UX143 (setrusumab): Monoclonal Antibody for Osteogenesis Imperfecta (OI)   

OI: Abnormal bone metabolism leads to decreased bone mass, and increased bone fragility and weakness

Approximately 85% to 90% of OI cases are caused by mutations in the COL1A1 or COL1A2 genes, leading to either reduced or abnormal collagen and changes in bone metabolism. As collagen represents the foundation upon which bone is formed, individuals with OI have increased bone resorption (breakdown of old bone) and inadequate production of new bone, which leads to decreased bone mass and causes bone fragility and weakness. Individuals with OI experience bone brittleness, which leads to a high rate of fractures, including at atypical sites, bone deformities, including abnormal spine curvature, pain, decreased mobility and short stature. There are no FDA or EMA approved treatments for OI, which affects approximately 60,000 people in our territories.

Evaluating UX143 (setrusumab) to improve bone formation and density

UX143 is an investigational, fully-human monoclonal antibody that inhibits sclerostin, a protein that acts on a key bone-signaling pathway and inhibits the activity of bone-forming cells. By blocking the inhibitory effects of sclerostin, UX143 is designed to increase bone formation and density, increase the production of collagen, and increase bone mineral density and strength. Sclerostin inhibition also reduces excessive bone resorption, further improving bone density.

Mereo BioPharma completed the Phase 2b ASTEROID study of UX143 in adults with OI, which demonstrated a dose-dependent increase in bone formation, density and strength, and improvements in serum P1NP (procollagen type I N propeptide), a biomarker of bone formation and direct measure of collagen production. Ultragenyx has initiated a late-stage clinical development program that includes an ongoing pivotal Phase 2/3 study of UX143 in pediatric patients with OI, the Orbit study.

UX143 was granted Orphan Drug Designation in the United States and EU and rare pediatric disease designation in the United States and accepted into the European Medicine Agency’s Priority Medicines program (PRIME).

UX143 is being developed under a collaboration and license agreement between Mereo BioPharma and Ultragenyx.

Learn more about UX143 clinical studies