TTR Stabilizers Research Articles

RV-PA uncoupling is associated with increased mortality in transthyretin amyloid cardiomyopathy treated with tafamidis.

The right ventricle to pulmonary artery coupling (RV-PAc) describes the right ventricle's ability to adjust to an increased afterload. In case of transthyretin amyloid cardiomyopathy (ATTR-CM), impaired RV-PAc can result from increased left ventricular diastolic stiffness due to fibril deposition. While RV-PAc is a validated prognostic parameter in pulmonary arterial hypertension (PAH), its prognostic relevance in ATTR-CM remains unknown. We sought to evaluate the prognostic implications of impaired RV-PAc on survival in ATTR-CM. In this multicentre study, RV-PAc was investigated by the echocardiographic surrogate of ratio of tricuspid annular plane systolic excursion to estimated pulmonary arterial systolic pressure (TAPSE/PASP) in 418 ATTR-CM patients, all treated with a TTR stabilizer. The primary outcome was all-cause mortality. Within a median time of 1.52 [IQR 0.72-2.56] years after diagnosis, 49 (11.7%) patients died. In multivariate Cox regression analysis impaired RV-PAc was a strong independent predictor of mortality (Hazard Ratio (HR) 2.16, 95% Confidence Interval (CI) 1.14-4.07, p=0.018). RV-PAc ratio at first presentation emerged as a robust marker for risk stratification with a determined optimal cut-off of 0.382mm/mmHg (area under the curve (AUC) 0.73, 95% CI 0.65-0.81). Patients with RV-PAc ratio ≤ 0.382mm/mmHg exhibited significantly lower survival (HR 4.17, 95% CI 2.21-7.87, p<0.001) within 3years of follow up than those with RV-PAc ratio above the cut-off (Graphical Abstract). Impaired adaptation of the RV to increased afterload is associated with worse outcome in ATTR-CM patients. RV-PAc ratio can serve as an echocardiographic predictor for all-cause mortality. Therefore, the determination of RV-PAc could improve risk stratification for ATTR-CM patients.

Relationship between changes in renal function after acute phase of tafamidis administration and left ventricular diastolic function at mid-term follow-up in transthyretin cardiac amyloidosis

Abstract Background A large number of heart failure (HF) patients present with various degrees of renal dysfunction, known as cardio-renal syndrome. Renal impairment in HF patients is also associated with an independent risk factor for morbidity and mortality. Transthyretin (TTR) amyloidosis (ATTR) is characterized by disintegrated liver-derived TTR that accumulates as amyloid fibrils in the myocardium, leading to initially presenting as left ventricular (LV) hypertrophy and LV diastolic dysfunction. Although there is no proven therapy for patients with ATTR cardiomyopathy (ATTR-CM), tafamidis meglumine, a TTR stabilizer, has been associated with favorable outcomes. Although the kidneys are also an important organ where amyloid deposition occurs, the effect of tafamidis on renal function and its relationship to LV diastolic function is unclear. Purpose The purpose of this study was to investigate the relationship between changes in renal function after the acute phase of tafamidis administration and LV diastolic function at mid-term follow-up in patients with ATTR-CM. Methods We studied 56 patients with biopsy-proven ATTR-CM who were treated with tafamidis. All patients underwent blood examinations before and 45.6 ± 23.0 days after the acute phase of tafamidis administration. Echocardiography was performed before and 15.6 ± 9.8 months after the mid-term of tafamidis administration. The primary endpoint was defined as a composite of cardiovascular death or HF hospitalization for 5.0 years. Results Twelve patients had improved renal function as assessed by estimated glomerular filtration rate in the acute phase after tafamidis administration, while 44 patients deteriorated. In the group with improved renal function in the acute phase after tafamidis administration, pulsed-wave Doppler-derived early diastolic velocity from the septal mitral annulus (E’) and left atrial volume index (LAVI) tended to improve at mid-term follow-up compared to the non-improved group. (E’: 0.8 ± 1.7 cm/s vs. 0.2 ± 1.1 cm/s, p=0.127, LAVI: -8.7 ± 12.0 mL/m2 vs. 0.2 ± 16.8 mL/m2, p=0.093). Furthermore, Kaplan-Meier curve indicated that the occurrence of cardiovascular events for patients with improved renal function in the acute phase after tafamidis administration tended to be lower than those without (log-rank P=0.137). Conclusions The improvement of renal function in the acute phase after tafamidis administration was associated with the improvement of LV diastolic function at mid-term follow-up, leading to favorable outcome. Our findings may provide new insights for the management of patients with ATTR-CM.

