Neurological affection and serum neurofilament light chain in wild type transthyretin amyloidosis.

In contrast to inherited transthyretin amyloidosis (A-ATTRv), neuropathy is not a classic leading symptom of wild type transthyretin amyloidosis (A-ATTRwt). However, neurological symptoms are increasingly relevant in A-ATTRwt as well. To better understand the role of neurological symptoms in A-ATTRwt, A-ATTRwt patients were prospectively characterized at Amyloidosis Center Charité Berlin (ACCB) between 2018 and 2023 using detailed neurological examination, quality of life questionnaires, and analysis of age- and BMI-adapted serum neurofilament light chain (NFL) levels. 16 out of 73 (21.9%) patients presented with a severe neuropathy which we defined by a Neuropathy Impairment Score (NIS) of 20 or more. In this group, quality of life was reduced, peripheral neuropathy was more severe, and spinal stenosis and joint replacements were frequent. Age- and BMI matched serum NFL levels were markedly elevated in patients with a NIS ≥ 20. We therefore conclude that highly abnormal values in neuropathy scores such as the NIS occur in A-ATTRwt, and have an important impact on quality of life. Both peripheral neuropathy and spinal canal stenosis are likely contributors. Serum NFL may serve as a biomarker for neurological affection in patients with A-ATTRwt. It will be important to consider neurological aspects of A-ATTRwt for diagnosis, clinical follow-up, and future treatment development.

Data-independent acquisition mass spectrometry reveals comprehensive plasma protein profiles in the natural history of patients with hereditary transthyretin amyloidosis (ATTRv).

OBJECTIVES: Hereditary transthyretin amyloidosis (ATTRv) is a rare, fatal, autosomal dominant disease with more than 140 mutations discovered. Three phenotypes of amyloid infiltration are neuropathy (ATTRv-PN), cardiopathy (ATTRv-CM), and neuropathy + cardiopathy (ATTRv-MIX). The lack of ATTR-specific biomarkers, difficulties in biopsy evidence, and limited known pathogenic mechanisms have made diagnosis difficult. Newly emerging noninvasive measures for monitoring progression and disease-modifying therapies have improved early diagnosis and patient management. METHODS: Our research applies the latest technology, Data-Independent Acquisition-Based Quantitative Proteomics (DIA), to reveal comprehensive plasma protein profiles in the natural history of Chinese patients with hereditary transthyretin amyloidosis (ATTRv). We analyzed differentially expressed proteins (DEPs) in three phenotypes (ATTRv-PN, ATTRv-CM, and ATTRv-MIX). RESULTS: Serum samples were collected from a total of 18 patients (6 ATTRv-PN, 5 ATTRv-CM, and 7 ATTRv-MIX patients) and 20 healthy participants as a control group. Combined with the results of the proteomic and bioinformatic analyses, we found 30 DEPs and protein interaction networks clustered in KRT family proteins and DSC3 between ATTRv-PN and the control, which were rich in the estrogen signaling pathway and the cell adhesion molecule (CAM) pathway. CONCLUSION: This study demonstrates a global and significant proteomic profile in different stages of ATTRv.

Nationwide prevalence and characteristics of transthyretin amyloid cardiomyopathy in Sweden.

OBJECTIVE: Transthyretin amyloid cardiomyopathy (ATTR-CM) is a rare, progressive and fatal condition caused by deposition of transthyretin amyloid fibrils in the heart. This study aims to identify all patients diagnosed with ATTR-CM in Sweden, estimate the prevalence of ATTR-CM, describe patient characteristics and mortality, assess the importance of early symptoms (red flags) for identification of ATTR-CM, and compare with patients with heart failure (HF). METHODS: This retrospective study combined multiple national health registers covering all specialist visits and prescriptions for the entire population of Sweden. Between January 2008 and December 2018, patients with ATTR-CM were identified retrospectively based on a combination of diagnosis codes and compared with matched, all-cause non-ATTR HF patients. RESULTS: Overall, a total of 994 patients diagnosed with ATTR-CM were identified, with an average age at diagnosis of 73 years, and 30% of whom were female. The prevalence of diagnosed ATTR-CM cases in 2018 was 5.0 per 100 000. The median survival from diagnosis was 37.6 months (CI 33.8 to 43.8), with a lower median survival in women (27.9 months, CI 23.3 to 33.8) compared with men (43.5 months, CI 37.6 to 49.6). Patients with ATTR-CM demonstrated reduced survival compared with patients with HF (p<0.001). Compared with patients with HF, clinical identification of carpal tunnel syndrome, spinal stenosis, and atrioventricular and left bundle branch block can facilitate earlier diagnosis of ATTR-CM. CONCLUSIONS: This study provides the first nationwide estimates of ATTR-CM prevalence and risk factors. The results reinforce the severity of the disease and the importance of earlier diagnosis, especially for female patients, in order to allow effective treatment and prevention of disease progression.

