Estimating the global prevalence of transthyretin familial amyloid polyneuropathy

Arginine: A potential prophylactic supplement for transthyretin amyloidosis

Transthyretin (TTR) is an amyloidogenic protein associated with TTR amyloidosis (ATTR). Dissociation of TTR tetramers into TTR monomers causes TTR misfolding, resulting in amyloid fibril formation and triggering the onset of ATTR. Low-molecular-weight tetrameric TTR stabilizers are potential therapeutic agents to delay ATTR progression. However, the currently available drugs are expensive and cannot be used for prophylaxis. Therefore, in this study, we aimed to identify a prophylactic supplement that suppresses TTR amyloid formation. We investigated whether arginine, an amyloidogenic protein aggregation inhibitor, stabilizes tetrameric TTR, thereby preventing amyloid fibril formation. Immunoblotting showed that arginine mixed with wild-type TTR (TTRwt), amyloidogenic TTR Val30Met (ATTR V30M), and human serum samples reduced the amount of monomeric TTR but increased the tetramer/monomer ratio of TTR compared to those in the samples without arginine. Additionally, oral administration of arginine (5000 mg for 5 days) to healthy volunteers effectively increased the tetramer/monomer ratio of TTR in the serum. Thioflavin T test, a quantitative analysis method for amyloid fibril formation, showed that amyloid fibril formation was significantly suppressed with arginine compared to that without arginine. As arginine is a common supplement and non-toxic amino acid, it can be used as a promising prophylactic supplement to suppress amyloid fibril formation in ATTR.

Clinical Cues for the Early Diagnosis of Transthyretin-Related Polyneuropathy

BACKGROUND AND PURPOSE

The estimated prevalence of hereditary transthyretin-related familial amyloid polyneuropathy (TTR-FAP) and the small number of known patients in Germany indicate that many patients with TTR-FAP remain undiagnosed, and may instead be classified as "idiopathic." The aim of this study was to identify biomarkers for detecting TTR-FAP among a cohort of patients with idiopathic polyneuropathy (PNP).

METHODS

Clinical evaluations (including the Neuropathy Impairment Score and Neuropathy Disability Score), nerve conduction studies (NCSs), quantitative sensory testing, and autonomic function tests were performed on 23 patients with TTR-FAP and 89 with idiopathic PNP. Discriminant analysis was then performed to identify variables useful for predicting TTR-FAP.

RESULTS

Patients with TTR-FAP had paresis of the finger and thumb muscles, and reduced vibration perception and increased pressure pain in the upper and lower extremities. The NCSs showed that action potentials were smaller in the median, ulnar (both motor and sensory), and sural nerves in TTR-FAP. The sensory nerve conduction velocity was also reduced in the ulnar nerve. Autonomic neuropathy was confirmed by reduced sympathetic skin responses in the hands and feet in TTR-FAP. Multivariate discriminant analysis revealed that finger abduction strength, sensory ulnar nerve action potential amplitude, and vibration detection and pressure pain thresholds in the upper extremities were sufficient to correctly identify TTR-FAP in 81.3% of cases.

CONCLUSIONS

Detailed clinical and neurophysiological investigations of standard parameters in the upper limb may help to identify the otherwise-rare TTR-FAP.

Switching from inotersen to eplontersen in patients with hereditary transthyretin-mediated amyloidosis with polyneuropathy: analysis from NEURO-TTRansform

BACKGROUND

The phase 3 NEURO-TTRansform trial showed eplontersen treatment for 65 weeks reduced transthyretin (TTR), halted progression of neuropathy impairment, and improved quality of life (QoL) in adult patients with hereditary TTR-mediated amyloidosis with polyneuropathy (ATTRv-PN), vs. historical placebo.

METHODS

NEURO-TTRansform enrolled patients with ATTRv-PN. A subset of patients were randomized to receive subcutaneous inotersen 300 mg weekly (Weeks 1-34) and subsequently switched to subcutaneous eplontersen 45 mg every 4 weeks (Weeks 37-81). Change in serum TTR and treatment-emergent adverse events (TEAEs) were evaluated through Week 85. Effects on neuropathy impairment, QoL, and nutritional status were also evaluated.

RESULTS

Of 24 patients randomized to inotersen, 20 (83%) switched to eplontersen at Week 37 and four discontinued due to AEs/investigator decision. Absolute change in serum TTR was greater after switching from inotersen (-74.3%; Week 35) to eplontersen (-80.6%; Week 85). From the end of inotersen treatment, neuropathy impairment and QoL were stable (i.e., did not progress) while on eplontersen, and there was no deterioration in nutritional status. TEAEs were fewer with eplontersen (Weeks 37-85; 19/20 [95%] patients) compared with inotersen (up to Week 35; 24/24 [100%] patients). Mean platelet counts decreased during inotersen treatment (mean nadir reduction ‒40.7%) and returned to baseline during eplontersen treatment (mean nadir reduction, ‒3.2%).

CONCLUSIONS

Switching from inotersen to eplontersen further reduced serum TTR, halted disease progression, stabilized QoL, restored platelet count, and improved tolerability, without deterioration in nutritional status. This supports a positive benefit-risk profile for patients with ATTRv-PN who switch from inotersen to eplontersen.

Amyloid Neuropathy: From Pathophysiology to Treatment in Light-Chain Amyloidosis and Hereditary Transthyretin Amyloidosis

Amyloid neuropathy is caused by deposition of insoluble β-pleated amyloid sheets in the peripheral nervous system. It is most common in: (1) light-chain amyloidosis, a clonal non-proliferative plasma cell disorder in which fragments of immunoglobulin, light or heavy chain, deposit in tissues, and (2) hereditary transthyretin (ATTRv) amyloidosis, a disorder caused by autosomal dominant mutations in the TTR gene resulting in mutated protein that has a higher tendency to misfold. Amyloid fibrils deposit in the endoneurium of peripheral nerves, often extensive in the dorsal root ganglia and sympathetic ganglia, leading to atrophy of Schwann cells in proximity to amyloid fibrils and blood-nerve barrier disruption. Clinically, amyloid neuropathy is manifested as a length-dependent sensory predominant neuropathy associated with generalized autonomic failure. Small unmyelinated nerves are involved early and prominently in early-onset Val30Met ATTRv, whereas other ATTRv and light-chain amyloidosis often present with large- and small-fiber involvement. Nerve conduction studies, quantitative sudomotor axon testing, and intraepidermal nerve fiber density are useful tools to evaluate denervation. Amyloid deposition can be demonstrated by tissue biopsy of the affected organ or surrogate site, as well as bone-avid radiotracer cardiac imaging. Treatment of light-chain amyloidosis has been revolutionized by monoclonal antibodies and stem cell transplantation with improved 5-year survival up to 77%. Novel gene therapy and transthyretin stabilizers have revolutionized treatment of ATTRv, improving the course of neuropathy (less change in the modified Neuropathy Impairment Score + 7 from baseline) and quality of life. With great progress in amyloidosis therapies, early diagnosis and presymptomatic testing for ATTRv family members has become paramount. ANN NEUROL 2024;96:423-440.

Transthyretin amyloid polyneuropathy in France: A cross-sectional study with 413 patients and real-world tafamidis meglumine use (2009-2019)

OBJECTIVE

We aimed to describe characteristics of patients with ATTR variant polyneuropathy (ATTRv-PN) and ATTRv-mixed and assess the real-world use and safety profile of tafamidis meglumine 20mg.

METHODS

Thirty-eight French hospitals were invited. Patient files were reviewed to identify clinical manifestations, diagnostic methods, and treatment compliance.

RESULTS

Four hundred and thirteen patients (296 ATTRv-PN, 117 ATTRv-mixed) were analyzed. Patients were predominantly male (68.0%) with a mean age of 57.2±17.2 years. Interval between first symptom(s) and diagnosis was 3.4±4.3 years. First symptoms included sensory complaints (85.9%), dysautonomia (38.5%), motor deficits (26.4%), carpal tunnel syndrome (31.5%), shortness of breath (13.3%), and unexplained weight loss (16.0%). Mini-invasive accessory salivary gland or punch skin and nerve biopsies were most common, with a performance of 78.8-100%. TTR genetic sequencing, performed in all patients, revealed 31 TTR variants. Tafamidis meglumine was initiated in 156/214 (72.9%) ATTRv-PN patients at an early disease stage. Median treatment duration was 6.00 years in ATTRv-PN and 3.42 years in ATTRv-mixed patients. Tafamidis was well tolerated, with 20 adverse events likely related to study drug among the 336 patients.

CONCLUSION

In France, ATTRv patients are usually identified early thanks to the national network and the help of diagnosis combining genetic testing and mini-invasive biopsies.

