Positive results for Ultragenyx and Mereo setrusumab in OI

Interim Phase II data from the Phase II/III Orbit study, presented this weekend at the at the American Society for Bone and Mineral Research (ASBMR) 2023 Annual Meeting, demonstrate setrusumab resulted in 67% reduction in annualized fracture rate, as well as continuous and meaningful improvements in bone mineral density (BMD) in patients with osteogenesis imperfecta (OI), a serious, rare genetic disorder characterized by fragile bones that fracture easily.

Setrusumab is being developed by the USA’s Ultragenyx Pharmaceuticals (Nasdaq: RARE) – whose shares rose 6.6% to $35.02 - and UK-based Mereo BioPharma (Nasdaq: MREO) – which rocketed 18.6% to $1.53 on the news. Mereo licensed the drug, already a Novartis (NOVN: VX) cast-off, to Ultragenyx in 2020, in a deal worth a potential $300 million to the British firm.

As of the cut-off date and following at least six months of treatment with setrusumab, the annualized fracture rate across all 24 patients in the Phase II portion of the study was reduced by 67%. In the two years prior to treatment with setrusumab all patients experienced at least one fracture. The median annualized fracture rate of 0.72 in the two years prior to treatment was reduced to 0.00 (n=24, p=0.042) during the mean treatment duration period of nine months. Following initiation of treatment with setrusumab, 20 patients experienced no radiographic-confirmed fractures, and four patients experienced seven radiographic-confirmed fractures in five separate events. These fractures exclude fractures of the fingers, toes, skull, and face consistent with the Phase III study design.