Alnylam Stock Plunges Over 25% on Revenue Miss and Drastic Guidance Cut

Shares of Alnylam Pharmaceuticals (NASDAQ: ALNY) plunged 25.7% in pre-market trading after the company announced a second-quarter revenue miss and a deeply disappointing revision to its full-year financial guidance. The sell-off erased roughly a quarter of the company's market value, pushing the stock to $212.95 from its previous close of $286.62.

Disappointing Results and Outlook

Alnylam reported second-quarter 2026 revenue of $1.29 billion, falling short of the consensus analyst estimate of $1.32 billion. The more significant driver of the stock's decline was a substantial cut to its full-year 2026 revenue forecast for its TTR franchise.

The company now expects total TTR net product revenue to be between $4.2 billion and $4.5 billion. This is a reduction from the prior range of $4.4 billion to $4.7 billion and lands far below the Wall Street consensus of approximately $5.61 billion. On a more positive note, the company's adjusted earnings per share of $1.84 beat the consensus estimate of $1.60.

Management Commentary

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Company management attributed the lowered guidance to a "normalization of second-line patient volumes" for its ATTR-CM treatment, Amvuttra. According to the company, this follows an initial surge in demand that occurred at the drug's launch.

In a statement, CEO Yvonne Greenstreet said the updated outlook reflects "learnings from the initial phase of the ATTR-CM launch." She expressed continued confidence in the long-term growth trajectory of the franchise. The company also highlighted progress in its pipeline, including the initiation of two Phase 2 studies.

Market Context and Investor Reaction

The sharp, company-specific sell-off contrasted with a positive day for the broader market, underscoring that the drop was not tied to macroeconomic factors. The news follows a period of growing caution from some analysts, with both JPMorgan and H.C. Wainwright having trimmed their price targets on Alnylam in recent months, citing concerns over competitive dynamics and the growth rate of the ATTR-CM market.