Comparative Effectiveness of TTR Stabilizers for the Treatment of ATTR-CM Using Real-World Evidence

This real-world study utilizing US claims data demonstrates that, compared to tafamidis, the newly approved TTR stabilizer acoramidis significantly reduces the risk of diuretic intensification and a composite of diuretic intensification, heart failure hospitalization, and mortality in patients with newly treated ATTR-CM.

The Gist

The Big Picture: A Race to Stabilize a Wobbly Bridge

Imagine your heart is a sturdy bridge made of a specific material called Transthyretin (TTR). In a condition called ATTR-CM, this material becomes unstable and starts to crumble, forming jagged piles of "amyloid" debris. This debris piles up on the bridge, making it weak and unable to carry traffic (blood) efficiently.

When the bridge gets too weak, water starts to leak through the cracks (congestion). To fix this, doctors usually have to pump the water out using strong pumps called diuretics. If the water keeps leaking and the pumps need to be turned up higher and higher, it's a sign the bridge is failing.

For a long time, there was only one tool available to stop the bridge from crumbling: a medication called Tafamidis. It acts like a "stabilizer," holding the bridge material together so it doesn't break down as fast.

However, in 2024, a new, super-strong stabilizer called Acoramidis arrived. The makers of this new drug claim it holds the bridge together almost perfectly (90%+ stability). But, because there hasn't been a direct race between the two tools yet, doctors didn't know which one was actually better at keeping patients stable in the real world.

The Study: A Real-World Race

This paper is like a report card comparing the two stabilizers using real-life data from insurance records (claims) rather than a controlled lab experiment.

The Setup:

• The Players: The researchers looked at patients who were newly diagnosed with the heart condition and started taking either the old stabilizer (Tafamidis) or the new one (Acoramidis) between late 2024 and early 2025.
• The Goal: They wanted to see who stayed stable longer without needing more help.
• The "Scoreboard": The main thing they watched for was Diuretic Intensification (DI). Think of this as the moment a patient has to call the doctor and say, "The water is leaking faster; I need a bigger pump." This is an early warning sign that the disease is getting worse. They also looked at a "composite score" which included needing that bigger pump, getting hospitalized for heart failure, or passing away.

The Method:
Since the two groups of patients might have been different to begin with (e.g., one group might have been sicker), the researchers used a statistical "magic trick" called propensity score weighting. Imagine they took a group of 170 people taking the new drug and matched them perfectly with 448 people taking the old drug, ensuring both groups had the same age, gender, and severity of illness. This made it a fair race.

The Results: The New Stabilizer Wins the Early Rounds

After following these patients for about 4 to 5 months (roughly 140 days), the results showed a clear difference:

1. The "Leak" Test (Diuretic Intensification):

   • Patients on the new drug (Acoramidis) were 43% less likely to need a bigger pump compared to those on the old drug.
   • Only about 12% of the new drug group needed extra help, compared to 20% of the old drug group.
   • Analogy: If the old drug was a standard umbrella, the new drug was like a heavy-duty storm shelter. Fewer people under the storm shelter got wet.

2. The "Big Trouble" Score (Composite Events):

   • When looking at the combination of needing more pumps, hospitalization, or death, the new drug group had a 34% lower risk of these bad events happening.
   • About 18% of the new drug group had a major event, versus 26% of the old drug group.

3. The Fine Print:

   • The study didn't find a huge difference in hospitalization rates or death rates during this short time, but the "needing more pumps" signal was strong and happened early.
   • The researchers checked for "fake" results (like checking if the new drug caused broken bones or pneumonia) and found no such links, suggesting the results are likely real and not a fluke.

What the Authors Conclude

The paper concludes that in this first real-world look at the two drugs, Acoramidis (the new drug) appears to keep patients more stable than Tafamidis (the old drug).

The curves showing the patients' health separated very early on, suggesting the new drug works faster or more effectively at stopping the disease from progressing. The authors suggest this data could help doctors decide which drug to prescribe to new patients, or perhaps consider switching patients from the old drug to the new one to prevent future problems.

Important Caveat:
The authors are careful to say this is just the beginning. The study was relatively short (about 5 months) and the number of patients was modest. They say we need to watch these patients for a longer time and with more people to be absolutely sure this advantage holds up over years, not just months.

Summary in One Sentence

This study suggests that the new heart drug, Acoramidis, is better at preventing the early warning signs of heart failure (needing stronger water pumps) compared to the older drug, Tafamidis, based on real-world data from newly treated patients.

Technical Summary

1. Problem Statement

Transthyretin Amyloid Cardiomyopathy (ATTR-CM) is a progressive infiltrative disease where unstable transthyretin (TTR) forms amyloid fibrils in the myocardium. Disease progression is clinically marked by worsening congestion requiring diuretic intensification (DI), heart failure hospitalizations (HFH), and increased mortality.

Prior to 2024, tafamidis was the only approved TTR stabilizer in the US. In 2024, acoramidis was approved; it is distinct in its ability to achieve near-complete (≥90%) TTR stabilization, compared to tafamidis. However, no head-to-head randomized controlled trials (RCTs) exist to compare the two agents. Consequently, there is a critical gap in evidence regarding which therapy offers superior clinical stability and outcomes in real-world settings, necessitating comparative effectiveness (CE) research to guide treatment selection.

