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 µM ± 143.7 µM (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 µM 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.

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.

[Specific pharmacological treatment guide for transthyretin amyloid cardiomyopathy, 2021]. / Guía de tratamiento farmacológico específico de la cardiomiopatía amiloidótica por transtiretina, 2021.

This clinical practice guideline for treating transthyretin amyloid (ATTR) cardiomyopathy is based on the best available evidence of clinical effectiveness. The PICO format was used to generate a list of questions focused on the effectiveness and safety of the specific treatment of patients with ATTR cardiomyopathy. The search was conducted in PubMed, Cochrane and Epistemokus, between July-August 2020, and selected articles between 2000-2020, in English and Spanish. The level of evidence and recommendations were analyzed and classified by the GRADE system. The following drugs were included in the analysis: tafamidis, diflunisal, inotersen, patisiran y doxycycline and ursodeoxycholic acid. The expert panel had an agreement that tafamidis 80mg/daily is the only available drug with moderate evidence and weak recommendation for the reduction of total mortality, cardiovascular morbidity, heart failure hospitalization and progression of the disease in patients with ATTR cardiomyopathy and NYHA class = 3. In contrast, tafamidis 20 mg/daily had low-quality evidence in this group of patients. The expert panel did not recommend inotersen, patisiran and diflunisal in patients with ATTR cardiomyopathy due to the lack of supporting evidence, local drug availability, and the potential risk of toxicity. When patients did not have access to tafamidis, the expert panel stated a weak recommendation to use doxycycline and ursodeoxycholic acid in patients with ATTR cardiomyopathy.

Con el propósito de confeccionar una guía con la mejor evidencia disponible en el tratamiento de la amiloidosis por depósito de transtiretina (ATTR), se generó un listado de preguntas en formato PICO centradas en la efectividad y seguridad y se realizó una búsqueda en PubMed, Cochrane y Epistemokus de los artículos publicados entre 2000-2020 y se incluyeron dos estudios de extensión en relación al tafamidis. Los niveles de evidencia y los grados de recomendación se basaron en el sistema GRADE, emitiéndose 11 recomendaciones para ATTRv y ATTwt. Se consideraron los siguientes fármacos: tafamidis, diflunisal, inotersen, patisiran y doxiciclina más ácido ursodesoxicolico. El grupo de expertos consensuó que el único tratamiento que demostró reducir de la mortalidad global, mortalidad cardiovascular, internaciones cardiovasculares y la progresión de la cardiopatía con un nivel moderado de evidencia fue el tafamidis 80 mg, mientras que para la formulación tafamidis 20 mg la calidad de evidencia es baja. Para inotersen y diflunisal, se formuló una recomendación en contra del tratamiento dada la falta de evidencia de calidad respecto a su efectividad, el perfil de toxicidad y la falta de disponibilidad en el ámbito local. Con respecto al patisirán, la recomendación se focalizó en la población ATTRv. El panel de expertos consensuó que el tratamiento con doxiciclina más ácido ursodeoxicólico podría ser utilizado ante la imposibilidad de iniciar tratamiento con tafamidis, recomendación débil y calidad de evidencia muy baja.

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.

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.

The Ultrastructure of Tissue Damage by Amyloid Fibrils.

Amyloidosis is a group of diseases that includes Alzheimer's disease, prion diseases, transthyretin (ATTR) amyloidosis, and immunoglobulin light chain (AL) amyloidosis. The mechanism of organ dysfunction resulting from amyloidosis has been a topic of debate. This review focuses on the ultrastructure of tissue damage resulting from amyloid deposition and therapeutic insights based on the pathophysiology of amyloidosis. Studies of nerve biopsy or cardiac autopsy specimens from patients with ATTR and AL amyloidoses show atrophy of cells near amyloid fibril aggregates. In addition to the stress or toxicity attributable to amyloid fibrils themselves, the toxicity of non-fibrillar states of amyloidogenic proteins, particularly oligomers, may also participate in the mechanisms of tissue damage. The obscuration of the basement and cytoplasmic membranes of cells near amyloid fibrils attributable to an affinity of components constituting these membranes to those of amyloid fibrils may also play an important role in tissue damage. Possible major therapeutic strategies based on pathophysiology of amyloidosis consist of the following: (1) reducing or preventing the production of causative proteins; (2) preventing the causative proteins from participating in the process of amyloid fibril formation; and/or (3) eliminating already-deposited amyloid fibrils. As the development of novel disease-modifying therapies such as short interfering RNA, antisense oligonucleotide, and monoclonal antibodies is remarkable, early diagnosis and appropriate selection of treatment is becoming more and more important for patients with amyloidosis.

