Treatment of hereditary and acquired forms of transthyretin amyloidosis in the era of personalized medicine: the role of randomized controlled trials

Longitudinal analysis of serum neurofilament light chain levels as marker for neuronal damage in hereditary transthyretin amyloidosis

OBJECTIVE

To evaluate serum neurofilament light chain (sNfL) as biomarker of disease onset, progression and treatment effect in hereditary transthyretin (ATTRv) amyloidosis patients and TTR variant (TTRv) carriers.

METHODS

sNfL levels were assessed longitudinally in persistently asymptomatic TTRv carriers (N = 12), persistently asymptomatic ATTRv amyloidosis patients (defined as asymptomatic patients but with amyloid detectable in subcutaneous abdominal fat tissue) (N = 8), in TTRv carriers who developed polyneuropathy (N = 7) and in ATTRv amyloidosis patients with polyneuropathy on treatment (TTR-stabiliser (N = 20) or TTR-silencer (N = 18)). Polyneuropathy was confirmed by nerve conduction studies or quantitative sensory testing. sNfL was analysed using a single-molecule array assay.

RESULTS

sNfL increased over 2 years in persistently asymptomatic ATTRv amyloidosis patients, but did not change in persistently asymptomatic TTRv carriers. In all TTRv carriers who developed polyneuropathy, sNfL increased from 8.4 to 49.8 pg/mL before the onset of symptoms and before polyneuropathy could be confirmed neurophysiologically. In symptomatic ATTRv amyloidosis patients on a TTR-stabiliser, sNfL remained stable over 2 years. In patients on a TTR-silencer, sNfL decreased after 1 year of treatment.

CONCLUSION

sNfL is a biomarker of early neuronal damage in ATTRv amyloidosis already before the onset of polyneuropathy. Current data support the use of sNfL in screening asymptomatic TTRv carriers and in monitoring of disease progression and treatment effect.

Cardiac [99mTc]Tc-hydroxydiphosphonate uptake on bone scintigraphy in patients with hereditary transthyretin amyloidosis: an early follow-up marker?

PURPOSE

There is a need for early quantitative markers of potential treatment response in patients with hereditary transthyretin (ATTRv) amyloidosis to guide therapy. This study aims to evaluate changes in cardiac tracer uptake on bone scintigraphy in ATTRv amyloidosis patients on different treatments.

METHODS

In this retrospective cohort study, outcomes of 20 patients treated with the transthyretin (TTR) gene silencer patisiran were compared to 12 patients treated with a TTR-stabilizer. Changes in NYHA class, cardiac biomarkers in serum, wall thickness, and diastolic parameters on echocardiography and NYHA class during treatment were evaluated.

RESULTS

Median heart/whole-body (H/WB) ratio on bone scintigraphy decreased from 4.84 [4.00 to 5.31] to 4.16 [3.66 to 4.81] (p < .001) in patients treated with patisiran for 29 [15-34] months. No changes in the other follow-up parameters were observed. In patients treated with a TTR-stabilizer for 24 [20 to 30] months, H/WB ratio increased from 4.46 [3.24 to 5.13] to 4.96 [ 3.39 to 5.80] (p = .010), and troponin T increased from 19.5 [9.3 to 34.0] ng/L to 20.0 [11.8 to 47.8] ng/L (p = .025). All other parameters did not change during treatment with a TTR-stabilizer.

CONCLUSION

A change in cardiac tracer uptake on bone scintigraphy may be an early marker of treatment-specific response or disease progression in ATTRv amyloidosis patients.

A Comprehensive Multidisciplinary Diagnostic Algorithm for the Early and Efficient Detection of Amyloidosis

Amyloidosis is a rare protein misfolding disease caused by the accumulation of amyloid fibrils in various tissues and organs. There are different subtypes of amyloidosis, with light chain (AL) amyloidosis being the most common. Amyloidosis is notoriously difficult to diagnose because it is clinically heterogeneous, no single test is diagnostic for the disease, and diagnosis typically involves multiple specialists. Here, we propose an integrated, multidisciplinary algorithm for efficiently diagnosing amyloidosis. Drawing on research from several medical disciplines, we have combined clinical decisions and best practices into a comprehensive algorithm to facilitate the early detection of amyloidosis. Currently, many patients are diagnosed more than 6 months after symptom onset, yet early diagnosis is the major predictor of survival. Our algorithm aims to shorten the time to diagnosis with efficient sequencing of tests and minimizing uninformative investigations. We also recommend typing and staging of confirmed amyloidosis to guide treatment. By reducing time to diagnosis, our algorithm could lead to earlier and more targeted treatment, ultimately improving prognosis and survival.

