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.

The FDA has approved a new drug for a serious heart condition that affects thousands of people. The drug, called Amvuttra (vutrisiran), is made by Alnylam Pharmaceuticals and is used to treat protein

Alnylam Pharmaceuticals’ Amvuttra (vutrisiran) has been approved by the Food and Drug Administration (FDA) to treat transthyretin amyloid cardiomyopathy (ATTR-CM), a potentially fatal disease of the heart muscle.