Can Alnylam Pharmaceuticals’ vutrisiran reverse cardiac damage? HELIOS-B Phase 3 ATTR-CM trial says yes

Alnylam Pharmaceuticals, Inc. has presented new post hoc analyses from its HELIOS-B Phase 3 study showing that treatment with its RNA interference therapeutic, AMVUTTRA (vutrisiran), led to significant improvements in both cardiac and renal outcomes in patients suffering from transthyretin-mediated amyloidosis with cardiomyopathy, also known as ATTR-CM. These new insights were presented at the 2025 American Heart Association Scientific Sessions and offer further clinical validation for vutrisiran as a first-line treatment for the systemic disease.

The newly released data focuses on the impact of vutrisiran on cardiac structure, function, and amyloid burden using cardiovascular magnetic resonance imaging and echocardiography. It also explores renal outcomes in patients with advanced chronic kidney disease, providing a fuller picture of the drug’s benefits across two of the most critically affected organ systems in ATTR-CM.

ATTR-CM is a progressive and often fatal disease caused by the accumulation of misfolded transthyretin proteins in the heart and other organs. It exists in two forms: hereditary (hATTR), caused by TTR gene mutations, and wild-type (wtATTR), which occurs without genetic predisposition. Collectively, ATTR affects an estimated 250,000 to 350,000 people worldwide. In its cardiac form, amyloid buildup leads to thickening and stiffening of the heart muscle, impaired function, heart failure, and death. The disease often affects the kidneys as well, accelerating systemic deterioration.

AMVUTTRA, developed by Alnylam Pharmaceuticals, Inc., is an RNA interference therapeutic that targets the TTR gene, preventing the production of the harmful protein at the source. Administered quarterly via subcutaneous injection, it is the first and only RNAi therapy approved for both cardiomyopathy and polyneuropathy manifestations of ATTR amyloidosis.

What does cardiovascular magnetic resonance data from HELIOS-B reveal about amyloid regression?

The post hoc CMR imaging data from the HELIOS-B trial shows promising evidence of structural cardiac improvement in patients treated with vutrisiran. The retrospective CMR analysis involved a cohort of patients from the National Amyloidosis Centre in London who underwent serial imaging at baseline, one year, two years, and three years. A mixed model analysis, pooling 24-month and 36-month data, revealed statistically significant and directionally favorable changes in multiple key measures of cardiac function and amyloid burden in the vutrisiran group.

Specifically, treatment with vutrisiran improved left and right ventricular ejection fractions, stroke volumes, and left ventricular mass compared to placebo. It also reduced extracellular volume, a key biomarker associated with amyloid accumulation in the myocardium. After three years, 22 percent of vutrisiran-treated patients exhibited measurable amyloid regression based on extracellular volume reductions. In contrast, none of the patients in the placebo group showed regression, and 63 percent of those on placebo experienced worsening amyloid burden. Only 11 percent of vutrisiran recipients showed disease progression.

Quantitatively, the vutrisiran group demonstrated an average extracellular volume reduction of 0.10 percent at Year 3, while the placebo group showed an increase of 7.86 percent. These findings suggest that vutrisiran may not only stabilize but potentially reverse some of the cardiac damage caused by ATTR-CM in a subset of patients.

How did echocardiographic markers of heart strain respond to vutrisiran treatment over 30 months?

Additional echocardiographic analyses further underscored the cardiac benefits of vutrisiran. The study examined left atrial strain and right ventricular free wall strain, both of which are recognized indicators of cardiac health and mortality risk. Results showed that left atrial strain was associated with baseline disease severity and future cardiovascular events. Patients treated with vutrisiran experienced less deterioration in left atrial strain over 30 months than those receiving placebo. Likewise, right ventricular free wall strain remained stable in the vutrisiran group over the same time period, whereas it worsened in patients who received placebo.

These findings are especially meaningful because they indicate that vutrisiran may preserve not just structural cardiac integrity but also functional performance over time. This could translate into delayed onset of heart failure symptoms and improved quality of life for patients with ATTR-CM. According to clinical investigators, the results point to the potential of vutrisiran to reverse disease-related structural damage in the heart and to improve long-term cardiovascular outcomes in affected patients.

What did HELIOS-B show about vutrisiran’s ability to protect kidney function in advanced CKD patients?