Evaluation of small fibre neuropathies

Small fibre neuropathies (SFNs) are common and can significantly affect patients' lives due to debilitating pain and autonomic symptoms. We explain the tests that neurologists can use to diagnose SFNs and how neurophysiologists perform and interpret them. This review focuses on neurophysiological tests that can be used to investigate SFNs, their sensitivity, specificity and limitations. Some of these tests are available only in specialist centres. However, newer technologies are emerging from scientific research that may make it easier to diagnose these conditions in the future.

"Living with a question mark": psychosocial experience of Portuguese young adults at risk for hereditary amyloid transthyretin amyloidosis with polyneuropathy

This study is the first to explore the psychosocial experience of young Portuguese adults at genetic risk for hereditary amyloid transthyretin amyloidosis with polyneuropathy (hATTR-PN). The work focuses on the developmental peculiarities of their experience with the disease. Sixteen semi-structured interviews were conducted with young adults coming for pre-symptomatic testing (PST) at a single genetics outpatient center in Portugal. The data were analyzed qualitatively. The main findings suggest that four themes mark the psychosocial experience of the young adults interviewed. The first refers to the development of psychological representations, namely beliefs, mental representations, and social perceptions about hATTR-PN. The second regards the experienced and anticipated psychosocial impacts, namely, suffering, anxiety, and relief related to the disease. The third is related to using strategies such as performing PST, strategies focused on emotional regulation and the meaning of hATTR-PN, and social strategies to deal with these impacts over time. Finally, the fourth aspect concerns the perceived and expected support for the participants' needs provided by social contexts, that is, family and genetic counseling. In a period of life also marked by qualitatively different characteristics and developmental tasks from other life cycle stages (e.g., identity explorations, instability, and independent decision-making), experience with the disease can add psychosocial challenges to young adults at risk for hATTR-PN. Genetic counseling practices and health policies can be optimized to respond to the psychosocial needs of young adults. Future research should deepen the understanding of the psychosocial experience of individuals and families with late-onset hATTR-PN to improve the clinical response in this population.

Structural and thermodynamic characterization of a highly amyloidogenic dimer of transthyretin involved in a severe cardiomyopathy

Transthyretin (TTR) is an homotetrameric protein involved in the transport of thyroxine. More than 150 different mutations have been described in the TTR gene, several of them associated with familial amyloid cardiomyopathy. Recently, our group described a new variant of TTR in Brazil, namely A39D-TTR, which causes a severe cardiac condition. Position 39 is in the AB loop, a region of the protein that is located within the thyroxine-binding channels and is involved in tetramer formation. In the present study, we solved the structure and characterize the thermodynamic stability of this new variant of TTR using urea and high hydrostatic pressure. Interestingly, during the process of purification, A39D-TTR turned out to be a dimer and not a tetramer, a variation that might be explained by the close contact of the four aspartic acids at position 39, where they face each other inside the thyroxine channel. In the presence of subdenaturing concentrations of urea, bis-ANS binding and dynamic light scattering revealed A39D-TTR in the form of a molten-globule dimer. Co-expression of A39D and WT isoforms in the same bacterial cell did not produce heterodimers or heterotetramers, suggesting that somehow a negative charge at the AB loop precludes tetramer formation. A39D-TTR proved to be highly amyloidogenic, even at mildly acidic pH values where WT-TTR does not aggregate. Interestingly, despite being a dimer, aggregation of A39D-TTR was inhibited by diclofenac, which binds to the thyroxine channel in the tetramer, suggesting the existence of other pockets in A39D-TTR able to accommodate this molecule.

Early diagnosis in ATTRv amyloidosis, how early is enough? How early is possible?

Hereditary transthyretin amyloidosis (ATTRv amyloidosis) is a rare, progressive, and debilitating genetic disorder characterized by the deposition of abnormal transthyretin (TTR) protein aggregates in various tissues, leading to organ dysfunction. Early diagnosis of ATTRv amyloidosis is critical for starting timely interventions and improving patient outcomes. This review explores the concepts of "how early is enough" and "how early is possible" in the context of diagnosing ATTRv amyloidosis, highlighting the challenges and opportunities for early recognition.

Transthyretin mutagenesis: impact on amyloidogenesis and disease

Transthyretin (TTR), a homotetrameric protein found in plasma, cerebrospinal fluid, and the eye, plays a pivotal role in the onset of several amyloid diseases with high morbidity and mortality. Protein aggregation and fibril formation by wild-type TTR and its natural more amyloidogenic variants are hallmarks of ATTRwt and ATTRv amyloidosis, respectively. The formation of soluble amyloid aggregates and the accumulation of insoluble amyloid fibrils and deposits in multiple tissues can lead to organ dysfunction and cell death. The most frequent manifestations of ATTR are polyneuropathies and cardiomyopathies. However, clinical manifestations such as carpal tunnel syndrome, leptomeningeal, and ocular amyloidosis, among several others may also occur. This review provides an up-to-date listing of all single amino-acid mutations in TTR known to date. Of approximately 220 single-point mutations, 93% are considered pathogenic. Aspartic acid is the residue mutated with the highest frequency, whereas tryptophan is highly conserved. "Hot spot" mutation regions are mainly assigned to β-strands B, C, and D. This manuscript also reviews the protein aggregation models that have been proposed for TTR amyloid fibril formation and the transient conformational states that convert native TTR into aggregation-prone molecular species. Finally, it compiles the various in vitro TTR aggregation protocols currently in use for research and drug development purposes. In short, this article reviews and discusses TTR mutagenesis and amyloidogenesis, and their implications in disease onset.

Identification and management of gastrointestinal manifestations of hereditary transthyretin amyloidosis: Recommendations from an Italian group of experts

Gastrointestinal manifestations are common across all hereditary transthyretin amyloidosis (ATTRv) genotypes. However, they are poorly specific, and their recognition as part of ATTRv is difficult, resulting in misdiagnosis with more common conditions. Moreover, delays in diagnosis occur because of fragmented knowledge, a shortage of centers of excellence and specialists dedicated to ATTRv management, and the scarce involvement of gastroenterologists in multidisciplinary teams. A group of Italian gastroenterologists with experience in the management of ATTRv took part in a project aimed at assessing the awareness of ATTRv among the community of Italian gastroenterologists through an online survey and providing education about practical aspects of ATTRv management. Survey results reported low participation, and very few patients with ATTRv were cared for by gastroenterologists. This highlights the need for greater attention to rare diseases in gastroenterology and emphasizes increasing awareness of ATTRv and diagnostic suspicion. Based on the experts' recommendations, a diagnosis of ATTRv should be suspected when at least one of the 'red flags' is detected. Subsequently, it is suggested to promptly ask for genetic testing and exclude a serum and urinary monoclonal protein, even before the detection of amyloid in biopsy samples, particularly in non-endemic areas.

Epidemiology and distribution of 207 rare diseases in China: A systematic literature review

Epidemiological data on rare diseases in China are currently limited. The objective of this study was to provide a comprehensive understanding of the prevalence and incidence of rare diseases by systematically analyzing the available epidemiological data. We conducted a comprehensive search of English and Chinese databases, the Incidence and Prevalence Database, the Chinese Rare Disease Guideline, and the Taiwan Health Promotion Administration from 2010 to 2023. We identified the top diseases and regions based on epidemiological data and present the maximum, minimum, and median prevalence and incidence values in tables and forest plots. 1,264 prevalence and incidence data were retrieved from 277 studies, guidelines and official websites, covering 110 rare diseases (53.1%) and 32 regions (94.1%). In terms of geographical regions, incidence or prevalence data were available for 32 regions (94.1%), excluding Tibet Hui Autonomous Region and Macao Special Administrative Region. In terms of rate, 60 and 77 out of 207 diseases (29.0% and 37.2%) had available incidence and prevalence data, respectively. Eight diseases had an incidence rate equal to or greater than that of 1,000 patients per million. The present study provides a comprehensive epidemiological analysis and valuable insights into the prevalence and incidence of rare diseases in China. Our findings underscore the pressing need for sustained drug research and medical support for individuals and families impacted by rare diseases.

A real-world pharmacovigilance analysis for transthyretin inhibitors: findings from the FDA adverse event reporting database

Objective

The purpose of this study is to investigate the drug safety of three Transthyretin (TTR) inhibitors in the real world using the United States Food and Drug Administration Adverse Event Reporting System (FAERS) database.

Methods

This study extracted reports received by the FAERS database from the first quarter of 2018 to the third quarter of 2023 for descriptive analysis and disproportionality analysis. Safety signal mining was conducted at the Preferred Term (PT) level and the System Organ Class (SOC) level using reporting odds ratio (ROR). The characteristics of the time-to-onset curves were analyzed using the Weibull Shape Parameter (WSP). The cumulative incidence of TTR inhibitors was evaluated using the Kaplan-Meier method. Subgroup analyses were conducted based on whether the reporter was a medical professional.

