Alnylam's Amvuttra Dominates Q2 Earnings, Reshaping ATTR-CM Market Landscape

Alnylam Pharmaceuticals has reported exceptional second-quarter earnings for 2025, largely driven by the remarkable performance of its siRNA therapy Amvuttra in treating ATTR-cardiomyopathy (ATTR-CM). The biotech company's strategic expansion and robust market penetration have not only exceeded analyst expectations but also prompted a significant upward revision of its full-year guidance.

Amvuttra's Stellar Performance in ATTR-CM

In its debut quarter for the ATTR-CM indication, Amvuttra generated an impressive $491.9 million in sales, marking a 112% increase from the same period last year. This figure substantially surpassed the Street's expectations of $342 million. Alnylam reported that approximately 1,400 ATTR-CM patients were on Amvuttra by the end of its first quarter of availability for this condition.

The drug's success has been attributed to a growing prescriber base, strong patient demand, and apparent penetration into both first and second-line treatment settings. Notably, this robust uptake has been achieved without price adjustments, suggesting a strong value proposition for healthcare providers and patients alike.

Financial Implications and Market Response

Alnylam's total revenues for Q2 reached $773.7 million, representing a 17% year-on-year growth and significantly outperforming the consensus forecast of $651 million. In response to Amvuttra's strong performance, Alnylam has substantially raised its full-year 2025 guidance. The company now projects annual sales between $2.65 billion and $2.8 billion, up from the previous forecast of $2.05 billion to $2.25 billion – a 27% increase.

The market has responded positively to these developments, with Alnylam's stock price surging more than 15% at market close following the earnings announcement. Analysts from Stifel characterized Amvuttra's Q2 performance as "very impressive," noting that it aligns with the bull case and enhances optimism regarding the drug's peak sales potential.

Competitive Landscape in ATTR-CM Treatment

While Alnylam celebrates Amvuttra's success, the ATTR-CM market remains highly competitive. Pfizer's transthyretin stabilizer tafamidis, marketed as Vyndaqel and Vyndamax, has maintained a strong position since its 2019 approval. In 2024, Pfizer reported $5.45 billion in sales for its tafamidis products, showcasing a robust 60% year-on-year growth.

Pfizer's CEO, Albert Bourla, has expressed confidence in maintaining the company's market share, citing their extensive network and deep understanding of physician prescription patterns. However, Alnylam's rapid gains suggest a potential shift in the competitive dynamics of the ATTR-CM market.

Adding to the competition is BridgeBio's Attruby, another transthyretin stabilizer approved in November 2024. In its first commercial quarter, Attruby treated over 2,000 unique patients and generated $36.7 million in sales, indicating a growing presence in the market.

As the ATTR-CM treatment landscape evolves, the impressive performance of Amvuttra signals a potential reshaping of market dynamics, with Alnylam positioned as a formidable challenger to established players in this therapeutic area.