Wild type transthyretin cardiac amyloidosis in a young individual: A case report.

RATIONALE: Senile systemic amyloidosis, a disease of elderly is caused by amyloid deposition of wild-type transthyretin. The symptoms often overlap with other heart diseases. Hence it is either misdiagnosed or considered as a normal aging process in majority of cases. PATIENT CONCERNS: We present a young patient of wild-type transthyretin amyloidosis, contradicting its only senile presence. The 34-year-old man presented with dyspnoea on exertion. He was suffering from hypertension for consecutive 3 years. DIAGNOSIS: Echocardiography demonstrated left ventricular hypertrophy with reduced global longitudinal strain and apical sparing. Congo red staining and immuno-histochemical staining of the abdominal fat biopsy confirmed transthyretin amyloid deposition. Genetic analysis revealed absence of any mutant variant/s of transthyretin gene, confirming wild-type transthyretin amyloidosis. INTERVENTION: A combination of amlodipine 5 mg, telmisartan 40 mg, and chlorthalidone 12.5 mg once daily was given to control the blood pressure of the patient. OUTCOME: Blood pressure was controlled but he continued to have exertional dyspnoea. The patient expired in December 2019. LESSONS: A systematic diagnosis for wild type transthyretin amyloid cardiomyopathy (ATTR-CM) shall be considered in young cardiac patients suffering from cardiac distress with unknown etiology.

Cardiac Transthyretin Amyloidosis: A Nuclear Medicine Leading Role. Situation in a Spanish Center and "State of the Art" in Nuclear Medicine.

PURPOSE: Amyloidosis is a heterogeneous group of diseases caused by abnormal extracellular deposition of insoluble proteins and can involve myocardium. One of the causes of myocardial involvement is TTR amyloidosis. Our objective has been to evaluate the situation of cardiac amyloidosis (CA) in our center and the role of nuclear medicine, and to review the state of the art of nuclear medicine in this entity. PATIENTS AND METHODS: We have evaluated retrospectively 186 patients with clinical suspicion of CA and analyzed the clinical characteristics, free light chains and immunofixation in serum and/or urine, and the most relevant biomarkers associated with transthyretin CA (C-ATTR) of these patients and compared them with the results of the 99mTc-DPD scintigraphy. RESULTS: We have verified the growing bibliographic evidence concerning C-ATTR. A total of 51 scintigraphies (27.4%) were positive, 2 (1.1%) indeterminate and 133 (71.5%) negative according to the Perugini score. ATTR was diagnosed in 22 (11.8%; 77.3% males; mean age, 79.4 years). Of these, 12 (75% men; 82.3 years) were ATTRwt (wild-type or age-associated) patients, 2 (50% men; 52 years) experienced ATTRv (variant or hereditary), and 8 (87.5% men; 82.3 years) were not classified because of the absence genetic test. The origin of amyloidosis could not be determined in 31 (16.7%; 80.7% males; 84.5 years). In 29 of them (93.6%), it was because there was no study of free light chains or immunofixation. CONCLUSIONS: Nuclear medicine is playing an increasing role in the diagnosis and classification of CA. However, the monitoring of these is still patchy.

Neurofilament Light Chain as a Biomarker of Hereditary Transthyretin-Mediated Amyloidosis.