Results

A total of 3,459 reports of adverse events (AEs) caused by TTR inhibitors as the primary suspect (PS) drug were extracted. The top three reported AEs for patisiran were fatigue, asthenia, and fall, with the most unexpectedly strong association being nonspecific reaction. The top three reported AEs for vutrisiran were fall, pain in extremity and malaise, with the most unexpectedly strong association being subdural haematoma. The top three reported AEs for inotersen were platelet count decreased, blood creatinine increased, and fatigue, with the most unexpectedly strong association being blood albumin decreased. Vitamin A decreased, arthralgia, and dyspnea were the same AEs mentioned in the drug labels of all three drugs, while malaise and asthenia were the same unexpected significant signals. This study offers evidence of the variability in the onset time characteristics of AEs associated with TTR inhibitors, as well as evidence of differences in adverse event reporting between medical professionals and non-medical professionals.

Conclusion

In summary, we compared the similarities and differences in drug safety of three TTR inhibitors in the real world using the FAERS database. The results indicate that not only do these three drugs share common AEs, but they also exhibit differences in drug safety profiles. This study contributes to enhancing the understanding of medical professionals regarding the safety of TTR inhibitors.

Late-onset familial amyloidosis polyneuropathy associated with c.186G>C in transthyretin

INTRODUCTION

The most common form of hereditary amyloidosis is associated with variants of transthyretin (TTR). Familial amyloidosis polyneuropathy associated with variants of TTR (FAP-TTR) is an infrequent, multisystemic disease, with predominant involvement of the peripheral nervous system. More than 130 pathogenic variants have been identified so far and most of them are amyloidogenic, being Val30Met the most frequently described.

CASE REPORT

A 74 year-old male was evaluated for progressive decreased sensitivity and associated loss of strength in four limbs in the previous two years, needing assistance for walking. Areflexia, bilateral tibialis anterior and gastrocnemius atrophy, bilateral anesthesia and apalesthesia were found in lower limbs. Bilateral hypoesthesia was reported in upper limbs. No painful dysesthesia, hyperalgesia or allodynia were found. DNA sequencing of the TTR gene led to the detection of the variant c.186G>C in heterozygous state. The resulting variant (Glu62Asp), located in the critical functional domain, has not been published before.

CONCLUSION

The importance of considering late onset, sporadic FAP-TTR as a differential diagnosis of cryptogenic polyneuropathy is highlighted.

Hereditary transthyretin amyloidosis in middle-aged and elderly patients with idiopathic polyneuropathy: a nationwide prospective study

BACKGROUND

Hereditary transthyretin amyloidosis (ATTRv) is an adult-onset autosomal dominant disease resulting from TTR gene pathogenic variants. ATTRv often presents as a progressive polyneuropathy, and effective ATTRv treatments are available.

METHODS

In this 5 year-long (2017-2021) nationwide prospective study, we systematically analysed the TTR gene in French patients with age >50 years with a progressive idiopathic polyneuropathy.

RESULTS

553 patients (70% males) with a mean age of 70 years were included. A TTR gene pathogenic variant was found in 15 patients (2.7%), including the Val30Met TTR variation in 10 cases. In comparison with patients with no TTR gene pathogenic variants (n = 538), patients with TTR pathogenic variants more often presented with orthostatic hypotension (53 vs. 21%, p = .007), significant weight loss (33 vs 11%, p = .024) and rapidly deteriorating nerve conduction studies (26 vs. 8%, p = .03). ATTRv diagnosis led to amyloid cardiomyopathy diagnosis in 11 cases, ATTRv specific treatment in all cases and identification of 15 additional ATTRv cases among relatives.

CONCLUSION

In this nationwide prospective study, we found ATTRv in 2.7% of patients with age >50 years with a progressive polyneuropathy. These results are highly important for the early identification of patients in need of disease-modifying treatments.

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.

The conformational landscape of human transthyretin revealed by cryo-EM

Transthyretin (TTR) is a natively tetrameric thyroxine transporter found in blood and cerebrospinal fluid whose misfolding and aggregation causes transthyretin amyloidosis. A rational drug design campaign identified the small molecule tafamidis (Vyndaqel/Vyndamax) as an effective stabilizer of the native TTR fold, and this aggregation inhibitor is regulatory agency-approved for the treatment of TTR amyloidosis. Despite 50 years of structural studies on TTR and this triumph of structure-based drug design, there remains a notable dearth of structural information available to understand ligand binding allostery and amyloidogenic TTR unfolding intermediates. We used single-particle cryo-electron microscopy (cryo-EM) to investigate the conformational landscape of this 55 kiloDalton tetramer in the absence and presence of one or two ligands, revealing inherent asymmetries in the tetrameric architecture and previously unobserved conformational states. These findings provide critical mechanistic insights into negatively cooperative ligand binding and the structural pathways responsible for TTR amyloidogenesis. This study underscores the capacity of cryo-EM to provide new insights into protein structures that have been historically considered too small to visualize and to identify pharmacological targets suppressed by the confines of the crystal lattice, opening uncharted territory in structure-based drug design.

Genetic screening for hereditary transthyretin amyloidosis with polyneuropathy in western Sicily: Two years of experience in a neurological clinic

BACKGROUND AND PURPOSE

Hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN) is caused by mutations in the TTR gene, leading to misfolded monomers that aggregate generating amyloid fibrils.

METHODS

A prospective systematic genetic screening for ATTRv-PN was proposed in patients presenting with a sensory-motor idiopathic polyneuropathy and two or more "red flags" among the following: family history of polyneuropathy or cardiopathy, bilateral carpal tunnel syndrome, cardiac insufficiency, renal amyloidosis, lumbar tract stenosis, autonomic dysfunction, idiopathic gastrointestinal disease, amyloid deposits on biopsy, and vitreous opacities. The detection rate was calculated, and nonparametric analyses were carried out to underline differences among screened positive versus negative patients.

RESULTS

In the first step, 145 suspected patients underwent genetic testing, revealing a diagnosis of ATTRv-PN in 14 patients (10%). Then, cascade screening allowed early recognition of 33 additional individuals (seven symptomatic ATTRv-PN patients and 26 presymptomatic carriers) among 84 first-degree relatives. Patients with a positive genetic test presented a higher frequency of unexplained weight loss, gastrointestinal symptoms, and family history of cardiopathy.

CONCLUSIONS

A systematic screening for ATTRv-PN yielded an increased recognition of the disease in our neurological clinic. Unexplained weight loss associated with axonal polyneuropathy had the highest predictive value in the guidance of clinical suspicion. A focused approach for the screening of ATTRv-PN could lead to an earlier diagnosis and identification of asymptomatic carriers, who will be promptly treated after a strict follow-up at the clinical onset.

Targeting the Liver with Nucleic Acid Therapeutics for the Treatment of Systemic Diseases of Liver Origin

Systemic diseases of liver origin (SDLO) are complex diseases in multiple organ systems, such as cardiovascular, musculoskeletal, endocrine, renal, respiratory, and sensory organ systems, caused by irregular liver metabolism and production of functional factors. Examples of such diseases discussed in this article include primary hyperoxaluria, familial hypercholesterolemia, acute hepatic porphyria, hereditary transthyretin amyloidosis, hemophilia, atherosclerotic cardiovascular diseases, α-1 antitrypsin deficiency-associated liver disease, and complement-mediated diseases. Nucleic acid therapeutics use nucleic acids and related compounds as therapeutic agents to alter gene expression for therapeutic purposes. The two most promising, fastest-growing classes of nucleic acid therapeutics are antisense oligonucleotides (ASOs) and small interfering RNAs (siRNAs). For each listed SDLO disease, this article discusses epidemiology, symptoms, genetic causes, current treatment options, and advantages and disadvantages of nucleic acid therapeutics by either ASO or siRNA drugs approved or under development. Furthermore, challenges and future perspectives on adverse drug reactions and toxicity of ASO and siRNA drugs for the treatment of SDLO diseases are also discussed. In summary, this review article will highlight the clinical advantages of nucleic acid therapeutics in targeting the liver for the treatment of SDLO diseases. SIGNIFICANCE STATEMENT: Systemic diseases of liver origin (SDLO) contain rare and common complex diseases caused by irregular functions of the liver. Nucleic acid therapeutics have shown promising clinical advantages to treat SDLO. This article aims to provide the most updated information on targeting the liver with antisense oligonucleotides and small interfering RNA drugs. The generated knowledge may stimulate further investigations in this growing field of new therapeutic entities for the treatment of SDLO, which currently have no or limited options for treatment.

Health care resource use, diagnostic delay and disease burden in transthyretin amyloid cardiomyopathy in Sweden

AIMS

To estimate healthcare resource use and direct healthcare costs of Transthyretin Amyloid Cardiomyopathy (ATTR-CM) in Sweden over 12 months across severity stages as defined by the New York Heart Association (NYHA). Secondary to investigate the current diagnostic trajectory for patients with ATTR-CM in Sweden.