RV-PA uncoupling is a strong predictor of 3-year all-cause mortality in transthyretin amyloid cardiomyopathy

Abstract Background Right ventricle to pulmonary artery coupling (RV-PAc) describes the right ventricle's ability to adjust to an increased afterload which, in case of transthyretin amyloid cardiomyopathy (ATTR-CM), can result from increased left ventricular diastolic stiffness due to fibril deposition. While RV-PAc is a validated prognostic parameter in pulmonary arterial hypertension (PAH), its prognostic relevance in ATTR-CM remains unclear. This study sought to evaluate the prognostic implications of impaired RV-PAc on survival in ATTR-CM. Methods In this two-centre study, RV-PAc was investigated by the echocardiographic surrogate of ratio of tricuspid annular plane systolic excursion to estimated pulmonary arterial systolic pressure (TAPSE/PASP) in 418 ATTR-CM patients, all treated with TTR stabilizer. The primary outcome was all-cause mortality. Receiver operation curves and Youden’s J analysis were applied to identify an optimal cut-off value of RV-PAc ratio. Results Within a median time of 631 (IQR 361-983) days after diagnosis, 14.4% of patients died. RV-PAc ratio at first presentation emerged as a robust marker for risk stratification with a determined optimal cut-off of 0.382mm/mmHg (area under the curve (AUC) 0.746, 95% CI 0.68-0.82). Patients with RV-PAc ratio ≤0.382mm/mmHg (impaired RV-PAc, n=158) exhibited significantly lower survival (HR 4.07, 95% CI 2.26-7.33, p&amp;lt;0.001) within 3 years of follow up than those with RV-PAc ratio &amp;gt; 0.382mm/mmHg. In multivariate Cox regression analysis, incorporating a range of known prognostic variables, reduced RV-PAc was a strong echocardiographic predictor of mortality (Hazard Ratio (HR) 2.99, 95% Confidence Interval (CI) 1.63-5.51, p &amp;lt;0.001). Conclusion Impaired adaption of the RV to increased afterload is associated with worse outcome in ATTR-CM patients. RV-PAc ratio can serve as an echocardiographic predictor for all-cause mortality within three years after diagnosis. Therefore, determination of RV-PAc could improve risk stratification for ATTR-CM patients.Figure_1_Kaplan-Meier curves

Transthyretin Cardiac Amyloidosis: Insights into Wild-Type Variants and Familial Amyloid Cardiomyopathy

Transthyretin (TTR) cardiac amyloidosis is a progressive condition characterized by amyloid fibril deposition in the heart, leading to heart failure. This review focuses on insights into wild-type (ATTRwt) and familial (ATTRm) variants of TTR amyloidosis. The pathophysiology involves TTR tetramer destabilization, monomer misfolding, and amyloid fibril formation. Therapeutic advances, including TTR stabilizers like tafamidis and Diflunisal, and gene-silencing agents such as patisiran and inotersen, show promise in managing the disease. Despite these advancements, early diagnosis remains challenging, and side effects of current therapies necessitate the development of safer, more effective treatments. Future research should focus on novel therapies, improved diagnostic methods, and personalized treatment strategies to enhance patient outcomes. This review underscores the importance of continued innovation and collaboration in tackling TTR cardiac amyloidosis.

