Safety profile of the first year of a paediatric long-term study investigating the safety and efficacy of subcutaneous immunotherapy with PQ Grass 27 600 SU: An Innovative Trial Design

Aim of the study: Several studies have demonstrated the efficacy and safety of subcutaneous immunotherapy with PQ Grass 27 600 SU in adults. To meet European Medicines Agency (EMA) Paediatric Investigation Plan (PIP) requirements long-term paediatric studies are required. The Phase III trial G308 evaluates the long-term safety and efficacy with PQ Grass 27 600 SU in children and adolescents suffering from seasonal allergic rhinitis (SAR) to grass. Methods: This long-term, double-blind, placebo-controlled Phase III trial is being conducted in seven EU countries in children and adolescents (5–16 years old) with SAR to grass pollen. This adaptive study design integrates a one-year short-term efficacy phase (Part A) with a 5-year long-term extension (Part B). Low placebo effect sensitive patients from the placebo group in Part A progress to the long-term phase (Part B). The innovative randomisation plans increase the chance of receiving at least one course of active treatment (87–92%). Measures to minimise placebo response make this trial unique in paediatric allergy research. Results: A total of 190 participants were enrolled and randomized in the first year of the study. The protocol-defined target of≥45% participants under 12 years of age was successfully achieved. The preliminary (blinded) safety profile was benign after completion of the six subcutaneous injections in the first year. In the second year, further 232 participants will be randomized to reach the planned sample size for Part A. In 9 patients (4.7%), systemic reactions were reported, predominantly grade 1 (n= 7) and grade 2 (n= 2). Local adverse events involved mostly mild intensity. No serious adverse events were reported. The discontinuation rate observed in the first year remains low (2.6%), with one case attributed to a local reaction. Conclusion: This is the first long-term study with an adaptive study design fulfilling the paediatric requirements of the EU marketing authorisation regulations for a SCIT product. It offers practical feasibility due to combined short- and long-term treatment components and optimised chances of receiving at least one active treatment cycle. Adherence to treatment and the positive safety profile in the first year of the study were confirmed by a low discontinuation rate and a low incidence of systemic reactions. Publication History Article published online: 26 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany