Shares of RNA-drug maker Alnylam Pharmaceuticals tumbled about 30% after the company unexpectedly trimmed its sales outlook, erasing roughly $12 billion in market value in a single day.
The stock fell to around $200 from a prior close of $286 on July 30. The trigger: Alnylam cut combined guidance for its medicines Amvuttra and Onpattro to $4.2–$4.5 billion from a prior $4.4–$4.7 billion — a $200 million reduction. Second-quarter Amvuttra sales of $1.01 billion also came in about 3% shy of the roughly $1.05 billion analysts expected.
Why the drop was so sharp
Management indicated that an initial sales spike driven by “pent-up demand” had “normalized,” unsettling investors who had priced in steeper growth. The company competes in the market for transthyretin (TTR) amyloidosis, a condition that can damage the heart and nerves, where rivals include Pfizer’s Vyndamax and BridgeBio’s Attruby.
Analysts caught off guard
“We knew expectations for 2026 were ambitious, but we weren’t expecting a guidance cut,” a Cantor Fitzgerald analyst wrote. A Jefferies analyst said the guidance raised real questions about the TTR outlook, adding that “the bull/bear debate…is real.” For a company long prized as a growth story in RNA interference, the reset is a reminder that even successful launches eventually settle into a slower, more competitive phase.