Arginine: A potential prophylactic supplement for transthyretin amyloidosis

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

Tetrameric Transthyretin as a Protective Factor Against Alzheimer's Disease.

Transthyretin (TTR) is a tetrameric protein traditionally recognized for its role in transporting thyroxine and retinol. Recent research has highlighted the potential neuroprotective functions of TTR in the setting of Alzheimer's disease (AD), which is the most common form of dementia and is caused by the deposition of amyloid beta (Aβ) and the resulting cytotoxic effects. This paper explores the mechanisms of TTR protective action, including its interaction with Aβ to prevent fibril formation and promote Aβ clearance from the brain. It also synthesizes experimental evidence suggesting that enhanced TTR stability may mitigate neurodegeneration and cognitive decline in AD. Potential therapeutic strategies such as small molecule stabilizers of TTR are discussed, highlighting their role in enhancing TTR binding to Aβ and facilitating its clearance. By consolidating current knowledge and proposing directions for future research, this review aims to underscore the significance of TTR as a neuroprotective factor in AD and the potential implications for future research.

Treatment of transthyretin cardiac amyloidosis.

Tafamidis is currently the only approved disease-modifying treatment for ATTR-CM. However, there have been important developments in the treatment of ATTR-CM, as the results of two phase 3 trials were published and several other trials are in their final stages. In this review, we summarize current and future therapies for ATTR-CM. Recently, acoramidis, a TTR stabilizer has been proven to be effective in reducing mortality and morbidity compared to placebo in the ATTRibute-CM trial. Additionally, patisiran, an RNA silencer, preserved functional capacity and quality of life compared to placebo in the APOLLO-B trial. However, the FDA declined to approve patisiran for ATTR-CM. The results of phase 1 trial of ALXN2220, an antiamyloid antibody raise hope for reversal of myocardial damage by amyloid depletion. Phase 3 trials evaluating the efficacy of different RNA silencers, gene editing with CRISPR-Cas9, and other anti-amyloid antibodies are ongoing. Therapies targeting different mechanism in the pathophysiology of ATTR-CM provide new alternatives for treating patients with ATTR-CM. Future research should focus on comparing their effectiveness, the potential of combined treatment with agents from different classes and on identifying the patients who will benefit most from each class of medication.

Efficacy and Safety of Acoramidis in Transthyretin Amyloid Cardiomyopathy

BackgroundTransthyretin amyloid cardiomyopathy is characterized by the deposition of misfolded monomeric transthyretin (TTR) in the heart. Acoramidis is a high-affinity TTR stabilizer that acts to inhibit dissociation of tetrameric TTR and leads to more than 90% stabilization across the dosing interval as measured ex vivo.MethodsIn this phase 3, double-blind trial, we randomly assigned patients with transthyretin amyloid cardiomyopathy in a 2:1 ratio to receive acoramidis hydrochloride at a dose of 800 mg twice daily or matching placebo for 30 months. Efficacy was assessed in the patients who had an estimated glomerular filtration rate of at least 30 ml per minute per 1.73 m2 of body-surface area. The four-step primary hierarchical analysis included death from any cause, cardiovascular-related hospitalization, the change from baseline in the N-terminal pro–B-type natriuretic peptide (NT-proBNP) level, and the change from baseline in the 6-minute walk distance. We used the Finkelstein–Schoenfeld method to compare all potential pairs of patients within strata to generate a P value. Key secondary outcomes were death from any cause, the 6-minute walk distance, the score on the Kansas City Cardiomyopathy Questionnaire–Overall Summary, and the serum TTR level.ResultsA total of 632 patients underwent randomization. The primary analysis favored acoramidis over placebo (P<0.001); the corresponding win ratio was 1.8 (95% confidence interval [CI], 1.4 to 2.2), with 63.7% of pairwise comparisons favoring acoramidis and 35.9% favoring placebo. Together, death from any cause and cardiovascular-related hospitalization contributed more than half the wins and losses to the win ratio (58% of all pairwise comparisons); NT-proBNP pairwise comparisons yielded the highest ratio of wins to losses (23.3% vs. 7.0%). The overall incidence of adverse events was similar in the acoramidis group and the placebo group (98.1% and 97.6%, respectively); serious adverse events were reported in 54.6% and 64.9% of the patients.ConclusionsIn patients with transthyretin amyloid cardiomyopathy, the receipt of acoramidis resulted in a significantly better four-step primary hierarchical outcome containing components of mortality, morbidity, and function than placebo. Adverse events were similar in the two groups. (Funded by BridgeBio Pharma; ATTRibute-CM ClinicalTrials.gov number, NCT03860935.)

