Alnylam cuts full-year sales forecast as post-launch TTR drug momentum fades

Alnylam Pharmaceuticals (ALNY) has lowered its full-year 2026 sales guidance by approximately $200mn, blaming slower-than-expected growth in its transthyretin, or TTR, amyloidosis franchise after initial launch demand normalized — a disclosure that sent the company's shares tumbling more than 28 per cent.

The guidance cut followed second-quarter results released on July 30 that fell short of expectations, compounding investor concern over the durability of the company's commercial trajectory. The steep share price decline has since drawn the attention of plaintiff law firms, at least one of which has launched an investigation into potential securities law violations and is soliciting contact from affected investors.

Alnylam has built its business around RNA interference, or RNAi, a gene-silencing technology, with its TTR product portfolio forming the cornerstone of its commercial operations. The normalization of early launch demand — a pattern common to specialty drug launches once initial patient uptake plateaus — now raises questions about the pace of longer-term market penetration.