidosis. The pathological mechanisms of ATTR-associated amyloid fibril formation are incompletely understood, and there is a need for identifying compounds that target ATTR. C-terminal TTR fragments are often present in amyloid-laden tissues of most patients with ATTR amyloidosis, and on the basis of in vitro studies, these fragments have been proposed to play important roles in amyloid formation. Here, we found that experimentally-formed aggregates of full-length TTR are cleaved into C-terminal fragments, which were also identified in patients' amyloid-laden tissues and in SH-SY5Y neuronal and U87MG glial cells. We observed that a 5-kDa C-terminal fragment of TTR, TTR81-127, is highly amyloidogenic in vitro, even at neutral pH. This fragment formed amyloid deposits and induced apoptosis and inflammatory gene expression also in cultured cells. Using the highly amyloidogenic TTR81-127 fragment, we developed a cell-based high-throughput screening method to discover compounds that disrupt TTR amyloid fibrils. Screening a library of 1280 off-patent drugs, we identified two candidate repositioning drugs, pyrvinium pamoate and apomorphine hydrochloride. Both drugs disrupted patient-derived TTR amyloid fibrils ex vivo, and pyrvinium pamoate also stabilized the tetrameric structure of TTR ex vivo in patient plasma. We conclude that our TTR81-127-based screening method is very useful for discovering therapeutic drugs that directly disrupt amyloid fibrils. We propose that repositioning pyrvinium pamoate and apomorphine hydrochloride as TTR amyloid-disrupting agents may enable evaluation of their clinical utility for managing ATTR amyloidosis.

Transthyretin stabilization activity of the catechol-O-methyltransferase inhibitor tolcapone (SOM0226) in hereditary ATTR amyloidosis patients and asymptomatic carriers: proof-of-concept study. Amyloid 2019;26:74-84. [PMID: 31119947 DOI: 10.1080/13506129.2019.1597702]

Objective: To assess the transthyretin (TTR) stabilization activity of tolcapone (SOM0226) in patients with hereditary ATTR amyloidosis, asymptomatic carriers and healthy volunteers. Methods: A phase IIa proof-of-concept trial included two phases separated by a 6-week washout period. Phase A: single 200 mg dose of tolcapone; phase B: three 100 mg doses taken at 4 h intervals. The primary efficacy variable was TTR stabilization. Results: Seventeen subjects were included (wild type, n = 6; mutation TTR Val30Met, n = 11). TTR stabilization was observed in all participants. Two hours after dosing, 82% of participants in phase A and 93% of those in phase B reached a TTR stabilization value of at least 20%. In phase A, there was an increase of 52% in TTR stabilization vs baseline values 2 h after dosing, which decreased to 22.9% at 8 h. In phase B, there was a significant increase of 38.8% in TTR stabilization 2 h after the first 100 mg dose. This difference was maintained after 10 h and decreased after 24 h. No serious adverse events were observed. Conclusions: The ability of tolcapone for stabilizing TTR supports further development and repositioning of the drug for the treatment of ATTR amyloidosis. EudraCT trial number: 2014-001586-27 ClinicalTrials.gov Identifier: NCT02191826.

Late-onset hereditary ATTR V30M amyloidosis with polyneuropathy: Characterization of Brazilian subjects from the THAOS registry

BACKGROUND

Despite growing numbers of patients diagnosed with late-onset hereditary ATTR V30M amyloidosis with polyneuropathy (ATTRv-PN), this condition remains poorly characterized in Brazil.

OBJECTIVE

Characterize late-onset V30M ATTRv-PN in Brazil.

MATERIAL AND METHODS

Demographic and clinical data at the time of enrolment for Brazilian subjects with symptomatic V30M ATTRv-PN were extracted from the ongoing, multinational, longitudinal, observational Transthyretin Amyloidosis Outcomes Survey (THAOS; cut-off date: January 30, 2017). Subjects were divided into those with symptom onset at age <50 years (EO-V30M), and at age ≥50 years (LO-V30M).

