Long-term effects of a house dust mite sublingual immunotherapy tablet in an environmental exposure chamber trial.

BACKGROUND: Treatment with SQ house dust mite (HDM) sublingual immunotherapy (SLIT) tablet is effective for HDM respiratory allergic disease, but data on long-term effects are lacking. OBJECTIVE: Post hoc analyses were conducted to determine the long-term effect of SQ HDM SLIT-tablet on nasal, ocular, and cough symptoms 1 year after discontinuation of treatment. METHODS: Study participants underwent environmental exposure chamber (EEC) challenges at baseline and week 24 in a randomized, placebo-controlled, double-blind trial (NCT01644617) during which participants received daily 12 SQ-HDM, 6 SQ-HDM, or placebo for 24 weeks. Asthma had to be stable, well controlled, and nonsevere. The mean total asthma symptom score (TASS; sum of 3 symptoms: cough, wheeze, and dyspnea) during baseline and week 24 EEC challenge was analyzed in all participants who completed the trial (n = 106). Approximately 1 year after trial completion, another EEC challenge was conducted in a subset of participants (n = 51). Total nasal symptom score (sum of 4 symptoms), total ocular symptom score (sum of 2 symptoms), and cough were assessed. RESULTS: Compared with baseline and end-of-treatment values, sustained improvement of all symptoms assessed at the 1-year follow-up EEC challenge was evident in participants treated with 12 SQ-HDM. Results with 6 SQ-HDM were less notable. After 24 weeks of 12 SQ-HDM, TASS during EEC challenge was improved 65% vs baseline; at 1-year follow-up, cough was improved 57% vs baseline. CONCLUSION: Persistent improvement of nasal and ocular symptoms was observed up to 1 year after completing 24 weeks of 12 SQ-HDM treatment. Beneficial effects on cough were also observed. TRIAL REGISTRATION: clinicaltrials.gov Identifier NCT01644617.