Disease-Modifying Drugs Extend Survival in Hereditary Transthyretin Amyloid Polyneuropathy.

Hereditary transthyretin (ATTRv) amyloidosis is a rare, fatal systemic disease, associated with polyneuropathy and cardiomyopathy, that is caused by mutant transthyretin (TTR). In addition to liver transplantation, several groundbreaking disease-modifying drugs (DMDs) such as tetrameric TTR stabilizers and TTR gene-silencing therapies have been developed for ATTRv amyloid polyneuropathy. They were based on a working hypothesis of the mechanisms of ATTRv amyloid formation. In this retrospective cohort study, we investigated survival of all 201 consecutive patients with ATTRv amyloidosis in our center. The effects of DMDs on survival improvements were significant not only in early-onset patients but also in late-onset patients. ANN NEUROL 2024;95:230-236.

Unveiling Alarming Trends: Worsening All Cause Mortality in US Adults over 25 with Amyloid 1999-2020 Analysis

Introduction: Amyloidosis is a collective term for conditions with an abnormal extracellular deposition of amyloid protein. Amyloidosis can be classified based on the location of deposition (localized vs systemic) and by the different subtypes of proteins which are created as a result of a variety of diseases (plasma cell dyscrasias, chronic inflammation, nephrotic syndrome, genetic). Depending on the affected organs, amyloidosis can present with, not limited to, hepatomegaly, renal impairment, nerve conduction impairment, cardiac conduction abnormalities, restrictive cardiomyopathy, and multiorgan failure. In the last century there has been an increase in innovations leading to a better understanding of the pathology, diagnostic tests, staging, and treatment options for amyloidosis. Our study aims to compare all cause mortality trends in adults over 25 years old diagnosed with amyloidosis in the United States. Methods: The national mortality trends from 1999 to 2020 for all subtypes of amyloid were analyzed from the CDC WONDER database. The data was extracted using ICD codes E85 (Amyloidosis) with subgroups E85.0 (Non-neuropathic heredofamilial amyloidosis), E85.3 (Secondary systemic amyloidosis), E85.4 (Organ-limited amyloidosis), E85.8 (Other amyloidosis), and E85.9 (Amyloidosis, unspecified. Data was stratified for age groups above 25 years old. Age-adjusted mortality rates (AAMRs) were calculated per 100,000 people and death certificate data was stratified by reported sex, race/ethnicity, and US census region. Results: Between 1999 and 2020 there were 40,015 deaths from amyloid. Our analysis revealed that all-cause AAMR per 100,000 people with amyloid showed an increasing trend between 1999 to 2020 (Figure 1). Subgroup analysis on race/ethnicity revealed the AAMR for the Black population has been consistently higher to other groups (Table 1). On average, from 1999 to 2020, the Black population had the highest AAMR (1.52 AAMR) followed by the White population (0.78 AAMR), Hispanic (0.55 AAMR), and Asian (0.5 AAMR). Further subgroup analysis revealed men have a higher AAMR (1.9 AAMR, 2020) compared to women (0.8 AAMR, 2020). Overall there are similar census region trends of all mortality in Amyloid: North (1.5 AAMR, 2020), Midwest (1.5 AAMR, 2020), South (1.0, AAMR, 2020) and West (1.3 AAMR, 2020). Conclusion: Due to advancement in technology, amyloid diseases are becoming more widely recognized and increasingly diagnosed. Unfortunately, treatment of amyloidosis remains limited to early diagnosis and treatment of the underlying condition. This includes modalities such as chemotherapy and stem cell transplantation for plasma cell dysplasias and TTR stabilizers for hereditary amyloidosis. These trends in increase in AAMR likely reflect the increased awareness/diagnostics of amyloid disease and complications. The African American population may have higher AAMR due to socioeconomic and environmental factors, health disparities, and research bias. We also suspect men have a higher ATTR than women as it has been reported that ATTR and AL Amyloidosis tends to occur more frequently in men than women and is associated with more severe disease (Kroi et al., 2020, Desport et al., 2012). Further research is necessary to expand on the disparities seen with the ultimate goal of providing targeted therapies to reverse this downward trend.