RESULTS

A total of 96 Val30Met patients were symptomatic. LO-V30M (n = 25, 26.0%) had a longer time to diagnosis (mean 5.1 vs. 2.8 yrs.; p = 0.006) and less frequently positive family history (40% vs. 95.8%; p < 0.0001) than EO-V30M. Clinically, subjects with LO-V30M had more imbalance (92% vs. 54.9%; p = 0.006), deep sensory loss (100% vs. 80%; p = 0.0178), electrocardiogram abnormalities (88.9% vs. 59.4; p = 0.0241), and interventricular septum hypertrophy (69.2% vs. 0%; p < 0001) and less frequently sensory dissociation (12% vs. 74%; p < 0.0001). Also, LO-V30M tended to have more severe mean Neurologic Composite Score (101 vs. 70 pts.; p = 0.1136).

CONCLUSIONS

LO-V30M ATTRv-PN is not unusual in Brazil, tending to be more difficult to diagnose and present with a more severe phenotype, with more large nerve fibers and cardiac involvement than EO-V30M.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00628745.

Amyloid fibril composition within hereditary Val30Met (p. Val50Met) transthyretin amyloidosis families

Background

The amyloid fibril in hereditary transthyretin (TTR) Val30Met (pVal50Met) amyloid (ATTR Val30Met) amyloidosis is composed of either a mixture of full-length and TTR fragments (Type A) or of only full-length TTR (Type B). The type of amyloid fibril exerts an impact on the phenotype of the disease, and on the outcome of diagnostic procedures and therapy. The aim of the present study was to investigate if the type of amyloid fibril remains the same within ATTR Val30Met amyloidosis families.

Methods

Fifteen families were identified in whom at least two first-degree relatives had their amyloid fibril composition determined. The type of ATTR was determined by Western blot in all but two patients. For these two patients a positive 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid scintigraphy indicated ATTR Type A.

Results

In 14 of the 15 families, the same amyloid fibril composition was noted irrespective of differences in age at onset. In the one family, different ATTR fibril types was found in two brothers with similar ages at onset.

Conclusions

Family predisposition appears to have an impact on amyloid fibril composition in members of the family irrespective of their age at onset of disease, but if genetically determined, the gene/genes are likely to be situated at another location than the TTR gene in the genome.

Ultrastructure in Transthyretin Amyloidosis: From Pathophysiology to Therapeutic Insights

Transthyretin (TTR) amyloidosis is caused by systemic deposition of wild-type or variant amyloidogenic TTR (ATTRwt and ATTRv, respectively). ATTRwt amyloidosis has traditionally been termed senile systemic amyloidosis, while ATTRv amyloidosis has been called familial amyloid polyneuropathy. Although ATTRwt amyloidosis has classically been regarded as one of the causes of cardiomyopathy occurring in the elderly population, recent developments in diagnostic techniques have significantly expanded the concept of this disease. For example, this disease is now considered an important cause of carpal tunnel syndrome in the elderly population. The phenotypes of ATTRv amyloidosis also vary depending on the mutation and age of onset. Peripheral neuropathy usually predominates in patients from the conventional endemic foci, while cardiomyopathy or oculoleptomeningeal involvement may also become major problems in other patients. Electron microscopic studies indicate that the direct impact of amyloid fibrils on surrounding tissues leads to organ damage, whereas accumulating evidence suggests that nonfibrillar TTR, such as oligomeric TTR, is toxic, inducing neurodegeneration. Microangiopathy has been suggested to act as an initial lesion, increasing the leakage of circulating TTR. Regarding treatments, the efficacy of liver transplantation has been established for ATTRv amyloidosis patients, particularly patients with early-onset amyloidosis. Recent phase III clinical trials have shown the efficacy of TTR stabilizers, such as tafamidis and diflunisal, for both ATTRwt and ATTRv amyloidosis patients. In addition, a short interfering RNA (siRNA), patisiran, and an antisense oligonucleotide (ASO), inotersen, have been shown to be effective for ATTRv amyloidosis patients. Given their ability to significantly reduce the production of both wild-type and variant TTR in the liver, these gene-silencing drugs seem to be the optimal therapeutic option for ATTR amyloidosis. Hence, the long-term efficacy and tolerability of novel therapies, particularly siRNA and ASO, must be determined to establish an appropriate treatment program.

