Efficacy and safety of SQ house dust mite sublingual immunotherapy-tablet (12 SQ-HDM) in children with allergic rhinitis/rhinoconjunctivitis with or without asthma (MT-12): a randomised, double-blind, placebo-controlled, phase III trial

Background Allergic rhinitis/rhinoconjunctivitis (AR/C) induced by house dust mites (HDM) often begins in childhood and negatively impacts a child's quality of life. The daily burden can be further compounded by comorbid asthma. Allergen immunotherapy is the only available treatment targeting the underlying cause of allergic disease. Efficacy and safety of the SQ HDM sublingual immunotherapy (SLIT)-tablet has been demonstrated in adults and adolescents with HDM AR/C with or without asthma, but data are lacking for younger children. Methods Phase III, randomised, double-blind, placebo-controlled trial in younger children (5-11 years) with HDM AR/C with or without asthma. Eligible subjects were randomised 1:1 to SQ HDM SLIT-tablet or placebo for similar to 1 year and had free access to AR/C symptom-relieving medications. The primary outcome was the total combined rhinitis score (TCRS) during the final 8 weeks of the treatment period (similar to 1 year). Secondary outcomes included the rhinitis daily symptom score (DSS) and medication score (DMS), the rhinoconjunctivitis total combined score (TCS), and the Paediatric Rhinoconjunctivitis Quality of Life Questionnaire (PRQLQ) score. Efficacy analyses were conducted on the full analysis set (observed cases). Asthma-related outcomes were also explored. The trial was registered on ClinicalTrials.gov: NCT04145219 and EudraCT: 2019-000560-22. Findings A total of 1460 subjects were randomised to SQ HDM SLIT-tablet (n = 729) or placebo (n = 731). The primary outcome, TCRS, was statistically significantly different for SQ HDM SLIT-tablet (n = 693) versus placebo (n = 706), with an absolute difference of 1.0 (95% CI: 0.5, 1.4; p < 0.0001) corresponding to a relative reduction of 22.0% (95% CI: 12.0, 31.1). Key secondary outcomes (DSS, DMS, TCS, PRQLQ) showed statistically significant reductions in symptoms and medication use, and improved disease-related quality of life for SQ HDM SLIT-tablet versus placebo. Improvements in asthma symptoms and reduced asthma medication use indicated an additional effect of SQ HDM-SLIT tablet versus placebo. The SQ HDM SLIT-tablet showed a higher event rate for treatment-related adverse events (AEs) than placebo. Most events were of mild or moderate severity and few subjects discontinued due to AEs (2.5%). Interpretation The trial confirmed the efficacy and safety of the SQ HDM SLIT-tablet for treating HDM AR/C in younger children (5-11 years) with or without asthma. The safety profile supports daily self-administration of the SQ HDM SLIT-tablet in children.