Injections of an experimental, genetically engineered drug may significantly reduce hay fever symptoms, research suggests.  The study involved 536 patients with ragweed-induced hay fever who were given shots of omalizumab, or Xolair. While the study involved only ragweed, the researchers said the drug would probably also work in people whose seasonal allergies are triggered by other substances.

The drug, which is awaiting Food and Drug Administration approval, represents a novel approach, targeting proteins known as IgE antibodies that susceptible people produce in large numbers in response to allergens like ragweed. Xolair binds to IgE antibodies in the blood and renders them inactive.

"If you don't have IgE available to bind to the ragweed, then you would not be able to mount an allergic response," said Dr. Thomas B. Casale, a Creighton University allergist who led the study.

With traditional allergy shots, patients get injections of gradually increasing amounts of ragweed or other allergens for several months to slowly desensitize the immune system. The effects can last for several years.

With Xolair, injections would probably need to continue indefinitely, Casale said. In the study, patients were given shots every three or four weeks throughout the season.

Casale said potential candidates for Xolair would include patients who get little relief from standard medication such as nasal steroids and antihistamines and those who have trouble taking medication daily.

Other studies have shown the drug is effective in patients with hard-to-treat asthma, which is usually triggered by an allergic reaction. Xolair's developers, Genentech Inc. and Novartis Pharmaceuticals Corp., are seeking government approval for its use in asthma treatment.

The FDA wants more safety data on its use in hay fever, since the condition affects so many people - about 40 million nationwide, versus about 17 million for asthma, said Genentech spokeswoman Shelley Schneiderman Ducker.

Few side effects were found in the Xolair study, Casale said.

The companies funded the latest research, which was published in Wednesday's Journal of the American Medical Association.

Patients in the study were given Xolair shots of different dosages before and during the season. Another group of patients received dummy shots.

Patients on the highest Xolair dose had more than double the percentage of days with only minimal allergy symptoms _ 41 percent versus 18 percent in the placebo group. Overall, Xolair patients missed 75 percent less work or school than those on placebos.

In a JAMA editorial, a National Institutes of Health researcher, Dr. Marshall Plaut, said studies comparing Xolair with existing allergy drugs are needed, and more information is needed on the relative costs before Xolair can be recommended.