OBJECTIVE: To identify changes in the proteome associated with onset and progression of hereditary transthyretin-mediated (hATTR) amyloidosis, also known as ATTRv amyloidosis, we performed an observational, case-controlled study that compared proteomes of patients with ATTRv amyloidosis and healthy controls. METHODS: Plasma levels of >1,000 proteins were measured in patients with ATTRv amyloidosis with polyneuropathy who received either placebo or patisiran in a Phase 3 study of patisiran (APOLLO), and in healthy controls. The effect of patisiran on the time profile of each protein was determined by linear mixed model at 0, 9, and 18 months. Neurofilament light chain (NfL) was further assessed with an orthogonal quantitative approach. RESULTS: Levels of 66 proteins were significantly changed with patisiran vs placebo, with NfL change most significant (p < 10-20). Analysis of changes in protein levels demonstrated that the proteome of patients treated with patisiran trended toward that of healthy controls at 18 months. Healthy controls' NfL levels were 4-fold lower than in patients with ATTRv amyloidosis with polyneuropathy (16.3 pg/mL vs 69.4 pg/mL, effect -53.1 pg/mL [95% confidence interval -60.5 to -45.9]). NfL levels at 18 months increased with placebo (99.5 pg/mL vs 63.2 pg/mL, effect 36.3 pg/mL [16.5-56.1]) and decreased with patisiran treatment (48.8 pg/mL vs 72.1 pg/mL, effect -23.3 pg/mL [-33.4 to -13.1]) from baseline. At 18 months, improvement in modified Neuropathy Impairment Score +7 score after patisiran treatment significantly correlated with reduced NfL (R = 0.43 [0.29-0.55]). CONCLUSIONS: Findings suggest that NfL may serve as a biomarker of nerve damage and polyneuropathy in ATTRv amyloidosis, enable earlier diagnosis of patients with ATTRv amyloidosis, and facilitate monitoring of disease progression. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that NfL levels may enable earlier diagnosis of polyneuropathy in patients with ATTRv amyloidosis and facilitate monitoring of disease progression.

Blinded potency comparison of transthyretin kinetic stabilisers by subunit exchange in human plasma.

Transthyretin (TTR) tetramer dissociation is rate limiting for aggregation and subunit exchange. Slowing of TTR tetramer dissociation via kinetic stabiliser binding slows cardiomyopathy progression. Quadruplicate subunit exchange comparisons of the drug candidate AG10, and the drugs tolcapone, diflunisal, and tafamidis were carried out at 1, 5, 10, 20 and 30 µM concentrations in 4 distinct pooled wild type TTR (TTRwt) human plasma samples. These experiments reveal that the concentration dependence of the efficacy of each compound at inhibiting TTR dissociation was primarily determined by the ratio between the stabiliser's dissociation constants from TTR and albumin, which competes with TTR to bind kinetic stabilisers. The best stabilisers, tafamidis (80 mg QD), AG10 (800 mg BID), and tolcapone (3 x 100 mg over 12 h), exhibit very similar kinetic stabilisation at the plasma concentrations resulting from these doses. At a 10 µM plasma concentration, AG10 is slightly more potent as a kinetic stabiliser vs. tolcapone and tafamidis (which are similar), which are substantially more potent than diflunisal. Dissociation of TTR can be limited to 10% of its normal rate at concentrations of 5.7 µM AG10, 10.3 µM tolcapone, 12.0 µM tafamidis, and 188 µM diflunisal. The potency similarities revealed by our study suggest that differences in safety, adsorption and metabolism, pharmacokinetics, and tissue distribution become important for kinetic stabiliser clinical use decisions.

A multi-modal diagnostic model improves detection of cardiac amyloidosis among patients with diagnostic confirmation by cardiac biopsy.

BACKGROUND: Timely recognition of cardiac amyloidosis is clinically important, but the diagnosis is frequently delayed. OBJECTIVES: We sought to identify a multi-modality approach with the highest diagnostic accuracy in patients evaluated by cardiac biopsy, the diagnostic gold standard. METHODS: Consecutive patients (N = 242) who underwent cardiac biopsy for suspected amyloidosis within an 18-year period were retrospectively identified. Cardiac biomarker, ECG, and echocardiography results were examined for correlation with biopsy-proven disease. A prediction model for cardiac amyloidosis was derived using multivariable logistic regression. RESULTS: The overall cohort was characterized by elevated BNP (median 727 ng/mL), increased left ventricular wall thickness (IWT; median 1.7 cm), and reduced voltage-to-mass ratio (median 0.06 mm/[g/m2]). One hundred and thirteen patients (46%) had either light chain (n = 53) or transthyretin (n = 60) amyloidosis by cardiac biopsy. A prediction model including age, relative wall thickness, left atrial pressure by E/e', and low limb lead voltage (<0.5 mV) showed good discrimination for cardiac amyloidosis with an optimism-corrected c-index of 0.87 (95% CI 0.83-0.92). The diagnostic accuracy of this model (79% sensitivity, 84% specificity) surpassed that of traditional screening parameters, such as IWT in the absence of left ventricular hypertrophy on ECG (98% sensitivity, 20% specificity) and IWT with low limb lead voltage (49% sensitivity, 91% specificity). CONCLUSION: Among patients with an advanced infiltrative cardiomyopathy phenotype, traditional biomarker, ECG, and echocardiography-based screening tests have limited individual diagnostic utility for cardiac amyloidosis. A prediction algorithm including age, relative wall thickness, E/e', and low limb lead voltage improves the detection of cardiac biopsy-proven disease.

