Alnylam Pharmaceuticals (ALNY) shares plummeted 27.20% in intraday trading on Thursday, following the company's second-quarter earnings report that fell short of revenue expectations and included a downward revision to its full-year product sales forecast.

The biotech firm reported adjusted earnings of $1.84 per share, which beat analyst estimates of $1.55. However, revenue for the quarter came in at $1.291 billion, missing the consensus estimate of $1.323 billion. More critically, the company lowered its 2026 net product revenue guidance to a range of $4.70 billion to $5.10 billion, down from the previous range of $4.90 billion to $5.30 billion, citing competitive pressures on key products.

Investors reacted sharply to the top-line miss and the reduced outlook, intensifying selling pressure that had already begun in pre-market trading. The stock decline reflects heightened market sensitivity to growth metrics for high-valuation biotech companies, with analysts previously noting concerns over long-term net price erosion for Alnylam's Amvuttra franchise.