Background: Topical mast cell stabilizers were previously shown to treat the signs and symptoms of seasonal and perennial allergic conjunctivitis safely and effectively in active and placebo-controlled trials. However, mast cell stabilizers have not been compared to topical corticosteroids for efficacy. We tested the non-inferiority of a topical mast cell stabilizer, N-acetyl aspartyl glutamic acid (4.9%, NAAGA), compared to fluorometholone (0.1%, FM) during controlled exposures to the airborne birch pollen allergen, Bet v 1, in an environmental exposure chamber (EEC).
Methods: This randomized, cross-over, investigator-blinded study included 24 patients with a history of birch pollen allergic conjunctivitis. Patients were randomized to 5 days of treatment with NAAGA, then FM (n = 12) or FM, then NAAGA (n = 12). After each treatment, patients were exposed to a fixed airborne concentration of Bet v 1 in ALYATEC EEC. The primary endpoint was the amount of allergen required to trigger a conjunctival response (Abelson score ≥5). Groups were compared with a linear model for cross-over studies. Non-inferiority was assumed, when the lower bound of the risk ratio confidence interval (CI) was >0.5.
Results: At screening, the mean time-to-conjunctival response was 72.5 ± 35.9 min. NAAGA and FM extended the response time to 114.8 ± 55.0 and 116.6 ± 51.5 min respectively. The mean amounts of allergen required to trigger a conjunctival response were 1.165 ng after NAAGA and 1.193 ng after FM treatment. The risk ratio for the conjunctival response was 0.977 (95% CI: 0.812; 1.174), which indicated non-inferiority. Adverse events occurred less frequently with NAAGA (29.2%) than with FM (58.3%).
Conclusion: In patients with allergic conjunctivitis to birch pollen, NAAGA was non-inferior to FM in exposures to airborne Bet v 1. The EEC was a good model for simulating real-life airborne allergen exposure and for demonstrating the efficacy and safety of eye drops for treating allergic conjunctivitis.
Trial registration: Not registered.
Keywords: N-acetyl aspartyl glutamic acid; allergic conjunctivitis; birch allergen; environmental exposure chamber; fluorometholone.
© 2022 The Authors. Clinical & Experimental Allergy published by John Wiley & Sons Ltd.