Ultragenyx and Mereo announce results from Phase 2/3 Orbit study

Ultragenyx Pharmaceutical (RARE) and Mereo BioPharma Group (MREO) announced positive 14-month results from the Phase 2 portion of the ongoing Phase 2/3 Orbit study demonstrating that, as of a May 24 data cut-off date, treatment with setrusumab continued to significantly reduce incidence of fractures in patients with OI with at least 14 months of follow-up. Treatment with setrusumab also resulted in ongoing and meaningful improvements in lumbar spine bone mineral density, or BMD, at month 12 without evidence of plateau. The large reduction in annualized radiologically confirmed fracture rate previously reported in patients treated for a minimum of 6 months was sustained in patients treated for at least 14 months with a high degree of significance. The median annualized rate of radiologically confirmed fractures across all 24 patients in the 2 years prior to treatment was 0.72. Following a mean treatment duration period of 16 months, the median annualized fracture rate was reduced 67% to 0.00. The annualized fracture rate excluded morphometric vertebral fractures and fractures of the fingers, toes, skull, and face, consistent with the Phase 3 study primary efficacy endpoint. The reduction in annualized fracture rates was associated with continued, clinically meaningful increases in BMD. Tests conducted at the 12-month timepoint demonstrated that treatment with setrusumab resulted in a mean increase in lumbar spine BMD from baseline of 22% across all age groups (5 to less than 26 years old), a further improvement from 14% observed at 6 months of treatment. This increase in BMD is reflected in the change from the mean baseline lumbar spine BMD Z-score of -1.73 to -0.49 at 12 months across all age groups, a substantial normalization in Z-score of +1.25. This is further improved from the mean 6-month Z-score change of +0.85. The improvements in BMD and Z-scores were significant and consistent across all OI sub-types studied.