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Abstract Background The National Amyloidosis Centre (NAC) staging system for transthyretin amyloid cardiomyopathy (ATTR-CM) is used to classify patients into prognostic categories based on N-terminal pro-B-type natriuretic peptide (NT-proBNP) level and estimated glomerular filtration rate (eGFR). The NAC staging system has been shown to predict ongoing survival throughout the course of ATTR-CM, with survival progressively decreasing from stage I to stage III. Acoramidis, a highly selective, oral transthyretin stabilizer that achieves near-complete (≥90%) transthyretin stabilization, has recently been approved in Europe and the USA for the treatment of wild-type or variant ATTR-CM in adults. In the phase 3 ATTRibute-CM study, acoramidis treatment was well tolerated and led to a 42% relative risk reduction in the composite of all-cause mortality and recurrent cardiovascular hospitalizations over 30 months compared with placebo (p=0.0005). Purpose To evaluate the ability of acoramidis treatment, as compared with placebo, to stabilize or improve NAC stage after 30 months in participants with ATTR-CM from the ATTRibute-CM study. Methods Participants in ATTRibute-CM were randomized 2:1 to receive acoramidis or placebo for 30 months. Efficacy analyses were conducted in the modified intention-to-treat population, which consisted of all randomized participants who had received at least one dose of acoramidis or placebo, had at least one efficacy evaluation after baseline and had a baseline eGFR ≥30 mL/min/1.73 m2. NAC stage at baseline and Month 30 was assessed. Changes from baseline to Month 30 were categorized as "stable", "improved" or "worsened". The "stable" category comprised participants who stayed within the same NAC stage at baseline and Month 30. The "improved" category comprised participants who moved from a higher NAC stage at baseline to a lower stage at Month 30. The "worsened or missing" category comprised participants who moved from a lower NAC stage at baseline to a higher stage at Month 30 and participants whose Month 30 NAC stage was missing. The change in NAC stage was compared between treatment groups using a stratified Cochran-Mantel-Haenszel test with stratification factors of genotype, NT-proBNP level and eGFR as recorded in the interactive voice/web response system at randomization. Results Overall, 611 participants were analysed (acoramidis: n=409; placebo: n=202). Baseline characteristics were comparable between treatment groups. Most participants had NAC stage I at baseline (acoramidis: 58.9%; placebo: 59.4%; Table). At Month 30, NAC stage remained stable or improved in 52.1% of acoramidis participants compared with 43.1% of placebo participants (p=0.0351; Figure). Conclusions Acoramidis treatment resulted in a greater proportion of participants whose NAC stage improved or remained stable at Month 30 compared with placebo, indicating better stabilization of their disease.

Context.— Treatments are available for common forms of systemic amyloidosis that show promise for extending and improving the quality of life for patients. Early diagnosis and accurate identification of amyloid fibril type are crucial for successful treatment, but the diagnosis and workup of amyloidosis is inconsistent among pathologists and laboratories. Thus, the goal of this guideline is to offer recommendations for proper testing and workup for amyloidosis to optimize patient care. Objective.— To establish evidence-based recommendations for appropriate laboratory testing to detect amyloidosis and identify the specific amyloidogenic protein. Design.— The College of American Pathologists convened a panel of experts to develop recommendations following the standards established by the National Academy of Medicine for developing trustworthy clinical practice guidelines. The panel conducted a systematic literature review addressing 6 key questions. Using the Grading of Recommendations Assessment, Development and Evaluation framework, recommendations were created based on the available evidence, certainty of that evidence, and key judgments as defined in the framework. Results.— Four conditional recommendations and 3 good practice statements were established to provide guidance for proper testing and workup of amyloidosis. Conclusions.— This guideline summarizes the available evidence on the diagnosis and workup of systemic amyloidosis in tissue samples, including the challenges and limitations of common approaches and techniques. Recommendations for pathologists and laboratories receiving these samples are provided.