Acoramidis produces near-complete TTR stabilization in blood samples from patients with variant transthyretin amyloidosis that is greater than that achieved with tafamidis

Abstract Introduction Transthyretin (TTR) amyloidosis (ATTR) is a progressive, fatal disease caused by destabilizing TTR variants (TTRv) and age-related factors. Dissociation of tetrameric TTR initiates protein misfolding, aggregation, and tissue deposition which constitutes the mechanism of disease. More destabilizing variants drive more severe clinical phenotypes. TTR stabilizers have demonstrated clinical benefits for neuropathic and cardiovascular outcomes correlated with the extent of TTR stabilization. Acoramidis (AG10) is a novel TTR stabilizer in development for the treatment of TTR amyloid cardiomyopathy. Hypothesis: Acoramidis achieves near-complete in vitro TTR stabilization, exceeding levels achieved with clinically relevant concentrations of tafamidis (a TTR stabilizer in clinical use), when added to blood samples from ATTRv patients across a spectrum of destabilizing TTR variants. Methods Two established assays assessed TTR stabilization: fluorescent probe exclusion (FPE; measures binding site occupancy), and Western blot (WB; quantifies tetrameric TTR persistence under conditions of accelerated dissociation). Over 60 individual patient samples representing 18 unique TTRv across a spectrum of intrinsic instability and clinical phenotypes were assayed. Acoramidis was added at its target clinical trough concentration (10 µM) and compared to tafamidis added at its clinical peak (26 µM) and trough (16 µM) concentrations reported for its maximal approved dose. Results Acoramidis bound serum TTR to a greater extent (103 ± 13%) than either peak (87 ± 14%) or trough (71 ± 14%) concentrations of tafamidis. WB assays showed that addition of acoramidis resulted in significantly greater and more durable TTR stabilization (93 ± 14%) than adding tafamidis (peak: 49 ± 14%, trough: 36 ± 13%) in all paired individual patient plasma samples tested (Figure 1, p &amp;lt; 0.0001). Rare variants (A97S, D38A, F64L, L58H, P24S, Y114C) also demonstrated near complete stabilization upon in vitro addition of acoramidis. Conclusions At its target therapeutic trough concentration, acoramidis achieved near-complete TTR stabilization across 18 unique genotypes; in the subset of paired samples, the stabilization was significantly greater for acoramidis than for tafamidis even at its peak clinical concentration. This observation held across a range of destabilizing mutations, including a∼2-fold greater stabilization than tafamidis for the prevalent cardiomyopathic V122I variant. Based on the mechanism of disease and the association between TTR destabilization and severity of clinical outcomes, these data suggest that acoramidis has the potential to be a clinically differentiated and efficacious treatment option for patients with ATTRv, independent of variant genotype.