METHODS

A stratified inclusion of patients with a confirmed diagnosis of ATTR-CM in different NYHA classes. Data was extracted from medical records in two cardiology clinics in Sweden. Healthcare resource use data were retrospectively collected for 12 months.

RESULTS

38 patients were included, of whom 7 were in NYHA class II, 20 in class III and 4 in class IV. The total cost of health care per patient increased from SEK 69,000 (€6800) in NYHA stage II, SEK 219,000 (€21,500) in NYHA stage III, to SEK 638,000 (€62,900) in stage IV, mainly due to an increase in inpatient stays. Mean time (standard deviation, SD) from any cardiac related diagnosis prior to ATTR-CM diagnosis was 3.5 (3.1) years.

CONCLUSIONS

Advanced ATTR-CM stages are associated with significant healthcare costs, as patients more often require resource-intensive inpatient care. The current diagnostic trajectory of ATTR-CM in this study was characterized by a diagnostic delay of several years.

Hereditary transthyretin amyloidosis in the era of RNA interference, antisense oligonucleotide, and CRISPR-Cas9 treatments

Hereditary transthyretin amyloidosis (ATTRv) is a rare autosomal dominant adult-onset disorder caused by point mutations in the transthyretin (TTR) gene encoding TTR, also known as prealbumin. ATTRv survival ranges from 3 to 10 years, and peripheral nervous system and heart are usually the 2 main tissues affected, although central nervous system and eye may also be involved. Because the liver is the main TTR protein secretor organ, it has been the main target of treatments developed these last years, including liver transplantation, which has been shown to significantly increase survival in a subset of patients carrying the so-called "early-onset Val30Met" TTR gene mutation. More recently, treatments targeting hepatic TTR RNA have been developed. Hepatic TTR RNA targeting is performed using RNA interference (RNAi) and antisense oligonucleotide (ASO) technologies involving lipid nanoparticle carriers or N-acetylgalactosamine fragments. RNAi and ASO treatments induce an 80% decrease in TTR liver production for a period of 1 to 12 weeks. ASO and RNAi phase 3 trials in patients with TTR-related polyneuropathy have shown a positive impact on neuropathy clinical scores and quality of life end points, and delayed RNAi treatment negatively affects survival. Clinical trials specifically investigating RNAi therapy in TTR cardiomyopathy are underway. Hepatic RNA targeting has revolutionized ATTRv treatment and may allow for the transforming a fatal disease into a treatable disorder. Because retina and choroid plexus secrete limited quantities of TTR protein, both tissues are now seen as the next targets for fully controlling the disease.

Hereditary transthyretin amyloid neuropathies: advances in pathophysiology, biomarkers, and treatment

Hereditary transthyretin (TTR) amyloid polyneuropathy is an autosomal dominant life-threatening disorder. TTR is produced mainly by the liver but also by the choroid plexus and retinal pigment epithelium. Detailed clinical characterisation, identification of clinical red flags for misdiagnosis, and use of biomarkers enable early diagnosis and treatment. In addition to liver transplantation and TTR stabilisers, three other disease-modifying therapies have regulatory approval: one antisense oligonucleotide (inotersen) and two small interfering RNAs (siRNAs; patisiran and vutrisiran). The siRNAs have been shown to stop progression of neuropathy and improve patients' quality of life. As none of the disease-modifying therapies can cross the blood-brain barrier, TTR deposition in the CNS, which can cause stroke and cognitive impairment, remains an important unaddressed issue. CRISPR-Cas9-based one-time TTR editing therapy is being investigated in a phase 1 clinical study. Identification of the earliest stages of pathogenesis in TTR variant carriers is a major challenge that needs addressing for optimal management.

Optimal practices for the management of hereditary transthyretin amyloidosis: real-world experience from Japan, Brazil, and Portugal

Hereditary transthyretin (ATTRv) amyloidosis is a rare and autosomal dominant disorder associated with mutations in the transthyretin gene. Patients present with diverse symptoms related to sensory, motor, and autonomic neuropathy, as well as gastrointestinal, ocular, cardiac, renal and orthopedic symptoms, resulting from the deposition of transthyretin amyloid fibrils in multiple organs. The progressive nature of ATTRv amyloidosis necessitates pre- and post-onset monitoring of the disease. This review article is primarily based on a collation of discussions from a medical advisory board meeting in August 2021. In this article, we summarize the best practices in amyloidosis centers in three major endemic countries for ATTRv amyloidosis (Japan, Brazil, and Portugal), where most patients carry the Val30Met mutation in the transthyretin gene and the patients' genetic background was proven to be the same. The discussions highlighted the similarities and differences in the management of asymptomatic gene mutation carriers among the three countries in terms of the use of noninvasive tests and tissue biopsies and timing of starting the investigations. In addition, this article discusses a set of practical tests and examinations for monitoring disease progression applicable to neurologists working in diverse medical settings and generalizable in non-endemic countries and areas. This set of assessments consists of periodic (every 6 to 12 months) evaluations of patients' nutritional status and autonomic, renal, cardiac, ophthalmologic, and neurological functions. Physical examinations and patient-reported outcome assessments should be also scheduled every 6 to 12 months. Programs for monitoring gene mutation carriers and robust referral networks can aid in appropriate patient management in pre- to post-onset stages. For pre- and post-symptom onset testing for ATTRv amyloidosis, various noninvasive techniques are available; however, their applicability differs depending on the medical setting in each country and region, and the optimal option should be selected in view of the clinical settings, medical environment, and available healthcare resources in each region.

Hereditary transthyretin amyloidosis: a comprehensive review with a focus on peripheral neuropathy

Amyloidoses represent a group of diseases characterized by the pathological accumulation in the extracellular area of insoluble misfolded protein material called "amyloid". The damage to the tissue organization and the direct toxicity of the amyloidogenic substrates induce progressive dysfunctions in the organs involved. They are usually multisystem diseases involving several vital organs, such as the peripheral nerves, heart, kidneys, gastrointestinal tract, liver, skin, and eyes. Transthyretin amyloidosis (ATTR) is related to abnormalities of transthyretin (TTR), a protein that acts as a transporter of thyroxine and retinol and is produced predominantly in the liver. ATTR is classified as hereditary (ATTRv) and wild type (ATTRwt). ATTRv is a severe systemic disease of adults caused by mutations in the TTR gene and transmitted in an autosomal dominant manner with incomplete penetrance. Some pathogenic variants in TTR are preferentially associated with a neurological phenotype (progressive peripheral sensorimotor polyneuropathy); others are more frequently associated with restrictive heart failure. However, many mutations express a mixed phenotype with neurological and cardiological involvement. ATTRv is now a treatable disease. A timely and definite diagnosis is essential in view of the availability of effective therapies that have revolutionized the management of affected patients. The purpose of this review is to familiarize the clinician with the disease and with the correct diagnostic pathways in order to obtain an early diagnosis and, consequently, the possibility of an adequate treatment.

Pharmacokinetics and Pharmacodynamics of Patisiran in Patients with hATTR Amyloidosis and with Polyneuropathy After Liver Transplantation

BACKGROUND AND OBJECTIVE

Variants of the transthyretin (TTR) gene cause hereditary transthyretin-mediated (hATTR) amyloidosis, or ATTRv amyloidosis (v for variant), which results from deposition of misfolded TTR protein as amyloid in organs and tissues. Patisiran is an RNA interference (RNAi) therapeutic that suppresses the hepatic production of TTR protein. Patisiran improves multiple clinical manifestations of hATTR amyloidosis in patients without liver transplantation (LT). Because the liver is the predominant source of circulating TTR, LT has been prescribed to eliminate the production of the variant TTR. However, the continued production of wild-type TTR can contribute to disease progression after LT. Patisiran could potentially address an unmet need in these affected patients. This clinical trial was conducted to evaluate the safety, efficacy, and pharmacokinetics (PK) and pharmacodynamics (PD) of patisiran in patients with hATTR amyloidosis with polyneuropathy progression after LT. In this paper, we describe the PK/PD of patisiran in post-LT patients and compare it with prior patisiran studies in healthy subjects and patients without LT.

METHODS

In an open-label study, patients (N = 23) with hATTR amyloidosis with polyneuropathy progression after LT received 0.3 mg/kg patisiran intravenously every 3 weeks (q3w) for 12 months. As a post hoc analysis, the PK and PD results from the current study were compared with prior patisiran studies in healthy volunteers from a Phase 1 study and in patients with hATTR amyloidosis without LT from Phase 2 and 3 studies.

RESULTS

The PK profile of patisiran siRNA (ALN-18328) and its 2 lipid excipients, DLin-MC3-DMA and PEG2000-C-DMG, in hATTR amyloidosis patients after LT was consistent with prior patisiran studies in non-LT subjects. Plasma PK profiles of ALN-18328 and DLin-MC3-DMA exhibited 2 phases, the first characterized by a short distribution half-life and the second by a minor peak and relatively long elimination half-life. The plasma concentrations of PEG2000-C-DMG reached Cmax at the end of infusion and declined in a multiphasic manner. There was no appreciable accumulation at steady state. Consistent with prior studies in non-LT subjects, the post-LT patients showed a robust, and sustained TTR reduction; with median TTR reduction from baseline of 91% (average of Month 6 and Month 12). No anti-drug antibodies were observed in any patient.