Osteosarcoma Stem Cell Potent Gallium(III)-Polypyridyl Complexes Bearing Diflunisal.

We report the anti-osteosarcoma stem cell (OSC) properties of a series of gallium(III)-polypyridyl complexes (5-7) containing diflunisal, a non-steroidal anti-inflammatory drug. The most effective complex within the series, 6 (containing 3,4,7,8-tetramethyl-1,10-phenanthroline), displayed similar potency towards bulk osteosarcoma cells and OSCs, in the nanomolar range. Remarkably, 6 exhibited significantly higher monolayer and sarcosphere OSC potency (up to three orders of magnitude) than clinically approved drugs used in frontline (cisplatin and doxorubicin) and secondary (etoposide, ifosfamide, and carboplatin) osteosarcoma treatments. Mechanistic studies show that 6 downregulates cyclooxygenase-2 (COX-2) and kills osteosarcoma cells in a COX-2 dependent manner. Furthermore, 6 induces genomic DNA damage and caspase-dependent apoptosis. To the best of our knowledge, 6 is the first metal complex to kill osteosarcoma cells by simultaneously inhibiting COX-2 and damaging nuclear DNA.

A Review of Novel Agents and Clinical Considerations in Patients With ATTR Cardiac Amyloidosis.

ABSTRACT: Transthyretin (ATTR) amyloidosis is a multisystem disease caused by organ deposition of amyloid fibrils derived from the misfolded transthyretin (TTR) protein. The purpose of this article is to provide an overview of current treatment regimens and summarize important considerations for each agent. A literature search was performed with the PubMed database for articles published through October 2020. Search criteria included therapies available on the market and investigational therapies used for ATTR amyloidosis treatment. Both prospective clinical trials and retrospective studies have been included in this review. Available therapies discussed in this review article are tafamidis, diflunisal, patisiran, and inotersen. Tafamidis is FDA approved for treatment of wild-type ATTR (ATTRwt) and hereditary ATTR (ATTRv) cardiomyopathy, and patisiran and inotersen are FDA approved for ATTRv polyneuropathy. Diflunisal does not have an FDA-labeled indication for amyloidosis but has been studied in ATTRv polyneuropathy and ATTRwt cardiomyopathy. Investigational therapies include a TTR stabilizer, AG10; 2 antifibril agents, PRX004 and doxycycline/tauroursodeoxycholic acid; and 2 gene silencers, vutrisiran and AKCEA-TTR-LRx; and clinical trials are ongoing. ATTR amyloidosis treatment selection is based on subtype and presence of cardiac or neurological manifestations. Additional considerations such as side effects, monitoring, and administration are outlined in this review.

Experience of patisiran with transthyretin stabilizers in patients with hereditary transthyretin-mediated amyloidosis.

Aim: Examine safety and pharmacodynamics of patisiran alone or with concomitant transthyretin stabilizers from the Phase II open-label extension study and safety and efficacy of patisiran in patients with prior transthyretin stabilizer use from the Phase III APOLLO study. Patients & methods:Post hoc analyses in patients with hereditary transthyretin-mediated amyloidosis with polyneuropathy. Results: Patisiran safety was consistent regardless of concomitant or prior transthyretin stabilizers. In the Phase II open-label extension (n = 27), transthyretin reduction was similar over 24 months, regardless of concomitant transthyretin stabilizers. In APOLLO (n = 225), patisiran-treated groups showed stabilization or improvements in neurological function (modified Neuropathy Impairment Score +7) and quality of life (Norfolk Quality of Life-Diabetic Neuropathy questionnaire) at 18 months, regardless of prior transthyretin stabilizers. Conclusion: Patients benefit from patisiran regardless of transthyretin stabilizer use.

