Alnylam's Amvuttra Continues Strong Performance in ATTR Market

Alnylam Pharmaceuticals' rare disease drug Amvuttra has once again exceeded Wall Street expectations, demonstrating robust growth in the third quarter of 2025. The company's transthyretin (TTR) franchise, led by Amvuttra, has prompted Alnylam to raise its full-year sales guidance, reflecting the drug's successful expansion into the transthyretin amyloid cardiomyopathy (ATTR-CM) market.

Amvuttra Sales Surge Past Estimates

Amvuttra generated $685 million in sales during the third quarter, surpassing analysts' consensus estimates by 11%. This strong performance has led Alnylam to increase its full-year sales guidance for the TTR franchise to between $2.475 billion and $2.525 billion, representing a $275 million (10%) increase at the midpoint.

The drug's success is largely attributed to its March expansion into the ATTR-CM indication. Tolga Tanguler, Alnylam's chief commercial officer, reported that ATTR-CM patient demand for Amvuttra approximately doubled in the U.S. compared to the previous quarter. While exact figures for ATTR-CM sales are difficult to determine due to the drug's reimbursement model, Tanguler estimated that U.S. sales from ATTR-CM uses roughly doubled to about $300 million in the third quarter.

Market Positioning and Competition

Amvuttra, an RNA interference therapy, is competing in a market that includes Pfizer's Vyndamax and BridgeBio's newer TTR stabilizer, Attruby. Despite this competition, Tanguler described Amvuttra as "highly competitive" in first-line treatment, indicating a strong market position.

The drug is gaining traction in both academic centers and community settings. Alnylam has established alternative sites of care to improve accessibility, with about 90% of patients having access to these sites within 10 miles of their homes. The company has also set up treatment processes at approximately 170 priority health systems for Amvuttra.

Global Expansion and Clinical Data

Outside the United States, Amvuttra received ATTR-CM approval from the European Commission in June and is also cleared in Japan. While the European launch is in its early stages, with availability only in Germany so far, Tanguler expressed encouragement about the drug's uptake in Japan, describing it as "category defining."

Recent clinical data from the phase 3 Helios-B trial has further supported Amvuttra's efficacy. After 48 months of treatment, Amvuttra demonstrated a 37% relative risk reduction in time to first cardiovascular event or all-cause mortality compared to patients who received placebo first. For patients not on any background TTR silencer, the treatment effect was even more pronounced at 42%.

As Alnylam continues to establish Amvuttra's dominance in the ATTR market, the company remains optimistic about its long-term prospects. However, Tanguler acknowledges that it will take time for the market to fully appreciate the drug's potential and for Alnylam to solidify its position in this competitive landscape.