Stabilization of Cardiac Function With Diflunisal in Transthyretin (ATTR) Cardiac Amyloidosis

Vutrisiran: a new drug in the treatment landscape of hereditary transthyretin amyloid polyneuropathy

INTRODUCTION

Hereditary transthyretin (ATTRv) amyloidosis is a progressive, fatal disorder caused by mutations in the transthyretin (TTR) gene leading to deposition of the misfolded protein in amyloid fibrils. The main phenotypes are peripheral neuropathy (PN) and cardiomyopathy (CM).

AREAS COVERED

Gene silencing therapy, by dramatically reducing liver production of TTR, has transformed ATTRv-PN patient care in the last decade. In this drug discovery case history, the authors discuss the treatment history of ATTRv-PN and focus on the latest siRNA therapy: vutrisiran. Vutrisiran is chemically enhanced and N-acetylgalactosamin-conjugated, allowing increased stability and specific liver delivery. HELIOS-A, a phase III, multicenter randomized study, tested vutrisiran in ATTRv-PN and showed significant improvement in neuropathy impairment, disability, quality of life (QoL), gait speed, and nutritional status. Tolerance was acceptable, no safety signals were raised.

EXPERT OPINION

Vutrisiran offers a new treatment option for patients with ATTRv-PN. Vutrisian's easier delivery and administration route, at a quarterly frequency, as well as the absence of premedication, are major improvements to reduce patients' disease burden and improve their QoL. Its place in the therapeutic strategy is to be determined, considering affordability.

Cardiac Amyloidosis Due to Transthyretin Protein: A Review

Importance

Systemic amyloidosis from transthyretin (ATTR) protein is the most common type of amyloidosis that causes cardiomyopathy.

Observations

Transthyretin (TTR) protein transports thyroxine (thyroid hormone) and retinol (vitamin A) and is synthesized predominantly by the liver. When the TTR protein misfolds, it can form amyloid fibrils that deposit in the heart causing heart failure, heart conduction block, or arrhythmia such as atrial fibrillation. The biological processes by which amyloid fibrils form are incompletely understood but are associated with aging and, in some patients, affected by inherited variants in the TTR genetic sequence. ATTR amyloidosis results from misfolded TTR protein deposition. ATTR can occur in association with normal TTR genetic sequence (wild-type ATTR) or with abnormal TTR genetic sequence (variant ATTR). Wild-type ATTR primarily manifests as cardiomyopathy while ATTR due to a genetic variant manifests as cardiomyopathy and/or polyneuropathy. Approximately 50 000 to 150 000 people in the US have heart failure due to ATTR amyloidosis. Without treatment, heart failure due to ATTR amyloidosis is associated with a median survival of approximately 5 years. More than 130 different inherited genetic variants in TTR exist. The most common genetic variant is Val122Ile (pV142I), an allele with an origin in West African countries, that is present in 3.4% of African American individuals in the US or approximately 1.5 million persons. The diagnosis can be made using serum free light chain assay and immunofixation electrophoresis to exclude light chain amyloidosis combined with cardiac nuclear scintigraphy to detect radiotracer uptake in a pattern consistent with amyloidosis. Loop diuretics, such as furosemide, torsemide, and bumetanide, are the primary treatment for fluid overload and symptomatic relief of patients with ATTR heart failure. An ATTR-directed therapy that inhibited misfolding of the TTR protein (tafamidis, a protein stabilizer), compared with placebo, reduced mortality from 42.9% to 29.5%, reduced hospitalizations from 0.7/year to 0.48/year, and was most effective when administered early in disease course.

Conclusions and Relevance

ATTR amyloidosis causes cardiomyopathy in up to approximately 150 000 people in the US and tafamidis is the only currently approved therapy. Tafamidis slowed progression of ATTR amyloidosis and improved survival and prevented hospitalization, compared with placebo, in people with ATTR-associated cardiomyopathy.

Molecular mechanisms and emerging therapies in wild-type transthyretin amyloid cardiomyopathy

Wild-type transthyretin amyloid cardiomyopathy (ATTRwt-CM) is an underrecognized cause of heart failure due to misfolded wild-type transthyretin (TTRwt) myocardial deposition. The development of wild-type TTR amyloid fibrils is a complex pathological process linked to the deterioration of homeostatic mechanisms owing to aging, plausibly implicating multiple molecular mechanisms. The components of amyloid transthyretin often include serum amyloid P, proteoglycans, and clusterin, which may play essential roles in the localization and elimination of amyloid fibrils. Oxidative stress, impaired mitochondrial function, and perturbation of intracellular calcium dynamics induced by TTR contribute to cardiac impairment. Recently, tafamidis has been the only drug approved by the U.S. Food and Drug Administration (FDA) for the treatment of ATTRwt-CM. In addition, small interfering RNAs and antisense oligonucleotides for ATTR-CM are promising therapeutic approaches and are currently in phase III clinical trials. Newly emerging therapies, such as antibodies targeting amyloid, inhibitors of seed formation, and CRISPR‒Cas9 technology, are currently in the early stages of research. The development of novel therapies is based on progress in comprehending the molecular events behind amyloid cardiomyopathy. There is still a need to further advance innovative treatments, providing patients with access to alternative and effective therapies, especially for patients diagnosed at a late stage.

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 Review on Chemistry and Biology of Tafamidis in Transthyretin Amyloidosis

Transthyretin amyloid cardiomyopathy and Transthyretin amyloid peripheral neuropathy are progressive disease conditions caused by Transthyretin amyloidosis (ATTR) fibril infiltration in the tissue. Transthyretin (TTR) protein misfolding and amyloid fibril deposits are pathological biomarkers of ATTR-related disorders. There are various treatment strategies targeting different stages in pathophysiology. One such strategy is TTR tetramer stabilization. Recently, a new TTR tetramer stabilizer, tafamidis, has been introduced that reduces the protein misfolding and amyloidosis and, consequently, disease progression in ATTR cardiomyopathy and peripheral neuropathy. This review will provide a comprehensive overview of the literature on tafamidis discovery, development, synthetic methods, pharmacokinetics, analytical methods and clinical trials. Overall, 7 synthetic methods, 5 analytical methods and 23 clinical trials have been summarized from the literature.

Emerging therapeutic avenues in cardiac amyloidosis

Cardiac Amyloidosis (CA) is a toxic infiltrative cardiomyopathy occurred by the deposition of the amyloid fibres in the extracellular matrix of the myocardium. This results in severe clinical complications such as increased left ventricular wall thickness and interventricular stiffness, a decrease in left ventricular stroke volume and cardiac output, diastolic dysfunction, arrhythmia, etc. In a prolonged period, this condition progresses into heart failure. The amyloid fibres affecting the heart include immunoglobulin light chain (AL - amyloidosis) and transthyretin protein (ATTR - amyloidosis) misfolded amyloid fibres. ATTRwt has the highest prevalence of 155 to 191 cases per million while ATTRv has an estimated prevalence of 5.2 cases per million. The pathological findings and therapeutic approaches developed recently have aided in the treatment regimen of cardiac amyloidosis patients. In recent years, understanding the pathophysiology of amyloid fibres formation and mechanistic pathways triggered in both types of cardiac amyloidosis has led to the development of new therapeutic approaches and agents. This review focuses on the current status of emerging therapeutic agents in clinical trials. Earlier, melphalan and bortezomib in combination with alkylating agents and immunomodulatory drugs were used as a standard therapy for AL amyloidosis. Tafamidis, approved recently by FDA is used as a standard for ATTR amyloidosis. However, the emerging therapeutic agents under development for the treatment of AL and ATTR cardiac amyloidosis have shown a potent and rapid effect with a safety profile.

