Ultragenyx and Mereo BioPharma Stocks Crash After Late-Stage Setrusumab Trials Fail in Osteogenesis Imperfecta

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Ultragenyx reported failures in Phase 3 ORBIT and COSMIC trials for setrusumab, missing primary endpoints of reducing annualized fracture rates vs. placebo and bisphosphonates.12

Trials met secondary endpoints with significant improvements in bone mineral density.12

Ultragenyx stock dropped 43% on announcement day, closing 33% down at $23; company plans major cost-cutting.13

Mereo BioPharma, holding European rights, saw shares fall nearly 90% initially; plans tight cost controls with $48.7M cash reserves.1

Unexpectedly low fracture rates in placebo arms contributed to failure; further data analysis ongoing, including subgroups like children.1

Sources:

1. https://www.noahai.co/discover/article/14086

2. https://www.mereobiopharma.com/news/phase-3-orbit-and-cosmic-results/

3. https://www.bizjournals.com/sanfrancisco/news/2025/12/29/ultragenyx-cuts-bone-osteogenesis-imperfecta-fail.html