Hereditary transthyretin amyloidosis: current treatment.

PURPOSE OF REVIEW: Hereditary transthyretin amyloidosis (ATTRv) is a rare autosomal dominant, life-threatening disease. Until recently only early stages of ATTRv-PN (polyneuropathy) had access to disease-modifying therapy (DMT), whereas there was no specific treatment for ATTRv-CM (cardiomyopathy). This review updates our knowledge about results of three phase 3 clinical trials, expert's consensus for early diagnosis and emerging biomarkers. RECENT FINDINGS: Two phase 3 studies using RNAi and antisense oligonucleotides (ASO) were successful. Primary endpoints were progression of neuropathic score mNIS +7 and quality of Life (QOL) in a population of ATTRv-PN at different levels of severity. They knock downed circulating amyloidogenic mutant and wild-type TTR. Safety concerned ASO with a risk of thrombocytopenia. RNAi showed possible reversibility of the disease. Phase 3 ATTRACT trial-tested tafamidis versus placebo in patients with ATTRv-CM and ATTRwt-CM and showed a significant reduction of all-cause mortality and rates of cardiovascular-related hospitalizations. All three drugs obtained marketing authorization by European Medicines Agency (EMA) and Food and drug administration (FDA). Early diagnosis criteria for ATTRv-PN and ATTRv-CM are available. Ongoing clinical trials for ATTRv are presented. New biomarkers are plasma neurofilament light chain, intraepidermal nerve fiber density. SUMMARY: The majority of patients with ATTRv may have now access to a DMT. Criteria for early diagnosis are available.

Clinical, histopathological, and in silico pathogenicity analyses in a pedigree with familial amyloidosis of the Finnish type (Meretoja syndrome) caused by a novel gelsolin mutation.

Purpose: Familial amyloidosis of the Finnish type (FAF) is an inherited amyloidosis arising from mutations in the gelsolin protein (GSN). The disease includes facial paralysis, loose skin, and lattice corneal dystrophy. To date, FAF has been invariably associated with substitution of Asp214 in GSN. We describe the clinical, histopathological, and genetic features of a family with FAF due to a novel GSN mutation. Methods: Five affected adult individuals in a three-generation FAF pedigree were included in the study. Histopathological analysis was performed on an eyelid skin biopsy from one patient. Genetic analysis included next-generation sequencing (NGS) and Sanger sequencing for confirmation of the GSN variant. Several tools for in silico analysis of pathogenicity for the novel variant and to predict the effect of the amino acid replacement on protein stability were used. Results: Three older adult affected patients exhibited corneal lattice dystrophy, cutis laxa, and facultative peripheral neuropathy. Two younger adult individuals presented only with corneal amyloid deposits. NGS identified a heterozygous GSN c.1631T>G transversion, predicting a novel p.Met544Arg mutation. All in silico tools indicated that p.Met544Arg is deleterious for GSN functionality or stability. Conclusions: The results expand the molecular spectrum of GSN-linked systemic amyloidosis. The novel p.Met544Arg pathogenic variant is predicted to affect gelsolin function, presumably by impairing a potential calcium-sensitive, actin-binding region.

Disease-Specific Biomarkers in Transthyretin Cardiac Amyloidosis.

