Alnylam Pharmaceuticals (ALNY) shares collapsed nearly 28% on Thursday, closing at $206.88 after the company reported disappointing Amvuttra sales and slashed its full-year outlook.
The RNA interference therapy crossed the $1 billion quarterly revenue threshold for the first time, posting $1.01 billion in sales, but still missed analyst expectations by 4%.
In the United States, Amvuttra generated $809 million during the second quarter of 2026, coming in roughly 2% below Wall Street consensus estimates.
Alnylam reported total Q2 revenue of $1.29 billion, falling short of the $1.32 billion analysts had anticipated heading into the announcement.
The company cut its full-year 2026 total TTR net product revenue guidance to a range of $4.2 billion to $4.5 billion, down from a prior range of $4.4 billion to $4.7 billion, representing a midpoint reduction of approximately $300 million.
That revised guidance landed dramatically below the Wall Street consensus estimate of approximately $5.61 billion, deepening investor concern about the trajectory of Alnylam’s flagship franchise.
Chief Executive Officer Yvonne Greenstreet attributed the reduced forecast to early lessons from the ATTR-CM launch, specifically the fading of pent-up patient demand that had initially boosted second-line volume.
“We have lowered our TTR product sales guidance for full-year 2026 to reflect learnings from the initial phase of our launch in the evolving ATTR-CM market, in particular the normalization of growth in second-line volume after satisfying pent-up demand from patients waiting for a new therapy,” Greenstreet said.
Chief Commercial Officer Tolga Tanguler offered a more optimistic read on certain underlying metrics, noting that adherence rates continued to exceed 90% and that U.S. ATTR revenues grew 15% sequentially versus the first quarter of 2026.
“Access remained broad, pull-through was strong, and adherence continued to exceed 90%,” Tanguler said, adding that the pace of underlying U.S. demand growth for Amvuttra more than doubled compared to the previous three months.
Among physicians already prescribing Amvuttra, the drug accounts for more than 50% of new patient starts, which Tanguler said underscores “the strong physician preference that develops with experience.”
Alnylam also raised its net revenues guidance from collaborations and royalties to between $575 million and $625 million, up from a prior range of $400 million to $500 million.
Jefferies analysts noted ahead of the results that investors had been positioned for a low-single-digit percentage beat, making the miss and guidance reduction a significant shock to market sentiment.
Cantor Fitzgerald analyst Olivia Brayer Saunders described the news as a “one-two punch” for Alnylam, following an earlier share price slide triggered by a study setback for eplontersen in July that raised questions about Amvuttra’s utility alongside other treatments.
“We knew expectations for 2026 were ambitious, but we weren’t expecting a guidance cut,” Saunders wrote, suggesting the overhang could persist until a failed study is presented at a medical conference in late August.
Oppenheimer analyst Kostas Biliouris said that while some investors may have anticipated a guidance reduction, “it comes as a surprise to us” that it arrived this early in the year, particularly given prescription data from healthcare specialist Iqvia suggesting the original targets may have been achievable.
To drive broader market penetration, Alnylam said it is accelerating investments in earlier patient diagnosis and expanding the number of physicians actively prescribing the therapy.
Chief Research and Development Officer Pushkal Garg acknowledged investor concern about the company’s pipeline, saying, “We understand that there have been many questions raised about the feasibility of delivering positive results from this clinical trial,” in reference to the Phase 3 TRITON-CM study of Nucresiran in ATTR-CM.
Amvuttra received its key FDA approval for ATTR-cardiomyopathy in March 2025, and had repeatedly exceeded Wall Street projections before Thursday’s results broke that run of outperformance.