Grass Sublingual Immunotherapy Tablet (SLIT-T) Treatment Is Associated With Similar Efficacy and Safety In Children and Adults: Subgroup Analysis Of Data From a Large North American Trial

Background: Trials of sublingual immunotherapy for allergic rhinitis with or without conjunctivitis (AR/C) in North American subjects are few, particularly among children. A previous North American pediatric trial found standardized timothy grass sublingual immunotherapy tablet (SLIT-T), MK-7243 (Merck/ALK; 2800 BAU of Phleum pratense) treatment to show efficacy and safety similar to that seen in a corresponding adult trial; however, other sublingual immunotherapy research has suggested treatment effect may be inconsistent between children and adults. Using data from a double-blind controlled trial including children and adults—the largest immunotherapy study yet presented—we evaluated a timothy grass sublingual immunotherapy tablet treatment in North American pediatric and adult subgroups with AR/C.

Methods: North American subjects (5-65 yrs) with grass allergy were randomized 1:1 to once-daily grass SLIT-T or placebo. The first dose was given on site; subsequent doses were self-administered. The primary efficacy endpoint was total combined score (TCS = rhinoconjunctivitis daily symptom score [DSS] plus daily medication score [DMS]) over entire grass pollen season (GPS). Approval was obtained from appropriate IRBs and informed consent obtained from all research subjects.

Results: 1501 subjects were randomized; 283 (19%) were aged 5 to <18 years. Among subjects aged 5 to <18 years, grass SLIT-T treatment was associated with a median reduction vs placebo of 32% (−1.32 score; 2.77 vs 4.09; P=.02) in TCS. Among subjects aged 18 to 65 years, grass SLIT-T treatment was associated with a median reduction vs placebo of 21% (−0.9 score; 3.33 vs 4.24; P<.001) in TCS. Adverse event rates were similar between treatment groups and among age categories (73-80% and 65-84% for grass immunotherapy and placebo respectively among age categories). Most adverse events were self-limited, mild or moderate local application-site reactions. No severe systemic allergic events were reported.

Conclusions: In this large North American trial, treatment with timothy grass SLIT-T was effective and well tolerated in grass-allergic children and adults with AR/C. The 2800 BAU sublingual tablet was associated with similar efficacy and safety between pediatric and adult subgroups.