Long-Term Durability and Clinical Stability of Acoramidis in Transthyretin Amyloid Cardiomyopathy: A 54-Month Synthesis

Highlights

• Continuous acoramidis treatment through 54 months significantly reduces all-cause mortality (HR 0.55) and cardiovascular-related mortality (HR 0.51) compared to delayed initiation.
• Near-complete serum transthyretin (sTTR) stabilization (≥90%) translates into long-term stability of NT-proBNP levels and functional capacity as measured by the 6-minute walk distance (6MWD).
• The benefit of acoramidis is cumulative and time-dependent, reinforcing the clinical necessity of early diagnosis and intervention before irreversible myocardial damage occurs.
• Safety data remains consistent over the long term, with no new safety signals identified during the 24-month open-label extension period.

Background

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressive, life-threatening infiltrative cardiomyopathy characterized by the deposition of misfolded transthyretin (TTR) protein in the myocardium. The primary pathogenic driver is the destabilization of the sTTR tetramer into monomers, which subsequently aggregate into amyloid fibrils. Acoramidis (formerly AG10) is a high-affinity, oral TTR stabilizer designed to mimic the naturally occurring T119M protective mutation, achieving near-complete (≥90%) stabilization of the protein. While the pivotal 30-month ATTRibute-CM trial established the efficacy of acoramidis, the long-term durability of these outcomes and the impact of switching from placebo to active therapy are critical for long-term clinical management.

Key Content

Durability of Clinical Outcomes: The ATTRibute-CM Open-Label Extension

The open-label extension (OLE) of the ATTRibute-CM trial represents the longest longitudinal assessment of acoramidis to date, reaching 54 months of total follow-up. In the original trial, 632 participants were randomized to acoramidis 800 mg twice daily or placebo. At month 30, eligible participants (n=389) entered the OLE, where all received acoramidis.

Analysis of the OLE data shows that continuous acoramidis therapy resulted in a 45% reduction in all-cause mortality (ACM; HR, 0.55; 95% CI, 0.42-0.74; P < .001) and a 49% reduction in cardiovascular-related mortality (CVM; HR, 0.51; 95% CI, 0.36-0.71; P < .001) compared to the group that initially received placebo. Furthermore, the risk of first cardiovascular hospitalization (CVH) was reduced by 47% (HR, 0.53; 95% CI, 0.42-0.69; P < .001). These findings underscore that the benefits observed at month 30 are not only maintained but continue to accrue over time.

Functional and Biomarker Stability

A notable finding from the OLE is the stabilization of disease progression markers. Participants on continuous acoramidis maintained stable NT-proBNP levels and sTTR concentrations through month 54. Health status, assessed by the Kansas City Cardiomyopathy Questionnaire-Overall Summary (KCCQ-OS), and functional capacity, assessed by 6MWD, also showed relative stability in the continuous acoramidis group.

Interestingly, participants who switched from placebo to acoramidis at month 30 experienced a subsequent stabilization of NT-proBNP and KCCQ-OS, and even improvements in 6MWD and sTTR levels. However, they did not “catch up” to the continuous therapy group in terms of mortality or hospitalization risk, suggesting that while acoramidis can halt further progression, it cannot reverse the cardiac damage sustained during the initial 30-month placebo period.

The Global Context of TTR Modulators

The timing of mortality benefit in ATTR-CM trials is a subject of intense investigation. Recent meta-analyses and pooled modeling of ATTR-ACT (tafamidis), ATTRibute-CM (acoramidis), and HELIOS-B (vutrisiran) suggest a uniform pattern where mortality curves begin to diverge at approximately 12 to 18 months post-initiation. This delay reflects the biological reality of the disease: stabilizers and silencers prevent *new* amyloid deposition rather than clearing existing fibrils. Acoramidis, by achieving ≥90% stabilization, addresses the upper bound of therapeutic potential for this mechanism.

Comparatively, the HELIOS-B study on vutrisiran (a TTR silencer) also showed significant KCCQ-OSS improvements, specifically in physical limitation domains. In contrast, emerging therapies like coramitug (a monoclonal antibody) aim to promote the clearance of existing deposits. Phase 2 data for coramitug showed significant reductions in NT-proBNP over 52 weeks, potentially representing a complementary approach to stabilization therapy.