PURPOSE OF REVIEW: Transthyretin amyloidosis is an increasingly recognized cause of restrictive cardiomyopathy related to amyloid fibril deposition in cardiac tissues. As treatment therapies have emerged for transthyretin amyloidosis (ATTR), so has interest in using biomarkers to identify disease prior to advanced presentation. RECENT FINDINGS: Lower levels of transthyretin and retinol binding protein-4 have been demonstrated in patients with pathogenic mutations of transthyretin either with or without clinical disease. Levels associate with the severity of mutations as well as response to treatment with transthyretin stabilizers or small interfering RNA molecules which silence transthyretin production. Transthyretin stability is the rate limiting step of amyloid fibril formation and directly measuring transthyretin kinetic stability has the potential to identify patients as risk as well as therapeutic response to treatment regardless of pathogenic or wild-type genetics. In addition, non-antibody protein-based peptide probes have been developed that directedly measure misfolded transthyretin oligomers due to transthyretin breakdown. Although promising, both TTR kinetic and protein peptide probes remain in early stages of clinical investigation. Transthyretin, retinol binding protein-4, transthyretin kinetic stability, and protein-based peptide probes have potential as biomarkers to facilitate an earlier ATTR diagnosis for patients with pathogenic transthyretin mutations.

Population Pharmacokinetic-Pharmacodynamic Modeling of Inotersen, an Antisense Oligonucleotide for Treatment of Patients with Hereditary Transthyretin Amyloidosis.

A population pharmacokinetic (PK) and pharmacodynamic (PD) model was developed for inotersen to evaluate exposure-response relationships and to optimize therapeutic dosing regimen in patients with hereditary transthyretin (TTR) amyloidosis polyneuropathy (hATTR-PN). Inotersen PK and TTR level (PD) data were composed of one Phase 1 study in healthy subjects, one Phase 2/3 study in hATTR patients, and its one open-label extension study. Effects of intrinsic and extrinsic factors (covariates) on PK and PK/PD of inotersen were evaluated using a full model approach. Inotersen PK was characterized by a two-compartment model with elimination from the central compartment. The population PK analysis identified disease status and lean body mass (LBM) as significant covariates for inotersen PK. Nonetheless, the contribution of disease status and LBM on PK was small, as the difference in clearance (CL/F) was 11.1% between healthy subjects and patients with hATTR-PN and 38% between the lowest and highest LBM quartiles of the patient population. Age, race, sex, baseline renal function estimated glomerular filtration rate, and hepatic function markers (baseline albumin, bilirubin, and alanine aminotransferase values) were not statistically significant covariates affecting inotersen PK. An inhibitory effect indirect-response model (inhibition of TTR production) was used to describe the drug effect on TTR-time profiles, with baseline TTR included as a covariate. The overall population Imax and IC50, together with 95% confidence interval, was estimated to be 0.913 (0.899-0.925) and 9.07 (8.08-10.1) ng/mL, respectively. V30M mutation showed no effect on the estimated IC50 value for hATTR patients. The final population PK and PK/PD model was used to simulate four different treatment regimens. The population PK/PD model developed well described the PK and PD of inotersen in patients with hATTR-PN and has been used for label recommendation and trial simulations.

Population Pharmacokinetic-Pharmacodynamic Model of Serum Transthyretin Following Patisiran Administration.

Hereditary transthyretin-mediated amyloidosis is an inherited, rapidly progressive, life-threatening disease caused by mutated transthyretin (TTR) protein. Patisiran is a small interfering RNA (siRNA) formulated in a lipid nanoparticle that inhibits hepatic TTR protein synthesis by RNA interference. We have developed an indirect-response pharmacokinetic-pharmacodynamic model relating plasma siRNA (ALN-18328) levels to serum TTR reduction across five clinical studies. A sigmoidal function described this relationship, with estimated Hill coefficient of 0.548, and half maximal inhibitory concentration (IC50), IC80, and IC90 values of 9.45, 118.5, and 520.5 ng/mL, respectively. Following patisiran 0.3 mg/kg every 3 weeks (q3w), steady-state plasma ALN-18328 exposures were between IC80 and IC90, yielding average serum TTR reductions of 80%-90% from baseline. Covariate analysis indicated similar TTR reduction across evaluated intrinsic and extrinsic factors, obviating the need for dose adjustment. Modeling results support the recommended patisiran dosing schedule of 0.3 mg/kg q3w, with a maximum dose of 30 mg for patients weighing ≥100 kg.

Biomarkers and Prediction of Prognosis in Transthyretin-Related Cardiac Amyloidosis: Direct Comparison of Two Staging Systems.