CONCLUSIONS

The consistency of patisiran PK and PD between patients with and without LT suggests that neither LT nor concomitantly administered immunosuppressants influence hepatic uptake or RNAi activity of patisiran. The patisiran dosing regimen of 0.3 mg/kg q3w is appropriate for hATTR amyloidosis patients with or without LT.

CLINICAL TRIAL REGISTRATION NO

NCT03862807.

Current Evidence Supporting the Role of Immune Response in ATTRv Amyloidosis

Hereditary transthyretin (ATTRv) amyloidosis with polyneuropathy, also known as familial amyloid polyneuropathy (FAP), represents a progressive, heterogeneous, severe, and multisystemic disease caused by pathogenic variants in the TTR gene. This autosomal-dominant neurogenetic disorder has an adult onset with variable penetrance and an inconstant phenotype, even among subjects carrying the same mutation. Historically, ATTRv amyloidosis has been viewed as a non-inflammatory disease, mainly due to the absence of any mononuclear cell infiltration in ex vivo tissues; nevertheless, a role of inflammation in its pathogenesis has been recently highlighted. The immune response may be involved in the development and progression of the disease. Fibrillary TTR species bind to the receptor for advanced glycation end products (RAGE), probably activating the nuclear factor κB (NF-κB) pathway. Moreover, peripheral blood levels of several cytokines, including interferon (IFN)-gamma, IFN-alpha, IL-6, IL-7, and IL-33, are altered in the course of the disease. This review summarizes the current evidence supporting the role of the immune response in ATTRv amyloidosis, from the pathological mechanisms to the possible therapeutic implications.

Long-term surgical results of trabeculectomy for secondary glaucoma in Val30Met hereditary transthyretin amyloidosis

This study reports the long-term results of trabeculectomy (LEC) for secondary glaucoma in hereditary transthyretin (ATTRv) amyloidosis patients and its correlation with prior vitrectomy. A retrospective case series was conducted involving 31 consecutive eyes of 20 ATTRv amyloidosis patients who underwent LEC between 2007 and 2020. The mean follow-up period was 73.2 ± 37.0 months (range: 20-181 months). Postoperative intraocular pressures (IOPs) were evaluated based on the following criteria: (a) IOP between 6 and 21 mmHg without additional glaucoma surgeries, except for laser suture lysis, (b) IOP between 6 and 15 mmHg without additional glaucoma surgeries, except for laser suture lysis, and (c) IOP between 6 and 21 mmHg without additional glaucoma surgeries, except for needling and laser suture lysis. Kaplan-Meier analysis revealed survival rates after LEC of 0.52 at 36 months, 0.42 at 60 months, and 0.25 at 84 months under criterion (a); 0.49 at 36 months, 0.27 at 60 months, and 0.11 at 84 months under criterion (b); and 0.76 at 36 months, 0.71 at 60 months, and 0.65 at 84 months under criterion (c). Eyes with a history of small gauge transconjunctival vitrectomy (SGTV) exhibited a tendency towards lower survival rates, although no statistically significant difference was observed (log-rank test; p = 0.193 under criterion (a) and p = 0.0553 under criterion (b)). Our findings suggest that LEC and additional needling procedures can provide some control over IOP; however, the overall postoperative outcomes of LEC for ATTRv amyloidosis remain unsatisfactory, even in the era of SGTV with reduced conjunctival scarring.

Clinical applications of gene therapy for rare diseases: A review

Rare diseases collectively exact a high toll on society due to their sheer number and overall prevalence. Their heterogeneity, diversity, and nature pose daunting clinical challenges for both management and treatment. In this review, we discuss recent advances in clinical applications of gene therapy for rare diseases, focusing on a variety of viral and non-viral strategies. The use of adeno-associated virus (AAV) vectors is discussed in the context of Luxturna, licenced for the treatment of RPE65 deficiency in the retinal epithelium. Imlygic, a herpes virus vector licenced for the treatment of refractory metastatic melanoma, will be an example of oncolytic vectors developed against rare cancers. Yescarta and Kymriah will showcase the use of retrovirus and lentivirus vectors in the autologous ex vivo production of chimeric antigen receptor T cells (CAR-T), licenced for the treatment of refractory leukaemias and lymphomas. Similar retroviral and lentiviral technology can be applied to autologous haematopoietic stem cells, exemplified by Strimvelis and Zynteglo, licenced treatments for adenosine deaminase-severe combined immunodeficiency (ADA-SCID) and β-thalassaemia respectively. Antisense oligonucleotide technologies will be highlighted through Onpattro and Tegsedi, RNA interference drugs licenced for familial transthyretin (TTR) amyloidosis, and Spinraza, a splice-switching treatment for spinal muscular atrophy (SMA). An initial comparison of the effectiveness of AAV and oligonucleotide therapies in SMA is possible with Zolgensma, an AAV serotype 9 vector, and Spinraza. Through these examples of marketed gene therapies and gene cell therapies, we will discuss the expanding applications of such novel technologies to previously intractable rare diseases.

Machine Learning for Early Diagnosis of ATTRv Amyloidosis in Non-Endemic Areas: A Multicenter Study from Italy

BACKGROUND

Hereditary transthyretin amyloidosis with polyneuropathy (ATTRv) is an adult-onset multisystemic disease, affecting the peripheral nerves, heart, gastrointestinal tract, eyes, and kidneys. Nowadays, several treatment options are available; thus, avoiding misdiagnosis is crucial to starting therapy in early disease stages. However, clinical diagnosis may be difficult, as the disease may present with unspecific symptoms and signs. We hypothesize that the diagnostic process may benefit from the use of machine learning (ML).

METHODS

397 patients referring to neuromuscular clinics in 4 centers from the south of Italy with neuropathy and at least 1 more red flag, as well as undergoing genetic testing for ATTRv, were considered. Then, only probands were considered for analysis. Hence, a cohort of 184 patients, 93 with positive and 91 (age- and sex-matched) with negative genetics, was considered for the classification task. The XGBoost (XGB) algorithm was trained to classify positive and negative TTR mutation patients. The SHAP method was used as an explainable artificial intelligence algorithm to interpret the model findings.

RESULTS

diabetes, gender, unexplained weight loss, cardiomyopathy, bilateral carpal tunnel syndrome (CTS), ocular symptoms, autonomic symptoms, ataxia, renal dysfunction, lumbar canal stenosis, and history of autoimmunity were used for the model training. The XGB model showed an accuracy of 0.707 ± 0.101, a sensitivity of 0.712 ± 0.147, a specificity of 0.704 ± 0.150, and an AUC-ROC of 0.752 ± 0.107. Using the SHAP explanation, it was confirmed that unexplained weight loss, gastrointestinal symptoms, and cardiomyopathy showed a significant association with the genetic diagnosis of ATTRv, while bilateral CTS, diabetes, autoimmunity, and ocular and renal involvement were associated with a negative genetic test.

CONCLUSIONS

Our data show that ML might potentially be a useful instrument to identify patients with neuropathy that should undergo genetic testing for ATTRv. Unexplained weight loss and cardiomyopathy are relevant red flags in ATTRv in the south of Italy. Further studies are needed to confirm these findings.

Peritoneal Amyloid as a Presenting Manifestation of AL Amyloid

Amyloid is a systemic disease characterized by extracellular deposition of misfolded protein. Gastrointestinal and peritoneal deposition of light chain (AL) amyloid is an under-recognized manifestation of this systemic disease, usually as a late sequela. Here we present a case of recently diagnosed AL peritoneal amyloid that presented in the context of recurrent, acute onset abdominal discomfort and was found to have bowel obstruction complicated by perforation in the setting of AL-mediated gastrointestinal tract infiltration and dysmotility.

Corneal confocal microscopy identifies corneal nerve loss and increased Langerhans cells in presymptomatic carriers and patients with hereditary transthyretin amyloidosis

BACKGROUND

Hereditary transthyretin amyloidosis (ATTRv amyloidosis) is a rare, but life-threatening protein misfolding disorder due to TTR gene mutations. Cardiomyopathy (ATTRv-CM) and polyneuropathy (ATTRv-PN) with early small nerve fibre involvement are the most common manifestations. Timely diagnosis and treatment initiation are key to limiting progression of disease. Corneal confocal microscopy (CCM) is a non-invasive method to quantify corneal small nerve fibres and immune cell infiltrates in vivo.

