Alnylam's TTR Guidance Cut Triggers 29% Plunge Despite Record Quarter
TTR Guidance Cut Sends Shares Down 29% Alnylam lowered its 2026 TTR revenue guidance to $4.2–4.5 billion from $4.4–4.7 billion, citing slower second-line demand for Amvuttra. The stock plunged 29% as investors feared the flagship franchise's growth is decelerating, overshadowing strong Q2 results.
This is the single biggest new event of the period and the main reason ALNY is moving right now.
Amvuttra Tops $1 Billion in a Quarter for First Time Amvuttra exceeded $1 billion in quarterly sales, with total product revenue up 74% and non-GAAP operating income tripling to $318 million. This shows the drug is still growing strongly, but the guidance cut signals the pace will slow.
It is the key new financial result that contrasts with the guidance cut and explains the mixed market reaction.
Rival ATTR-CM Drug Fails, Boosting Alnylam's Competitive Edge AstraZeneca and Ionis's Wainua failed a Phase 3 ATTR-CM trial, removing a potential competitor. Alnylam shares initially rose 18% as its Amvuttra faces less competition in the cardiomyopathy market, though the later guidance cut reversed those gains.
This is a major new competitive development that initially drove the stock up and remains a positive force.
Securities Fraud Investigation Adds Legal Uncertainty Kirby McInerney launched an investigation into potential securities law violations following the guidance cut. While no lawsuit has been filed, the probe adds uncertainty and could pressure the stock as investors weigh legal risks.
It is a new negative development that could affect investor sentiment and is directly tied to the guidance cut.