Relative potency in SPT of solution and tablet SLIT allergen extracts of Timothy grass pollen from 2 European manufacturers compared to a US reference extract

Methods This is a prospective, multicenter, triple blinded, randomized study in which the in vivo extract potency was determined, based on the wheal size obtained in TIM allergic patients. The four tested TIM extracts were: Soluprick, Staloral 300IR, and Grazax and Oralair 300IR dissolved in 1mL 50% glycerin (under GMP standards). The SPTs were carried out in quadruplicate with the concentrate extracts and three serial half-log dilutions, and +/controls. The study took place at study sites with different climatologic conditions. To determine if there exists a statistically significant difference between the relative potency of the TIM extracts a parallel line bioassay was carried out using the mean surface of the four wheals of the SPTs per extract and per concentration (Wilcoxon, Asymp. Sig.(2-tailed)). Based on the wheal sizes of the concentrate extracts in relation to the REF, BAU values were calculated.