Saturation of fatty acids in phosphatidic acid uniquely alters transthyretin stability changing morphology and toxicity of amyloid fibrils

Transthyretin (TTR) is a small, β-sheet-rich tetrameric protein that transports thyroid hormone thyroxine and retinol. Phospholipids, including phosphatidic acid (PA), can uniquely alter the stability of amyloidogenic proteins. However, the role of PA in TTR aggregation remains unclear. In this study, we investigated the effect of saturation of fatty acids (FAs) in PA on the rate of TTR aggregation. We also reveal the extent to which PAs with different length and saturation of FAs altered the morphology and secondary structure of TTR aggregates. Our results showed that TTR aggregation in the equimolar presence of PAs with different length and saturation of FAs yielded structurally and morphologically different fibrils compared to those formed in the lipid-free environment. We also found that PAs drastically lowered the toxicity of TTR aggregates formed in the presence of this phospholipid. These results shed light on the role of PA in the stability of TTR and transthyretin amyloidosis.

Treating amyloid transthyretin cardiomyopathy: lessons learned from clinical trials.

An increasing awareness of the disease, new diagnostic tools and novel therapeutic opportunities have dramatically changed the management of patients with amyloid transthyretin cardiomyopathy (ATTR-CM). Supportive therapies have shown limited benefits, mostly related to diuretics for the relief from signs and symptoms of congestion in patients presenting heart failure (HF). On the other hand, huge advances in specific (disease-modifying) treatments occurred in the last years. Therapies targeting the amyloidogenic cascade include several pharmacological agents that inhibit hepatic synthesis of TTR, stabilize the tetramer, or disrupt fibrils. Tafamidis, a TTR stabilizer that demonstrated to prolong survival and improve quality of life in the ATTR-ACT trial, is currently the only approved drug for patients with ATTR-CM. The small interfering RNA (siRNA) patisiran and the antisense oligonucleotide (ASO) inotersen have been approved for the treatment of patients with hereditary ATTR polyneuropathy regardless of the presence of cardiac involvement, with patisiran also showing preliminary benefits on the cardiac phenotype. Ongoing phase III clinical trials are investigating another siRNA, vutrisiran, and a novel ASO formulation, eplontersen, in patients with ATTR-CM. CRISPR-Cas9 represents a promising strategy of genome editing to obtain a highly effective blockade of TTR gene expression.

P203 PLASMA TRANSTHYRETIN FORMS IN PATIENTS WITH WILD–TYPE TRANSTHYRETIN CARDIAC AMYLOIDOSIS: INFLUENCED OF TAFAMIDIS TREATMENT

Abstract Introduction Transthyretin (TTR) is a plasma protein that transports thyroxin and retinol complexed to retinol–binding protein (RBP). TTR misfolding and aggregation can lead to the extracellular deposition of amyloid in the myocardium, causing TTR cardiac amyloidosis (ATTR–CA). Aim of this study is to develop a native electrophoretic method to characterize circulating TTR forms in plasma samples of ATTR–CA patients, before and after administration of tafamidis, a TTR stabilizer. Material &amp; Methods Plasma samples from patients affected by wild–type ATTR amyloidosis (ATTRwt, n=10) were collected before (T0) and during tafamidis treatment at 14, 30 and 90 days. Plasma samples of sex– and age–matched healthy controls (n=6) were also collected. All samples were separated on a native 4–20% Tris–Gly polyacrylamide gel. Western blot analysis was performed with anti–TTR or anti–RBP antibodies. Proteins were detected by Clarity ECL substrate. ImageLab software was used for image acquisition and densitometric analysis of the blots. Total TTR (mg/dl) and RBP (mg/dl) were quantified by nephelometry. Results In both groups, the most represented forms were: TTR dimers or trimers (37–50kDa), TTR tetramers complexed with RBP protein in 1:1 (75kDa,) or 1:2 ratio (100kDa), and high molecular weight aggregates (&amp;gt;150kDa). RBP protein was detectable in association with TTR tetramers and some of the TTR aggregates (250kDa, 480kDa). Based on TTR electrophoretic pattern at T0, patients could be divided in 2 groups: ATTR–1, characterised by the presence of TTR tetramers (55kDa), and ATTR–2, characterised by its absence. The ATTR–1 group showed also higher levels of total TTR in comparison with ATTR–2 (mean±SD 25.5±3.8, 16.6±4.2 respectively, p=0.004), while plasma RBP levels were similar (5.1±0.7, 5.1±1.4 respectively). The electrophoretic patterns of ATTR–1 at T0, as well as TTR and RBP levels were comparable to those of controls (TTR 22.6±3.8, RBP 4.4±0.9). Tafamidis treatment was associated with a progressive increase of total TTR levels both in ATTR–1 and –2 (T90 31.4±5.8, 28.7±6.8) but the 2 groups continued to be distinguishable by the electrophoretic pattern. Conclusions The native electrophoresis allowed us to detect diverse circulating TTR forms and to classify patients in 2 groups according to their electrophoretic pattern. TTR quali/quantitative evaluation by electrophoresis could represent a valid tool to assess the individual pharmacological response to tafamidis.

