Alnylam’s stock slid sharply after the company lowered full-year guidance for its transthyretin amyloidosis franchise, citing normalized Amvuttra demand after a pent-up launch surge. The update came as investors focused on whether Amvuttra could sustain growth after earlier expectations. Amvuttra generated $1.01 billion in the quarter, missing analysts’ estimates by about 4%, while Alnylam said second-line growth has normalized. Management emphasized that first-line starts remain the focus and that physician preference and adherence metrics are holding up in the U.S. The guidance cut raises questions about the trajectory for the broader TTR cardiomyopathy market amid intensifying competition, including other ATTR cardiomyopathy therapies and upcoming franchise pressure from pipeline and performance data.