On Mar. 28, 2025, the U.S. Food and Drug Administration (FDA) announced approval of Alnylam Pharmaceuticals Qfitlia™ (fitusiran), the sixth Alnylam-discovered RNAi therapeutic approved in the U.S., and the first and only therapeutic to lower antithrombin (AT), a protein that inhibits blood clotting, with the goal of promoting thrombin generation to rebalance hemostasis and prevent bleeds.

Qfitlia is indicated in the U.S. for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adult and pediatric patients 12 years of age and older with hemophilia A or B, with or without factor VIII or IX inhibitors (neutralizing antibodies).

Alnylam scientists discovered Qfitlia, published the first clinical data in the New England Journal of Medicine in 2017 showing reduced bleeding rates in hemophilia patients, and initiated the Phase 3 development program. In 2014,

Sanofi obtained global rights to co-develop and co-commercialize Qfitlia under a license and collaboration agreement. The agreement was amended in 2018, with Sanofi obtaining global development and commercialization rights to Qfitlia, and Alnylam becoming eligible to receive tiered royalties of 15 to 30 percent on global net sales.

Qfitlia is the sixth Alnylam-discovered medicine using its RNAi therapeutic platform to be approved to date. The approval marks the completion of the “products” goal in Alnylam’s P⁵x25 strategy, a set of corporate goals for 2025. Qfitlia has the potential to benefit the estimated one million people living with hemophilia A and B around the world.