Overview of treatments used in transthyretin-related hereditary amyloidosis: a systematic review.

OBJECTIVE: To carry out a systematic review of the literature to analyse the efficacy and safety of treatments available or under investigation for amyloidosis due to mutations in the transthyretin gene (ATTR). METHODS: A bibliographic search was carried out in the following electronic databases up to September 2017: PubMed, Cochrane Library and EMBASE. The inclusion criteria were: efficacy and/or safety studies conducted in humans, studies that included treatments, including treatments in the research phase, and studies that included 10 or more patients. RESULTS: A total of 21 articles were included; 16 were clinical trials, eight of them (50%) phase III trials, and five were observational studies. Of the total number of studies selected, 11 were on tafamidis, four on diflunisal, two on liver transplantation, two on patisiran and two on other therapeutic alternatives. Of the 11 studies related to the drug, the pivotal trial, the results of its two extension studies and an additional post hoc analysis were selected. In addition, two phase III trials were included in specific populations, two phase II studies, one safety study and two observational studies. Regarding the four included studies related to the drug, one was the pivotal trial that gave the indication to diflunisal, another a safety summary of the pivotal trial, and the other two trials were carried out in specific populations, one in a Japanese population and another phase I trial in cardiac amyloidosis in the USA. As far as other alternatives are concerned, of the six studies included in this section, two were related to liver transplantation, two to patisiran and two to different therapeutic alternatives. CONCLUSIONS: Sufficient evidence has not been found that demonstrates superiority among the available oral alternatives, diflunisal or tafamidis, in the treatment of ATTR. Direct comparisons between both drugs and pharmacoeconomic studies would be necessary to select the most efficient treatment.

Pharmacological treatment for familial amyloid polyneuropathy.