Importance Transthyretin amyloid cardiomyopathy (ATTR-CM), a progressive disease caused by misfolded transthyretin (TTR), occurs as wild-type (ATTRwt-CM) or variant (ATTRv-CM) forms. p.Val142Ile is the most common variant in the US, linked to rapid progression and increased mortality. Acoramidis achieves near-complete (≥90%) TTR stabilization and showed clinical benefit in the 30-month ATTRibute-CM trial and through month 42 in the ongoing open-label extension (OLE). Objective To evaluate the efficacy of acoramidis in ATTRwt-CM, ATTRv-CM, and variant subgroups (p.Val142Ile and non-p.Val142Ile). Design, Setting, and Participants This international, multicenter, phase 3, randomized placebo-controlled study took place from April 2019 to May 2023 with ongoing OLE (month 42). ATTRibute-CM enrolled 632 participants with ATTR-CM; 611 of 632 were included in the modified intention-to-treat (mITT) population. There were 380 participants who continued into the OLE. These data were analyzed from January 2025 to July 2025. Interventions Oral acoramidis, 712 mg, or placebo twice daily for 30 months, followed by 12 months of open-label treatment. Main Outcomes and Measures All-cause mortality (ACM), cardiovascular-related hospitalizations (CVH), serum TTR, 6-minute walk distance, Kansas City Cardiomyopathy Questionnaire Overall Summary score, and N-terminal pro B-type natriuretic peptide in participants with ATTRwt-CM and ATTRv-CM. Post-hoc analyses were conducted in variant subgroups, including p.Val142Ile. Results Overall, 552 participants with wild-type ATTR-CM (mean [SD] age, 78 [6.3] years; 92.0% male and 8.0% female) and 59 participants with variant ATTR-CM (mean [SD] age, 73 [7.7] years; 77.3% male and 22.7% female) were randomized (mITT population), including 35 with p.Val142Ile. Consistent efficacy was observed in wild-type and variant subgroups for ACM/CVH through month 30 and ACM through month 42. At month 30, acoramidis reduced the risk of ACM/first CVH vs placebo by 31% in ATTRwt-CM (hazard ratio [HR], 0.69; 95% CI, 0.52-0.90; P = .007) and by 59% in ATTRv-CM (HR, 0.41; 95% CI, 0.21-0.81; P = .01). ACM was reduced through month 42 with HRs of 0.70 (95% CI, 0.50-0.98; P = .04) and 0.41 (95% CI, 0.19-0.93; P = .03) in the ATTRwt-CM and ATTRv-CM groups, respectively. Consistent treatment benefit was observed in participants with ATTRwt-CM and ATTRv-CM for secondary end points. Within variant subgroups (p.Val142Ile vs non-p.Val142Ile), consistent treatment benefits were observed for ACM/CVH through month 30 and ACM through month 42. Conclusions and Relevance The beneficial effect of acoramidis was observed consistently in ATTRwt-CM and ATTRv-CM groups. These hypothesis-generating results indicate that further studies are warranted to better characterize the therapeutic benefit of acoramidis in variant subgroups. Trial Registration ClinicalTrials.gov Identifiers: NCT03860935 ; NCT04988386