Development of transgenic Caenorhabditis elegans expressing human transthyretin as a model for drug screening

Familial amyloid polyneuropathy is a hereditary systemic amyloidosis caused by a mutation in the transthyretin (TTR) gene. Amyloid deposits in tissues of patients contain not only full-length TTR but also C-terminal TTR fragments. However, in vivo models to evaluate the pathogenicity of TTR fragments have not yet been developed. Here, we generated transgenic Caenorhabditis elegans strains expressing several types of TTR fragments or full-length TTR fused to enhanced green fluorescent protein in the body wall muscle cells and analyzed the phenotypes of the worms. The transgenic strain expressing residues 81-127 of TTR, which included the β-strands F and H, formed aggregates and caused defective worm motility and a significantly shortened lifespan compared with other strains. These findings suggest that the C-terminal fragments of TTR may contribute to cytotoxicity of TTR amyloidosis in vivo. By using this C. elegans model system, we found that (-)-epigallocatechin-3-gallate, a major polyphenol in green tea, significantly inhibited the formation of aggregates, the defective motility, and the shortened lifespan caused by residues 81-127 of TTR. These results suggest that our newly developed C. elegans model system will be useful for in vivo pathological analyses of TTR amyloidosis as well as drug screening.

Origin of sporadic late-onset hereditary ATTR Val30Met amyloidosis in Japan

Hereditary transthyretin (ATTRm) amyloidosis, formerly known as familial amyloid polyneuropathy, is a major type of hereditary systemic amyloidosis, in which the disease is caused by mutant transthyretin (TTR). Although more than 140 different point mutations have been identified in the TTR gene, ATTRm amyloidosis patients with the TTR Val30Met mutation are most frequently found worldwide. Interestingly, the onset age of the ATTR Val30Met amyloidosis is highly varied among countries and regions. The reason for these differences in onset age and penetrance remains to be elucidated. We recently performed an epidemiological study to analyze the clinical and genetic characteristics of ATTRm amyloidosis patients in Japan. Our results led us to the following questions: Why did most of the non-endemic patients with the same TTR Val30Met mutation not have a family history of the disease, a typical autosomal dominant hereditary disorder? Why does ATTR Val30Met amyloidosis alone demonstrate foci of occurrence? Why is only this type of ATTRm amyloidosis nationally and globally distributed? In this mini-review, we discuss these unanswered questions based on recent genetic epidemiological studies on ATTR Val30Met amyloidosis.

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.

Newer Therapies for Amyloid Cardiomyopathy

The heart and the kidneys are the most commonly involved organs in systemic amyloidosis. Cardiac involvement is associated with an increased morbidity, treatment intolerance, and poorer overall survival. The most common types of amyloidosis that are associated with cardiac involvement include light chain (AL) amyloidosis and transthyretin (TTR) amyloidosis (both mutant and wild type). The traditional first-line treatment for AL amyloidosis includes alkylator-based chemotherapy or high-dose melphalan followed by autologous stem cell transplantation (ASCT). Novel agents, including proteasome inhibitors, immunomodulators, and monoclonal antibodies, have shown promising activity in both frontline and relapsed settings. Orthotopic heart transplantation (OHT) followed by ASCT has led to superior outcomes compared to OHT alone. Orthotopic liver transplantation (OLT) is the first-line treatment for TTR amyloidosis. However, progression of cardiac amyloidosis after OLT is often noted due to deposition of wild TTR. Combined OLT and OHT also has a role in treatment and leads to superior outcomes in carefully selected candidates. Pharmacologic agents, including diflunisal, tafamidis, small interfering ribonucleic acid, and doxycycline, have shown promising activity in stabilizing TTR from misfolding into fibrils and are being actively investigated. Best supportive care and management of heart failure symptoms with diuretics are a mainstay of treatment in all cardiac amyloidosis subtypes. Robust data on the benefit of angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, or beta blockers in amyloid cardiomyopathy is lacking.

