Methods: Safety data from four phase 2 prospective, randomized, double-blind, placebo-controlled studies and one follow-up study were integrated and Adverse Events (AE), vital signs, and inspection of the injection site were compared for Cat-PAD treated subjects (n=320) and placebo (n=143).
Results: Two serious adverse events occurred: migraine 11 days after a dose of 3 nmol Cat-PAD and a skin laceration following placebo, both classed as unrelated by the Investigator. The overall incidence of AE was comparable between Cat-PAD and placebo: headache (Cat-PAD 15.6%; placebo 18.2%), upper respiratory tract infection (Cat-PAD 15.6%; placebo 12.6%), bronchospasm (Cat-PAD 8.1%; placebo 8.4% and cough (Cat-PAD 4.7%; placebo 4.9%). None of the subjects who experienced bronchospasm in Cat-PAD treatment arms had such an occurrence within 24 hours of dosing and the majority of instances were associated with an EEC visit; all bronchospasm in placebo treated subjects were associated with an EEC visit. Asthma was reported in 3.1% of subjects on Cat-PAD and 7.7% on placebo. Two injection site reactions were reported as adverse events: one each following 3 nmol Cat-PAD and placebo. Injection sites were reported as abnormal at one or more assessments in 7.4%, 4.4% and 4.7% of patients following 3 nmol Cat-PAD, 6 nmol Cat-PAD and placebo respectively.
Conclusions: Studies to date demonstrate Cat-PAD is well tolerated with a systemic and local reactions profile that is indistinguishable from placebo. Local reactions following conventional immunotherapy have a reported frequency ranging from 26% to 82% of patients and 0.7% to 4% of injections (Cox et al. JACI 2011). The apparent lower rate following treatment with Cat-PAD, the first in a new class of SPIREs, may enhance acceptability, assist in removing bias from blinded pivotal studies and reflect an enhanced safety profile compared to conventional immunotherapy making it a potentially exciting new approach to treating cat allergy.