Recent Progress in the Development and Clinical Application of New Drugs for Transthyretin Cardiac Amyloidosis

ABSTRACT

Transthyretincardiac amyloidosis is a rare disease that has gained significant attention in recent years because of misfolding of transthyretin fibrils produced by the liver, leading to their deposition in the myocardium. The disease has an insidious onset, nonspecific clinical manifestations, and historically lacked effective drugs, making early diagnosis and treatment challenging. The survival time of patients largely depends on the extent of heart involvement at the time of diagnosis, and conventional treatments for cardiovascular disease do not provide significant benefits. Effective management of the disease requires treatment of its underlying cause. Orthotopic liver transplantation and combined hepato-heart transplantation have been clinically effective means of treating transthyretin cardiac amyloidosis mutants for many years. However, transplantation has many limitations in clinical practice. In recent years, the development of new drugs has brought new hope to patients. This review presents the latest advances in drug development and clinical application to provide a reference for clinicians managing transthyretin cardiac amyloidosis.

World Heart Federation Consensus on Transthyretin Amyloidosis Cardiomyopathy (ATTR-CM)

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressive and fatal condition that requires early diagnosis, management, and specific treatment. The availability of new disease-modifying therapies has made successful treatment a reality. Transthyretin amyloid cardiomyopathy can be either age-related (wild-type form) or caused by mutations in the TTR gene (genetic, hereditary forms). It is a systemic disease, and while the genetic forms may exhibit a variety of symptoms, a predominant cardiac phenotype is often present. This document aims to provide an overview of ATTR-CM amyloidosis focusing on cardiac involvement, which is the most critical factor for prognosis. It will discuss the available tools for early diagnosis and patient management, given that specific treatments are more effective in the early stages of the disease, and will highlight the importance of a multidisciplinary approach and of specialized amyloidosis centres. To accomplish these goals, the World Heart Federation assembled a panel of 18 expert clinicians specialized in TTR amyloidosis from 13 countries, along with a representative from the Amyloidosis Alliance, a patient advocacy group. This document is based on a review of published literature, expert opinions, registries data, patients' perspectives, treatment options, and ongoing developments, as well as the progress made possible via the existence of centres of excellence. From the patients' perspective, increasing disease awareness is crucial to achieving an early and accurate diagnosis. Patients also seek to receive care at specialized amyloidosis centres and be fully informed about their treatment and prognosis.

Safety and Efficacy of Traditional Heart Failure Therapies in Patients With Cardiac Amyloidosis and Heart Failure

Randomized controlled trials have demonstrated mortality benefits for several medication classes in patients with heart failure (HF), especially with reduced ejection fraction (EF). However, the benefit of these traditional HF therapies in patients with HF from cardiac amyloidosis is unclear. our study aimed to evaluate the safety and efficacy of traditional HF therapies in patients with cardiac amyloidosis and HF with reduced EF or HF with mid-range EF (HFmrEF). We conducted a single-center retrospective study. Patients were included if they were diagnosed with cardiac amyloidosis and HF with reduced EF or HF with mid-range EF between January 2012 and 2022. The primary outcomes of interest were medication use patterns (for β blockers [BB], angiotensin-converting enzyme inhibitors [ACEI], angiotensin receptor blockers [ARBs], angiotensin receptor neprilysin inhibitors [ARNI], and mineralocorticoid receptor antagonists [MRAs]); potential medication side effects (symptomatic bradycardia, fatigue, hypotension, lightheadedness, and syncope); hospitalization; and death. The associations of BB, ACEI/ARB/ARNI, and MRA use with clinical outcomes were evaluated using Kaplan-Meier and Cox proportional hazards regression. A total of 82 patients met study criteria. At time of cardiac amyloidosis diagnosis, 63.4% were on a BB, 51.2% were on an ACEI/ARB/ARNI, and 43.9% were on an MRA. At last follow-up, 51.2% were on a BB, 35.4% were on an ACEI/ARB/ARNI, and 43.9% were on an MRA. There were no statistically significant differences in rates of potential medication side effects in patients on the medication class compared with those who were not. There was no association with hospitalization or mortality for baseline or follow-up BB, ACEI/ARB/ARNI, or MRA use. In conclusion, BBs, ACEI/ARB/ARNIs, and MRAs may be safely used in this population. However, their use does not appear to improve mortality or hospitalization.

Targeted Therapeutics for Transthyretin Amyloid Cardiomyopathy

BACKGROUND

Deposition of wild-type or mutant transthyretin (TTR) amyloid fibrils in the myocardium causes TTR amyloid cardiomyopathy (ATTR-CM). Targeted therapeutics for ATTR-CM include TTR stabilizers (tafamidis and diflunisal) and oligonucleotide drugs (revusiran, patisiran, and inotersen). TTR stabilizers prevent dissociation of transthyretin tetramers. Transthyretin monomers can misfold and form amyloid fibrils. TTR stabilizers thereby limit amyloid fibrils development and deposition. Oligonucleotide drugs inhibit hepatic synthesis of transthyretin, which decreases transthyretin protein levels and thus the amyloid fibril substrate.

AREAS OF UNCERTAINTY

To study the safety and efficacy of targeted therapeutics in patients with ATTR-CM, we performed a pooled analysis. A random-effects model with the Mantel-Haenszel method was used to pool the data.

DATA SOURCES

A literature search was performed using PubMed, Cochrane CENTRAL, and Embase databases using the search terms "cardiac amyloidosis" AND "tafamidis" OR "patisiran" OR "inotersen" OR "revusiran" OR "diflunisal."

THERAPEUTIC ADVANCES

We identified 6 studies that compared targeted therapeutics with placebo. One study was stopped prematurely because of increased mortality in the targeted therapeutics arm. Pooled analysis included 1238 patients, of which 738 patients received targeted therapeutics and 500 patients received placebo. When compared with placebo, targeted therapeutics significantly reduced all-cause mortality [OR 0.39, 95% confidence interval (CI): 0.16-0.97, P = 0.04]. Only 2 studies reported the effect on cardiovascular-related hospitalizations. There was a trend toward an improvement in global longitudinal strain (mean difference -0.69, 95% CI: -1.44 to 0.05, P = 0.07). When compared with placebo, there was no increase in serious adverse events with targeted therapeutics (OR 1.06, 95% CI: 0.78-1.44, P = 0.72).

CONCLUSION

Evidence from the pooled analysis revealed targeted therapeutics improve survival and are well-tolerated. These findings suggest a potential role for targeted therapeutics in the treatment of patients with ATTR-CM.

