Alnylam’s stock sold off after the company cut full-year guidance for its ATTR franchise following disappointing Amvuttra growth. Shares dropped as much as 29% after Amvuttra’s second-quarter revenue totaled $1.01 billion, missing analysts’ expectations by about 4%. The period also marked normalized growth after a prior year benefited from pent-up demand after FDA approval. Alnylam lowered its full-year forecast for total ATTR revenue to $4.2 billion to $4.5 billion, a $200 million cut at both ends. On the investor call, CEO Yvonne Greenstreet attributed the change to normalization of second-line growth, while insisting confidence in Amvuttra’s first-line trajectory remains strong. Commercial execution signals were cited as access and pull-through stayed robust in the U.S., including adherence reportedly above 90%. The market reaction highlights how sensitive the ATTR complex remains to quarterly launch dynamics and how quickly expectations can shift once growth decelerates versus consensus.