BACKGROUND: The severity of heart disease varies widely among patients with transthyretin-related cardiac amyloidosis (ATTR-CA) at presentation, and availability of tools able to predict prognosis is essential for clinical and research purposes. Currently, two biomarker-based staging systems are available. The aim of this study was to compare their predictive performance. METHODS: A total of 175 patients diagnosed with ATTR-CA (133 wild-type and 42 hereditary) were stratified into different stages based on 2 systems: the first system included N-terminal pro-B-type natriuretic peptide (NT-proBNP) and estimated glomerular filtration rate (eGFR), and the second one included NT-proBNP and troponin I (TnI). Survival estimates and age-adjusted survival for all-cause mortality were analysed over a median follow-up of 27 months (interquartile range 16-43 months). RESULTS: Predictive performance was more accurate when NT-proBNP and eGFR were used, resulting in effective survival stratification: 64.4 months for stage 1, 44.6 months for stage 2, and 20.5 months for stage 3 (P < 0.01 for stages 1 vs 2; P < 0.0001 for stages 1 vs 3; P < 0.0001 stages 2 vs 3). The combination of NT-proBNP and TnI was unable to effectively differentiate survival: 64.5 months for stage 1, 50.9 months for stage 2, and 27.3 months for stage 3 (P = 0.223 for stages 1 vs 2; P < 0.0001 for stages 1 vs 3; P < 0.0001 for stages 2 vs 3). The same results were seen after age adjustment. CONCLUSIONS: A staging system using NT-proBNP and eGFR had better prognostic accuracy for ATTR-CA patients compared with one using NTproBNP and TnI.

Phase 3 Multicenter Study of Revusiran in Patients with Hereditary Transthyretin-Mediated (hATTR) Amyloidosis with Cardiomyopathy (ENDEAVOUR).

PURPOSE: The Phase 3 ENDEAVOUR study evaluated revusiran, an investigational RNA interference therapeutic targeting hepatic transthyretin (TTR) production, for treating cardiomyopathy caused by hereditary transthyretin-mediated (hATTR) amyloidosis. METHODS: Patients with hATTR amyloidosis with cardiomyopathy were randomized 2:1 to receive subcutaneous daily revusiran 500 mg (n = 140) or placebo (n = 66) for 5 days over a week followed by weekly doses. Co-primary endpoints were 6-min walk test distance and serum TTR reduction. RESULTS: Revusiran treatment was stopped after a median of 6.71 months; the study Sponsor prematurely discontinued dosing due to an observed mortality imbalance between treatment arms. Eighteen (12.9%) patients on revusiran and 2 (3.0%) on placebo died during the on-treatment period. Most deaths in both treatment arms were adjudicated as cardiovascular due to heart failure (HF), consistent with the natural history of the disease. A post hoc safety investigation of patients treated with revusiran found that, at baseline, a greater proportion of those who died were ≥ 75 years and showed clinical evidence of more advanced HF compared with those who were alive throughout treatment. Revusiran pharmacokinetic exposures and TTR lowering did not show meaningful differences between patients who died and who were alive. Revusiran did not deleteriously affect echocardiographic parameters, cardiac biomarkers, or frequency of cardiovascular and HF hospitalization events. CONCLUSIONS: Causes for the observed mortality imbalance associated with revusiran were thoroughly investigated and no clear causative mechanism could be identified. Although the results suggest similar progression of cardiac parameters in both treatment arms, a role for revusiran cannot be excluded. CLINICAL TRIAL REGISTRATION: NCT02319005.

Plasma neurofilament light chain: an early biomarker for hereditary ATTR amyloid polyneuropathy.