Characterising diflunisal as a transthyretin kinetic stabilizer at relevant concentrations in human plasma using subunit exchange

Transthyretin (TTR) dissociation is the rate limiting step for both aggregation and subunit exchange. Kinetic stabilisers, small molecules that bind to the native tetrameric structure of TTR, slow TTR dissociation and inhibit aggregation. One such stabiliser is the non-steroidal anti-inflammatory drug (NSAID), diflunisal, which has been repurposed to treat TTR polyneuropathy. Previously, we compared the efficacy of diflunisal, tafamidis, tolcapone, and AG10 as kinetic stabilisers for transthyretin. However, we could not meaningfully compare diflunisal because we were unsure of its plasma concentration after long-term oral dosing. Herein, we report the diflunisal plasma concentrations measured by extraction, reversed phase HPLC separation, and fluorescence detection after long-term 250 mg BID oral dosing in two groups: a placebo-controlled diflunisal clinical trial group and an open-label Japanese polyneuropathy treatment cohort. The measured mean diflunisal plasma concentration from both groups was 282.2 μ M ±   143.7 μ M (mean ± standard deviation). Thus, quantification of TTR kinetic stabilisation using subunit exchange was carried out at 100, 200, 300, and 400 μM diflunisal concentrations, all observed in patients after 250 mg BID oral dosing. A 250 μ M diflunisal plasma concentration reduced the wild-type TTR dissociation rate in plasma by 95%, which is sufficient to stop transthyretin aggregation, consistent with the clinical efficacy of diflunisal for ameliorating transthyretin polyneuropathy.

Transthyretin Stabilizers and Seeding Inhibitors as Therapies for Amyloid Transthyretin Cardiomyopathy

Transthyretin (TTR) amyloid cardiomyopathy (ATTR-CM) is a progressive and increasingly recognized cause of heart failure which is associated with high mortality and morbidity. ATTR-CM is characterized by the misfolding of TTR monomers and their deposition within the myocardium as amyloid fibrils. The standard of care for ATTR-CM consists of TTR-stabilizing ligands, such as tafamidis, which aim at maintaining the native structure of TTR tetramers, thus preventing amyloid aggregation. However, their efficacy in advanced-staged disease and after long-term treatment is still a source of concern, suggesting the existence of other pathogenetic factors. Indeed, pre-formed fibrils present in the tissue can further accelerate amyloid aggregation in a self-propagating process known as “amyloid seeding”. The inhibition of amyloidogenesis through TTR stabilizers combined with anti-seeding peptides may represent a novel strategy with additional benefits over current therapies. Finally, the role of stabilizing ligands needs to be reassessed in view of the promising results derived from trials which have evaluated alternative strategies, such as TTR silencers and immunological amyloid disruptors.

Treatment of amyloidosis: present and future

Cardiac amyloidosis (CA) is an infiltrative heart disease resulting from the deposition of amyloid fibrils in the interstitial spaces of the myocardium. The two main forms of CA are represented by light chain amyloidosis (AL) and transthyretin amyloidosis (ATTR) in the two forms familial or variant or wild-type or senile. Although considered a rare disease, CA is an underdiagnosed disease. Delay in diagnosis has a negative impact on the prognosis, delaying the initiation of specific therapy. The treatment of both forms of CA is based on: (i) prevention and slowing of the generation and deposition of amyloid fibrils and (ii) supportive care of complications. The main success of recent years has been the development of effective therapies that have been possible thanks to the understanding of the pathophysiology of amyloidosis. For the AL form, new therapeutic combinations between a proteasome inhibitor and a monoclonal antibody have been developed. For ATTR forms, the main strategies are transthyretin (TTR) production 'silencers' and TTR tetramer stabilizers. Supportive care of patients with CA involves various clinical aspects including treatment of heart failure, arrhythmias, conduction disturbances, thrombo-embolism, and the concomitant presence of aortic stenosis.

Iron(III) Complexes with Non-Steroidal Anti-Inflammatory Drugs: Structure, Antioxidant and Anticholinergic Activity, and Interaction with Biomolecules

One the main research goals of bioinorganic chemists is the synthesis of novel coordination compounds possessing biological potency. Within this context, three novel iron(III) complexes with the non-steroidal anti-inflammatory drugs diflunisal and diclofenac in the presence or absence of the nitrogen donors 1,10-phenanthroline or pyridine were isolated and characterized by diverse techniques. The complexes were evaluated for their ability to scavenge in vitro free radicals such as hydroxyl, 1,1-diphenyl-2-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radicals, revealing their selective potency towards hydroxyl radicals. The in vitro inhibitory activity of the complexes towards the enzymes acetylcholinesterase and butyrylcholinesterase was evaluated, and their potential to achieve neuroprotection appeared promising. The interaction of the complexes with calf-thymus DNA was examined in vitro, revealing their ability to intercalate in-between DNA nucleobases. The affinity of the complexes for serum albumins was evaluated in vitro and revealed their tight and reversible binding.

Emerging Therapies for Transthyretin Amyloidosis

PURPOSE OF REVIEW

This review provides an overview of the available therapies for treating neuropathic and/or cardiac manifestations of transthyretin amyloidosis (ATTR), as well as investigational therapeutic agents in ongoing clinical trials. We discuss additional emergent approaches towards thwarting this life-threatening disease that until recently was considered virtually untreatable.

RECENT FINDINGS

Advances in noninvasive diagnostic methods for detecting ATTR have facilitated easier diagnosis and detection at an earlier stage of disease when therapeutic interventions are likely to be more effective. There are now several ATTR-directed treatments that are clinically available, as well as investigational agents that are being studied in clinical trials. Therapeutic strategies include tetramer stabilization, gene silencing, and fibril disruption. ATTR has been historically underdiagnosed. With advances in diagnostic methods and the advent of disease-modifying treatments, early diagnosis and initiation of treatment is revolutionizing management of this disease.

Structure restoration and aggregate inhibition of V30M mutant transthyretin protein by potential quinoline molecules

Transthyretin (TTR) is a tetrameric protein found in human plasma and cerebrospinal fluid that functions as a transporter of thyroxine (T4) and retinol. A mutation resulting in the substitution of valine to methionine at position 30 (V30M) is the most common mutation that destabilizes the tetramer structure of TTR protein resulting in a fatal neuropathy known as TTR amyloidosis. The V30M TTR-induced neuropathy can be inhibited through stabilization of the TTR tetramer by the binding of small molecules. We accessed the potential of in-house synthesized quinoline molecules to stabilize the V30M TTR structure and analyzed the impact of protein-ligand interactions through molecular docking, molecular dynamics (MD) simulations, steered MD, and umbrella sampling simulations. This study revealed that the binding of quinoline molecules reverted back the structural changes including the residual flexibility, changes in secondary structural elements, and also restored the alterations in the electrostatic surface potential induced by the V30M mutation. Further, the top-most 4G and 4R molecules were compared with an FDA-approved drug (Tafamidis) and a reference quinoline molecule 14C. Here, we intend to suggest that the quinoline molecules could revert the structural changes, cease tetramer dissociation, prevent abnormal oligomerization and therefore could be developed as an effective therapeutics against TTR amyloidosis.

Impact of tafamidis on myocardial strain in transthyretin amyloid cardiomyopathy

AIMS

The impact of tafamidis on myocardial strain in patients with transthyretin amyloid cardiomyopathy (ATTR-CM) have been barely investigated. We aimed to determine tafamidis-induced changes using serial speckle tracking echocardiography and to identify imaging parameters for specific therapy monitoring.

