A phase I single blind, placebo controlled multicenter 42 day study was conducted to determine the safety, tolerance, pharmacokinetics and pharmacodynamics of rhuMAb-E25 in adolescents and children with allergic asthma. Thirty-four patients with moderate to severe allergic asthma (at least one positive skin reaction), assigned to one of 3 dose groups:Groups I and III, 12 adolescents (12-17 years) and: 12 children (6-11 years) received multiple (3) administrations (over a: 14 day period); Group II, 8 children(6-11 years) received a single administration. Each dose group included 2 dose levels (0.15mg/kg SC or 0.5mg/kg IV) and was placebo controlled. The PK/PD analyses indicate that the PK profile of rhuMAb-E25 and changes in free and total serum IgE are comparable to those in adults. rhuMAb-E25 had a slow absorption phase over several days after SC dosing and a long elimination half life of several weeks. Free serum IgE decreased in a dose dependent manner. Observed serum profiles of total IgE and rhuMAb-E25 levels across age groups and baseline total serum IgE levels confirm the previous clinical and pre-clinical data indicating that rhuMAb-E25: IgE complexes have a slower clearance rate than free IgE, but are more rapidly cleared from the circulation than uncomplexed rhuMAb-E25. Reported adverse events were related to asthma symptoms or upper respiratory infections, were of mild or moderate severity, and were similarly observed in both the placebo and rhuMAb-E25 dosed groups. Study findings suggest a favorable safety profile and supports continued examination of this drug in children. Funded by Genentech, Inc.