Major Allergen Content of SQ-House Dust Mite Slit-Tablets Is Consistent and in Concordance with Patient Sensitivity Profiles in North America and Europe

Consistency in composition and potency, particularly regarding major allergens, is crucial for allergen immunotherapy efficacy and safety. We compared allergen sensitivity profiles for house dust mite (HDM) in North American and European patients with the allergen content of commercially available US HDM extracts and an SQ-HDM sublingual immunotherapy tablet (SLIT-tablet; MK-8237; Merck/ALK). Sensitivity towards Der p 1, Der p 2, and Der p 10 allergens was determined in randomly selected subgroups of 220 subjects from European and North American SQ-HDM SLIT-tablet trials. Der 1/Der 2 ratios were determined in 10,000 and 30,000 AU/mL HDM extracts from 3 US companies. SQ-HDM SLIT-tablets are produced by mixing body and fecal fractions of Dermatophagoides farinae and Dermatophagoides pteronyssinus to achieve a 1:1:1:1 ratio between Der f 1/2 and Der p 1/2 allergens. Allergen content was analyzed by ELISA and compared with an in-house reference. Subject sensitization profiles indicated high reactivity frequencies towards Der p 1 and Der p 2 regardless of geographic region. The average Der 1/Der 2 ratio in US extracts ranged from 1:1 to 5:1. For SQ-HDM SLIT-tablet (20 batches), normalized mean (SD) content for Der f 1, Der p 1, and combined Der 2 allergens was 1.000 (0.119), 1.000 (0.061), and 1.000 (0.064) units, respectively. Other HDM allergens were also present. Der 1/Der 2 are major HDM allergens in North American and European populations. The described process enables content control of each major allergen and results in SQ-HDM SLIT-tablets containing both mites, and consistent and equivalent Der 1/Der 2 content.