In phase 2 testing of Circassia's vaccine ToleroMune, the synthetic peptide vaccine was three times more potent in its disease-modifying effects than other treatments, including antihistamines and steroids. The cat allergen–tolerizing benefits of four injections over 12 weeks remained after a one-year follow-up study. “That's when the allergy world started to sit up and take notice,” says Steve Harris, CEO of Circassia. The picture grew even more interesting in February, when the company unveiled data from 50 patients that researchers followed for two years. ToleroMune subjects maintained a 50% improvement from baseline in nasal and ocular allergy symptoms over placebo's 14.9%, as measured by the commonly accepted total rhinoconjunctivitis symptom score (TRSS). Even when exposed to a four-day challenge of cat allergens, individuals on ToleroMune turned up a 38.3% TRSS improvement, over 13.4% for placebo. “These are data that have never been seen in immunotherapy in any field, let alone allergy,” Harris claims.
Circassia's technology, developed at Imperial College in London, involves the scanning of allergen molecules to identify T-cell epitopes. In the case of ToleroMune, linear stretches of amino acids within the cat (Felis domesticus) allergen Fel d 1 (chains 1 and 2) sequence were identified that bind major histocompatibility complex class II on antigen-presenting cells and have the capacity to induce regulatory T cells. The selected peptide epitopes were then synthesized by F-moc chemistry and tested with blood from allergic subjects to identify those epitopes that produce the desired cytokine profile (Lancet 360, 47–53, 2002).
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