AstraZeneca (NASDAQ: AZN) reported that its drug Ultomiris (ravulizumab) failed to achieve statistical significance for the primary endpoint in a Phase III clinical trial involving adults and adolescents with thrombotic microangiopathy after haematopoietic stem cell transplant (HSCT-TMA).

The ALXN1210-TMA-313 trial measured event-free survival through 26 weeks compared to placebo in patients aged 12 years or older. The primary endpoint was defined as the time from randomization until TMA-related clinical worsening or death, whichever occurred first. Ultomiris showed a trend toward treatment benefit at 26 weeks, and AstraZeneca said discussions with health authorities are ongoing regarding interpretation of the data, including in the context of real-world evidence.

In a separate open-label Phase III trial of pediatric patients with HSCT-TMA, Ultomiris demonstrated overall survival of 87.2% at 26 weeks and 73.4% at 52 weeks. Alexion, AstraZeneca Rare Disease is advancing regulatory filings for Ultomiris in pediatric patients based on those results and data from an external control study.

HSCT-TMA is estimated to affect fewer than 6,000 people in the U.S. Ultomiris holds Orphan Drug Designation in the U.S. and Japan for the treatment of HSCT-TMA, as well as Breakthrough Therapy designation from the FDA for treatment of pediatric patients with the condition.

The safety profile observed across both trials was consistent with the known safety profile of Ultomiris. AstraZeneca said it plans to present the data at a forthcoming medical meeting.