EAACI 2025: Effectiveness of Allergy Immunotherapy on Symptom-Relieving Medication Use: Results From the Real World Evidence of Allergy Immunotherapy (RELY) Study

Introduction:
The burden of allergic rhinitis (AR), often accompanied by asthma, on quality of life was acknowledged. While sublingual immunotherapy (SLIT)-tablets had been shown to reduce AR symptoms and medication use, their long-term effects in real-world settings had remained insufficiently studied. The RELY study was designed to evaluate the prolonged impact of SQ SLIT-tablets (grass and house dust mite [HDM]) on the use of symptom-relieving medications in AR patients, with or without asthma, using Nordic registry data.

Methods:
The RELY study was a predefined, retrospective cohort analysis that utilized propensity score matching to evaluate the long-term impact of SQ sublingual immunotherapy (SLIT) tablets for grass and house dust mite (HDM) allergies in patients with allergic rhinitis (AR), with or without coexisting asthma. Eligible patients had either an ICD-10 diagnosis of AR or at least two annual prescriptions for intranasal corticosteroids (INCS) or antihistamines across two consecutive years. AR patients who received allergy immunotherapy (AIT) were matched 1:1 with untreated controls and followed for up to 14 years. Patients aged 5 years and older were included in the grass allergy cohort, while those aged 12 and above were included in the HDM cohort. The primary outcome was the number of AR symptom-relieving medications used per patient—assessed during April to July for grass allergies and across the full year for HDM. Additional analyses were performed on a subgroup of patients who had received at least one INCS prescription during the year before treatment initiation.

Results:

• A total of 20,280 patients with allergic rhinitis (AR) received SQ Grass SLIT-tablet treatment, and 3,584 received SQ HDM SLIT-tablets.
• Among them, 6,622 (33%) in the grass group and 1,703 (48%) in the HDM group had pre-existing asthma.
• Compared to matched controls, treatment with SQ Grass SLIT-tablets led to long-term, sustained reductions in the use of AR symptom-relieving medications during the grass pollen season, with effects lasting up to 14 years.
• Similarly, patients treated with SQ HDM SLIT-tablets showed consistent reductions in year-round AR medication use for up to 5 years.
• Notably, patients who had received at least one prescription for intranasal corticosteroids (INCS) during the baseline period experienced significantly greater reductions in AR medication use compared to controls, indicating that allergen immunotherapy (AIT) may be particularly beneficial in individuals with more severe baseline symptoms.

Conclusion:
Long-term effectiveness of allergy immunotherapy (AIT) with SQ SLIT-tablets was demonstrated, supporting a disease-modifying effect in AR patients, regardless of asthma status.

European Academy of Allergy and Clinical Immunology 2025,13-16 June, Glasgow, United Kingdom.