Abstract
Purpose:
Mediators released from the mast cell initiate the signs and symptoms of allergic conjunctivitis, and can cause the disease to progress to allergic inflammation. The antihistamine, alcaftadine , indicated for prevention of itching associated with allergic conjunctivitis, has been shown preclinically to have anti-inflammatory effects. The purpose of this study was to characterize the anti-inflammatory effects (via blood vessel confocal microscopy) and anti-histaminic effects of alcaftadine in human subjects.
Methods:
This was a single-center, double-masked, randomized, placebo-controlled, conjunctival allergen challenge (CAC) study comprised of 3 visits (N=16). Main entry criteria were: a positive history of allergic conjunctivitis; a positive allergic CAC reaction; and a bilateral conjunctival inflammation score (CIS: leukocyte migration and adherence) of ≥ 2 (0-4 scale) at 60-90 mins post-CAC at Visit 1. At Visits 2 and 3, subjects received one drop of alcaftadine in one eye and placebo in the contralateral eye. Visit 2 measured the prophylactic effects of alcaftadine instilled 15 min prior to CAC. Visit 3 measured the treatment effects of alcaftadine administered 20 min post-CAC. The primary endpoint was CIS of confocal images of conjunctival blood vessels 60 mins post-CAC, scored by a masked grader. Secondary endpoints included ocular itching, eyelid swelling, redness and chemosis.
Results:
At Visit 2, the CIS in alcaftadine-treated eyes (2.34 ± 0.98; mean, SD) was lower than placebo eyes (2.94 ± 1.01): p=0.07. Itching scores were > 1 unit (0-4 scale) lower in the alcaftadine-treated eyes (p<0.0008). At Visit 3, itching scores remained > 1 unit lower in alcaftadine-treated eyes even after the second challenge, 24 hours post-instillation of study drug at Visit 1 (p<0.0005). At Visit 3, alcaftadine-treated eyes had a lower CIS (2.84 ± 0.87) than placebo eyes (3.16 ± 0.87), but the differences were less than when treatment was given prior to challenge (p=0.17).
Conclusions:
Alcaftadine had a long-lasting (>24 hrs) effect on itching, and inhibited the inflammation of an acute allergic reaction. Prevention was more effective than treatment after allergy had ensued. Consistent coverage will prevent the allergic response from occurring, and the progression to a more complex and difficult to treat allergic inflammation.