Similar biological activity in skin prick test for Oralair® (8200 BAU) and Grazax® (6200 BAU) reinforces effective SLIT dosing level.

In Europe, allergen extracts are standardized based on skin prick wheal size in 20-30 allergic subjects. To understand the biological activity of clinically effective Sublingual immunotherapy, we used this method to determine the biological activity of solution and tablet Timothy grass pollen ( TIM) extracts, compared to an FDA-approved extract (Reference) of 10 000 BAU/ml. Blinded, quadruplicate skin prick tests with concentrate and three serial half-log dilutions allowed the construction of a semilogarithmic regression line per extract. Bioequivalent allergy units ( BAU) values were obtained from the comparison with reference. Extracts and dilutions showed a neat linear dose response (all: R² > 0.98) in 33 rhinitis patients. Relative potencies: Staloral^® 12 000 BAU/ml, Soluprick^® 10 300 BAU/ml, Oralair^® 8200 BAU, and Grazax^® 6200 BAU. Even though all extract concentrates differed in wheal size ( P = 0.01-0.001), Grazax^® producing a 25% smaller wheal size than Oralair^®, and the biological activity of these clinically effective TIM tablets led in the same range (6200-8200 BAU; 0.92-1.23 cm²). SLIT dose-finding studies for other pollens might start with allergen extracts producing 1.1 cm² wheal surface. [ABSTRACT FROM AUTHOR]