BACKGROUND: Disease-modifying pharmacological agents for transthyretin (TTR)-related familial amyloid polyneuropathy (FAP) have become available in the last decade, but evidence on their efficacy and safety is limited. This review focuses on disease-modifying pharmacological treatment for TTR-related and other FAPs, encompassing amyloid kinetic stabilisers, amyloid matrix solvents, and amyloid precursor inhibitors. OBJECTIVES: To assess and compare the efficacy, acceptability, and tolerability of disease-modifying pharmacological agents for familial amyloid polyneuropathies (FAPs). SEARCH METHODS: On 18 November 2019, we searched the Cochrane Neuromuscular Specialised Register, the Cochrane Central Register of Controlled Trials, MEDLINE, and Embase. We reviewed reference lists of articles and textbooks on peripheral neuropathies. We also contacted experts in the field. We searched clinical trials registries and manufacturers' websites. SELECTION CRITERIA: We included randomised clinical trials (RCTs) or quasi-RCTs investigating any disease-modifying pharmacological agent in adults with FAPs. Disability due to FAP progression was the primary outcome. Secondary outcomes were severity of peripheral neuropathy, change in modified body mass index (mBMI), quality of life, severity of depression, mortality, and adverse events during the trial. DATA COLLECTION AND ANALYSIS: We followed standard Cochrane methodology. MAIN RESULTS: The review included four RCTs involving 655 people with TTR-FAP. The manufacturers of the drugs under investigation funded three of the studies. The trials investigated different drugs versus placebo and we did not conduct a meta-analysis. One RCT compared tafamidis with placebo in early-stage TTR-FAP (128 randomised participants). The trial did not explore our predetermined disability outcome measures. After 18 months, tafamidis might reduce progression of peripheral neuropathy slightly more than placebo (Neuropathy Impairment Score (NIS) in the lower limbs; mean difference (MD) -3.21 points, 95% confidential interval (CI) -5.63 to -0.79; P = 0.009; low-certainty evidence). However, tafamidis might lead to little or no difference in the change of quality of life between groups (Norfolk Quality of Life-Diabetic Neuropathy (Norfolk QOL-DN) total score; MD -4.50 points, 95% CI -11.27 to 2.27; P = 0.19; very low-certainty evidence). No clear between-group difference was found in the numbers of participants who died (risk ratio (RR) 0.65, 95% CI 0.11 to 3.74; P = 0.63; very low-certainty evidence), who dropped out due to adverse events (RR 1.29, 95% CI 0.30 to 5.54; P = 0.73; very low-certainty evidence), or who experienced at least one severe adverse event during the trial (RR 1.16, 95% CI 0.37 to 3.62; P = 0.79; very low-certainty evidence). One RCT compared diflunisal with placebo (130 randomised participants). At month 24, diflunisal might reduce progression of disability (Kumamoto Score; MD -4.90 points, 95% CI -7.89 to -1.91; P = 0.002; low-certainty evidence) and peripheral neuropathy (NIS plus 7 nerve tests; MD -18.10 points, 95% CI -26.03 to -10.17; P < 0.001; low-certainty evidence) more than placebo. After 24 months, changes from baseline in the quality of life measured by the 36-Item Short-Form Health Survey score showed no clear difference between groups for the physical component (MD 6.10 points, 95% CI 2.56 to 9.64; P = 0.001; very low-certainty evidence) and the mental component (MD 4.40 points, 95% CI -0.19 to 8.99; P = 0.063; very low-certainty evidence). There was no clear between-group difference in the number of people who died (RR 0.46, 95% CI 0.15 to 1.41; P = 0.17; very low-certainty evidence), in the number of dropouts due to adverse events (RR 2.06, 95% CI 0.39 to 10.87; P = 0.39; very low-certainty evidence), and in the number of people who experienced at least one severe adverse event (RR 0.77, 95% CI 0.18 to 3.32; P = 0.73; very low-certainty evidence) during the trial. One RCT compared patisiran with placebo (225 randomised participants). After 18 months, patisiran reduced both progression of disability (Rasch-built Overall Disability Scale; least-squares MD 8.90 points, 95% CI 7.00 to 10.80; P < 0.001; moderate-certainty evidence) and peripheral neuropathy (modified NIS plus 7 nerve tests - Alnylam version; least-squares MD -33.99 points, 95% CI -39.86 to -28.13; P < 0.001; moderate-certainty evidence) more than placebo. At month 18, the change in quality of life between groups favoured patisiran (Norfolk QOL-DN total score; least-squares MD -21.10 points, 95% CI -27.20 to -15.00; P < 0.001; low-certainty evidence). There was little or no between-group difference in the number of participants who died (RR 0.61, 95% CI 0.21 to 1.74; P = 0.35; low-certainty evidence), dropped out due to adverse events (RR 0.33, 95% CI 0.13 to 0.82; P = 0.017; low-certainty evidence), or experienced at least one severe adverse event (RR 0.91, 95% CI 0.64 to 1.28; P = 0.58; low-certainty evidence) during the trial. One RCT compared inotersen with placebo (172 randomised participants). The trial did not explore our predetermined disability outcome measures. From baseline to week 66, inotersen reduced progression of peripheral neuropathy more than placebo (modified NIS plus 7 nerve tests - Ionis version; MD -19.73 points, 95% CI -26.50 to -12.96; P < 0.001; moderate-certainty evidence). At week 65, the change in quality of life between groups favoured inotersen (Norfolk QOL-DN total score; MD -10.85 points, 95% CI -17.25 to -4.45; P < 0.001; low-certainty evidence). Inotersen may slightly increase mortality (RR 5.94, 95% CI 0.33 to 105.60; P = 0.22; low-certainty evidence) and occurrence of severe adverse events (RR 1.48, 95% CI 0.85 to 2.57; P = 0.16; low-certainty evidence) compared to placebo. More dropouts due to adverse events were observed in the inotersen than in the placebo group (RR 8.57, 95% CI 1.16 to 63.07; P = 0.035; low-certainty evidence). There were no studies addressing apolipoprotein AI-FAP, gelsolin-FAP, and beta-2-microglobulin-FAP. AUTHORS' CONCLUSIONS: Evidence on the pharmacological treatment of FAPs from RCTs is limited to TTR-FAP. No studies directly compare disease-modifying pharmacological treatments for TTR-FAP. Results from placebo-controlled trials indicate that tafamidis, diflunisal, patisiran, and inotersen may be beneficial in TTR-FAP, but further investigations are needed. Since direct comparative studies for TTR-FAP will be hampered by sample size and costs required to demonstrate superiority of one drug over another, long-term non-randomised open-label studies monitoring their efficacy and safety are needed.

