This was a randomized, placebo-controlled, double-blind, dose-ranging, onset-of-action, single-site trial (Vienna Challenge Chamber [VCC] Site, Vienna, Austria) conducted between October 29, 2012, and August 27, 2013. The challenge sessions during the trial were conducted outside of the regional tree and grass pollen seasons to avoid having subjects who were symptomatic to other environmental allergens at the time of the efficacy assessments. The clinicaltrials.gov identifier was NCT01644617.