UX143-CL203 is a long-term extension study in adults with OI who participated in the ASTEROID study (also referred to as MBPS205) [NCT03118570]. The UX143-CL203 study comprises Observation, Retreatment, and Extension Periods. There is no intervention during the Observation Period. During the single-arm Retreatment Period, participants receive open-label setrusumab once a month (QM) for 12 months. Following the Retreatment Period, participants enter an Extension Period in which they will continue treatment with open-label setrusumab at different dosing frequencies.
The primary objective of the study is to evaluate bone mineral density (BMD) after 12 months of retreatment with monthly setrusumab in adults with osteogenesis imperfecta (OI).