METHODS AND RESULTS

ATTR-CM patients underwent serial TTE with two-dimensional (2 D) speckle tracking imaging. Patients receiving tafamidis free acid 61 mg (n = 62) or tafamidis meglumine 20 mg (n = 21) once daily (QD) showed stable measurements at follow-up (61 mg: 8.5 months, 20 mg: 7.0 months) in LV global longitudinal strain (GLS) (61 mg: -11.75% vs. -11.58%, p = 0.534; 20 mg: -10.61% vs. -10.12%, p = 0.309), right ventricular (RV) GLS (61 mg: -14.18% vs. -13.72%, p = 0.377; 20 mg: -14.53% vs. -13.99%, p = 0.452) and left atrial (LA) reservoir strain (LASr; 61 mg: 8.80% vs. 9.42%, p = 0.283; 20 mg: 8.23% vs. 8.67%, p = 0.589), whereas treatment-naïve ATTR-CM patients (n = 54) had clear signs of disease progression at the end of the observation period (10.5 months; LV-GLS: -11.71% vs. -10.59%, p = 0.001; RV-GLS: -14.36% vs. -12.99%, p = 0.038; LASr: 10.67% vs. 8.41%, p = 0.005). Between-group comparison at follow-up revealed beneficial effects of tafamidis free acid 61 mg on LASr (p = 0.003) and the LV (LV-GLS: p = 0.030, interventricular septum (IVS): p = 0.006), resulting in clinical benefits (six-minute walk distance (6-MWD): p = 0.006, NT-proBNP: p= <0.001), while patients treated with tafamidis meglumine 20 mg QD showed positive effects on LASr (p = 0.039), but no differences with respect to the LV (LV-GLS: p = 0.274, IVS: p = 0.068) and clinical status (6-MWD: p = 0.124, NT-proBNP: p = 0.053) compared to the natural course.

CONCLUSIONS

Treatment with tafamidis free acid 61 mg in ATTR-CM patients delays the deterioration of LA and LV longitudinal function, resulting in significant clinical benefits compared with natural history. Serial TTE with 2 D speckle tracking imaging may be appropriate for disease-specific therapy monitoring.

RNA Targeting and Gene Editing Strategies for Transthyretin Amyloidosis

Transthyretin (TTR) is a tetrameric protein synthesized primarily by the liver. TTR can misfold into pathogenic ATTR amyloid fibrils that deposit in the nerves and heart, causing a progressive and debilitating polyneuropathy (PN) and life-threatening cardiomyopathy (CM). Therapeutic strategies, which are aimed at reducing ongoing ATTR amyloid fibrillogenesis, include stabilization of the circulating TTR tetramer or reduction of TTR synthesis. Small interfering RNA (siRNA) or antisense oligonucleotide (ASO) drugs are highly effective at disrupting the complementary mRNA and inhibiting TTR synthesis. Since their development, patisiran (siRNA), vutrisiran (siRNA) and inotersen (ASO) have all been licensed for treatment of ATTR-PN, and early data suggest these drugs may have efficacy in treating ATTR-CM. An ongoing phase 3 clinical trial will evaluate the efficacy of eplontersen (ASO) in the treatment of both ATTR-PN and ATTR-CM, and a recent phase 1 trial demonstrated the safety of novel in vivo CRISPR-Cas9 gene-editing therapy in patients with ATTR amyloidosis. Recent results from trials of gene silencer and gene-editing therapies suggest these novel therapeutic agents have the potential to substantially alter the landscape of treatment for ATTR amyloidosis. Their success has already changed the perception of ATTR amyloidosis from a universally progressive and fatal disease to one that is treatable through availability of highly specific and effective disease-modifying therapies. However, important questions remain including long-term safety of these drugs, potential for off-target gene editing, and how best to monitor the cardiac response to treatment.Kindly check and confirm the processed running title.This is correct.

Research trends and hotspots evolution of cardiac amyloidosis: a bibliometric analysis from 2000 to 2022

In the new century, cardiac amyloidosis has received more attention from many countries and institutions, leading to innovations in the essence of the pathology, biological markers, noninvasive tests, and staging diagnoses and treatments for this disease. However, few reviews have summarized the research trends and hotspots in cardiac amyloidosis. Bibliometrics analysis is a statistically based approach to research that visualizes the contributions of academic institutions and changes in research hotspots. Therefore, in this paper, we used Citespace and VOSviewer software to conduct co-occurrence analysis and collaborative network analysis on the countries, institutions, and authors in the articles related to cardiac amyloidosis since the new century. And further find out burst keywords and references to obtain the research history, disciplinary development, and new hotspots and topics.

Oral Therapy for the Treatment of Transthyretin-Related Amyloid Cardiomyopathy

The care of systemic amyloidosis has improved dramatically due to improved awareness, accurate diagnostic tools, the development of powerful prognostic and companion biomarkers, and a continuous flow of innovative drugs, which translated into the blooming of phase 2/3 interventional studies for light chain (AL) and transthyretin (ATTR) amyloidosis. The unprecedented availability of effective drugs ignited great interest across various medical specialties, particularly among cardiologists who are now recognizing cardiac amyloidosis at an extraordinary pace. In all amyloidosis referral centers, we are observing a substantial increase in the prevalence of wild-type transthyretin (ATTRwt) cardiomyopathy, which is now becoming the most common form of cardiac amyloidosis. This review focuses on the oral drugs that have been recently introduced for the treatment of ATTR cardiac amyloidosis, for their ease of use in the clinic. They include both old repurposed drugs or fit-for-purpose designed compounds which bind and stabilize the TTR tetramer, thus reducing the formation of new amyloid fibrils, such as tafamidis, diflunisal, and acoramidis, as well as fibril disruptors which have the potential to promote the clearance of amyloid deposits, such as doxycycline. The development of novel therapies is based on the advances in the understanding of the molecular events underlying amyloid cardiomyopathy.

Overview of Current and Emerging Therapies for Amyloid Transthyretin Cardiomyopathy

Recent efforts in basic science have elucidated the pathobiology of amyloid transthyretin (ATTR) amyloidosis, leading to the development of the first generation of transthyretin (TTR)-targeted therapies for this disease. Along with tafamidis, the first approved therapy for ATTR-cardiomyopathy (CM), several other agents are in late-stage clinical development for ATTR-CM. TTR-stabilizing and -silencing agents with various mechanisms target TTR, preventing disaggregation of tetrameric TTR, and subsequent misfolding of TTR and formation of amyloid fibrils in the myocardium. These agents, including the TTR-super-stabilizing agent acoramidis, TTR-silencing agents patisiran, vutrisiran, and eplontersen, and TTR gene silencing with clustered, regularly interspaced, short palindromic repeats and associated Cas9 endonuclease-based therapy NTLA-2001, are in varying stages of development. The nonsteroidal anti-inflammatory diflunisal has been shown to have TTR-stabilizing properties and may play a role off-label as treatment in selected patients, particularly allele carriers of TTR variants and patients unable to afford current therapies. Anti-amyloid treatments represent another strategy for treating patients with advanced ATTR amyloidosis. These agents are designed to bind to epitopes on amyloid fibril and extract amyloid by activation of macrophage-mediated phagocytosis addressing amyloid already deposited in organs and tissues. Since many patients with ATTR-CM present with advanced disease and the presence of significant amyloid burden in the heart, anti-amyloid therapy represents an important area of unmet treatment need. Various investigational anti-amyloid therapies are in early-stage clinical development.

