U.S. Food and Drug Administration approved Alnylam's drug to treat a rare and deadly heart disease on Thursday, allowing the entry of a new type of medicine in a market dominated by Pfizer's blockbuster Vyndaqel.

Alnylam’s drug, vutrisiran, was approved for patients with transthyretin amyloid cardiomyopathy, or ATTR-CM, to reduce cardiovascular-related death and hospitalizations. This indication was widely expected among investors and is similar to the indications given for competing therapies.

Heart disease patients now have another treatment option. The U.S. Food and Drug Administration has approved Alnylam Pharmaceuticals’ treatment for a progr