Factors Associated with Increased Health-Related Quality of Life Benefits in Patients with Hereditary Transthyretin Amyloidosis with Polyneuropathy (ATTRv-PN) Treated with Inotersen

INTRODUCTION/AIMS

Hereditary transthyretin amyloidosis with polyneuropathy (ATTRv-PN) is a genetic condition associated with significant morbidity and mortality. We aimed to identify patient subgroups exhibiting the greatest health-related quality of life [HRQL] benefit from inotersen treatment.

METHODS

We examined data from the inotersen phase 2/3 randomized controlled trial for ATTRv-PN, NEURO-TTR (NCT01737398, 66 weeks). LASSO regression models predicted changes in Norfolk QoL-DN total score (TQoL, range -4 to 136; higher scores indicate poorer HRQL) from baseline in the inotersen and placebo arm, respectively. Individualized efficacy scores (ES) were calculated as differences between predicted change-scores had patients received inotersen vs. placebo. Patients were ranked by ES to define the greatest-benefit subpopulation (top 50%). Characteristics of the top 50% and bottom 50% of patients were compared.

RESULTS

The overall mean ± standard deviation TQoL change was -0.20±19.13 for inotersen (indicating no change) and 10.77±21.13 for placebo (indicating deterioration). Within the highest-benefit patients, mean TQoL change was -11.03±17.06 (improvement) for inotersen and 11.24±22.97 (deterioration) for placebo (P<0.001). Compared with the overall population, patients in the greatest-benefit subpopulation were younger, more likely to have polyneuropathy disability (PND) scores 1 or 2, less likely to have received prior tafamidis or diflunisal treatment, and more likely to have Val30Met mutations and higher (worse) baseline TQoL.

CONCLUSION

Patients who were younger and/or at earlier polyneuropathy stages experienced greater HRQL benefits from inotersen over 66 weeks. These findings underscore the need for early diagnosis and treatment initiation, especially among more severely affected patients in early stages of ATTRv-PN. This article is protected by copyright. All rights reserved.

A circulating, disease-specific, mechanism-linked biomarker for ATTR polyneuropathy diagnosis and response to therapy prediction

The transthyretin (TTR) amyloidoses (ATTR) are progressive, degenerative diseases resulting from dissociation of the TTR tetramer to monomers, which subsequently misfold and aggregate, forming a spectrum of aggregate structures including oligomers and amyloid fibrils. To determine whether circulating nonnative TTR (NNTTR) levels correlate with the clinical status of patients with V30M TTR familial amyloid polyneuropathy (FAP), we quantified plasma NNTTR using a newly developed sandwich enzyme-linked immunosorbent assay. The assay detected significant plasma levels of NNTTR in most presymptomatic V30M TTR carriers and in all FAP patients. NNTTR was not detected in age-matched control plasmas or in subjects with other peripheral neuropathies, suggesting NNTTR can be useful in diagnosing FAP. NNTTR levels were substantially reduced in patients receiving approved FAP disease-modifying therapies (e.g., the TTR stabilizer tafamidis, 20 mg once daily). This NNTTR decrease was seen in both the responders (average reduction 56.4 ± 4.2%; n = 49) and nonresponders (average reduction of 63.3 ± 4.8%; n = 32) at 12 mo posttreatment. Notably, high pretreatment NNTTR levels were associated with a significantly lower likelihood of clinical response to tafamidis. Our data suggest that NNTTR is a disease driver whose reduction is sufficient to ameliorate FAP so long as pretreatment NNTTR levels are below a critical clinical threshold.

Does protein aggregation drive postmitotic tissue degeneration?

Pharmacological evidence, from clinical trials where patients with systemic amyloid diseases are treated with disease-modifying therapies, supports the notion that protein aggregation drives tissue degeneration in these disorders. The protein aggregate structures driving tissue pathology and the commonalities in etiology between these diseases and Alzheimer's disease are under investigation.

Multidisciplinary Approaches for Transthyretin Amyloidosis

Amyloidosis caused by systemic deposition of transthyretin (TTR) is called ATTR amyloidosis and mainly includes hereditary ATTR (ATTRv) amyloidosis and wild-type ATTR (ATTRwt) amyloidosis. Until recently, ATTRv amyloidosis had been considered a disease in the field of neurology because neuropathic symptoms predominated in patients described in early reports, whereas advances in diagnostic techniques and increased recognition of this disease revealed the presence of patients with cardiomyopathy as a predominant feature. In contrast, ATTRwt amyloidosis has been considered a disease in the field of cardiology. However, recent studies have suggested that some of the patients with ATTRwt amyloidosis present tenosynovial tissue complications, particularly carpal tunnel syndrome, as an initial manifestation of amyloidosis, necessitating an awareness of this disease among neurologists and orthopedists. Although histopathological confirmation of amyloid deposits has traditionally been considered mandatory for the diagnosis of ATTR amyloidosis, the development of noninvasive imaging techniques in the field of cardiology, such as echocardiography, magnetic resonance imaging, and nuclear imaging, enabled nonbiopsy diagnosis of this disease. The mechanisms underlying characteristic cardiac imaging findings have been deciphered by histopathological studies. Novel disease-modifying therapies for ATTR amyloidosis, such as TTR stabilizers, short interfering RNA, and antisense oligonucleotides, were initially approved for ATTRv amyloidosis patients with polyneuropathy. However, the indications for the use of these disease-modifying therapies gradually widened to include ATTRv and ATTRwt amyloidosis patients with cardiomyopathy. Since the coronavirus disease 2019 (COVID-19) pandemic, which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, occurred, the minimization of hospital visits and telemedicine have become increasingly important. As older age and cardiovascular disease are major factors associated with increased disease severity and mortality of COVID-19, many ATTR amyloidosis patients are at increased risk of disease aggravation when they are infected with SARS-CoV-2. From this viewpoint, close interspecialty communication to determine the optimal interval of evaluation is needed for the management of patients with ATTR amyloidosis.