Progression of echocardiographic parameters and prognosis in ATTR cardiac amyloidosis

AIMS

Transthyretin amyloid cardiomyopathy (ATTR-CM) is an increasingly diagnosed disease. Echocardiography is widely utilized, but studies to confirm the value of echocardiography for tracking changes over time are not available. We sought to describe: (1) changes in multiple echocardiographic parameters; (2) differences in rate of progression of three predominant genotypes; and (3) the ability of changes in echocardiographic parameters to predict prognosis.

METHODS AND RESULTS

We prospectively studied 877 ATTR-CM patients attending our centre between 2000 and 2020. Serial echocardiography findings at baseline, 12-months and 24-months were compared with survival. Five-hundred-and-sixty-five patients had wild-type ATTR-CM and 312 hereditary ATTR-CM (201 with V122I; 90 with T60A).There was progressive worsening of structural and functional parameters over time, patients with V122I ATTR-CM showing more rapid worsening of left and right ventricular structural and functional parameters compared to both wild-type and T60A ATTR-CM. Among a wide range of echocardiographic analyses, including deformation-based parameters, only worsening in the degree of mitral and tricuspid regurgitation (MR and TR) at 12-and 24 month assessments was associated with worse prognosis (change at 12-months: MR, hazard ratio 1.43 (1.14-1.80,p=0.002); TR, hazard ratio 1.38 (1.10-1.75,p=0.006). Worsening in MR remained independently associated with poor prognosis after adjusting for known predictors.

CONCLUSION

In ATTR-CM, echocardiographic parameters progressively worsen over time. Patients with V122I ATTR-CM demonstrate the most rapid deterioration. Worsening of MR and TR were the only parameters associated with mortality, MR remaining independent after adjusting for known predictors. This article is protected by copyright. All rights reserved.

Diflunisal treatment is associated with improved survival for patients with early stage wild-type transthyretin (ATTR) amyloid cardiomyopathy: the Boston University Amyloidosis Center experience

BACKGROUND

Diflunisal is a non-steroidal anti-inflammatory drug that stabilises transthyretin (TTR) and reduces neurologic deterioration in patients with polyneuropathy caused by hereditary transthyretin amyloidosis (ATTRv).

METHODS

We conducted a retrospective cohort study of patients with wild-type transthyretin cardiac amyloidosis (ATTRwt-CM) treated with diflunisal for at least one year between 2009 and 2016 at the Boston University Amyloidosis Centre. Baseline and one year follow up characteristics were measured, including plasma chemistries and echocardiography. Cox proportional hazards analysis assessed the primary outcome of all-cause mortality.

RESULTS

A total of 104 ATTRwt-CM patients were evaluated with 35 patients receiving diflunisal. Patients in the diflunisal group were younger (73.8 vs 76.8 years, p = 0.034), with lower B-type natriuretic peptide (BNP, 335 +/- 67 vs. 520 +/- 296 pg/mL, p = 0.006), similar troponin I (0.1 +/- 0.1 vs 0.2 +/- 0.3 ng/mL, p = 0.09), and better renal function (eGFR 67 +/- 17 vs 53 +/- 18 mL/min/1.73m2, p = 0.0002) at baseline. Over a median follow-up of 3.2 years, 52 deaths occurred. Diflunisal administration was associated with improved survival in unadjusted analysis (HR 0.13, 95% CI 0.05 - 0.36, p < 0.001) that persisted after adjustment for age, baseline BNP, eGFR, troponin I, interventricular septal thickness, and left ventricular ejection fraction (HR 0.18, 95% CI 0.06 - 0.51, p = 0.0006). Over the observation period, no significant changes in BNP, troponin I, interventricular septal thickness or left ventricular ejection fraction were observed with diflunisal treatment. A total of 14 patients (40%) discontinued diflunisal in this study, but only 3 within the first year. Mean eGFR in treated patients was 59 ml/min/1.73m² at 1 year (change from baseline p = 0.03).

CONCLUSION

Diflunisal administration in ATTRwt-CM was associated with improved survival and overall stability in clinical and echocardiographic markers of disease with decrement renal function.

Imaging-Guided Treatment for Cardiac Amyloidosis

Purpose of Review

This review will explore the role of cardiac imaging in guiding treatment in the two most commonly encountered subtypes of cardiac amyloidosis (immunoglobulin light-chain amyloidosis [AL] and transthyretin amyloidosis [ATTR]).

Recent Findings

Advances in multi-parametric cardiac imaging involving a combination of bone scintigraphy, echocardiography and cardiac magnetic resonance imaging have resulted in earlier diagnosis and initiation of treatment, while the evolution of techniques such as longitudinal strain and extracellular volume quantification allow clinicians to track individuals’ response to treatment. Imaging developments have led to a deeper understanding of the disease process and treatment mechanisms, which in combination result in improved patient outcomes.

Summary

The rapidly expanding treatment regimens for cardiac amyloidosis have led to an even greater reliance on cardiac imaging to help establish an accurate diagnosis, monitor treatment response and aid the adjustment of treatment strategies accordingly.

Treatment With Diflunisal in Domino Liver Transplant Recipients With Acquired Amyloid Neuropathy

Objectives: To analyze the efficacy and tolerability of diflunisal for the treatment of acquired amyloid neuropathy in domino liver transplant recipients. Methods: We performed a retrospective longitudinal study of prospectively collected data for all domino liver transplant recipients with acquired amyloid neuropathy who received diflunisal at our hospital. Neurological deterioration was defined as an score increase of ≥2 points from baseline on the Neurological Impairment Scale/Neurological Impairment Scale-Lower Limbs. Results: Twelve patients who had received compassionate use treatment with diflunisal were identified, of whom seven had follow-up data for ≥12 months. Five patients (71.4%) presented with neurological deterioration on the Neurological Impairment Scale after 12 months (p = 0.0382). The main adverse effects were cardiovascular and renal, leading to diflunisal being stopped in five patients and the dose being reduced in two patients. Conclusion: Our study suggests that most domino liver transplant recipients with acquired amyloid neuropathy will develop neurological deterioration by 12 months of treatment with diflunisal. This therapy was also associated with a high incidence of adverse effects and low treatment retention. The low efficacy and low tolerability of diflunisal treatment encourage the search for new therapeutic options.

Treatment of Transthyretin Amyloid Cardiomyopathy: The Current Options, the Future, and the Challenges

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressively debilitating, rare disease associated with high mortality. ATTR-CM occurs when TTR amyloid protein builds up in the myocardium along with different organs, most commonly the peripheral and the autonomic nervous systems. Managing the cardiac complications with standard heart failure medications is difficult due to the challenge to maintain a balance between the high filling pressure associated with restricted ventricular volume and the low cardiac output. To date, tafamidis is the only agent approved for ATTR-CM treatment. Besides, several agents, including green tea, tolcapone, and diflunisal, are used off-label in ATTR-CM patients. Novel therapies using RNA interference also offer clinical promise. Patisiran and inotersen are currently approved for ATTR-polyneuropathy of hereditary origin and are under investigation for ATTR-CM. Monoclonal antibodies in the early development phases carry hope for amyloid deposit clearance. Despite several drug candidates in the clinical development pipeline, the small ATTR-CM patient population raises several challenges. This review describes current and future therapies for ATTR-CM and sheds light on the clinical development hurdles facing them.

