Up to 1,200 patients are enrolling in an international study to evaluate a new form of allergy immunotherapy which, if successful, will require as few as four allergy shots, given monthly, to rid a patient of an allergy to cat dander.

Current immunotherapy for cats takes about three years and often more than a hundred shots to complete.

“Use of immunotherapy has always been limited by the long treatment required,” said allergist Dr. Harold Nelson of National Jewish Health in Denver, who is heading the project. “If the current study confirms earlier findings, it could be a major step forward for allergy treatment,” he said in a news release.

With traditional allergy immunotherapy, multiple injections of protein triggers like cat dander or pollen are given in small then increasing amounts over a long period of time. The idea is to gradually build tolerance and, ultimately, to desensitize the patient to the allergen. While this type of vaccination is currently the only way to treat the underlying allergic disease (rather than just allergy symptoms), it is a fairly invasive, costly and time-consuming, since patients must make numerous visits to the doctor.

Cat allergy is one of the most common allergic disorders, and a frequent trigger for asthma. The protein in cat dander that causes almost all symptoms is “fel d 1”, and the new vaccination therapy, called ToleroMune, works by injecting seven tiny protein fragments or “peptides” of this cat protein, as opposed to the whole protein.

By using the fragments, which aren’t large enough to provoke an allergic reaction, studies to date show that patients can become desensitized to cat much more rapidly and with far few side effects. Unlike the proteins used in traditional immunotherapy, as the protein fragments are not large enough to cause a reaction.

The study is expected to involve about 1,200 participants at National Jewish Health as well as at more than 100 centers in the United States, Canada, and Europe. Researchers hope to confirm earlier findings which showed that after four shots of ToleroMune, which has been developed by the British firm Circassia Ltd., many patients became desensitized and remained so a year later.

The study, which put 123 people with ragweed allergy in a specially-controlled room with their allergen for three hours, found that those who were also allergic to dogs, cats and dust mites developed symptoms faster, or experienced stronger symptoms, than those who didn’t have the other allergies.

However, the differences between the two groups lessened as the hours went on (they filled out questionnaires every 30 minutes) suggesting that once ragweed season is in full swing, everyone is affected equally.

Lead author of the study, Dr. Anne Ellis, and her team at Kingston General Hospital in Ontario suggest that to avoid this early, intense reaction, ragweed, allergy sufferers should treat their other allergies with immunotherapy or year-round allergy medication.

Another option is to limit exposure to dogs or cats leading up to ragweed season.