Diagnostic Challenges and Risk Stratification

The efficacy of long-term therapy is frequently undermined by delays in diagnosis. Retrospective data from the Veterans Health Administration (VHA) indicate a median delay of 490 days between a heart failure diagnosis and an ATTR-CM diagnosis, often reaching over 800 days after the first loop diuretic prescription. AI-augmented screening models, such as ATTRACTnet, have demonstrated the ability to improve detection rates by nearly three-fold, highlighting a path toward earlier intervention.

Furthermore, new prognostic markers are emerging. MR-proADM (mid-regional pro-adrenomedullin) has shown superior prognostic performance for mortality (C-index 0.788) compared to traditional staging systems. Additionally, the role of atrial mechanical contraction in predicting cerebrovascular risk in ATTR-CM patients in sinus rhythm suggests that specialized echocardiographic monitoring (speckle-tracking strain) may be necessary to manage long-term complications such as stroke, which remain a threat even with TTR stabilization.

Expert Commentary

The results of the ATTRibute-CM OLE signify a shift in the treatment paradigm for ATTR-CM. For years, the goal was merely to slow a terminal decline; we are now seeing evidence of “clinically meaningful improvement” (CMI) in a subset of patients. Post-hoc analyses of ATTRibute-CM show that 22.7% of acoramidis-treated patients achieved CMI in NT-proBNP or 6MWD, triple the rate of the placebo group.

However, a critical controversy remains: the management of comorbidities such as bleeding. Long-term observational data show that ATTR-CM patients have a high incidence of bleeding (50 bleeds per 100 patient-years), particularly when on anticoagulants (AC). This is especially relevant given the high prevalence of atrial fibrillation in this population. The discovery of “atrial electromechanical dissociation” (AEMD) in ATTR-CM patients suggests that standard rhythm monitoring may be insufficient, and some patients in sinus rhythm may require prophylactic anticoagulation despite the associated bleeding risks.

Mechanistically, the discovery of the “amyloid double act” between medin and TTR in the aortic wall suggests that the vascular implications of amyloidosis are more complex than previously understood. This co-aggregation may influence the long-term cardiovascular outcomes observed in OLE studies and warrants further investigation as we move toward combination therapies.

Conclusion

Continuous acoramidis therapy provides robust, durable efficacy through 54 months, with significant survival benefits and stabilization of functional status. The data from the ATTRibute-CM OLE reinforce the “early and continuous” treatment mandate: delaying therapy by 30 months leads to irreversible loss of survival benefit that cannot be recovered. Future research must focus on optimizing early detection through AI and novel biomarkers (like MR-proADM and ACE2 activity), and exploring the potential of combination therapies that both stabilize TTR and deplete existing fibrils to further improve the prognosis of this once-intractable disease.

References

• Soman P, et al. Long-Term Durability of Acoramidis Efficacy in Transthyretin Amyloid Cardiomyopathy: Open-Label Extension of the ATTRibute-CM Randomized Clinical Trial. JAMA Cardiol. 2026 Mar 30:e260819. PMID: 41911489.
• Cheng RK, et al. Effect of Acoramidis on Recurrent and Cumulative Cardiovascular Outcomes in ATTR-CM: Exploratory Analysis From ATTRibute-CM. J Am Coll Cardiol. 2026 Feb 10;87(5):490-501. PMID: 41143759.
• Sutherland T, et al. Timing of Mortality Benefit in Outcomes Trials in Transthyretin Amyloidosis. J Am Coll Cardiol. 2026 Feb 10;87(5):522-529. PMID: 41225306.
• Hanna M, et al. Impact of acoramidis on clinical stability in transthyretin amyloid cardiomyopathy: Observations from ATTRibute-CM. Eur J Heart Fail. 2026 Feb 20:xuag048. PMID: 41771146.
• Akinboboye O, et al. MR-ProADM Predicts Mortality and Heart Failure Events in ATTR Cardiac Amyloidosis. Circulation. 2026 Mar 31. PMID: 41914183.