The use of diflunisal for transthyretin cardiac amyloidosis: a review

Transthyretin cardiac amyloidosis (ATTR-CM) is caused by the accumulation of misfolded transthyretin (TTR) protein in the myocardium. Diflunisal, an agent that stabilizes TTR, has been used as an off-label therapeutic for ATTR-CM. Given limited data surrounding the use of diflunisal, a systematic review of the literature is warranted. We searched the PubMed, MEDLINE, and Embase databases for studies that reported on the use of diflunisal therapy for patients with ATTR-CM. We included English language studies which assessed the effect of diflunisal in adult patients with ATTR-CM who received diflunisal as primary treatment and reported clinical outcomes with emphasis on studies that noted the safety and efficacy of diflunisal in cardiac manifestations of ATTR amyloidosis. We excluded studies which did not use diflunisal therapy or used diflunisal therapy for non-cardiac manifestations of TTR amyloidosis. We also excluded case reports, abstracts, oral presentations, and studies with fewer than 10 subjects. Our search yielded 316 records, and we included 6 studies reporting on 400 patients. Non-comparative single-arm small non-randomized trials for diflunisal comprised 4 of the included studies. The 2 studies that compared diflunisal versus no treatment found improvements in TTR concentration, left atrial volume index, cardiac troponin I, and global longitudinal strain. Overall, diflunisal use was associated with decreased mortality and number of orthotopic heart transplant in ATTR-CM patients. Although a smaller number of patients had to stop treatment due to gastrointestinal side effects and transient renal dysfunction, there were no severe reactions reported in the studies included in our review. This systematic review supports the use of diflunisal for ATTR-CM. Additional long-term analyses and randomized clinical trials are needed to confirm these results.

A Late Diagnosis of Transthyretin Amyloidosis

Cardiac amyloidosis is a rare disease caused by the accumulation of protein-based fibrils that deposit into the myocardium, causing disease. The accumulation of amyloid in the heart tissue causes the heart to become increasingly stiff, reducing compliance, with the eventual decline of the heart’s systolic function over time as the disease progresses. The restrictive physiology of the disease usually prompts investigation; however, if allowed to progress, the systolic function becomes affected in the later stages of the disease. We present a case of late-stage transthyretin-related amyloidosis (ATTR).

OUP accepted manuscript

Aims

In patients with transthyretin amyloid cardiomyopathy (ATTR-CM), the effect of tafamidis on myocardial function using serial speckle tracking echocardiography has not been reported. The purpose of this study was to describe the natural history of myocardial function in untreated ATTR-CM and determine the effect of tafamidis on myocardial functional parameters over 12 months of treatment.

Methods and results

A total of 45 subjects with ATTR-CM were retrospectively studied: 23 treated with tafamidis and 22 untreated. Two-dimensional speckle tracking echocardiography was analysed at baseline and 1 year. Serial longitudinal, circumferential, and radial strain, twist, torsion, and myocardial work were measured. Over 1 year, absolute global longitudinal strain (GLS) deteriorated more in the untreated group by a median of 1.1% [inter-quartile range (IQR) 0.95] compared with 0.3% (IQR 1) in the tafamidis group (P = 0.02). Myocardial work index and efficiency also deteriorated to a greater degree: 142.5 mmHg% (IQR 197) and 4% (IQR 8), respectively, in the untreated group compared with 61.5 mmHg% (IQR 210) and 1% (IQR 7) in the tafamidis group (P = 0.04). There were no significant between group differences in left ventricular ejection fraction (LVEF), tissue Doppler velocities, circumferential or radial strain, LV twist or torsion at 1 year. The stabilization effect of tafamidis on myocardial function at 1 year did not differ according to baseline GLS, LVEF, or National Amyloidosis Centre disease stage.

Conclusions

In ATTR-CM, tafamidis resulted in a lesser deterioration in GLS, myocardial work index, and efficiency over a 12-month period compared with a cohort not treated with tafamidis.

Targeted treatments of AL and ATTR amyloidosis

The therapeutic landscape for cardiac amyloidosis is rapidly evolving. In the last decade, our focus has shifted from dealing with the inevitable complications of continued extracellular infiltration of amyloid fibrils to earlier identification of these patients with prompt initiation of targeted therapy to prevent further deposition. Although much of the focus on novel targeted therapies is within the realm of transthyretin amyloidosis, light chain amyloidosis has benefited due to an overlap particularly in the final common pathway of fibrillogenesis and extraction of amyloid fibrils from the heart. Here, we review the targeted therapeutics for transthyretin and light chain amyloidosis. For transthyretin amyloidosis, the list of current and future therapeutics continues to evolve; and therefore, it is crucial to become familiar with the underlying mechanistic pathways of the disease. Although targeted therapeutic choices in AL amyloidosis are largely driven by the hematology team, the cardiac adverse effect profiles of these therapies, particularly in those with advanced amyloidosis, provide an opportunity for early recognition to prevent decompensation and can help inform recommendations regarding therapy changes when required.

Cardiovascular Involvement in Transthyretin Cardiac Amyloidosis

Transthyretin cardiac amyloidosis (ATTR-CA) is a systemic disorder resulting from the extracellular deposition of amyloid fibrils of misfolded transthyretin protein in the heart. ATTR-CA is a life-threatening disease, which can be caused by progressive deposition of wild type transthyretin (wtATTR) or by aggregation of an inherited mutated variant of transthyretin (mATTR). mATTR Is a rare condition transmitted in an autosomal dominant manner with incomplete penetrance, causing heterogenous phenotypes which can range from predominant neuropathic involvement, predominant cardiomyopathy, or mixed. Diagnosis of ATTR-CA is complex and requires integration of different imaging tools (echocardiography, bone scintigraphy, magnetic resonance) with genetics, clinical signs, laboratory tests, and histology. In recent years, new therapeutic agents have shown good efficacy and impact on survival and quality of life in this subset of patients, nevertheless patients affected by ATTR-CA may still carry an unfavorable prognosis, thus highlighting the need for new therapies. This review aims to assess cardiovascular involvement, diagnosis, and management of patients affected by ATTR-CA.

ATTR Amyloidosis: Current and Emerging Management Strategies: JACC: CardioOncology State-of-the-Art Review

Transthyretin cardiac amyloidosis (ATTR-CA) is increasingly diagnosed owing to the emergence of noninvasive imaging and improved awareness. Clinical penetrance of pathogenic alleles is not complete and therefore there is a large cohort of asymptomatic transthyretin variant carriers. Screening strategies, monitoring, and treatment of subclinical ATTR-CA requires further study. Perhaps the most important translational triumph has been the development of effective therapies that have emerged from a biological understanding of ATTR-CA pathophysiology. These include recently proven strategies of transthyretin protein stabilization and silencing of transthyretin production. Data on neurohormonal blockade in ATTR-CA are limited, with the primary focus of medical therapy on judicious fluid management. Atrial fibrillation is common and requires anticoagulation owing to the propensity for thrombus formation. Although conduction disease and ventricular arrhythmias frequently occur, little is known regarding optimal management. Finally, aortic stenosis and ATTR-CA frequently coexist, and transcatheter valve replacement is the preferred treatment approach.

