A safety study conducted by the manufacturer of the asthma drug omalizumab (Xolair, Genentech) suggests it poses a slightly elevated but serious risk for heart attacks and ministrokes known as transient ischemic attacks, the FDA announced today.

The FDA qualified its warning by saying that because of “weaknesses” in the 5-year study’s design and implementation, the agency is “unable to definitively confirm or determine the exact increased level of these risks with Xolair.”

The label of omalizumab, also indicated for chronic idiopathic urticaria, features a boxed warning about the risk for anaphylaxis presenting as bronchospasm, hypotension, syncope, urticaria, and angioedema of the throat or tongue.

The FDA today said it will add label information about the potential risks for cardiovascular and cerebrovascular problems, which also include unstable angina, venous thrombosis and pulmonary embolism, and pulmonary hypertension.