Cardiac Amyloidosis: Overlooked, Underappreciated, and Treatable.

Cardiac amyloidosis (CA) is an infiltrative and restrictive cardiomyopathy that leads to heart failure, reduced quality of life, and death. The disease has two main subtypes, transthyretin cardiac amyloidosis (ATTR-CA) and immunoglobulin light chain cardiac amyloidosis (AL-CA), characterized by the nature of the infiltrating protein. ATTR-CA is further subdivided into wild-type (ATTRwt-CA) and variant (ATTRv-CA) based on the presence or absence of a mutation in the transthyretin gene. CA is significantly underdiagnosed and increasingly recognized as a cause of heart failure with preserved ejection fraction. Advances in diagnosis that employ nuclear scintigraphy to diagnose ATTR-CA without a biopsy and the emergence of effective treatments, including transthyretin stabilizers and silencers, have changed the landscape of this field and render early and accurate diagnosis critical. This review summarizes the epidemiology, pathophysiology, diagnosis, prognosis, and management of CA with an emphasis on the significance of recent developments and suggested future directions.

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

There have now been randomized controlled trials of four different therapeutics for hereditary amyloid polyneuropathy related to transthyretin (TTR) deposition and one for amyloidotic cardiomyopathy of both genetic and sporadic origin. It is likely that in the next few months those not already approved by either the US Food and Drug Administration (FDA) and/or the European Medicines Authority (EMA) will receive similar approvals for treatment for all or particular groups of patients. This is a far cry from circumstances less than 10 years ago when the only available therapy was gene replacement by liver transplant. The randomized controlled trials have shown that all the treatments (tafamidis, diflunisal, patisiran, and inotersen) are effective in the context of a clinical trial. However, we have very little idea of whether individual patients will respond in an equally positive way to all the drugs or whether there will be some who respond better to one or another or not respond at all, nor do we know whether combinations will be additive or synergistic. We lack validated markers of clinical response. While the small molecule TTR stabilizers increase serum TTR levels, the RNA-based drugs lower serum TTR. In the latter case, it is not clear that the reduction in serum TTR is related to the clinical response in a 1:1 fashion. Pharmaceutical companies have made substantial investments in the development of these agents and will clearly attempt to recoup those investments quickly. It is incumbent upon those of us who care for these patients to develop ways to assess the effects of therapy in the shortest possible time at the lowest possible cost. The better we are able to accomplish this the more likely it is that we will be able to treat the most patients in the most clinically efficient fashion regardless of their economic status. We now have the drugs we just have to figure out who should get them and when.

Diflunisal tolerability in transthyretin cardiac amyloidosis: a single center's experience.

OBJECTIVE: Transthyretin (ATTR) amyloidosis is an under-recognized, progressive disease manifesting as cardiomyopathy and/or polyneuropathy. Diflunisal, a nonsteroidal anti-inflammatory drug (NSAID), has demonstrated transthyretin stabilization in vitro and slowing of polyneuropathy progression in the hereditary ATTR subtype (ATTRm). However, the use of diflunisal has only been described in a small cohort of patients with ATTR cardiac amyloidosis (CA). We hypothesized that selected patients with ATTR-CA, both hereditary and wild-type (ATTRwt), would tolerate diflunisal with limited adverse events. MATERIALS AND METHODS: This is a retrospective, longitudinal study of 23 patients with ATTR-CA (10 ATTRm and 13 ATTRwt) diagnosed at the Cleveland Clinic from May 2007 to August 2017 who were treated with diflunisal. Patients were prescribed diflunisal, fully informed of the risks of side effects. Patient characteristics and subsequent adverse events were recorded. RESULTS: The duration of diflunisal therapy ranged from 1-89 months (median 15 months). Average eGFR at diflunisal initiation was 61.9 ± 15.4 mL/min/m2. Only one patient had a transient rise in Cr of 0.31 mg/dL. There were no clinically significant bleeding events, despite most of the patients being on anticoagulants or antiplatelet agents. Three of 23 patients (13%) withdrew treatment due to drug side effects (erosive gastritis, epigastric pain and decreased appetite). No patients died or were hospitalized for heart failure. CONCLUSION: Diflunisal was well-tolerated in both the ATTRm- and ATTRwt-CA populations. Withdrawal due to side effects was related to gastrointestinal complaints, but most patients had no adverse events. Diflunisal can be safely used in a selected group of ATTR-CA patients with appropriate clinical, renal and hematologic monitoring.

