Ultragenyx and Mereo BioPharma Announce UX143 Phase 3 Orbit Study for Osteogenesis Imperfecta Progressing to Final Analysis

Data from Orbit and Cosmic studies expected around the end of the year

NOVATO, Calif., July 09, 2025 (GLOBE NEWSWIRE) -- Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) and Mereo BioPharma Group plc (NASDAQ: MREO), today announced that the randomized, placebo-controlled Phase 3 portion of the Orbit study evaluating UX143 (setrusumab) in pediatric and young adult patients with osteogenesis imperfecta (OI) is progressing toward a final analysis consistent with the original plan, around the end of the year.

The Data Monitoring Committee (DMC) met and informed the company that UX143 demonstrates an acceptable safety profile and the company should continue the study to the final analysis.

“Based on the feedback we hear from investigators and families who participated in the studies, we are confident that increasing bone mass leads to stronger bone, less fractures, and improved physical abilities,” said Emil D. Kakkis, M.D., Ph.D., chief executive officer and president of Ultragenyx. “While we had hoped to be able to stop the study early, we look forward to having results from both Orbit and Cosmic around the end of this year.”

Consistent with the statistical analysis plan, data from the Cosmic study were not analyzed at this interim timepoint. Study conduct is going well and safety in this younger patient population is consistent with the safety profile in the other studies.

Patients will continue dosing in the ongoing Phase 3 Orbit and Cosmic clinical studies with the final analyses to be conducted after patients have been on therapy for at least 18-months. The threshold for the Phase 3 Orbit final analysis is p