Background: Transthyretin amyloidosis due to V30M mutation (ATTR-V30M) is the most frequent hereditary ATTR amyloidosis. Besides neurophysiological measures, there are no biomarkers to detect preclinical disease or monitor disease progression. CSF or plasma neurofilament light chain (pNfL) have recently been considered sensitive biomarkers to quantitate neuro-axonal damage in several disorders of the peripheral and central nervous system.Objective: Characterise plasma NfL levels in a series of untreated ATTR-V30M patients stratified by clinical severity using a cross-sectional retrospective study design.Methods: Sixty ATTR-V30M patients and 16 controls from 2 independent cohorts were analysed for pNfL by single-molecule array assay (SIMOA) technique. Disease severity was assessed with Polyneuropathy Disability Score.Results: pNfL is elevated in ATTR-V30M patients as a function of disease severity in both cohorts. Moreover, pNfL discriminates asymptomatic mutation carriers from early symptomatic patients (AUC = 0.97; p < .001) with high sensitivity (92.3%) and specificity (93.8%). pNfL elevation (>66.9 pg/mL) also discriminates patients with sensory neuropathy from patients with motor neuropathy (AUC = 0.91; p < .01) with a sensitivity of 61.5% and a specificity of 92.3%.Conclusion: pNfL is an easily accessible biomarker to establish ATTR-V30M disease conversion and to monitor disease progression. pNfL could be used as efficacy measure of disease-oriented therapies in clinical and pre-clinical trials.

Patisiran Pharmacokinetics, Pharmacodynamics, and Exposure-Response Analyses in the Phase 3 APOLLO Trial in Patients With Hereditary Transthyretin-Mediated (hATTR) Amyloidosis.

Hereditary transthyretin-mediated (hATTR) amyloidosis is an inherited, rapidly progressive, life-threatening disease caused by deposition of abnormal transthyretin protein. Patisiran is an RNA interference therapeutic comprising a novel, small interfering ribonucleic acid (ALN-18328) formulated in a lipid nanoparticle targeted to inhibit hepatic transthyretin protein synthesis. The lipid nanoparticle also contains 2 novel lipid excipients (DLin-MC3-DMA and PEG2000 -C-DMG). Here we report patisiran pharmacokinetics (PK), pharmacodynamics (PD), and exposure-response analyses from the phase 3 APOLLO trial, in which patients with hATTR amyloidosis with polyneuropathy were randomized 2:1 to receive patisiran 0.3 mg/kg or placebo intravenously every 3 weeks over 18 months. In patisiran-treated patients, mean maximum reduction in serum transthyretin level from baseline was 87.8%. Patisiran PK exposure was stable following chronic dosing. There were no meaningful differences in PK exposure, serum transthyretin reduction, and efficacy (change from baseline in modified Neuropathy Impairment Score+7) across all subgroups analyzed (age, sex, race, body weight, genotype status of valine-to-methionine mutation at position 30 [V30M] and non-V30M, prior use of tetramer stabilizers, mild/moderate renal impairment, and mild hepatic impairment). transthyretin reduction and efficacy were similar across the interpatient PK exposure range for ALN-18328. There was no trend in the incidence of adverse events or serious adverse events across the interpatient PK exposure range for all 3 analytes. Incidence of antidrug antibodies was low (3.4%) and transient, with no impact on PK, PD, efficacy, or safety. The patisiran dosing regimen of 0.3 mg/kg every 3 weeks is appropriate for all patients with hATTR amyloidosis.

Integrated diagnostic approach to wild-type transthyretin cardiac amyloidosis with the use of high-sensitivity cardiac troponin T measurement and 99mTc-pyrophosphate scintigraphy.

BACKGROUND: The diagnosis of wild-type transthyretin cardiac amyloidosis (ATTRwt) is frequently missed or delayed because of the limited specificity of manifestations. We investigated the utility of combined assessment of high-sensitivity cardiac troponin T (hs-cTnT) measurement and 99mTc-pyrophosphate (99mTc-PYP) scintigraphy as diagnostic modalities in ATTRwt. METHODS: We divided 39 consecutive ATTRwt patients into two groups depending on whether serum hs-cTnT measurement and 99mTc-PYP scintigraphy were adopted as diagnostic tools: group A patients (n=8) who were diagnosed before the introduction of these two tools and group B patients (n=31) who were diagnosed after the introduction of the two tools. We retrospectively evaluated the two groups. RESULTS: Diagnostic yield was higher in group B than in group A (1.2 vs. 5.4 ATTRwt patients per 1000 hospitalized patients, p<0.01). Group B patients presented broad clinical features that were different from group A patients with classical characteristics. Atrial fibrillation was more frequent (12.5% vs. 58.1%, p=0.044) and inter-ventricular septum (IVS) thickness and relative wall thickness (RWT) were smaller in group B patients than in group A patients (IVS thickness: 16.1±2.4mm vs. 13.6±2.8mm, p=0.023; RWT: 0.71±0.11mm vs. 0.58±0.13mm, p=0.014). Furthermore, left ventricular hypertrophy (LVH) (IVS thickness ≥15mm) was more frequent in patients in group A than in patients in group B (87.5% vs. 33.3%, p=0.013). No significant difference was observed in the mean value of left ventricular ejection fraction (LVEF), whereas the dispersion of LVEF was high in group B (interquartile range: 47-58% vs. 39-57%). CONCLUSIONS: An integrated approach consisting of hs-cTnT measurement and 99mTc-PYP scintigraphy significantly increases the diagnostic rate of ATTRwt and has a high potential to identify ATTRwt patients with a variety of clinical phenotypes.

