Comparison of the biological potency of different allergen extracts: implications for future galenic application forms of SLIT

Background: The ARIA (Allergic Rhinitis and its Impact on Asthma) group recommends an at least 50-100 times higher dose for sublingual immunotherapy (SLIT) compared to the subcutaneous route to be effective. However, it is difficult for the allergologist in daily practice to identify solutions with a sufficient concentration due to the fact that all manufacturers have chosen different allergen standardization methods. The dosage question is also important in the development of new galenic forms for SLIT. Methods: The biological activity of the two SLIT products most often prescribed in Germany (SLIT-one (R) und Staloral (R))was investigated in a randomized, double-blind trial with three parallel groups of 30 patients allergic to birch, grasses and mites using skin prick tests according to the Nordic Guidelines as described in the EAACI (European Academy of Allergology and Clinical Immunology) position paper about allergen standardization and skin prick testing with different allergen concentrations (10 IR/ml, 100 IR/ml, 300 IR/ml, 1,000 STU/ml). Results: The concentration of SLITone (R) (1,000 STU/ml) was significantly higher than the concentration of Staloral (R) 10 IR and significantly below the solutions with 100 IR/ml and 300 IR/ml. Based on the usual daily dose, the biological activity as determined by skin prick testing is eight times higher for birch and grasses and 22 times higher for mites with Staloral (R). Conclusion: Exchange rates for allergen solutions of the two leading manufacturers on the market were calculated which allow a comparison of different standardization units. These results may also be of relevance to the decision which dose window to choose in the development of new galenic forms of SLIT.