Early skin denervation in hereditary and iatrogenic transthyretin amyloid neuropathy

Objective:

To elucidate early skin denervation in hereditary transthyretin (TTR) amyloidosis and iatrogenic TTR amyloidosis.

Methods:

We investigated intraepidermal nerve fiber density (IENFD) and clinical findings in 32 patients with hereditary TTR amyloidosis, 11 asymptomatic mutation carriers, 6 patients with iatrogenic TTR amyloidosis, and 23 healthy volunteers.

Results:

IENFD values were reduced in patients with the V30M mutation (1.9 ± 2.1 per 1 mm), patients with non-V30M mutations (5.8 ± 3.2 per 1 mm), and patients with iatrogenic TTR amyloidosis (3.5 ± 1.8 per 1 mm) compared with healthy volunteers (11.8 ± 3.2 per 1 mm) (p < 0.01). Skin denervation also occurred, even in presymptomatic V30M mutation carriers (5.0 ± 2.2 per 1 mm). The IENFD was correlated with disease duration (ρ = −0.533, p = 0.002) and various peripheral neuropathy parameters such as sensory impairment in the Kumamoto clinical score (ρ = −0.575, p = 0.001), heat-pain detection threshold (ρ = −0.704, p < 0.001), and sural sensory nerve action potential (ρ = 0.481, p = 0.005). TTR amyloid deposits frequently occurred in connective tissues and vessels of the dermal reticular layer in patients with hereditary TTR amyloidosis and those with iatrogenic TTR amyloidosis.

Conclusions:

Patients with hereditary TTR amyloidosis and those with iatrogenic TTR amyloidosis may show early skin denervation even in the presymptomatic stage. IENFD may thus be useful for early diagnosis and may serve as a biomarker in clinical trials for hereditary and iatrogenic TTR amyloidosis.

CSP-1103 (CHF5074) stabilizes human transthyretin in healthy human subjects

Hereditary amyloid polyneuropathy is a type of protein misfolding disease. Transthyretin (TTR) is a homotetrameric serum protein and TTR tetramer dissociation is the limiting step in amyloid fibril formation. Thus, prevention of TTR dissociation is a promising therapeutic approach and some TTR stabilizers have been approved for the treatment of TTR amyloidosis. CSP-1103 (CHF5074) is a non-steroidal anti-inflammatory derivative that lacks cyclooxygenase inhibitory activity. In vitro, CSP-1103 stabilizes the TTR tetramer by binding to the thyroxine (T4) binding site. We have previously shown that serum TTR levels were increased by oral CSP-1103 administration through stabilization of TTR tetramers in humanized mice at both the Ttr locus and the Rbp4 locus. To determine whether CSP-1103 stabilizes TTR tetramers in humans, multiple CSP-1103 oral doses were administered for two weeks to 48 healthy human volunteers in a double-blind, placebo-controlled, parallel-group study. CSP-1103 treatment stabilized TTR tetramers in a dose-dependent manner under normal or denaturing stress conditions, thereby increasing serum TTR levels. Preincubation of serum with CSP-1103 or diflunisal in vitro increased the TTR tetramer stability. Computer simulation analysis revealed that the binding affinities of CSP-1103 with TTR at pH 7.0 were similar to those of tafamidis, thus confirming that CSP-1103 has potent TTR-stabilizing activity.

Clinicopathological and biochemical findings of thyroid amyloid in hereditary transthyretin amyloidosis with and without liver transplantation

