AstraZeneca and Amgen have announced that a phase III trial of their new medicine tezepelumab failed to meet the primary endpoint in patients with severe, oral corticosteroid-dependent asthma.

The SOURCE trial failed to meet the primary endpoint of a statistically significant reduction in the daily oral corticosteroids dose, without loss of asthma control, with tezepelumab compared to placebo.

However, the drug’s effect on other measures of efficacy was similar to those observed in previous trials, AZ said in a statement.

“Based on the totality of evidence, including the compelling exacerbation reduction results seen in the registrational NAVIGATOR phase III trial and the PATHWAY phase IIb trial, we remain confident that tezepelumab has the potential to improve care for a broad population of severe asthma patients,” said Mene Pangalos, executive vice president, BioPharmaceuticals R&D.

“Our initial analysis of SOURCE in oral corticosteroid-dependent asthma indicates that the trial design may have contributed to the result of the primary endpoint. We are in the process of further analysing the data from SOURCE and look forward to sharing these results with the medical community,” he added.

Tezepelumab is a monoclonal antibody designed to inhibit the action of  thymic stromal lymphopoietin, a key epithelial cytokine which is critical in the initiation and persistence of allergic, eosinophilic and other types of airway inflammation associated with severe asthma.

In November, AZ and Amgen announced positive results from the NAVIGATOR phase III trial, which met the primary endpoint and demonstrated a statistically significant reduction in the annualised asthma exacerbation rate.