Merck & Co has been boosted by the US Food and Drug Administration's decision to approve its anti-platelet agent Zontivity.

The agency has given the green light to Zontivity (vorapaxar) to reduce the risk of heart attack, stroke, cardiovascular death, and need for procedures to restore blood flow to the heart in patients with a previous heart attack or blockages in the arteries to the legs. The tablet is the first in a new class of drug, called a protease-activated receptor-1 (PAR-1) antagonist, designed to decrease the tendency of platelets to clump together to form a blood clot.

Like other blood clot inhibitors, Zontivity increases the risk of bleeding so the label includes a boxed warning about the risk. The FDA added that the drug must not be used in people who have had a stroke, transient ischemic attack or bleeding in the head.

The approval is principally based on a trial with over 25,000 participants where Zontivity, added to other anti-platelet agents (generally aspirin and clopidogrel), reduced the rate of a combined endpoint of heart attack, stroke, CV death, and urgent procedures to improve blood flow to the heart when compared to placebo.

The thumbs-up was expected given that the FDA's Cardiovascular and Renal Drugs Advisory Committee  voted 10-1 in support of Zontivity.