METHODS

This cross-sectional study investigated the utility of CCM in 20 patients with ATTRv amyloidosis (ATTRv-CM, n = 6; ATTRv-PN, n = 14) and presymptomatic carriers (n = 5) compared to 20 age- and sex-matched healthy controls. Corneal nerve fibre density, corneal nerve fibre length, corneal nerve branch density, and cell infiltrates were assessed.

RESULTS

Corneal nerve fibre density and nerve fibre length were significantly lower in patients with ATTRv amyloidosis compared to healthy controls regardless of the clinical phenotype (ATTRv-CM, ATTRv-PN) and corneal nerve fibre density was significantly lower in presymptomatic carriers. Immune cell infiltrates were only evident in patients with ATTRv amyloidosis, which correlated with reduced corneal nerve fibre density.

CONCLUSIONS

CCM identifies small nerve fibre damage in presymptomatic carriers and symptomatic patients with ATTRv amyloidosis and may serve as a predictive surrogate marker to identify individuals at risk of developing symptomatic amyloidosis. Furthermore, increased corneal cell infiltration suggests an immune-mediated mechanism in the pathogenesis of amyloid neuropathy.

[Systemic forms of amyloidosis with cardiac manifestation]

The term amyloidosis summarizes heterogeneous diseases in which a misfolding of protein structures occurs. These misfolded proteins can fundamentally be deposited anywhere in the body and lead to malfunction of the affected organ. There are preferential sites of deposition depending on which protein is misfolded. Cardiac transthyretin (ATTR) amyloidosis is a rare cause of cardiomyopathy and part of an underdiagnosed systemic disease. For cardiac ATTR amyloidosis, which involves deposition of misfolded tranthyretin either as a wild type (wtATTR) or as a mutated form (mATTR or hATTR), evidence-based treatment options have recently become available with slowing of the progression of the cardiomyopathy and a significant reduction of hospitalization rates. Therefore, it is important to diagnose this severe disease at an early stage and to differentiate it from other forms of amyloidosis. A clinical screening is easily possible by determination of free light chains using imaging examinations (cardiac magnetic resonance imaging or scintigraphic procedures) and immunofixation before the definitive diagnosis is made based on a biopsy and/or genetic tests. An interdisciplinary work-up involving hemato-oncology, nephrology, neurology and other disciplines, is indispensable when cardiac amyloidosis is suspected.

Epidemiology, Pathophysiology, Diagnosis, and Therapy of Heart Failure With Preserved Ejection Fraction in Japan

Heart failure (HF) with preserved ejection fraction (HFpEF) is a global health care problem, with diagnostic difficulty, limited treatment options and high morbidity and mortality rates. The prevalence of HFpEF is increasing because of the aging population and the increasing burden of cardiac and metabolic comorbidities, such as systemic hypertension, diabetes, chronic kidney disease, and obesity. The knowledge base is derived primarily from the United States and Europe, and data from Asian countries, including Japan, remain limited. Given that phenotypic differences may exist between Japanese and Western patients with HFpEF, careful characterization may hold promise to deliver new therapy specific to the Japanese population. In this review, we summarize the current knowledge regarding the epidemiology, pathophysiology and diagnosis of and the potential therapies for HFpEF in Japan.

Tafamidis polyneuropathy amelioration requires modest increases in transthyretin stability even though increases in plasma native TTR and decreases in non-native TTR do not predict response

BACKGROUND

TTR aggregation causes hereditary transthyretin (TTR) polyneuropathy (ATTRv-PN) in individuals with destabilised TTR variants. ATTRv-PN can be treated with ligands that bind TTR and prevent aggregation. One such ligand, tafamidis, is widely approved to treat ATTRv-PN. We explore how TTR stabilisation markers relate to clinical efficacy in 210 ATTRv-PN patients taking tafamidis.

METHODS

TTR concentration in patient plasma was measured before and after tafamidis treatment using assays for native or combined native + non-native TTR. TTR tetramer dissociation kinetics, which are slowed by tafamidis binding, were also measured.

RESULTS

Native TTR levels increased by 56.8% while combined native + non-native TTR levels increased by 3.1% after 24 months of tafamidis treatment, implying that non-native TTR decreased. Accordingly, the fraction of native TTR increased from 0.54 to 0.71 with tafamidis administration. Changes in native and non-native TTR levels were uncorrelated with clinical response to tafamidis. TTR tetramer dissociation generally slowed to an extent consistent with ∼40% of TTR being tafamidis-bound. Male non-responders had a lower extent of binding.

CONCLUSIONS

Native and non-native TTR concentration changes cannot be used as surrogate measures for therapeutic efficacy. Also, successful tafamidis therapy requires only moderate TTR stabilisation. Male patients may benefit from higher tafamidis doses.

A retrospective survey of patients with hereditary transthyretin-mediated (hATTR) amyloidosis treated with patisiran in real-world clinical practice in Belgium

INTRODUCTION

Hereditary transthyretin-mediated (hATTR) amyloidosis, a genetic disease caused by mutations in the transthyretin gene, leads to progressive sensory and autonomic neuropathy and/or cardiomyopathy and is associated with renal and ophthalmologic manifestations and a poor prognosis.

METHODS

This is a retrospective study based on data collected from the medical records of patients with hATTR amyloidosis treated with patisiran between 01 July 2018 and 01 February 2021. Six Belgian neuromuscular reference centers participated, covering all patisiran-treated hATTR amyloidosis patients at the study time. This study was conducted to collect data requested in the context of the reimbursement of patisiran in Belgium.

RESULTS

Thirty-one patients were diagnosed with hATTR amyloidosis with polyneuropathy, Coutinho stage 1 or 2, and eligible for active treatment during the data collection period. Of the hATTR amyloidosis patients treated with patisiran (n = 12), seven and five had polyneuropathy stages 1 and 2, respectively. Six patients had cardiac symptoms (New York Heart Association class 2 or above). Follow-up information was available for nine patients. Following patisiran treatment, eight patients showed stable or improved assessments for most neurological or cardiological parameters. Only one patient presented with worsening statuses at the end of the data collection period.

CONCLUSIONS

The patients with hATTR amyloidosis in Belgium have similar baseline demographics and disease characteristics to those studied in the patisiran APOLLO study and show a similar therapeutic response in the real-world, altering the expected disease progression in most patients.

Lessons from the first-in-human in vivo CRISPR/Cas9 editing of the TTR gene by NTLA-2001 trial in patients with transthyretin amyloidosis with cardiomyopathy

Introduction: Transthyretin amyloidosis (ATTR amyloidosis) is a progressive fatal disease characterized by accumulation of amyloid fibrils composed of misfolded transthyretin (TTR) protein in tissues, resulting in cardiomyopathy and heart failure. Approximately 50,000 people have hereditary ATTR amyloidosis, and up to 500,000 have wild-type ATTR amyloidosis globally, leading to poor quality of life and high morbidity, resulting in death within a median of 2 to 6 years after diagnosis. However, data on the prevalence of ATTR-CM is limited and poorly characterized. NTLA-2001, an in vivo gene-editing therapeutic agent designed to treat ATTR amyloidosis by reducing the concentration of TTR in serum by knocking out the TTR gene, has been shown to be effective, presenting a new therapeutic strategy. However, the safety, tolerability, and pharmacodynamic response to IV NTLA-2001 administration has not been yet demonstrated. Study and results: The first-in-human in vivo CRISPR/Cas9 trial of TTR Gene editing by NTLA-2001 in patients with Transthyretin Amyloidosis and cardiomyopathy was designed to evaluate the safety, tolerability, efficacy, and pharmacokinetic and pharmacodynamic responses to IV NTLA-2001 administration and its effect on serum transthyretin (TTR) levels in patients with ATTR amyloidosis and cardiomyopathy. Twelve subjects received NTLA-2001 (three NYHA I/II subjects at 0.7 mg/kg, three subjects at 1.0 mg/kg, and six NYHA III subjects at 0.7 mg/kg). Serum TTR levels were reduced from the baseline in all subjects (mean>90% after 28 days). Mean % reductions (+/-SEM) from baseline to day 28 were: NYHA I/II at 0.7 mg/kg = 92% (1%), at 1.0 mg/kg = 92% (2%), and for NYHA III at 0.7 mg/kg = 94% (1%) maintained through 4-6 months. Two of the 12 patients (16.7%) reported a transient infusion reaction. One patient experienced a grade 3 infusion-related reaction that resolved without any clinical sequelae. Lessons learned: This study showed a significant and consistent reduction in serum TTR protein levels after a single admission, while being generally well tolerated, representing a potential new option for the treatment and improvement of the prognosis of cardiac ATTR amyloidosis. Further research into the long-term safety and efficacy of NTLA-2001, particularly in higher-risk patients, including continued monitoring of whether knockout of the TTR gene results in sustained TTR reduction over the long term, is essential. Evaluation of the potential effects of markedly reduced TTR levels on patients' clinical outcomes, with a focus on functional capacity, quality of life, and mortality benefits are essential. The analysis of the use of this technology for an array of other diseases is vital.

