Sublingual immunotherapy for aeroallergens: status in the United States

Sublingual immunotherapy (SLIT) has been used in the treatment of allergic disease for nearly 30 years and is prescribed at least as frequently as subcutaneous immunotherapy (SCIT). Several large U.S. clinical trials using single allergen tablets (grass and ragweed) or extract solution (ragweed) have met their primary clinical efficacy outcome. In December, 2013 the Federal Drug Administration (FDA) Allergenic Products Advisory Committee favorably reviewed two grass tablet product formulations; the FDA usually follows the recommendations of their advisory committees. Industry-sponsored and investigator-initiated aeroallergen SLIT clinical trials conducted in the United States are the focus of this article. To provide a basis for evaluation of this treatment, SLIT mechanisms, pharmacokinetics, efficacy as reported in systematic reviews, and safety are also discussed. Practical considerations of SLIT in the clinical setting are reviewed. These include patient instructions and adherence, which appear to be as poor as SCIT. Estimated treatment costs based on U.S.-licensed allergen extract manufacturers' list prices and doses reported to be effective in studies using U.S.-licensed allergen extracts or the allergen immunotherapy practice parameters are presented. Unmet needs, which include unknown effective dose for many allergen extracts, optimal schedule (daily versus other) and timing of treatment initiation (perennial versus precoseasonal, ≥8 weeks before or just at the start of season), and whether epinephrine autoinjectors should be routinely prescribed for SLIT patients are discussed.