AstraZeneca and MedImmune announced tralokinumab, an anti-interleukin-13 (IL-13) human monoclonal antibody, did not meet its primary endpoint of a significant reduction in the annual asthma exacerbation rate (AAER) in the overall population of severe, uncontrolled asthma patients, compared with placebo in Stratos 1, the first of two pivotal Phase III trials.

In a planned analysis, a clinically-relevant reduction in AAER was observed in a sub-population of patients with an elevated biomarker associated with increased IL-13 activity. This sub-group of patients will now be the focus for the future analysis of Stratos 2, the second ongoing pivotal Phase III trial.

"Severe asthma is a heterogeneous disease with significant unmet needs and we will now await the Stratos 2 results in the second half of 2017 to explore the potential to treat a sub-group of uncontrolled asthma patients with tralokinumab," Sean Bohen, Executive Vice President, Global Medicines Development and Chief Medical Officer said.

The Stratos 1 and Stratos 2 trials evaluate the efficacy and safety of tralokinumab in reducing the rate of asthma exacerbations in adults and adolescents with severe asthma, inadequately controlled despite receiving inhaled corticosteroids (ICS) plus long-acting beta2-agonist (LABA). Stratos 1 explored the potential to use biomarkers to identify patients with an enhanced response to tralokinumab. Stratos 2 is designed to validate the biomarker population identified in Stratos 1.

The safety and tolerability findings in Stratos 1 were consistent with those observed in previous trials with tralokinumab.

Potential future regulatory submissions for tralokinumab will be dependent on the combined analysis of both Stratos 1 and Stratos 2, the two pivotal trials in the Atmosphere clinical program.

Asthma affects 315 million individuals worldwide, and up to 10% of asthma patients have severe asthma which may be uncontrolled despite high doses of standard-of-care asthma controller medicines and can require the use of chronic oral corticosteroids (OCS).

The Atmosphere program is comprised of 2,298 patients at 571 sites across 27 countries including the pivotal efficacy trials, Stratos 1 and Stratos 2, along with the Tropos, Mesos and Japan Long-Term Safety (LTS) trials.

Stratos 1 and 2 are Phase III multicenter, randomized, double-blinded, parallel-group, placebo-controlled trials designed to evaluate the efficacy and safety of a regular, subcutaneous administration of tralokinumab for 52 weeks in adult and adolescent patients with severe asthma inadequately controlled despite treatment with ICS plus LABA.

Tropos is a Phase III multicenter, randomized, double-blinded, parallel-group, placebo-controlled trial for 40 weeks in adult and adolescent patients with severe asthma who require continuous treatment with ICS plus LABA, and chronic treatment with maintenance oral corticosteroid (OCS) therapy.