This is a single-center randomised controlled pilot trial conducted in Canada. Subjects will be randomised (1:1) to receive vestibular or sublingual birch pollen, grass pollen, ragweed pollen, or HDM AIT in tablet form for 28±4 days, followed by 28±4 days of sublingual administration only. The ratio will be ~ 1:1:1:1 for tree-, grass-, ragweed-pollen and HDM AIT tablet treatments, with a minimum of 30 patients in each allergen group for a total of approximately 200 randomised subjects.~Adults (18-65 years of age) who demonstrate birch, grass, ragweed, or HDM allergen skin prick test (SPT) positivity and with a history of birch pollen-, grass pollen-, ragweed pollen-, or HDM allergen-induced AR/C, with or without asthma are eligible for the trial.~Data for the primary endpoint of severity of treatment-related AEs will be collected during the first 28±4 days of treatment. The trial consists of 3 trial periods: a screening period (up to 12 weeks), a randomised two-arm treatment period of 28±4 days, and a single-arm sublingual treatment follow-up period of 28±4 days.~Screening period: Subjects will be evaluated based on eligibility criteria at visit 1 (V1).~Treatment period: the randomisation visit will be performed (V2) and eligible subjects randomised in a 1:1 ratio to vestibular or sublingual AIT tablet with the appropriate allergen for their allergen sensitization. At day 28±4, a visit will be conducted (V3) for all subjects previously receiving vestibular AIT to be switched to sublingual AIT with the appropriate allergen for their allergen sensitization. Subjects previously receiving sublingual AIT will remain on their previous treatment. All subjects will discontinue treatment after 56±8 days on treatment (V4). Subjects who would like to continue the sublingual immunotherapy tablets will be permitted to do so based on physician judgment and own expense but will no longer be part of the study.
To evaluate the tolerability of the vestibular administration route of birch pollen, grass pollen, ragweed pollen, and house dust mite (HDM) AIT tablets compared with the sublingual route in adult subjects with allergic rhinitis/conjunctivitis (AR/C)