Astrazeneca's (AZN) Ultomiris missed the primary endpoint in a phase 3 trial in patients with thrombotic microangiopathy after stem-cell transplant, the company said Monday.

The therapy failed to achieve statistical significance for event-free survival at 26 weeks in adult and adolescent patients, though the study showed a trend toward benefit versus placebo, the company said.

Astrazeneca said discussions with regulators are ongoing regarding interpretation of the data.

In a separate phase 3 trial in pediatric patients, Ultomiris delivered clinically meaningful overall survival of 87.2% at 26 weeks at 73.4% at 52 weeks, and the company said it will advance regulatory filings for use in children.