MALDI mass spectrometry imaging unravels organ and amyloid-type specific peptide signatures in pulmonary and gastrointestinal amyloidosis

PURPOSE

Amyloidosis is a disease group caused by pathological aggregation and deposition of peptides in diverse tissue sites. Recently, matrix-assisted laser desorption/ionization mass spectrometry imaging coupled with ion mobility separation (MALDI-IMS MSI) was introduced as a novel tool to identify and classify amyloidosis using single sections from formalin-fixed and paraffin-embedded cardiac biopsies. Here, we tested the hypothesis that MALDI-IMS MSI can be applied to lung and gastrointestinal specimens.

EXPERIMENTAL DESIGN

Forty six lung and 65 gastrointestinal biopsy and resection specimens with different types of amyloid were subjected to MALDI-IMS MSI. Ninety three specimens included tissue areas without amyloid as internal negative controls. Nine cases without amyloid served as additional negative controls.

RESULTS

Utilizing a peptide filter method and 21 known amyloid specific tryptic peptides we confirmed the applicability of a universal peptide signature with a sensitivity of 100% and a specificity of 100% for the detection of amyloid deposits in the lung and gastrointestinal tract. Additionally, the frequencies of individual m/z-values of the 21 tryptic marker peptides showed organ- and tissue-type specific differences.

CONCLUSIONS AND CLINICAL RELEVANCE

MALDI-IMS MSI adds a valuable analytical approach to diagnose and classify amyloid and the detection frequency of individual tryptic peptides is organ-/tissue-type specific.

Use of Drugs for ATTRv Amyloidosis in the Real World: How Therapy Is Changing Survival in a Non-Endemic Area

Background: Over the past decade, three new drugs have been approved for the treatment of hereditary amyloid transthyretin (ATTRv) polyneuropathy. The aim of this work was to analyze whether current therapies prolong survival for patients affected by ATTRv amyloidosis. Methods: The study was conducted retrospectively, analyzing the medical records of 105 patients with genetic diagnoses of familial amyloidotic polyneuropathy followed at the two referral centers for the disease in Sicily, Italy. Of these, 71 received disease-modifying therapy, while 34 received only symptomatic treatment or no therapy. Results: The most used treatment in our patient cohort was tafamidis, followed by liver transplantation, patisiran, inotersen, and diflunisal. The median survival was significantly longer for treated vs. untreated patients (12 years vs. 8 years). In the 71 patients who received disease-modifying treatment, the presence of cardiac involvement, weight loss, or autonomic dysfunction at diagnosis was not related to survival. Conversely, patients diagnosed in the early stage of the disease (PND 1) had significantly longer survival than those diagnosed in the late stage (PND 2–4).

Expression of Amyloidogenic Transthyretin Drives Hepatic Proteostasis Remodeling in an Induced Pluripotent Stem Cell Model of Systemic Amyloid Disease

The systemic amyloidoses are diverse disorders in which misfolded proteins are secreted by effector organs and deposited as proteotoxic aggregates at downstream tissues. Although well described clinically, the contribution of synthesizing organs to amyloid disease pathogenesis is unknown. Here, we utilize hereditary transthyretin amyloidosis (ATTR amyloidosis) induced pluripotent stem cells (iPSCs) to define the contribution of hepatocyte-like cells (HLCs) to the proteotoxicity of secreted transthyretin (TTR). To this end, we generated isogenic, patient-specific iPSCs expressing either amyloidogenic or wild-type TTR. We combined this tool with single-cell RNA sequencing to identify hepatic proteostasis factors correlating with destabilized TTR production in iPSC-derived HLCs. By generating an ATF6 inducible patient-specific iPSC line, we demonstrated that enhancing hepatic ER proteostasis preferentially reduces the secretion of amyloidogenic TTR. These data highlight the liver's capacity to chaperone misfolded TTR prior to deposition, and moreover suggest the potential for unfolded protein response modulating therapeutics in the treatment of diverse systemic amyloidoses.