[Severe hypocupremia and familial amyloid polyneuropathy]. / Hipocupremia severa y polineuropatía amiloidótica familiar por transtiretina.

INTRODUCTION: Introduction: we report a patient with transthyretin familial amyloid polyneuropathy (TTR-FAP) and severe hypocupremia. Case report: a 79-year-old male with TTR-FAP and severe malnutrition. Laboratory tests showed low serum copper (Cu) and ceruloplasmin levels, as well as low urinary Cu levels. The patient reported neither digestive symptoms nor previous gastrointestinal surgery. Liver function tests, iron metabolism, hemoglobin, leukocytes and zinc were normal. Discussion: Cu is a trace element. It is part of the cuproenzymes involved in several physiological functions. Hypocupremia can be related to genetic or acquired etiologies, including low intake, bariatric surgery, increased losses, etc. Primary clinical manifestations include hematological (anemia and leukopenia) and neurological (myelopathy, peripheral neuropathy) features. Treatment is empirical. In severe cases it may be initiated with endovenose administration, followed by oral supplementation.

INTRODUCCIÓN: Introducción: presentamos el caso de un paciente con antecedentes de polineuropatía amiloidótica familiar por transtiretina (TTR-FAP) diagnosticado de hipocupremia severa. Caso clínico: varón de 79 años afecto de TTR-FAP. Visto en consulta de nutrición por desnutrición severa. En el estudio analítico presenta cifras de cobre (Cu) sérico y ceruloplasmina bajas, con Cu en orina también bajo. No tiene clínica digestiva ni antecedentes de cirugía gastrointestinal. Las pruebas de función hepática, la ferrocinética, las cifras de Hb y leucocitos y los niveles de zinc (Zn) no presentan alteraciones relevantes. Discusión: el Cu es un oligoelemento que participa como componente de las cuproenzimas en múltiples funciones fisiológicas. Los niveles séricos bajos pueden relacionarse con causas genéticas o adquiridas, como la baja ingesta, la cirugía bariátrica, el aumento de las pérdidas, etc. Las principales manifestaciones clínicas son hematológicas (anemia, leucopenia) o neurológicas (mielopatía, neuropatía periférica). El tratamiento tiene base empírica. En los casos severos puede iniciarse con administración intravenosa, seguido de mantenimiento por vía oral.

APOE polymorphism in ATTR amyloidosis patients treated with lipid nanoparticle siRNA.

The novel class of compounds represented by lipid nanoparticle (LNP)-encapsulated siRNA formulations has an enormous potential to target disease, notably of the liver. Endocytosis of LNPs is believed to be mediated by APOE, an important serum protein of lipoprotein homeostasis. APOE polymorphisms affect binding to hepatic receptors and have been associated with development of specific disease. Here, the role of APOE was investigated with regard to the efficacy of Patisiran, the first LNP-siRNA recently approved for clinical use in patients having transthyretin amyloidosis (ATTR amyloidosis). Patisiran was evaluated in the human hepatoma cell line HepG2 after knockdown of APOE. The APOE genotype was determined in ATTR amyloidosis patients treated with Patisiran. TTR knockdown was monitored in consecutive plasma up to week 12. Downregulation of APOE suppressed efficacy of Patisiran in HepG2 cells. TTR levels were found to be robustly reduced (84.7% ± 1%) following Patisiran treatment in patients plasma. Analysis of APOE polymorphisms in ATTR amyloidosis patients revealed three most frequent genotypes E3/3, E3/4 and E3/2. APOE stratification of patients did not show significant differences of TTR plasma concentrations following treatment. Our results suggest that APOE is an important mediator of TTR silencing by Patisiran, however efficacy is independent of the APOE genotype.