Beyond cardiac health, vutrisiran also demonstrated protective effects on renal function in patients with advanced chronic kidney disease. In the HELIOS-B trial, a subgroup analysis focused on patients who progressed to Stage 4 CKD or higher, which is defined as an estimated glomerular filtration rate of less than 30 milliliters per minute per 1.73 square meters. These patients were at greater risk of mortality and cardiovascular complications.

Among patients who advanced to severe CKD, vutrisiran treatment was associated with a 53 percent reduction in the risk of all-cause mortality and recurrent cardiovascular events compared to placebo. Furthermore, in the overall population, only 12.7 percent of vutrisiran-treated patients experienced a decline in estimated glomerular filtration rate of 40 percent or more from baseline, compared to 21.2 percent in the placebo group. The results were consistent across multiple analysis groups, including patients treated with vutrisiran monotherapy and those previously receiving tafamidis.

Importantly, the safety profile of vutrisiran remained favorable even in this advanced CKD population, with no new safety concerns reported. Alnylam Pharmaceuticals, Inc. highlighted these findings as further confirmation of the systemic benefit profile of AMVUTTRA, particularly in preserving organ function in a disease known for its multisystem impact.

How are analysts interpreting the long-term commercial and clinical value of AMVUTTRA?

The cumulative data from HELIOS-B are reinforcing investor confidence in the long-term prospects of AMVUTTRA. Alnylam Pharmaceuticals, Inc. has received approvals for the therapy across major markets including the United States, European Union, United Kingdom, Japan, Brazil, and the United Arab Emirates. With over 8,000 patient-years of global exposure, AMVUTTRA is emerging as a preferred treatment option in the ATTR-CM therapeutic space.

Institutional sentiment around Alnylam Pharmaceuticals, Inc. has grown increasingly optimistic following these data updates. Analysts see the potential for expanded market penetration and increased adoption among patients with both early- and late-stage disease. The possibility of amyloid regression positions AMVUTTRA as not just a stabilizing treatment, but potentially a disease-modifying therapy, which is something that could differentiate it from competitors in a market largely focused on slowing disease progression rather than reversing it.

Alnylam Pharmaceuticals, Inc. continues to explore label expansions and broader clinical applications of its RNA interference platform. The company’s strategic bet on RNAi as a foundational therapeutic modality appears to be paying off, especially in diseases like ATTR-CM, where precision gene-silencing offers a targeted approach to halting disease at the molecular level.

What broader implications could HELIOS-B’s post hoc findings have for ATTR-CM clinical practice?

For patients, these new data offer a hopeful signal. If replicated in broader populations and validated in future trials, the cardiac and renal benefits of vutrisiran could redefine treatment expectations for a disease that has long lacked effective, disease-modifying options.

The HELIOS-B dataset is expected to play a central role in shaping clinical guidelines and payer decisions in the coming years. With continued regulatory traction and growing real-world evidence, Alnylam Pharmaceuticals, Inc. is positioning AMVUTTRA as a cornerstone therapy in the evolving landscape of transthyretin-mediated amyloidosis care.

Key takeaways: What are the most important clinical and strategic insights from the HELIOS-B Phase 3 vutrisiran analysis?

• Alnylam Pharmaceuticals, Inc. presented new post hoc analyses from the HELIOS-B Phase 3 study evaluating AMVUTTRA (vutrisiran) in patients with transthyretin-mediated amyloidosis with cardiomyopathy (ATTR-CM).

• Cardiovascular magnetic resonance imaging showed measurable amyloid regression in 22 percent of patients treated with vutrisiran, compared to zero percent in the placebo group.

• Patients receiving vutrisiran demonstrated improvements in cardiac structure and function, including better ventricular ejection performance and reduced extracellular volume associated with amyloid burden.

• Echocardiographic findings showed that patients treated with vutrisiran experienced less deterioration in left atrial strain and stabilization of right ventricular free wall strain relative to placebo.

• In patients who progressed to severe chronic kidney disease during the study, vutrisiran treatment reduced the risk of all-cause mortality and recurrent cardiovascular events by more than 50 percent compared to placebo.

• Fewer vutrisiran-treated patients experienced large declines in estimated glomerular filtration rate during the study period, indicating kidney function preservation.

• The safety profile of vutrisiran remained consistent even in patients with advanced chronic kidney disease, with no new safety signals identified.

• AMVUTTRA continues to gain regulatory and market traction internationally, supported by more than 8,000 patient-years of real-world experience.

• Investor and clinical sentiment around Alnylam Pharmaceuticals, Inc. has strengthened as data increasingly supports the potential of vutrisiran as a first-line therapy in ATTR-CM.