--- title: "Alnylam rebuked by FDA over efficacy claims on Amvuttra website" type: "News" locale: "en" url: "https://longbridge.com/en/news/285521285.md" description: "The FDA has issued an untitled letter to Alnylam regarding its Amvuttra website, claiming it presents misleading efficacy data. The agency criticized the use of open-label trial results, stating that the lack of a true placebo group after 3.5 years introduces bias. Despite a caveat on the website, the FDA concluded that the claims misbrand Amvuttra, violating the Federal Food, Drug, and Cosmetic Act. Alnylam has 15 working days to respond, and this is the second untitled letter the company has received from the FDA in recent months." datetime: "2026-05-07T09:34:49.000Z" locales: - [zh-CN](https://longbridge.com/zh-CN/news/285521285.md) - [en](https://longbridge.com/en/news/285521285.md) - [zh-HK](https://longbridge.com/zh-HK/news/285521285.md) --- # Alnylam rebuked by FDA over efficacy claims on Amvuttra website The FDA has hit (PDF) Alnylam with an untitled letter over the consumer website for Amvuttra, accusing the biotech of presenting open-label data that create a misleading impression of the drug’s effects. A page on the website about how Amvuttra may help transthyretin amyloid cardiomyopathy patients features data from Helios-B, the phase 3 trial that Alnylam ran to assess the RNAi therapy. The trial compared Amvuttra to placebo. After the three-year double-blind period of the trial, Alnylam ran an open-label extension that allowed all participants, including those in the placebo arm, to take Amvuttra. The website includes data from the double-blind period, plus analyses performed six months into the open-label extension. The FDA’s problems with the website relate to claims supported by the open-label analysis, such as the statement that the risk of death was 36% lower on Amvuttra than placebo over 3.5 years. After 3.5 years, no true placebo comparator group remained because patients had been unblinded and switched to Amvuttra, the FDA said. The open-label nature of the trial introduced bias and confounding, the FDA said, and the lack of a concurrent control means it is unclear whether Amvuttra or other factors drove outcomes after the double-blind period. Alnylam’s website includes the caveat that the analysis wasn’t in the original plan and that other factors could have influenced the results. Yet while the FDA noted the caveat, it concluded the claims were still misleading because the open-label extension study was incapable of supporting the conclusions. The misleading claims misbrand Amvuttra and make distributing the drug a violation of the Federal Food, Drug and Cosmetic Act, the FDA said. The agency, which sent the letter on April 23, asked Alnylam to take immediate action and gave the biotech 15 working days to respond. As of May 7, the website still featured the claims challenged by the FDA. Alnylam has received two untitled letters since the FDA began clamping down on direct-to-consumer marketing last year. The FDA sent (PDF) the first letter in September in response to a TV ad for Amvuttra. The ad misleadingly suggested that “patients treated with Amvuttra can be carefree regarding the effects of cardiomyopathy,” the FDA said. The agency said Alnylam lacked trial data to support that impression. The FDA closed out (PDF) the first untitled letter in November after concluding that Alnylam had addressed its concerns. The agency has published close-out notices for most of the untitled letters it sent in its initial flurry of activity in early September. Untitled letters from that batch without close-out notices include communications the agency sent to Alexion, Amgen, Novartis and UCB. ### Related Stocks - [ALNY.US](https://longbridge.com/en/quote/ALNY.US.md) - [TBXU.US](https://longbridge.com/en/quote/TBXU.US.md) - [XLV.US](https://longbridge.com/en/quote/XLV.US.md) - [IXJ.US](https://longbridge.com/en/quote/IXJ.US.md) - [ARKG.US](https://longbridge.com/en/quote/ARKG.US.md) - [LABU.US](https://longbridge.com/en/quote/LABU.US.md) - [PBE.US](https://longbridge.com/en/quote/PBE.US.md) - [FBT.US](https://longbridge.com/en/quote/FBT.US.md) - [XBI.US](https://longbridge.com/en/quote/XBI.US.md) - [IBB.US](https://longbridge.com/en/quote/IBB.US.md) - [VHT.US](https://longbridge.com/en/quote/VHT.US.md) - [BIB.US](https://longbridge.com/en/quote/BIB.US.md) - [BBH.US](https://longbridge.com/en/quote/BBH.US.md) - [SBIO.US](https://longbridge.com/en/quote/SBIO.US.md) - [IBBQ.US](https://longbridge.com/en/quote/IBBQ.US.md) - [IHE.US](https://longbridge.com/en/quote/IHE.US.md) - [AMGN.US](https://longbridge.com/en/quote/AMGN.US.md) - [NVS.US](https://longbridge.com/en/quote/NVS.US.md) - [NOT.DE](https://longbridge.com/en/quote/NOT.DE.md) - [UCBJY.US](https://longbridge.com/en/quote/UCBJY.US.md) ## Related News & Research - [Corvus Pharmaceuticals presents Phase 1 soquelitinib data showing durable remissions, favorable safety](https://longbridge.com/en/news/286404245.md) - [14:05 ETLupin Receives Tentative Approval from U.S. FDA for Revefenacin Inhalation Solution](https://longbridge.com/en/news/286805922.md) - [](https://longbridge.com/en/news/286807703.md) - [Sanofi says rare lung disease drug outperforms standard care in trial](https://longbridge.com/en/news/286810610.md) - [](https://longbridge.com/en/news/286601439.md)