Alnylam Pharmaceuticals Inc. won expanded US approval for a heart drug that could be the biggest boon yet for the 23-year-old biotech — if it can beat out stiff competition from the likes of Pfizer Inc.

Alnylam Pharmaceuticals shares rose 10% Friday after the company nabbed FDA approval to sell its drug Amvuttra to a larger population of patients with a genetic heart condition. The FDA

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.