Daclizumab (Zenapax®), a humanized monoclonal antibody directed against the IL-2 receptor ⍺ chain (CD25, Tac), is approved for prevention of renal allograft rejection and is under evaluation for treatment of patients with asthma and autoimmune diseases. Daclizumab inhibits Th1 and Th2 cytokine secretion and acts synergistically with dexamethasone in vitro (JACI, 2002, 109(1): S27). In this phase II trial, we studied the safety and efficacy of daclizumab in patients with moderate to severe chronic asthma.

Non-smoking asthmatics age 18-70 with baseline FEV1 50-80% predicted despite use of ≥1200 μg daily inhaled triamcinolone (TAA) or equivalent were enrolled in a randomized, multi-center, double-blind, placebo-controlled, parallel trial. Patients with demonstrated requirement for inhaled corticosteroids during run-in were randomized (3:1 active: placebo) to daclizumab (loading dose of 2 mg/kg i.v. followed by 1 mg/kg i.v. every 2 weeks) or placebo added to stable dose TAA. Starting at week 12, patients underwent 25% reduction of TAA every two weeks while continuing study drug. The primary efficacy endpoint was the change in FEV1 from baseline at week 12.

Baseline characteristics of the 116 randomized patients included: (mean ± SD) age 42.6 ± 12.5 years, disease duration 22.9 ± 13.5 years, FEV1 (% predicted) pre-bronchodilator 68.8 ± 8.7 and post-bronchodilator 80.3 ± 10.8. Eight patients have reported serious adverse events, of which 3 patients had events assessed as related to (blinded) study drug.

Preliminary safety and efficacy will be assessed following completion of study follow up visits. Unblinded analysis will be presented.