P357 DOES CARDIAC AMYLOIDOSIS EVER HIDE A SEVERE AORTIC STENOSIS A CASE REPORT

Abstract Case presentation: A 89-year-old man, with an history of paroxysmal atrial fibrillation and chronic renal disease, was admitted to our ER for acute decompensated heart failure. He reported dyspnea on minimal exertion and worsening peripheral edema. He had a history of heart failure and a severe aortic stenosis first diagnosed in 2020 with an echocardiogram demonstrating a left ventricular ejection fraction (LVEF) of 30% and a low-flow low-gradient aortic stenosis (AVA=0,6 cmq, mean pressure gradient=21 mmHg). Besides, in 2019, he underwent a 99m Tc MDP scintigraphy for a prostatic nodule which showed important myocardial uptake of the bone tracer highly suggestive of cardiac amyloidosis. Urinary light chain assessment and determination of immunoglobulin light chain levels were negative for AL amyloidosis. The electrocardiogram showed: sinus rhythm, low voltage in the frontal leads and complete left bundle branch block with secondary repolarization abnormalities. The patient underwent transthoracic echocardiography for staging the severity of the aortic valve stenosis, which revealed borderline results: the aortic valve area was 0.5 cmq with a transaortic mean pressure gradient of 20 mmHg (EF 25%, with GLS of −5%). Low-dose dobutamine stress echocardiography was performed. At rest conditions, there was global hypokinesia with an ejection fraction of 24%. Aortic valve mean pressure was 19 mmHg referring to a calculated aortic valve opening area of 0,78 cmq. Under peak dobutamine stress (30 mcg/kg/min), LVEF increased to 36%. On the basis of these diagnostic findings, aortic stenosis was classified as pseudo-severe due to systolic dysfunction of the left ventricle with preserved contractile reserve. Besides, aortic calcium score of 574 confirmed that the aortic stenosis was non severe. Conclusions This case results exemplary of the fact that amyloidosis does not always hide a severe stenosis. Actually the echo with dobutamine indicates a non-valvular reason for heart-failure and no indication for valve replacement.The discharge suggestions consists of clinical/ echo follow ups and TTR stabilizers. Anyway, Tafamidis is not recommended because of the age and the patient short life expectancy. The implantation of CCM which, during the action potential platea delivers non-excitatory electrical currents and enhances systolic function in patients with heart failure, is proposed to obtain an improvement of symptoms.