Inhibition of the Amyloidogenesis of Transthyretin by Natural Products and Synthetic Compounds.

Hereditary transthyretin (TTR)-related amyloidosis is caused by mutations in the TTR gene. The mutations destabilize the tetramer and/or monomer of TTR, and thus the stabilization of TTR is a key strategy for the treatment of TTR-related amyloidosis. In this review, we summarized the natural products and synthetic compounds that have been shown to inhibit the amyloidogenesis of TTR. The stabilizers and/or the amyloid fibril disrupters isolated from natural sources may become lead compounds for the treatment of TTR-related amyloidosis.

Unusual duplication mutation in a surface loop of human transthyretin leads to an aggressive drug-resistant amyloid disease.

Transthyretin (TTR) is a globular tetrameric transport protein in plasma. Nearly 140 single amino acid substitutions in TTR cause life-threatening amyloid disease. We report a one-of-a-kind pathological variant featuring a Glu51, Ser52 duplication mutation (Glu51_Ser52dup). The proband, heterozygous for the mutation, exhibited an unusually aggressive amyloidosis that was refractory to treatment with the small-molecule drug diflunisal. To understand the poor treatment response and expand therapeutic options, we explored the structure and stability of recombinant Glu51_Ser52dup. The duplication did not alter the protein secondary or tertiary structure but decreased the stability of the TTR monomer and tetramer. Diflunisal, which bound with near-micromolar affinity, partially restored tetramer stability. The duplication had no significant effect on the free energy and enthalpy of diflunisal binding, and hence on the drug-protein interactions. However, the duplication induced tryptic digestion of TTR at near-physiological conditions, releasing a C-terminal fragment 49-129 that formed amyloid fibrils under conditions in which the full-length protein did not. Such C-terminal fragments, along with the full-length TTR, comprise amyloid deposits in vivo. Bioinformatics and structural analyses suggested that increased disorder in the surface loop, which contains the Glu51_Ser52dup duplication, not only helped generate amyloid-forming fragments but also decreased structural protection in the amyloidogenic residue segment 25-34, promoting misfolding of the full-length protein. Our studies of a unique duplication mutation explain its diflunisal-resistant nature, identify misfolding pathways for amyloidogenic TTR variants, and provide therapeutic targets to inhibit amyloid fibril formation by variant TTR.

Therapeutic Strategies Targeting Inherited Cardiomyopathies.

PURPOSE OF REVIEW: Cardiomyopathies due to genetic mutations are a heterogeneous group of disorders that comprise diseases of contractility, myocardial relaxation, and arrhythmias. Our goal here is to discuss a limited list of genetically inherited cardiomyopathies and the specific therapeutic strategies used to treat them. RECENT FINDINGS: Research into the molecular pathophysiology of the development of these cardiomyopathies is leading to the development of novel treatment approaches. Therapies targeting these specific mutations with gene therapy vectors are on the horizon, while other therapies which indirectly affect the physiologic derangements of the mutations are currently being studied and used clinically. Many of these therapies are older medications being given new roles such as mexiletine for Brugada syndrome and diflunisal for transthyretin amyloid cardiomyopathy. A newer targeted therapy, the inhibitor of myosin ATPase MYK-461, has been shown to suppress the development of ventricular hypertrophy, fibrosis, and myocyte disarray and is being studied as a potential therapy in patients with hypertrophic cardiomyopathy. While this field is too large to be completely contained in a single review, we present a large cross section of recent developments in the field of therapeutics for inherited cardiomyopathies. New therapies are on the horizon, and their development will likely result in improved outcomes for patients inflicted by these conditions.