Hereditary transthyretin (TTR) amyloidosis is a fatal disease causing systemic organ dysfunctions. Histopathological studies revealed that thyroid glands are major target tissues. However, details about thyroid functions remain to be fully elucidated in this disease. For patient treatment, liver transplantation (LT) reportedly prolongs patient survival, but thyroid gland function after LT still remains poorly understood. In this study, we investigated the thyroid functions in 101 patients with hereditary TTR amyloidosis and the effects of LT on thyroid functions in those patients. In addition, we investigated histopathological and biochemical findings of thyroid specimens obtained at autopsy. Disease duration and age at examination inversely correlated with serum levels of free triiodothyronine (fT3) in hereditary TTR amyloidosis. On the contrary, in patients who underwent transplantation, time from disease onset to transplantation and age at transplantation clearly correlated with serum fT3and thyroid stimulating hormone (TSH) levels. In autopsy studies, amounts of thyroid amyloid deposits in patients with transplantation were significantly lower than those in patients without transplantation. Mass spectrometric analyzes also revealed that proportions of wild-type (WT) TTR in thyroid amyloid deposits in patients with hereditary TTR amyloidosis who underwent transplantations were higher than those in patients without transplantation. Thyroid hormone functions may diminish according to the disease progression. LT could prevent thyroid dysfunction in hereditary TTR amyloidosis.

Iatrogenic amyloid polyneuropathy after domino liver transplantation

Liver transplantation has been used in treatment of transthyretin amyloidosis, and some patients undergo domino liver transplantation (DLT) with explanted liver being transplanted to another patient with liver failure as the liver is otherwise usually functionally normal. Until end of 2015, there were 1154 DLT performed worldwide. DLT for transthyretin amyloidosis is associated with the risk of developing de novo systemic amyloidosis and amyloid neuropathy, and the risk may be greater with some non-Val30Met mutations. De novo amyloid neuropathy has been described in up to 23% of transplant recipients. Neuropathy may be preceded by asymptomatic amyloid deposition in various tissues and symptoms of neuropathy started after a median of 7 years following DLT (5.7 ± 3.2 years; range 2 mo to 10 years). Typical initial symptoms include neuropathic pain and sensory loss, while dysautonomia usually starts later. Progression of neuropathy may necessitate liver re-transplantation, and subsequent improvement of neuropathy has been reported in some patients. Explant allograft recipients need close monitoring for signs of systemic amyloidosis, neuropathy and dysautonomia as progressive symptoms may require re-transplantation.

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.

Advances in proteomic study of cardiac amyloidosis: progress and potential

INTRODUCTION

More than ten distinct forms of amyloidoses that can involve the heart have been described, classified according to which protein originates the deposits. Cardiac amyloid infiltration translates into progressive and often life-threatening cardiomyopathy, but disease severity, prognosis and treatment drastically differ according to the amyloidosis type. The notion that protein misfolding and aggregation play a more general role in human cardiomyopathies has further raised attention towards the definition of the proteotoxicity mechanisms. Areas covered: Mass spectrometry-based proteomics plays an important role as a diagnostic tool and for understanding the molecular bases of amyloid cardiomyopathies. The landscape of applications of proteomics to the study of cardiac amyloidoses and amyloid-related cardiotoxicity is summarized, with a critical synthesis of the major achievements. Expert commentary: Current strengths and limitations of proteomics in the clinical setting and in translational research on amyloid cardiomyopathy are discussed, with the foreseen potential future directions in the field.

Involvement of Macrophages in the Pathogenesis of Familial Amyloid Polyneuropathy and Efficacy of Human iPS Cell-Derived Macrophages in Its Treatment

We hypothesized that tissue-resident macrophages in familial amyloid polyneuropathy (FAP) patients will exhibit qualitative or quantitative abnormalities, that may accelerate transthyretin (TTR)-derived amyloid deposition. To evaluate this, we examined the number and subset of tissue-resident macrophages in heart tissue from amyloid-deposited FAP and control patients. In both FAP and control patients, tissue-resident macrophages in heart tissue were all Iba⁺/CD163⁺/CD206⁺ macrophages. However, the number of macrophages was significantly decreased in FAP patients compared with control patients. Furthermore, the proportion of intracellular TTR in CD14⁺ monocytes was reduced in peripheral blood compared with healthy donors. Based on these results, we next examined degradation and endocytosis of TTR in human induced pluripotent stem (iPS) cell-derived myeloid lineage cells (MLs), which function like macrophages. iPS-MLs express CD163 and CD206, and belong to the inhibitory macrophage category. In addition, iPS-MLs degrade both native and aggregated TTR in a cell-dependent manner in vitro. Further, iPS-MLs endocytose aggregated, and especially polymerized, TTR. These results suggest that decreased tissue-localized macrophages disrupt clearance of TTR-derived amyloid deposits, leading to progression of a pathological condition in FAP patients. To improve this situation, clinical application of pluripotent stem cell-derived MLs may be useful as an approach for FAP therapy.

