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Fel d 1-derived synthetic peptide immuno-regulatory epitopes show a long-term treatment effect in cat allergic subjects

Significance Statement


Cat allergy is common with 17% of the US population testing positive in skin prick tests (equating to over 50 million people) and 30% of allergic asthma is attributable to cat allergen sensitization.  Treatment with Cat-PAD, the first in a new class of Synthetic Peptide Immuno-Regulatory Epitopes (SPIREs) consisting of a mixture of T-cell epitopes, down regulates allergic responses, without triggering the release of histamine and associated side effects.  A previous study demonstrated that treatment with four injections of Cat-PAD over a twelve week period improved patients’ cat allergy symptoms following a short course.  The original double-blind, randomized study involved 202 patients with cat allergen induced rhinoconjunctivitis.  Prior to treatment, the participants recorded their nasal and eye symptoms while exposed to cat allergens in an environmental exposure chamber. Nasal and ocular symptom scores were combined to give a total rhinoconjunctivitis symptom score [TRSS].  Over the subsequent 12 – 14 weeks, patients received either four doses of Cat-PAD, eight lower doses, or placebo. In this paper the authors report findings from a further visit to the exposure chamber two years after the start of the initial study. This follow-up study found the improvement in patients’ symptoms following the four doses of Cat-PAD regimen, which was originally demonstrated one year after the start of treatment, was maintained two years after the start of short-course treatment without further dosing, when compared with both placebo and treatment with the more frequent but lower dose.  Cat-PAD was well tolerated with a safety profile similar to placebo.  Cat-PAD, the first in a new class of SPIREs, can reduce rhinoconjunctivitis symptoms associated with cat allergy, with improvements continuing two years after the start of short-course treatment.  The decrease in TRSS achieved in the study represents a substantial improvement over a range of allergy therapies investigated previously using similar methodology, and reached two – three times the level of symptom reduction in some cases.  Consequently, the study has identified the optimal dose and regimen for this potential new and exciting cat allergy treatment, which has now progressed to large-scale phase III testing.

Fel d 1-derived synthetic peptide immuno-regulatory epitopes show a long-term treatment effect in cat allergic subjects. . Global Medical Discovery







Journal Reference

Couroux P, Patel D, Armstrong K, Larché M, Hafner RP. Clin Exp Allergy. 2015 Jan 20. Cetero Research, Mississauga, Ontario, Canada.



Cat-PAD, the first in a new class of Synthetic Peptide Immuno-Regulatory Epitopes (SPIREs), was shown to significantly improve rhinoconjunctivitis symptoms in subjects with cat allergy up to 1 year after the start of a short course of treatment.


To evaluate the long-term effects of Cat-PAD on rhinoconjunctivitis symptoms following standardized allergen challenge 2 years aftertreatment. Methods In a randomised, double-blind, placebo-controlled, parallel group study, subjects were exposed to cat allergen in an environmental exposure chamber (EEC) before and after treatment with two regimens of Cat-PAD (either 8 doses of 3 nmol or 4 doses of 6 nmol) given intradermally over a 12-week period. In this follow-up study, changes from baseline in rhinoconjunctivitis symptoms were reassessed 2 years after the start of treatment.


The primary endpoint showed a mean reduction in total rhinoconjunctivitis symptom scores of 3.85 units in the 4 x 6 nmol Cat-PAD group compared to placebo 2 years after the start of treatment (P = 0.13) and this difference was statistically significant in the secondary endpoint at the end of day 4 when the cumulative allergen challenge was greatest (P = 0.02). Consistent reductions in nasal symptoms of between 2 to 3 units were observed for 4 x 6 nmol Cat-PAD compared to placebo between the 2 to 3 hour time points on days 1 to 4 of EEC challenge at 2 years (P < 0.05). The 8 x 3 nmol dose did not show a meaningful effect in this study.


A persistent, clinically meaningful reduction in rhinoconjunctivitis symptoms was observed on EEC challenge 2 years after the start of a short course of treatment with 4 x 6 nmol Cat-PAD. This study is the first to provide evidence of a long-term therapeutic effect with this new class of SPIREs.

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