2. Methodology

The study employed a retrospective, new-user, active-comparator cohort design using US claims data.

• Data Source: Komodo Healthcare Map® US claims data, tokenized to Claritas (a data aggregator linking specialty pharmacies and the manufacturer's hub) via Datavant. This allowed for precise identification of acoramidis prescriptions.
• Study Period: December 11, 2024, to April 30, 2025 (Index Date). Follow-up continued until July 31, 2025, or earlier disenrollment/death/switch.
• Cohort Selection:
  • Inclusion: Patients ≥18 years with a new prescription for acoramidis or tafamidis, ≥6 months of continuous enrollment prior to the index date.
  • Exclusion: Patients with multiple myelosis, light chain amyloidosis, prior TTR silencer/stabilizer use, or multiple ATTR-CM treatments on the index date.
• Statistical Analysis:
  • Propensity Score Weighting (PSW): Used to balance baseline characteristics, disease severity, comorbidity burden, and medication use between the two groups. Balance was defined as absolute standardized mean differences <0.1.
  • Outcomes:
    • Primary: Diuretic Intensification (DI), defined as initiation/escalation of oral loop diuretics, parenteral loop diuretic use, or addition of thiazide-like diuretics.
    • Secondary: A composite of DI, HFH (inpatient admission with HF ICD-10 code), and all-cause mortality.
    • Sub-analysis: Oral loop DI specifically.
  • Models: Weighted Cox proportional hazards models were used to estimate Hazard Ratios (HR). Kaplan-Meier estimates assessed cumulative incidence.
  • Bias Control: Falsification outcomes (fracture, pneumonia, UTI, vaccination) were assessed to detect residual bias.

3. Key Contributions

• First Real-World CE Study: This is the first study to directly compare acoramidis and tafamidis in a real-world setting for newly treated ATTR-CM patients.
• Novel Data Integration: The study uniquely tokenized claims data to hub data, overcoming the limitation of standard claims data which often lacks specificity for new, high-cost specialty drugs like acoramidis.
• Clinically Meaningful Endpoints: Instead of relying solely on hard endpoints like mortality (which require long follow-up), the study utilized Diuretic Intensification (DI) as an early, sensitive marker of disease progression and clinical instability.
• Diverse Cohort: The real-world dataset included higher proportions of under-represented populations (Black and female patients) compared to previous pivotal RCTs.

4. Results

After propensity score weighting, the study analyzed 170 patients on acoramidis and a weighted sample of 448 patients on tafamidis. Baseline characteristics (mean age ~78.6 years, ~80% male) were well-balanced. Mean follow-up was approximately 140 days.

• Diuretic Intensification (DI):
  • Acoramidis significantly reduced the risk of DI compared to tafamidis.
  • Incidence: 11.8% (Acoramidis) vs. 20.5% (Tafamidis).
  • Hazard Ratio (HR): 0.57 (95% CI, 0.35–0.92; P=0.021).
  • This represents a 43% reduction in the hazard of DI events.
• Composite Outcome (DI + HFH + Mortality):
  • Acoramidis showed a significantly lower risk of composite events.
  • Incidence: 17.6% (Acoramidis) vs. 26.4% (Tafamidis).
  • Hazard Ratio (HR): 0.66 (95% CI, 0.44–0.99; P=0.046).
  • This represents a 34% reduction in the hazard of composite events.
• Oral Loop DI (Sub-analysis):
  • Significant reduction with acoramidis: HR 0.52 (95% CI, 0.31–0.87; P=0.014).
• Individual Components:
  • HFH: 10.6% vs. 12.3% (HR 0.90, P=0.71) – Trend toward reduction, not statistically significant.
  • Mortality: 1.2% vs. 2.3% (HR 0.52, P=0.41) – Low event rate, not statistically significant.
• Bias Check: All falsification outcomes were nonsignificant, suggesting no major residual confounding.

5. Significance and Implications

• Clinical Stability: The early separation of cumulative incidence curves for DI suggests that acoramidis may provide superior and faster clinical stability compared to tafamidis. Since DI is a known precursor to hospitalization and death, this finding is clinically critical.
• Treatment Selection: The data supports the potential use of acoramidis as a preferred first-line therapy for newly diagnosed ATTR-CM patients, or potentially as a switch therapy for those on tafamidis who are experiencing instability.
• Mechanistic Correlation: The results align with the pharmacological profile of acoramidis, which achieves near-complete TTR stabilization (≥90%), potentially offering a more robust halt to amyloid deposition than tafamidis.
• Limitations & Future Directions: The study is limited by the short follow-up period (approx. 4.5 months) and the lack of granular clinical data (e.g., NYHA class, NT-proBNP, genotype) inherent to claims data. The authors conclude that longer follow-up and larger prospective cohorts are necessary to confirm these findings and assess long-term mortality benefits.

Funding: The study was funded by BridgeBio Pharma, Inc., the manufacturer of acoramidis. Several authors have financial ties to BridgeBio and other pharmaceutical companies, which is disclosed in the manuscript.