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.

Representation of illness in Familial Amyloidotic Polyneuropathy Portuguese Association newspaper: A documental study

This study explores illness representations within Familial Amyloidotic Polyneuropathy Portuguese Association newspaper . A content analysis was performed of the issue data using provisional coding related to the conceptual framework of the study. All dimensions of illness representation in Leventhal's Common Sense Model of illness cognitions and behaviors are present in the data and reflect the experience of living with this disease. Understanding how a person living with an hereditary, rare, neurodegenerative illness is important for developing community nursing interventions. In conclusion, we suggest an integration of common sense knowledge with other approaches for designing an intervention program centered on people living with an hereditary neurodegenerative illness, such as familial amyloidotic polyneuropathy.

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.

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

OBJECTIVES

Since liver transplant (LT) was introduced to treat patients with familial amyloid polyneuropathy carrying the V30M mutation (ATTR-V30M), ocular and cardiac complications have developed. Long-term central nervous system (CNS) involvement was not investigated. Our goals were to: (1) identify and characterise focal neurological episodes (FNEs) due to CNS dysfunction in ATTR-V30M patients; (2) characterise neuropathological features and temporal profile of CNS transthyretin amyloidosis.

METHODS

We monitored the presence and type of FNEs in 87 consecutive ATTR-V30M and 35 non-ATTR LT patients. FNEs were investigated with CT scan, EEG and extensive neurovascular workup. MRI studies were not performed because all patients had cardiac pacemakers as part of the LT protocol. We characterised transthyretin amyloid deposition in the brains of seven ATTR-V30M patients, dead 3-13 years after polyneuropathy onset.

RESULTS

FNEs occurred in 31% (27/87) of ATTR-V30M and in 5.7% (2/35) of the non-ATTR transplanted patients (OR=7.0, 95% CI 1.5 to 33.5). FNEs occurred on average 14.6 years after disease onset (95% CI 13.3 to 16.0) in ATTR-V30M patients, which is beyond the life expectancy of non-transplanted ATTR-V30M patients (10.9, 95% CI 10.5 to 11.3). ATTR-V30M patients with FNEs had longer disease duration (OR=1.24; 95% CI 1.07 to 1.43), renal dysfunction (OR=4.65; 95% CI 1.20 to 18.05) and were men (OR=3.57; 95% CI 1.02 to 12.30). CNS transthyretin amyloidosis was already present 3 years after polyneuropathy onset and progressed from the meninges and its vessels towards meningocortical vessels and the superficial brain parenchyma, as disease duration increased.

CONCLUSIONS

Our findings indicate that CNS clinical involvement occurs in ATTR-V30M patients regardless of LT. Longer disease duration after LT can provide the necessary time for transthyretin amyloidosis to progress until it becomes clinically relevant. Highly sensitive imaging methods are needed to identify and monitor brain ATTR. Disease modifying therapies should consider brain TTR as a target.

Oligomeric TTR V30M aggregates compromise cell viability, erythropoietin gene expression and promoter activity in the human hepatoma cell line Hep3B

