Does omalizumab (Xolair) have any serious side effects?
In scientific studies, cancer was seen in a small number of patients receiving omalizumab, as well as in those receiving placebo injections. The rate was higher in patients treated with omalizumab than placebo (0.5% vs. 0.2%). This difference has not been conclusively linked to the omalizumab. Some patients in the studies had a serious allergic reaction called anaphylaxis. This was rare, occurring in less than 0.1% of patients. Doctors have been advised to observe patients for a period after omalizumab injection to make sure that no anaphylaxis develops. If it does, it can be treated.
