AstraZeneca's Ultomiris misses main goal in adult HSCT-TMA trial

AstraZeneca's Alexion unit reported on July 27, 2026 that its Phase III trial of Ultomiris (ravulizumab) in patients with thrombotic microangiopathy after hematopoietic stem cell transplant (HSCT-TMA) failed to reach statistical significance on its main goal. In the trial, Ultomiris did not achieve statistical significance for the primary endpoint of event-free survival through 26 weeks compared to placebo in adults and adolescents aged 12 years or older with HSCT-TMA.¹ That endpoint was defined as the time from randomisation until TMA-related clinical worsening or death, whichever occurred first.¹ Despite the miss, the company said Ultomiris showed a trend toward treatment benefit in adults and adolescents with HSCT-TMA at 26 weeks compared to placebo.¹ The company said discussions with health authorities are ongoing about how to interpret these data, including alongside real-world evidence.¹

Separately, in the open-label pediatric study ALXN1210-TMA-314, overall survival reached 87.2% at 26 weeks and 73.4% at 52 weeks, according to previously disclosed data¹, and Alexion said it is moving ahead with regulatory filings for the pediatric indication based on this data plus results from an external control study, ALX-TMA-502.

The adult study enrolled 146 patients from 18 countries across North America, South America, Europe, Asia and Australia¹, while the pediatric study enrolled 41 patients from seven countries across North America, Europe and Asia.¹

Across both trials, the safety findings held steady with the drug's established profile, matching what has been observed generally among HSCT patients. Alexion said it intends to share the full data set at an upcoming medical conference. The company noted that Ultomiris has Orphan Drug Designation in the US and Japan for HSCT-TMA, along with Breakthrough Therapy designation from the FDA for pediatric HSCT-TMA patients.¹