Can Alnylam Rely on Amvuttra to Sustain Its Rapid Sales Momentum?

Alnylam Pharmaceuticals' Amvuttra generated $801.9 million in H1 2025 sales, an 89% year-over-year increase, largely driven by its recent label expansion for ATTR-CM in the US and EU, establishing it as the company's primary revenue driver. However, Amvuttra faces significant competition in the ATTR market from Pfizer's Vyndaqel ($3.1 billion H1 2025 sales) and BridgeBio's Attruby, which offer advantages like oral administration and potentially lower pricing. Despite Alnylam shares surging 93% year-to-date and improved analyst EPS estimates, the stock's valuation appears expensive, trading at a 24.10 price-to-sales ratio.

Analysis

Alnylam Pharmaceuticals is demonstrating significant commercial momentum, primarily driven by its RNAi therapeutic, Amvuttra. The drug's sales reached $801.9 million in the first half of 2025, an 89% year-over-year increase, solidifying its role as the company's main revenue generator. This growth is underpinned by a crucial label expansion for ATTR amyloidosis with cardiomyopathy (ATTR-CM) in the U.S. and EU, making Amvuttra the first and only RNAi therapy approved for both ATTR-CM and hATTR-PN. Despite this success, the competitive landscape in the ATTR-CM market is intense. Amvuttra faces formidable rivals in Pfizer's Vyndaqel, which posted $3.1 billion in H1 2025 sales, and BridgeBio's newly launched Attruby, which is showing rapid uptake with $108.2 million in H1 sales. A key risk for Alnylam is that both competing drugs offer the convenience of oral administration and lower list prices, which could challenge Amvuttra's adoption rate. The market has rewarded Alnylam's growth with a 93% year-to-date share price increase, but this has resulted in a steep valuation, with the stock trading at a price-to-sales ratio of 24.10, well above the industry average of 2.12. However, analyst expectations remain highly bullish, reflected in the dramatic upward revisions of 2025 and 2026 EPS estimates to $3.39 and $8.75, respectively, suggesting a strong belief in sustained future growth.

Key Decisions for Investors

• Given the significant upward revisions to 2025 and 2026 earnings estimates, investors should weigh the potential for Amvuttra's continued market penetration and future approvals to justify the stock's current premium valuation.
• It is critical to monitor Amvuttra's market share performance against Pfizer's Vyndaqel and BridgeBio's Attruby, as their oral administration and pricing advantages represent a material risk to Alnylam's growth trajectory.
• With the stock up 93% year-to-date and trading at a high price-to-sales multiple of 24.10, investors should scrutinize upcoming quarterly reports for evidence that Amvuttra's sales can continue to meet or exceed the elevated market expectations already priced into the shares.