Familial amyloidotic polyneuropathy, ATTRV30M (p. TTRV50M) amyloidosis, is a neurodegenerative disease characterized by systemic extracellular amyloid deposition of a mutant transthyretin, TTR V30M. Anemia, with low erythropoietin (EPO) levels and spared kidney function, affects about 25% of symptomatic patients, suggesting a blockage of EPO-producing cells. Early non-fibrillar TTR aggregates are highly cytotoxic, inducing oxidative stress, the expression of apoptosis-related molecules and secretion of pro-inflammatory cytokines, factors capable of inhibiting EPO production. Low EPO levels in these patients are not related to renal amyloid deposition or the presence of circulating TTR V30M. However, the role of early non-fibrillar TTR aggregates remains unexplored. We used the EPO producing Hep3B human hepatoma cell line to study the effect of TTR oligomeric aggregates on EPO expression. Hep3B cells were incubated with soluble and oligomeric TTR V30M, and cell proliferation as well as caspase 3/7 activation was evaluated. Relative quantification of EPO mRNA transcripts was performed by real-time PCR. Significant reductions in cell viability (13 ± 7.3%) and activation of caspases 3/7 were seen after 24 h in the presence of oligomeric TTR V30M. Also, EPO expression was significantly reduced (50 ± 2.8%), in normoxic conditions. A reporter assay was constructed with a PCR fragment of the EPO promoter linked to the luciferase gene to evaluate the role of transcription factors targeting the promoter. A significant reduction of EPO promoter activity (53 ± 6.5%) was observed in transfected cells exposed to TTR oligomers. Our results show that oligomeric TTR V30M reduces EPO expression, at least in part through inhibition of promoter activity.

FAP neuropathy and emerging treatments

Transthyretin familial amyloid polyneuropathy (TTR-FAP) classically presents as a length dependent small fiber polyneuropathy in endemic countries like Portugal. In nonendemic countries, it may mimic a variety of chronic polyneuropathies, with several phenotypes: ataxic, upper limb onset neuropathy, or motor. In these cases, there is usually a late onset and no positive family history. TTR gene sequencing appears the most pertinent first-line test for diagnosis. Cardiac involvement of various severities is common in FAP. Liver transplantation remains the standard antiamyloid therapy with better results in Val30Met TTR-FAP of early onset. Antiamyloid medication has been developed. (1) TTR stabilizers: Tafamidis was the first drug approved in Europe in stage 1 (walking unaided) TTR-FAP to slow progression of the disease; diflunisal has been assessed in a phase 3 clinical trial; (2) TTR gene silencing is a new strategy to inhibit production of both mutant and nonmutant TTR with antisense oligonucleotides or SiRNA (2 ongoing phase 3 clinical trials).

Recent advances in transthyretin amyloidosis therapy

Mutant (MT) forms of transthyretin (TTR) cause the most common type of autosomal-dominant hereditary systemic amyloidosis-familial amyloidotic polyneuropathy (FAP). Until 20 years ago, FAP was thought to be an endemic disease, but FAP is known to occur worldwide. To date, more than 130 mutations in the TTR gene have been reported. Genotype-phenotype correlations are seen in FAP, and some variation in clinical presentation is often observed in individual kindreds with the same mutation and even among family members. Of the pathogenic TTR mutations, Val30Met was the first to be identified and is the most frequent known mutation found throughout the world. Studies of patients with FAP amyloidogenic TTR (ATTR) Val30Met documented sensorimotor polyneuropathy, autonomic dysfunction, heart and kidney failure, gastrointestinal tract (GI) disorders, and other symptoms leading to death, usually within 10 years of the onset of disease. Diagnosis is sometimes delayed, especially in patients without a clear family history and typical clinical manifestations, since diagnosis requires various studies and techniques such as histopathology, genetic testing, and mass spectrometry. For treatment of FAP, liver transplantation (LT) reportedly halts the progression of clinical manifestations. Exchange of an FAP patient's diseased liver with a healthy liver causes MT TTR in the body to be replaced by wild-type (WT) TTR. Although clinical evaluations indicated that progression of other clinical symptoms such as peripheral neuropathy, GI symptoms, and renal involvement usually halted after LT in FAP ATTR Val30Met patients, recent studies suggested that LT failed to prevent progression of cardiac amyloidosis in FAP ATTR Val30Met patients after LT, with this failure reportedly being due to continued formation of amyloid that derived mainly from WT TTR secreted from the transplanted non-mutant liver graft. In recent years, many therapeutic strategies have been proposed, and several ongoing therapeutic trials involve, for example, stabilizers of TTR tetramers (tafamidis and diflunisal) and gene therapies to suppress TTR expression (antisense methods and use of small interfering RNAs). These novel therapies may prove to prevent progression of FAP.