In the study, the team of American and European researchers injected a 300-milligram dose of the drug, sold under the brand name Xolair, once a month for three months. Saini says initial relief from symptoms was quick and occurred after a week. After three months, 53 percent of people experienced a total elimination of all hives and 44 percent had no further incidents of hives or itch. Lower doses of the drug, at 150 milligrams and 75 milligrams, and the placebo (or 0 milligrams) proved half as effective as the next larger dose, or had almost no effect at all, researchers say.
Saini, who also serves as director of Johns Hopkins' medical fellowship training program in allergy and clinical immunology, had conducted earlier research on the test doses, which he says are different from those used in omalizumab therapy for asthma. Single, uniform doses of omalizumab can be used to treat hives, whereas dosing for asthma is calculated based on the patient's weight and blood levels of IgE antibodies, known to play a key role in allergic reactions.
Researchers say it remains unclear as to precisely how omalizumab, first approved in the United States in 2003 as a treatment for severe asthma, stops the runaway allergy-like reactions underpinning chronic hives and itching. What is known, he says, is that omalizumab binds up free IgE circulating in the body, and lowers the number of IgE receptors on other histamine-carrying immune system cells. Saini says that in a typical allergic reaction, allergens, such as pollen and dust particles, bind to IgE receptors that sit on these immune system cells. This process quickly results in a controlled, wave-like release of histamine, a key triggering chemical involved in inflammation. But in the itchy rash of chronic hives, histamine release appears to be more spontaneous, suggesting that the histamine-carrying mast cells and basophils are abnormal.
Saini next plans more studies on omalizumab's effects on IgE, and how it contributes to chronic hives and rash. He says his goal is to understand the underlying mechanism of the disease and explain why the drug is effective.
Source: Johns Hopkins Medicine