Prevalence estimation of ATTRv in China based on genetic databases

Introduction: Amyloid transthyretin (ATTR) is divided into either hereditary (ATTRv) or sporadic (ATTRwt) and ATTRv is a rare hereditary disease transmitted as an autosomal dominant manner. Its global prevalence is traditionally estimated as 5,000 to 10,000 persons. However, it may be underestimated and the exact prevalence of ATTRv in China mainland remains unknown. Methods: The Genome Aggregation database (gnomAD) database (containing 125,748 exomes) and two genomic sequencing databases--China Metabolic Analytics Project (ChinaMAP) (containing 10588 individuals) and Amcarelab gene database (containing 45392 exomes), were integrated to estimate the prevalence of ATTRv in the world and mainland Chinese populations. Pathogenic variants allele frequency and the prevalence of ATTRv was calculated. Results: Six variants, counting 470 alleles, were defined as pathogenic variants in gnomAD. The prevalence of ATTRv in the world population was 57.4/100,000. Two variants (2 allele counts) and 15 variants (34 individuals) were defined as pathogenic variants in the ChinaMAP database and the Amcarelab exome database, respectively. Thus, the estimated prevalence interval of ATTRv in mainland China was 18.9/100,000-74,9/100,000. Conclusion: The present study demonstrated that the previous prevalence was greatly underestimated using traditional methods. Therefore, raising awareness of the disease is essential for recognizing ATTRv in its early stage.

Strategy for genetic analysis in hereditary neuropathy

Inherited neuropathies are a heterogeneous group of slowly progressive disorders affecting either motor, sensory, and/or autonomic nerves. Peripheral neuropathy may be the major component of a disease such as Charcot-Marie-Tooth disease or a feature of a more complex multisystemic disease involving the central nervous system and other organs. The goal of this review is to provide the clinical clues orientating the genetic diagnosis in a patient with inherited peripheral neuropathy. This review focuses on primary inherited neuropathies, amyloidosis, inherited metabolic diseases, while detailing clinical, neurophysiological and potential treatment of these diseases.

Drug and Gene Therapy for Treating Variant Transthyretin Amyloidosis (ATTRv) Neuropathy

Variant Transthyretin Amyloidosis (ATTRv) neuropathy is an adult-onset, autosomal dominant, lethal, multisystemic disease due to the deposition of mutated transthyretin (TTR) in various organs, commonly involving the peripheral nerves and the heart. Circulating TTR tetramers are unstable due to the presence of mutated TTR and dissociate into monomers, which misfold and form amyloid fibrils. Although there are more than 140 mutations in the TTR gene, the p.Val50Met mutation is by far the commonest. In the typical, early-onset cases, it presents with a small sensory fibre and autonomic, length-dependent, axonal neuropathy, while in late-onset cases, it presents with a lengthdependent sensorimotor axonal neuropathy involving all fibre sizes. Treatment is now available and includes TTR stabilizers, TTR amyloid removal as well as gene silencing, while gene editing therapies are on the way. Its timely diagnosis is of paramount importance for a better prognosis.

Microhook ab interno trabeculotomy for secondary glaucoma in patients with hereditary transthyretin amyloidosis

PURPOSE

To report surgical outcomes of a Microhook ab interno trabeculotomy (µLOT) procedure for glaucoma secondary to hereditary transthyretin amyloidosis (ATTRv).

STUDY DESIGN

Retrospective case series.

METHODS

Medical records of patients with glaucoma secondary to ATTRv with transthyretin Val30Met variant, who underwent µLOT, were retrospectively reviewed. Surgical success was categorized according to the postoperative intraocular pressures (IOPs, mmHg) as follows: (a) 6 ≤ IOP ≤ 21; (b) 6 ≤ IOP ≤ 18; and (c) 6 ≤ IOP ≤ 15, without light perception loss or additional glaucoma surgery. Secondary outcomes were glaucoma medication scores and postoperative complications.

RESULTS

This study included 18 eyes (13 patients, 6 men). The mean follow-up period was 25.2±9.8 months (7-38 months). Kaplan-Meier analysis indicated success rates of (a) 1.00 at 6, 1.00 at 12, and 0.43 at 24 months; (b), 1.00 at 6, 0.93 at 12, and 0.43 at 24 months; (c) 0.94 at 6, 0.75 at 12, and 0.27 at 24 months after operation. Postoperative IOPs were significantly reduced from the baseline of 25.2±5.8 mmHg to 11.5±2.7 at 3, 12.3±4.1 at 6, and 13.8±3.9 at 12 months (Dunnett's test). Medication scores were also improved at 3 and 6 months but without a significant reduction at 12 months. There were no severe complications requiring surgical intervention except for additional glaucoma surgery.

CONCLUSION

µLOT for secondary glaucoma in ATTRv is safe and effective 1 year after surgery, but the effects diminish after 2 years.

The Role of Proteolysis in Amyloidosis

Amyloidoses are a group of diseases associated with deposits of amyloid fibrils in different tissues. So far, 36 different types of amyloidosis are known, each due to the misfolding and accumulation of a specific protein. Amyloid deposits can be found in several organs, including the heart, brain, kidneys, and spleen, and can affect single or multiple organs. Generally, amyloid-forming proteins become prone to aggregate due to genetic mutations, acquired environmental factors, excessive concentration, or post-translational modifications. Interestingly, amyloid aggregates are often composed of proteolytic fragments, derived from the degradation of precursor proteins by yet unidentified proteases, which display higher amyloidogenic tendency compared to precursor proteins, thus representing an important mechanism in the onset of amyloid-based diseases. In the present review, we summarize the current knowledge on the proteolytic susceptibility of three of the main human amyloidogenic proteins, i.e., transthyretin, β-amyloid precursor protein, and α-synuclein, in the onset of amyloidosis. We also highlight the role that proteolytic enzymes can play in the crosstalk between intestinal inflammation and amyloid-based diseases.

Patisiran Enhances Muscle Mass after Nine Months of Treatment in ATTRv Amyloidosis: A Study with Bioelectrical Impedance Analysis and Handgrip Strength

BACKGROUND AND AIMS

Hereditary transthyretin amyloidosis with polyneuropathy (ATTRv) is caused by mutations in the TTR gene, leading to misfolded monomers that aggregate generating amyloid fibrils. The clinical phenotype is heterogeneous, characterized by a multisystemic disease affecting the sensorimotor, autonomic functions along with other organs. Patisiran is a small interfering RNA acting as a TTR silencer approved for the treatment of ATTRv. Punctual and detailed instrumental biomarkers are on demand for ATTRv to measure the severity of the disease and monitor progression and response to treatment.

METHODS

Fifteen patients affected by ATTRv amyloidosis (66.4 ± 7.8 years, six males) were evaluated before the start of therapy with patisiran and after 9-months of follow-up. The clinical and instrumental evaluation included body weight and height; Coutinho stage; Neuropathy Impairment Score (NIS); Karnofsky performance status (KPS); Norfolk QOL Questionnaire; Six-minute walking test (6 MWT); nerve conduction studies; handgrip strength (HGS); and bioimpedance analysis (BIA).

RESULTS

Body composition significantly changed following the 9-months pharmacological treatment. In particular, the patients exhibited an increase in fat free mass, body cell mass, and body weight with a decrease in fat mass. A significant increase after 9 months of treatment was observed for the 6 MWT. Coutinho stage, KPS, NIS, NIS-W, nerve conduction studies, Norfolk, COMPASS-31 scale, and HGS remained unchanged.

CONCLUSIONS

BIA might represent a useful tool to assess the effects of multiorgan damage in ATTRv and to monitor disease progression and response to treatments. More evidence is still needed for HGS. Patisiran stabilizes polyneuropathy and preserves motor strength by increasing muscle mass after 9 months of treatment.

Hereditary Transthyretin Amyloidosis with Polyneuropathy: Monitoring and Management

Our aim in this review is to discuss current treatments and investigational products and their effect on patients with hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN) and provide suggestions for monitoring disease progression and treatment efficacy.

Characteristics of Patients with Hereditary Transthyretin Amyloidosis-Polyneuropathy (ATTRv-PN) in NEURO-TTRansform, an Open-label Phase 3 Study of Eplontersen

INTRODUCTION

Hereditary transthyretin (ATTRv) amyloidosis is a rare, severe, progressive, debilitating, and ultimately fatal disease caused by systemic deposition of transthyretin (TTR) amyloid fibrils. ATTRv amyloidosis occurs in both males and females. Eplontersen (ION-682884), a ligand-conjugated antisense oligonucleotide designed to degrade hepatic TTR mRNA, is being evaluated for the treatment of ATTRv amyloidosis with polyneuropathy (ATTRv-PN) in the phase 3, international, multicenter, open-label NEURO-TTRansform study (NCT04136184). To describe the study population of this pivotal trial, here we report the baseline characteristics of patients enrolled in the NEURO-TTRansform study.

