BACKGROUND: Allergen immunotherapy (AIT) aims at modulating the immune response by administration of allergen preparations at regular intervals over several years (1). For subcutaneous AIT (SCIT), the treatment is initiated with a dose escalation phase followed by a maintenance dose administration. Over the last decade, there has been a trend towards shortening dose escalation regimens to increase patient adherence. This open-label, phase II trial aimed to investigate the safety and tolerability of a house dust mites (HDMs) SCIT product when used in a newly designed one-strength dose escalation scheme.

METHOD: Patients, aged 12-65, suffering from HDM-allergic rhinitis/rhinoconjunctivitis ± asthma were included. Patients were randomized to the one-strength (6 injections from the highest strength 3) or the Standard dose escalation regimen (14 injections from strengths 1 to 3) using the HDMs-SCIT product. All adverse events were reported. Tolerability was assessed on the Likert scale.

RESULTS: One hundred and forty-three patients were randomized, 79 adults and 64 adolescents. In total, the one-strength regimen caused more adverse drug reactions (ADRs) than the Standard regimen (p = .0457). With both regimens most ADRs were local reactions which occurred more often in the one-strength group (p = .0393). But there was no significant difference in the number of patients affected by systemic or serious ADRs between both regimens. No relevant differences occurred between the two age groups and no other risks were observed for adolescents compared to adults.

CONCLUSION: The safety and tolerability of both regimens can be considered comparable, as most ADRs were local reactions, primarily rated as mild in intensity. Nevertheless, the one-strength regimen caused more ADRs. Reducing the number of injections from 14 to 6 while using only one strength offers the potential to improve patient adherence which further might increase clinical efficacy. Future trials could confirm this hypothesis.