Why has the FDA challenged Alnylam's Amvuttra survival claims?
The FDA said Amvuttra's website "36% Lower Risk" and "80% Survival Rate" figures came from an open-label extension with no true control group — data "incapable of supporting the conclusions" — and yet the claims remained live weeks later.
In April 2026 the FDA sent Alnylam an untitled letter about the ATTR-CM page of the Amvuttra consumer website. The page carried the headline "Proven to help people with ATTR-CM live longer" and said the risk of death was lower over 3.5 years with Amvuttra, with graphics showing a "36% Lower Risk compared to placebo" and an "80% Survival Rate". The FDA said these created a misleading impression that Amvuttra had shown a definitive and quantified survival benefit. The problem was the data source: the 3.5-year figures came from an open-label extension in which all placebo patients had switched to the drug, leaving no true control group, so the FDA said the extension was "incapable of supporting the conclusions." As of early May 2026, the claims were still on the website. It was Alnylam's second FDA letter over Amvuttra promotion, after a September 2025 letter about a TV ad. The episode matters because there are no head-to-head trials in ATTR-CM, so cardiologists and patients rely heavily on how each company frames its own survival data.