Introduction
The mean prevalence of sensitisation to birch pollen has been estimated to range from approximately 8% to 16% in general European populations, from 9.4% to 22% across different regions of Canada and from 11% to 20% across US regions1-3. Pollen from birch and other members of the birch homologous group including alder, hornbeam, hazel, beech and oak is a major reason for allergic rhinitis and possibly also asthma symptoms1,4-6. The members of the birch homologous group are all characterized by containing allergen homologous to the major birch allergen Bet v 1.
Allergen immunotherapy (AIT) is the only available treatment modality with the potential to modify the natural course of the allergic disease by induction of tolerance7. Recently, the SQ tree sublingual immunotherapy (SLIT)-tablet received regulatory approval across Europe, Canada and Switzerland for the treatment of tree pollen allergy. Hence, a detailed analysis of existing safety data obtained with this tablet in clinical trials will be of high interest to physicians and other health care providers within the field of allergy immunotherapy. The objective of this pooled safety analysis is therefore to provide detailed safety data for health care workers to be used in their clinical practice.
It has been estimated that SLIT is used in 45 % of patients receiving allergen immunotherapy7, and the safety profile of SLIT appears to be favourable when compared with subcutaneous immunotherapy (SCIT)7-10. Anaphylactic reactions occur with SLIT as well as SCIT products, but they are more frequently observed with SCIT products. This is why SLIT rather than SCIT products are recommended for at-home administration. Local application site reactions occur commonly with both products7, and the local application site reactions with SLIT tend to be mild in nature, transient and self-resolving and occur most frequently early in the treatment period9,11.
Around 70 percent of individuals with tree pollen allergy also develop allergic symptoms against certain foods such as nuts and apples containing Bet v 1 homologous allergens, and the symptoms are manifested as a condition called pollen food syndrome (PFS)1,12. The safety profile of individuals with PFS will be of special interest in the present safety analysis.
The clinical programme conducted so far with the SQ tree SLIT-tablet comprise one phase-I trial, two phase II trials and one pivotal phase-III trial. All trials were conducted as randomised, parallel-group, double-blind, placebo-controlled clinical trials. This pooled safety analysis includes the two phase-II and the pivotal phase-III trials.