Effect of Tafamidis on Serum Transthyretin Levels in Non-Trial Patients With Transthyretin Amyloid Cardiomyopathy

Background

Transthyretin amyloid (ATTR) cardiomyopathy is slowed by tafamidis, which stabilizes the TTR molecule and reduces the formation of amyloidogenic oligomers. Stabilizers in clinical doses raise serum TTR, which may be a surrogate for the degree of stabilization.

Objectives

This study aims to determine, in a non-trial, unselected population of patients with ATTR cardiomyopathy, the effect of tafamidis on serum levels of TTR, and to compare these with published data of changes in TTR.

Methods

TTR levels were measured before therapy and 3 to 12 months following initiation of tafamidis therapy in all patients seen between May 20, 2019, and March 1, 2021, who had a follow-up visits within 12 months of therapy initiation.

Results

Among 72 patients with ATTR cardiomyopathy (67 patients with wild-type and 5 patients with variant TTR), administration of tafamidis increased serum TTR from 21.8 mg ± 0.7 mg/dL to 29.3 ± 0.86 mg/dL, an increase of 34.5%. In 5 patients with variant TTR, the increase was 70.9%, compared to 32.0% in the wild-type patients. Mean N-terminal pro-brain natriuretic peptide increased over a mean follow-up of 21 ± 1.2 weeks, but the change was not statistically significant. Over the same period there was a small increase in high-sensitivity troponin T that was of borderline statistical significance (P = 0.057).

Conclusions

Tafamidis consistently increases serum TTR levels in patients with ATTR cardiomyopathy, consistent with its effect on stabilizing TTR. Measurement of TTR level change post-TTR stabilizing therapy might be a surrogate for stabilization and could be a more accurate measure of drug efficacy than an in vitro nonphysiologic test of stabilization.

Current and Emerging Therapies for Hereditary Transthyretin Amyloidosis: Strides Towards a Brighter Future

The past few years have witnessed an unprecedented acceleration in the clinical development of novel therapeutic options for hereditary transthyretin amyloidosis. Recently approved agents and drugs currently under investigation not only represent a major breakthrough in this field but also provide validation of the therapeutic potential of innovative approaches, like RNA interference and CRISPR-Cas9-mediated gene editing, in rare inherited disorders. In this review, we describe the evolving therapeutic landscape for hereditary transthyretin amyloidosis and discuss how this highly disabling and fatal condition is turning into a treatable disease. We also provide an overview of the molecular mechanisms involved in transthyretin (TTR) amyloid formation and regression, to highlight how a deeper understanding of these processes has contributed to the identification of novel treatment targets. Finally, we focus on major areas of uncertainty and unmet needs that deserve further efforts to improve long-term patients' outcomes and allow for a brighter future.

Advances in Diagnosis and Treatment of Cardiac and Renal Amyloidosis

Diagnoses of amyloidosis are increasing annually, and advances in bone scintigraphy and cardiac MRI accompanied by development of nonbiopsy diagnostic criteria have specifically led to a huge increase in transthyretin amyloidosis cardiomyopathy (ATTR-CM) diagnoses worldwide. Tafamidis use is increasing, and there are several ongoing phase III clinical trials of novel agents that promise to transform the treatment landscape for patients with ATTR-CM. In systemic light chain (AL) amyloidosis, more effective chemotherapeutic agents continue to improve patient outcomes. Accelerating the removal of amyloid deposits to accompany these therapies remains the holy grail. However, in the meantime, early diagnosis is undoubtedly key in improving patient outcomes.

Progress and challenges in the treatment of cardiac amyloidosis: a review of the literature

Cardiac amyloidosis is a restrictive cardiomyopathy determined by the accumulation of amyloid, which is represented by misfolded protein fragments in the cardiac extracellular space. The main classification of systemic amyloidosis is determined by the amyloid precursor proteins causing a very heterogeneous disease spectrum, but the main types of amyloidosis involving the heart are light chain (AL) and transthyretin amyloidosis (ATTR). AL, in which the amyloid precursor is represented by misfolded immunoglobulin light chains, can involve almost any system carrying the worst prognosis among amyloidosis patients. This has however dramatically improved in the last few years with the increased usage of the novel therapies such as proteasome inhibitors and haematopoietic cell transplantation, in the case of timely diagnosis and initiation of treatment. The treatment for AL is directed by the haematologist working closely with the cardiologist when there is a significant cardiac involvement. Transthyretin (TTR) is a protein that is produced by the liver and is involved in the transportation of thyroid hormones, especially thyroxine and retinol binding protein. ATTR results from the accumulation of transthyretin amyloid in the extracellular space of different organs and systems, especially the heart and the nervous system. Specific therapies for ATTR act at various levels of TTR, from synthesis to deposition: TTR tetramer stabilization, oligomer aggregation inhibition, genetic therapy, amyloid fibre degradation, antiserum amyloid P antibodies, and antiserum TTR antibodies. Treatment of systemic amyloidosis has dramatically evolved over the last few years in both AL and ATTR, improving disease prognosis. Moreover, recent studies revealed that timely treatment can lead to an improvement in clinical status and in a regression of amyloid myocardial infiltration showed by imaging, especially by cardiac magnetic resonance, in both AL and ATTR. However, treating cardiac amyloidosis is a complex task due to the frequent association between systemic congestion and low blood pressure, thrombo-embolic and haemorrhagic risk balance, patient frailty, and generally poor prognosis. The aim of this review is to describe the current state of knowledge regarding cardiac amyloidosis therapy in this constantly evolving field, classified as treatment of the cardiac complications of amyloidosis (heart failure, rhythm and conduction disturbances, and thrombo-embolic risk) and the disease-modifying therapy.

Cardiac Amyloidosis: Multimodal Imaging of Disease Activity and Response to Treatment

Cardiac amyloidosis (CA) is a disease characterized by the deposition of misfolded protein deposits in the myocardial interstitium. Although advanced CA confers significant morbidity and mortality, the magnitude of deposition and ensuing clinical manifestations vary greatly. Thus, an improved understanding of disease pathogenesis at both cellular and functional levels would afford critical insights that may improve outcomes. This review will summarize contemporary therapies for the 2 major types of CA, transthyretin and light chain amyloidosis, and outline the capacity of imaging modalities to both diagnose CA, inform prognosis, and follow response to available therapies. We explore the current landscape of echocardiography, cardiac magnetic resonance, and bone scintigraphy in the assessment of functional and cellular parameters of dysfunction in CA throughout disease pathogenesis. Finally, we examine the impact of concurrent advances in both therapeutics and imaging on future research questions that improve our understanding of underlying disease mechanisms. Multimodal imaging in CA affords an indispensable tool to offer individualized treatment plans and improve outcomes in patients with CA.

Pathophysiology and Therapeutic Approaches to Cardiac Amyloidosis

Often considered a rare disease, cardiac amyloidosis is increasingly recognized by practicing clinicians. The increased rate of diagnosis is in part due the aging of the population and increasing incidence and prevalence of cardiac amyloidosis with advancing age, as well as the advent of noninvasive methods using nuclear scintigraphy to diagnose transthyretin cardiac amyloidosis due to either variant or wild type transthyretin without a biopsy. Perhaps the most important driver of the increased awareness is the elucidation of the biologic mechanisms underlying the pathogenesis of cardiac amyloidosis which have led to the development of several effective therapies with differing mechanisms of actions. In this review, the mechanisms underlying the pathogenesis of cardiac amyloidosis due to light chain (AL) or transthyretin (ATTR) amyloidosis are delineated as well as the rapidly evolving therapeutic landscape that has emerged from a better pathophysiologic understanding of disease development.

Clinical approach to genetic testing in amyloid cardiomyopathy: from mechanism to effective therapies

PURPOSE OF REVIEW

To highlight the evolving understanding of genetic variants, utility of genetic testing, and the selection of novel therapies for cardiac amyloidosis.

RECENT FINDINGS

The last decade has seen considerable progress in cardiac amyloidosis recognition given the advancement in cardiac imaging techniques and widespread availability of genetic testing. A significant shift in the understanding of a genetic basis for amyloidosis has led to the development of disease-modifying therapeutic strategies that improve survival.

SUMMARY

The systemic amyloidoses are disorders caused by extracellular deposition of misfolded amyloid fibrils in various organs. Immunoglobulin light-chain or transthyretin amyloidosis are the most common types associated with cardiac manifestations. Genetic testing plays a central role in the identification of genotypes that are associated with different clinical phenotypes and influence prognosis. Given the emergence of effective therapies, a systematic approach to the diagnosis of cardiac amyloidosis, with the elucidation of genotype when indicated, is essential to select the appropriate treatment.

Recent Advances and Current Dilemmas in the Diagnosis and Management of Transthyretin Cardiac Amyloidosis

Cardiac amyloidosis (CA) is an increasingly recognized cause of heart failure, arrhythmias, and sudden cardiac death. While CA was previously rapidly fatal, recent advances in diagnosis and treatment have significantly improved outcomes. Advances in cardiac imaging and biomarkers have critically improved the accuracy and efficiency with which CA is diagnosed, even allowing for the noninvasive diagnosis of transthyretin CA. Cardiac magnetic resonance imaging, technetium nuclear imaging, echocardiography, and blood-based biomarkers have established important and complementary roles in the management and advancement of care. At the same time, the development of novel targeted amyloid therapies has allowed patients with CA to live longer and potentially achieve better quality of life. Still, despite this significant progress, there remain critical ongoing questions in the field. Accordingly, within this review we will highlight recent advances in cardiac imaging and therapeutics for CA, while focusing on key opportunities for further optimization of care and outcomes among this growing population. Specifically, we will discuss ongoing debates in the diagnosis of CA, including the interpretation of indeterminate cardiac imaging findings, the best technique to screen asymptomatic transthyretin amyloidosis gene mutation carriers for cardiac involvement, and the ideal method for monitoring response to CA treatment. We will additionally focus on recent advances in treatment for transthyretin amyloidosis-CA, including a discussion of available agents as well as highlighting ongoing clinical trials. Together, these data will allow clinicians to emerge with a greater understanding of the present and future of diagnosis, management, and potentially enhanced outcomes in this rapidly advancing field.

Canadian Guidelines for Hereditary Transthyretin Amyloidosis Polyneuropathy Management

Hereditary transthyretin-mediated (hATTR) amyloidosis is a progressive disease caused by mutations in the TTR gene leading to multisystem organ dysfunction. Pathogenic TTR aggregation, misfolding, and fibrillization lead to deposition of amyloid in multiple body organs and frequently involve the peripheral nerve system and the heart. Common neurologic manifestations include: sensorimotor polyneuropathy (PN), autonomic neuropathy, small-fiber PN, and carpal tunnel syndrome. Many patients have significant progression due to diagnostic delays as hATTR PN is not considered within the differential diagnosis. Recently, two effective novel disease-modifying therapies, inotersen and patisiran, were approved by Health Canada for the treatment of hATTR PN. Early diagnosis is crucial for the timely introduction of these disease-modifying treatments that reduce impairments, improve quality of life, and extend survival. In this guideline, we aim to improve awareness and outcomes of hATTR PN by making recommendations directed to the diagnosis, monitoring, and treatment in Canada.

Practical recommendations for the diagnosis and management of transthyretin cardiac amyloidosis

Cardiac amyloidosis (CA) is an infiltrative restrictive cardiomyopathy caused by accumulation in the heart interstitium of amyloid fibrils formed by misfolded proteins. Most common CA types are light chain amyloidosis (AL) caused by monoclonal immunoglobulin light chains and transthyretin amyloidosis (ATTR) caused by either mutated or wild-type transthyretin aggregates. Previously considered a rare disease, CA is increasingly recognized among patients who may be misdiagnosed as undifferentiated heart failure with preserved ejection fraction (HFPEF), paradoxical low-flow/low-gradient aortic stenosis, or otherwise unexplained left ventricular hypertrophy. Progress in diagnosis has been due to the refinement of cardiac echocardiographic techniques (speckle tracking imaging) and magnetic resonance (T1 mapping) and mostly due to the advent of bone scintigraphy that has enabled noninvasive diagnosis of ATTR, limiting the need for endomyocardial biopsy. Importantly, proper management of CA starts from early recognition of suspected cases among high prevalence populations, followed by advanced diagnostic evaluation to confirm diagnosis and typing, preferentially in experienced amyloidosis centers. Differentiating ATTR from other types of amyloidosis, especially AL, is critical. Emerging targeted ATTR therapies offer the potential to improve outcomes of these patients previously treated only palliatively.

Transthyretin amyloid cardiomyopathy

Transthyretin (TTR) cardiac amyloidosis is a severe, progressive, infiltrative disease caused by the deposition of TTR at cardiac level. It may be due to a genetic alteration in its hereditary form (ATTRv) or as a consequence of an age-related degenerative process (ATTRwt). Thanks to advances in imaging techniques and the possibility of achieving a non-invasive diagnosis, we now know that ATTR is more frequent than traditionally considered and that it is particularly relevant in patients over 65 years with heart failure or with aortic stenosis. With the appearance of several treatment options capable of modifying the natural history of ATTR, it is necessary for clinicians to be familiar with the diagnostic process and treatment of this disease. This review will cover the clinical spectrum of presentation of ATTR, its diagnosis and treatment.

Diagnosis and Screening of Patients with Hereditary Transthyretin Amyloidosis (hATTR): Current Strategies and Guidelines

The outlook for transthyretin amyloidosis (ATTR) is changing with the availability of new and emerging treatments. ATTR now appears to be more common than previously thought and is no longer viewed as an obscure diagnosis with a grim prognosis. Now more than ever, there is growing emphasis on the need for early diagnosis because the treatments appear to be most effective if started in earlier stages of the disease. Diagnosing ATTR is a challenge as it may initially present with nonspecific symptoms and it is often thought of as a diagnosis of exclusion. Increased awareness is imperative as new treatments offer hope and have the potential to change the disease trajectory. ATTR commonly presents with neurological and cardiac features. Transthyretin (TTR) is a protein produced in the liver which misfolds either due to genetic mutations or due to aging and results in deposition of amyloid fibrils in organs and tissues. Apart from the traditional imaging modalities, newer techniques including echocardiographic strain imaging, magnetic resonance imaging (MRI), and nuclear scintigraphy, as well as the increased availability of genetic testing are aiding in making a timely diagnosis. In this review, we present the current understanding of the ATTR disease process, diagnostic and surveillance approaches, newer treatment modalities, and the future directions.