P350 LOOKING FOR RED FLAGS

Abstract Case report: a 81 years old man with systemic hypertension, dyslipidemia, past smoking habit, was admitted to the ER of our hospital with acute decompensated heart failure. Since July he complained of worsening of dyspnea and paroxysmal nocturnal dyspnea. His blood pressure was of 155/80 mmHg, the HR was of 78 bpm in atrial fibrillation. He reported past myocardial infarction at the age of 32, thenceforth he underwent periodic cardiac check–up. From 2013 he had developed atrial fibrillation. He had suspended Amiodarone because of dysthyroidism, rate control was obtained with Bisoprolol. In 2015, he underwent coronary angiography for a positive scintigraphy showed absence of lesions. During the same hospitalization there was evidence of nocturnal bradycardia (35 bpm). In 2016, a cardiac MR showed subendocardial and intramyocardial fibrosis at mid–basal wall resembling post ischemic events. He underwent past carpal tunnel syndrome surgery. During the actual hospitalization, the EKG showed atrial fibrillation (78 bpm), complete left bundle branch block (both already known). Serum and urinary light–chain assessment and determination of immunoglobulin light chains levels were negative for AL amyloidosis. The echocardiogram documented: hypertrophy of the interventricular septum, mildly reduced LV systolic function (EF=43%). Invasive coronary angiography showed absence of lesions. CMR showed: left ventricular size at the upper limit of normal with hypertrophy of the interventricular septum and the anterior wall, diffused left transmural LGE, focal fibroadipose infiltration of lower basal SIV. During the hospitalization multiple episodes of non sustained ventricular tachycardia occurred, so that a CRT–D device was implanted in secondary prevention. There was a strong suspicion of cardiac amyloidosis so that definitive diagnosis was obtained by the use of 99m Tc scintigraphy coupled with haematologic tests (already done, resulted negative). Scintigraphy showed myocardial uptake of the radiotracer greater than the bone (Grade 3 Perugini score). Conclusion cardiac amyloidosis is a restrictive cardiomyopathy. Early diagnosis is really important, firstly, because new treatments, such as a TTR stabilizer, have transformed this once incurable disease to a treatable condition. Secondly, diagnostic tools now allow earlier and more accurate non–invasive diagnosis. It is crucial to put the attention on red flags which have to be found to rise the clinical suspicion.

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.

Annals for Hospitalists - March 2023

Annals for Hospitalists - March 2023

Advancements in the Treatment of Transthyretin Amyloidosis

Transthyretin (TTR) amyloidosis is a protein misfolding disorder where tetramers of TTR dissociate, causing the formation of insoluble amyloids leading to organ dysfunction and damage. Worldwide, the disease currently affects between 5,000-10,000 people and many novel therapeutic techniques are appearing with the potential to treat TTR amyloidosis. Of the non-CRISPR treatments, they can be broken down into three categories: TTR stabilizers, human monoclonal antibodies, and gene silencers. In this paper, I will discuss both the current state of research and treatment of TTR amyloidosis treatments, as well as the role of CRISPR’s potential future therapeutic applications.

The Regulatory Mechanism of Transthyretin Irreversible Aggregation through Liquid-to-Solid Phase Transition.

Transthyretin (TTR) aggregation and amyloid formation are associated with several ATTR diseases, such as senile systemic amyloidosis (SSA) and familial amyloid polyneuropathy (FAP). However, the mechanism that triggers the initial pathologic aggregation process of TTR remains largely elusive. Lately, increasing evidence has suggested that many proteins associated with neurodegenerative diseases undergo liquid-liquid phase separation (LLPS) and subsequent liquid-to-solid phase transition before the formation of amyloid fibrils. Here, we demonstrate that electrostatic interactions mediate LLPS of TTR, followed by a liquid-solid phase transition, and eventually the formation of amyloid fibrils under a mildly acidic pH in vitro. Furthermore, pathogenic mutations (V30M, R34T, and K35T) of TTR and heparin promote the process of phase transition and facilitate the formation of fibrillar aggregates. In addition, S-cysteinylation, which is a kind of post-translational modification of TTR, reduces the kinetic stability of TTR and increases the propensity for aggregation, while another modification, S-sulfonation, stabilizes the TTR tetramer and reduces the aggregation rate. Once TTR was S-cysteinylated or S-sulfonated, they dramatically underwent the process of phase transition, providing a foundation for post-translational modifications that could modulate TTR LLPS in the context of pathological interactions. These novel findings reveal molecular insights into the mechanism of TTR from initial LLPS and subsequent liquid-to-solid phase transition to amyloid fibrils, providing a new dimension for ATTR therapy.