METHODS

Patients eligible for NEURO-TTRansform were 18-82 years old with a diagnosis of ATTRv-PN and Coutinho stage 1 (ambulatory without assistance) or stage 2 (ambulatory with assistance) disease; documented TTR gene variant; signs and symptoms consistent with neuropathy associated with ATTRv; no prior liver transplant; and New York Heart Association (NYHA) functional class I or II.

RESULTS

The NEURO-TTRansform study enrolled 168 patients across 15 countries/territories (North America, 15.5%; Europe, 38.1%; South America/Australia/Asia, 46.4%). At baseline, the study cohort had a mean age of 52.8 years, 69.0% of patients were male, and 78.0% of patients were White. The V30M variant was most prevalent (60.1% of patients), and prevalence varied by region. Overall, 56.5% and 17.3% of patients had received previous treatment with tafamidis or diflunisal, respectively. A majority of patients (79.2%) had Coutinho stage 1 disease (unimpaired ambulation) and early (before age 50) disease onset (53.0%). Time from diagnosis to enrollment was 46.6 (57.4) months (mean [standard deviation]). Most patients had a baseline polyneuropathy disability (PND) score of I (40.5%) or II (41.1%), and the mean modified Neuropathy Impairment Score + 7 (mNIS + 7) was 79.0.

CONCLUSION

The recruited population in the ongoing NEURO-TTRansform study has global representation characteristic of contemporary clinical practice.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT04136184.

Systemic amyloidosis journey from diagnosis to outcomes: a twelve-year real-world experience of a single center in a middle-income country

BACKGROUND

Systemic amyloidosis is caused by the deposition of misfolded protein aggregates in tissues, leading to progressive organ dysfunction and death. Epidemiological studies originate predominantly from high-income countries, with few data from Latin America. Due to the non-specific clinical manifestations, diagnosing amyloidosis is often challenging and patients experience a long journey and delay in diagnosis. This study aimed to assess clinical and laboratory characteristics, the diagnostic journey, and outcomes of patients with biopsy-proven systemic amyloidosis diagnosed between 2009 and 2020 at a university referral center in a middle-income Latin American country. Patients´ medical records were retrospectively reviewed.

RESULTS

One hundred and forty-three patients were included. The median age at diagnosis was 60 years and 54% were male. Until the diagnosis, most of the patients (52%) were seen by at least 3 specialists, the main ones being: general practitioners (57%), nephrologists (45%), and cardiologists (38%). The most common manifestations were renal (54%) and cardiac (41%) disorders, and cachexia was seen in 36% of patients. In 72% of the cases, ≥ 2 biopsies were required until the final diagnosis. The median time from symptoms onset to diagnosis was 10.9 months, and most patients (75%) had ≥ 2 organs involved. The following subtypes were identified: AL (68%), ATTR (13%), AA (8%), AFib (4%), and inconclusive (7%). Median OS was 74.3 months in the non-AL subgroup and 18.5 months in AL. Among AL patients, those with advanced cardiac stage had the worst outcome [median OS 8.6 months versus 52.3 for stage III versus I-II, respectively (p < 0.001)]. AL subtype, cardiac involvement, and ECOG ≥ 2 were identified as independent risk factors for reduced survival.

CONCLUSIONS

Systemic amyloidosis is still an underdiagnosed condition and the delay in its recognition leads to poor outcomes. Medical education, better diagnostic tools, improvement in access to therapies, and establishment of referral centers may improve patient outcomes in middle-income countries.

Hereditary transthyretin amyloidosis overview

Hereditary amyloidogenic transthyretin (ATTRv) amyloidosis is a rare autosomal dominantly inherited disorder caused by mutations in the transthyretin (TTR) gene. The pathogenetic model of ATTRv amyloidosis indicates that amyloidogenic, usually missense, mutations destabilize the native TTR favouring the dissociation of the tetramer into partially unfolded species that self-assemble into amyloid fibrils. Amyloid deposits and monomer-oligomer toxicity are the basis of multisystemic ATTRv clinical involvement. Peripheral nervous system (autonomic and somatic) and heart are the most affected sites. In the last decades, a better knowledge of pathomechanisms underlying the disease led to develop novel and promising drugs that are rapidly changing the natural history of ATTRv amyloidosis. Thus, clinicians face the challenge of timely diagnosis for addressing patients to appropriate treatment. As well, the progressive nature of ATTRv raises the issue of presymptomatic testing and risk management of carriers. The main aim of this review was to focus on what we know about ATTRv so far, from pathogenesis to clinical manifestations, diagnosis and hence patient's monitoring and treatment, and from presymptomatic testing to management of carriers.

Nephrotoxicity of marketed antisense oligonucleotide drugs

The field of antisense oligonucleotide (ASO)-based therapies have been making strides in precision medicine due to their potent therapeutic application. Early successes in treating some genetic diseases are now attributed to an emerging class of antisense drugs. After two decades, the US Food and Drug Administration (FDA) has approved a considerable number of ASO drugs, primarily to treat rare diseases with optimal therapeutic outcomes. However, safety is one of the biggest challenges to the therapeutic utility of ASO drugs. Due to patients' and health care practitioners' urgent demands for medicines for untreatable conditions, many ASO drugs have been approved. However, a complete understanding of the mechanisms of adverse drug reactions (ADRs) and toxicities of ASOs still need to be resolved. The range of ADRs is unique to a specific drug, while few ADRs are common to a section of drugs as a whole. Nephrotoxicity is an important concern that needs to be addressed considering the clinical translation of any drug candidates ranging from small molecules to ASO-based drugs. This article encompasses what is known about the nephrotoxicity of ASO drugs, the potential mechanisms of action(s), and recommendations for future investigations on the safety of ASO drugs.

Suture trabeculotomy ab interno for secondary glaucoma in Japanese patients with Val30Met hereditary transthyretin amyloidosis

We retrospectively evaluated surgical outcomes of suture trabeculotomy (SLOT) ab interno for secondary glaucoma in 18 eyes of 12 patients with hereditary transthyretin (ATTRv) amyloidosis with Val30Met mutation. SLOT ab interno was performed between May 2015 and January 2020. All the participants were followed up for at least 12 months. The primary outcome measure was Kaplan-Meier survival. Failure of this treatment was defined as an intraocular pressure (IOP) of ≥ 22 mmHg and a < 20% IOP reduction with or without medication or as additional operations needed to reduce IOP. The mean postoperative follow-up period was 3.5 years (1.2-6.1 years). The SLOT ab interno procedure alone was performed in 17 eyes (94%). Fifteen eyes (83%) had a 360° incision made in Schlemm's canal and 3 eyes (17%) had a 180° incision performed. Cumulative survival values were 0.83, 0.63, and 0.22 at 1, 2, and 3 years, respectively. Ten eyes (56%) needed additional surgery, such as repeated SLOT ab interno, Ahmed glaucoma valve implantation, or MicroPulse transscleral cyclophotocoagulation. Our results here, as well as our previous results with trabeculectomy, suggest that SLOT ab interno may not have a sufficiently long-term effect on secondary glaucoma because of ATTRv amyloidosis.

High Hereditary Transthyretin-Related Amyloidosis Prevalence in Crete

Background and Objectives

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

Methods

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

Results

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

Discussion

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

RNA-targeting and gene editing therapies for transthyretin amyloidosis

Transthyretin (TTR) is a tetrameric protein synthesized mostly by the liver and secreted into the plasma. TTR molecules can misfold and form amyloid fibrils in the heart and peripheral nerves, either as a result of gene variants in TTR or as an ageing-related phenomenon, which can lead to amyloid TTR (ATTR) amyloidosis. Some of the proposed strategies to treat ATTR amyloidosis include blocking TTR synthesis in the liver, stabilizing TTR tetramers or disrupting TTR fibrils. Small interfering RNA (siRNA) or antisense oligonucleotide (ASO) technologies have been shown to be highly effective for the blockade of TTR expression in the liver in humans. The siRNA patisiran and the ASO inotersen have been approved for the treatment of patients with ATTR variant polyneuropathy, regardless of the presence and severity of ATTR cardiomyopathy. Preliminary data show that therapy with patisiran improves the cardiac phenotype rather than only inducing disease stabilization in patients with ATTR variant polyneuropathy and concomitant ATTR cardiomyopathy, and this drug is being evaluated in a phase III clinical trial in patients with ATTR cardiomyopathy. Furthermore, ongoing phase III clinical trials will evaluate another siRNA, vutrisiran, and a novel ASO formulation, eplontersen, in patients with ATTR variant polyneuropathy or ATTR cardiomyopathy. In this Review, we discuss these approaches for TTR silencing in the treatment of ATTR amyloidosis as well as the latest strategy of genome editing with CRISPR-Cas9 to reduce TTR gene expression.