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.