Alnylam Pharmaceuticals (ALNY) lost a quarter of its market value after its chief executive conceded that demand for its top-selling drug was growing too slowly, even as third-quarter sales from its transthyretin franchise rose 59 per cent.
The shares closed at $174, leaving the RNAi specialist down 56 per cent this year with a market capitalization of $23.3bn. The franchise, which includes Amvuttra and Onpattro, generated $1.15bn in the quarter. Oppenheimer said the slump had strengthened the case for a takeover, with Sanofi (SNY) the most likely buyer.
Yvonne Greenstreet, Alnylam's chief executive, acknowledged that the uptake of Amvuttra had fallen short of the company's hopes despite a substantial investment in its launch. "We're not satisfied with the pace of our future demand growth, and we need to do better," she told analysts. She stressed that sales had grown strongly since the launch, that it was still early days, and that market fundamentals remained favorable.
The US Food and Drug Administration first approved Amvuttra in 2022 for polyneuropathy caused by the disease, and cleared it for the cardiomyopathy indication in March 2025. The second launch has proved bumpier. Alnylam cut its guidance earlier this year after sales trailed expectations, while rivals BridgeBio Pharma (BBIO) and Pfizer (PFE) have been taking market share.
A forthcoming change to the 340B drug pricing programme adds to the pressure. The proposed rule would not take effect until January 1 2027, but Jeffrey Poulton, Alnylam's chief financial officer, said conversations with health systems suggested it could trigger volatile ordering in the fourth quarter as providers weigh the effect on their finances and choice of care setting. The company declined to say how much Amvuttra volume would be affected. Truist Securities estimated that 15-20 per cent could be directly exposed.
Greenstreet said Alnylam was targeting the two-thirds of potential prescribers who have yet to write a prescription, arguing that doctors who try Amvuttra tend to prefer it. "What we need to do is build familiarity to drive adoption," she said, adding that the company was pursuing the strategy "with urgency". She cautioned analysts not to expect sequential growth in the fourth quarter.
The company has typically published its outlook before the J.P. Morgan Healthcare Conference in mid-January but now plans to do so in February. Truist described the shift as "another indication of heightened uncertainty entering 2027".