Conventional
immunotherapy for cat
allergy is effective in reducing cat
allergy symptoms in many patients, but this type of
immunotherapy can cause severe reactions, including
anaphylaxis, and often requires years of
injections for successful desensitization. To improve the efficacy of
immunotherapy for cat allergic patients, synthetic cat
allergen peptides (
ALLERVAX CAT) were generated, based on analysis of the immunodominant
T cell epitopes of cat
allergen. These
peptides lack the tertiary structure of native Fel d1 and possess a significantly reduced capacity to bind to Fel d1-specific
IgE. Using these
peptides, we performed a multicenter, randomized, double-blind, placebo-controlled study of 133 cat allergic patients chronically exposed to cats or who had failed previous conventional cat
immunotherapy. We evaluated the safety of
ALLERVAX CAT treatment and determined whether
ALLERVAX CAT treatment improved tolerance to cat
allergen, as measured by symptom analysis and pulmonary function testing. Three of the
ALLERVAX CAT-treated patients required systemic
epinephrine for adverse reactions, but the frequency of all adverse reactions in both groups was not statistically different from that of the placebo group. The majority of adverse events were "late" events, most commonly associated with respiratory symptoms, and these events declined with successive
injections.
ALLERVAX CAT given at a dose of 750 microg/dose improved pulmonary function in patients with reduced baseline FEV1, and global evaluation of the subjects' ability to tolerate cats improved significantly in the actively treated groups relative to placebo. Thus, although
therapy with
ALLERVAX CAT is associated with some adverse events in patients with severe cat sensitivity, such
therapy is an effective approach for the management of cat
allergy, since it improves tolerance to cats and improves pulmonary function in cat allergic patients with reduced FEV1.