TOPLINE:

Subcutaneous allergen immunotherapy (SCIT) showed safety and efficacy specifically in patients with moderate-to-severe allergic rhinoconjunctivitis induced by house dust mites, despite not meeting the primary endpoint in the intention-to-treat population.

METHODOLOGY:

• Researchers conducted a randomized study of 767 adults with moderate-to-severe allergic rhinoconjunctivitis induced by house dust mites across multiple centers in Europe between October 2016 and April 2017.
• Participants received subcutaneous injections of either house dust mite allergoid at 50,000 AUeq/mL (n = 381; mean age, 32 years; 50.4% women) or placebo (n = 386; mean age, 32 years; 51.6% women) for approximately 1 year, with 6-weekly up-dosing injections followed by 4-weekly maintenance doses up to 5 mL.
• Researchers compared the mean Combined Symptom and Medication Score (CSMS), focusing on nasal symptoms, between active and placebo groups during the final 8 weeks of treatment.

TAKEAWAY:

• In the intention-to-treat population, a borderline significant difference in the mean CSMS was observed between the intervention and placebo groups (P = .0767). The treatment effect was -0.12 points (95% CI, -0.26 to 0.01), below the prespecified minimal clinically relevant difference of 0.25 points.
• In the subgroup analysis, the difference in the mean CSMS was highly significant (P = .0031) between the intervention and placebo groups.
• Treatment-emergent adverse events occurred more frequently in the house dust mite group (63.2%) than in the placebo group (31.1%), with most events being mild (70.9%) or moderate (27.6%) in intensity.
• A total of 25 serious adverse events were nearly equally distributed between the treatment group (13 events) and the placebo group (12 events), with none related to the study medication.

IN PRACTICE:

"In house dust mite AIT [allergen immunotherapy], the placebo effect presents specific challenges due to the constant, year-round exposure to allergens. Clinical trials often target patients with moderate to severe symptoms, as these cases allow for clearer, more measurable improvements essential to demonstrating treatment efficacy. However, this focus does not imply that AIT is without benefit for those with milder symptoms; it may still provide symptom relief and potential long-term advantages,” the authors wrote. 

SOURCE:

Ronald van Ree , PhD, with Amsterdam University Medical Centers, Amsterdam, Netherlands , was the corresponding author of the study, which was published online on September 18, 2025, in Allergy.

LIMITATIONS:

The appropriateness of CSMS for evaluating house dust mite allergy was uncertain. Inclusion of ocular symptoms and patients with mild symptoms may have diminished the overall treatment effect. Additionally, the authors point out that the nasal provocation test and its derived Lebel score showed only a weak correlation with baseline symptom severity, limiting their utility in identifying patients most likely to benefit from allergen immunotherapy.

DISCLOSURES:

This study was funded by HAL Allergy BV, Leiden, Netherlands. Several authors reported receiving grants, research support, speaker fees, personal fees, consulting fees, honoraria, travel support, or stock options from various pharmaceutical companies. One author reported being the vice president of the European Academy of Allergy and Clinical Immunology, a member of the external board of directors of the German Society of Allergy and Clinical Immunology, editor-in-chief of Clinical and Translational Allergy, and associate editor of Allergy. Another author is deputy editor-in-chief of Allergy. Five authors reported being employees of the funding company.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.