Methods: 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.
Results: 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.
Conclusions: 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.