Immunotherapy for allergic rhinoconjunctivitis (ARC) in North America is generally administered subcutaneously, but alternative formulations might be safer and more convenient. Trials of sublingual formulations in North America are needed to confirm European efficacy and safety data.

We sought to investigate the efficacy and safety of timothy grass allergy immunotherapy tablet (AIT) treatment in North American subjects with ARC.

Four hundred thirty-nine adults with grass pollen–induced ARC with or without asthma were randomized to once-daily 2,800 bioequivalent allergen units of standardized grass AIT (oral lyophilisate, Phleum pratense, 75,000 standardized quality tablet, containing approximately 15 μg of Phl p 5) or placebo approximately 16 weeks before the 2009 grass pollen season (GPS). The primary end point was the average total combined score of the daily symptom score and the daily medication score during the GPS. Rhinoconjunctivitis Quality of Life Questionnaire with standardized activities (RQLQ[S]) scores, Phl p 5–specific IgG4 levels, and IgE-blocking factor levels were additional end points. Adverse events (AEs) were monitored for safety.

Relative to placebo, grass AIT treatment improved total combined scores by 20% (P = .005), daily symptom scores by 18% (P = .02), and RQLQ(S) scores by 17% (P = .02). Daily medication scores were improved by 26% and trended toward significance (P = .08). Phl p 5–specific IgG4 and IgE-blocking factor levels were higher after grass AIT treatment compared with those after placebo at the end of the GPS (P < .001). Grass AIT treatment was safe and well tolerated. The majority of AEs were transient mild local reactions with no investigator-diagnosed grass AIT–related serious AEs or reports of anaphylactic shock/respiratory compromise. In the grass AIT group, 1 subject received epinephrine after experiencing a possible grade 1 systemic reaction (local site reactions, chest discomfort, and rash).

Timothy grass AIT treatment (cross-reactive with related Pooideae grasses) was demonstrated to be effective, generally safe, and well tolerated in North American adults with grass pollen–induced ARC.