Introduction: Transthyretin (TTR) amyloid cardiomyopathy (ATTR-CM) arises from amyloidogenic aggregates of destabilized TTR protein in variant (ATTRv-CM) or acquired wild-type TTR (ATTRwt-CM). The p.V142I (V122I) variant is the most common pathogenic TTR allele in the USA and has higher mortality vs wild type. Acoramidis, an oral TTR stabilizer achieving ≥90% stabilization, is approved in USA, UK, Europe, and Japan for treating ATTR-CM in adults. In ATTRibute-CM (NCT03860935), acoramidis showed a reduction in all-cause mortality (ACM) or first cardiovascular-related hospitalization (CVH) vs placebo (PBO), with consistent benefit in ATTRwt-CM and ATTRv-CM (all variants). We report clinical outcomes in participants with p.V142I ATTRv-CM. Research Question: What was the efficacy of acoramidis for clinical outcomes (ACM, CVH) in participants with p.V142I ATTRv-CM in ATTRibute-CM? Methods: In ATTRibute-CM, 632 participants were randomized 2:1 to receive acoramidis HCl 800 mg or PBO twice daily for 30 months. All participants enrolled in open-label extension (OLE) received acoramidis only. Exploratory post hoc analyses were done in the p.V142I ATTRv-CM subgroup. Time-to-event analyses used a stratified Cox proportional hazards model using treatment group as an explanatory factor and baseline 6MWD as a covariate, stratified by randomization factors: serum NT-proBNP and eGFR. ACM was analyzed at Month 42 (ATTRibute-CM 30 months + 12 months OLE). Results: Of the 59 patients with ATTRv-CM reported at randomization, 35 (59.3%) had p.V142I (23 acoramidis, 12 PBO) with comparable baseline characteristics; 4 were homozygous for p.V142I (1 acoramidis, 3 PBO). Through Month 30, ACM/first CVH occurred in 43.5% (10/23) of acoramidis vs 83.3% (10/12) in PBO (HR 0.311; 95% CI 0.120–0.805; Figure 1 ). Through Month 42, ACM occurred in 26.1% (6/23) of continuous acoramidis vs 66.7% (8/12) in PBO to acoramidis (HR 0.307; 95% CI 0.097–0.973; Figure 2 ). Conclusions: In participants with p.V142I ATTRv-CM, acoramidis use was associated with 69% risk reduction in ACM/first CVH through Month 30 and ACM through Month 42 vs PBO. This is the first report of clinical benefit of this magnitude observed in this high-risk population. These findings have biologic plausibility and may reflect the near-complete stabilization observed experimentally with acoramidis in p.V142I ATTR fibrils. These observations require confirmation in larger cohort studies.

AbstractLittle is known about the post heart transplantation management of extra cardiac manifestations in patients with hereditary transthyretin amyloid cardiomyopathy (hATTR‐CM) in the new era of disease modifying treatment for ATTR amyloidosis. This is a retrospective study of all patients with hATTR‐CM associated with the Val142Ile variant who underwent heart transplantation (HT) from January 2014 to February 2022. All 10 patients with the Val142Ile mutation were successfully transplanted, with a 1 year survival post heart transplantation (HT) of 90%, comparable to an age, sex, and race matched cohort of patients transplanted for non‐amyloid indications. However, 4 (40%) of these patients developed progressive extracardiac manifestations requiring initiation of TTR silencer therapy with the small interfering RNA (siRNA) drug patisiran, which was well tolerated with no significant side effects in this population. We recommend formal neurologic evaluation and assessment of extracardiac manifestations annually as part of routine post‐transplant care, and disease modifying therapy, aimed at TTR stabilization or silencing, should be initiated in the context of previously untreated extracardiac manifestations or evidence of subclinical neuropathy to prevent progression.

AbstractBackgroundAs targeted treatments for amyloid transthyretin cardiomyopathy (ATTR‐CM) are becoming available, we aim to characterize the rates of ventricular arrhythmias (VAs), implantable cardioverter‐defibrillator (ICD) utilization, and their impact on survival.MethodsThis is a retrospective cohort study of 130 patients with ATTR‐CM diagnosed at Emory University's Cardiac Amyloidosis Center between April 2012 and September 2020. VAs were defined as nonsustained or sustained ventricular tachycardia and ventricular fibrillation.ResultsOf 130 patients, 42 had wild‐type disease (wtATTR) and 88 had hereditary variants (hATTR), most commonly Val122Ile (89%). At ATTR‐CM diagnosis, 80 (62%) patients had EF ≤ 40% consistent with systolic heart failure. Of the 69 (53%) patients with documented VAs significantly higher rates occurred among those with EF ≤ 40% compared with EF > 40% (67% vs. 28%, p = .001). Thirty‐two patients (25 hATTR, 7 wtATTR) had primary prevention ICDs implanted. Eight (25%) of these patients received appropriate ICD therapy while two (6%) experienced inappropriate therapy. Comparing patients with EF ≤ 35% with and without ICDs did not reveal any survival difference (3.3 ± 0.5 vs. 2.8 ± 0.4 years, p = .699).ConclusionsHigh rates of VAs and appropriate ICD therapy were found among a unique cohort of largely hereditary ATTR‐CM patients with a high rate of systolic heart failure.