Similar biological activity in skin prick test for Oralair® (8.200BAU) and Grazax®(6.200BAU) reinforces effective SLIT dosing level

Abstract

In Europe, allergen extracts are standardized based on skin-prick wheal-size in 20-30 allergic subjects. To understand the biologic activity of clinically effective SLIT, we used this method to determine the biologic activity of solution and tablet Timothy grass pollen (TIM) extracts, compared to an FDA approved extract (Reference) of 10.000BAU/mL.

Blinded, quadruplicate SPTs with concentrate and three serial half-log dilutions, allowed construction of a semi-logarithmic regression line per extract. BAU values were obtained from comparison with Reference.

Extracts and dilutions showed a neat linear dose-response (all: R²>0.98) in 33 rhinitis patients. Relative potencies: Staloral^® 12.000BAU/mL, Soluprick^® 10.300BAU/mL, Oralair^® 8.200BAU, Grazax^® 6.200BAU. Even though all extract concentrates differed in wheal-size (p= 0.01-0.001), Grazax^® producing a 25% smaller wheal-size than Oralair^®, the biological activity of these clinically effective TIM tablets led in the same range (6.200-8.200BAU; 0.92-1.23cm²). SLIT dose-finding studies for other pollens might start with allergen extracts producing 1.1cm² wheal surface.

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