Amgen and AstraZeneca announced the SOURCE trial did not meet the primary endpoint of a statistically significant reduction in the daily oral corticosteroid (OCS) dose, without loss of asthma control, with tezepelumab compared to placebo.

The 48-week trial assessed the efficacy and safety of the potential new medicine tezepelumab compared to placebo in 150 severe asthma patients who required maintenance use of oral corticosteroids (OCS) on top of standard of care (SoC). Tezepelumab's effect on other efficacy parameters was similar to those observed in previous studies, including the registrational Phase 3 NAVIGATOR study. Further analyses of the data are ongoing.

The safety profile of tezepelumab in the trial was consistent with previous trials. Detailed results from the SOURCE trial will be presented at a future medical meeting.

"The recent results from our NAVIGATOR trial were impressive, both in terms of the overall clinical data and the reduction in exacerbation rate with tezepelumab treatment, and we continue to work with AstraZeneca on planned regulatory filings in 2021. While the SOURCE results were surprising, they provide important insights into the use of oral corticosteroids and the patients who are receiving them, which we look forward to exploring further," said David M. Reese, M.D., executive vice president of Research and Development at Amgen. "On initial review, the study design may have contributed to the results observed on the primary endpoint."

On November 10th, 2020, AstraZeneca and Amgen announced positive results from the NAVIGATOR Phase 3 trial which met the primary endpoint and demonstrated a statistically significant and clinically meaningful reduction in the annualized asthma exacerbation rate (AAER) in a broad population of patients with severe asthma, including those with low levels of eosinophils.

Tezepelumab is a potential first-in-class medicine that blocks the action of thymic stromal lymphopoietin (TSLP), an epithelial derived cytokine that plays a key role across the spectrum of asthma inflammation.

Severe asthma is a complex, heterogenous disease and many patients continue to face debilitating symptoms despite receiving standard of care inhaled medicines and currently approved biologics.

In September 2018, the US Food and Drug Administration granted Breakthrough Therapy Designation for tezepelumab in patients with severe asthma, without an eosinophilic phenotype. Tezepelumab is being developed by AstraZeneca in collaboration with Amgen.