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RARE, MREO Fall as Osteogenesis Study Likely to Continue Till Year End
ZACKSยท 2025-07-10 15:20
Core Insights - Ultragenyx Pharmaceutical (RARE) and Mereo BioPharma (MREO) have provided an update on the mid-to-late-stage Orbit study for UX143 (setrusumab) aimed at treating osteogenesis imperfecta (OI) in pediatric and young adult patients, with final analysis expected by the end of 2025 [1][5] - The shares of both companies experienced a significant decline in premarket trading following the announcement of the delay in new data from the Orbit study [2][5] - UX143 is a fully human monoclonal antibody that inhibits sclerostin, and interim safety data has shown an acceptable safety profile, allowing the study to proceed as planned [2][5] Study Details - The Orbit study is assessing the impact of UX143 on fracture rates in patients aged 5 to 25 with OI, with a pivotal phase III portion enrolling 159 additional patients [7] - The primary efficacy endpoint of the Orbit study is to reduce the annualized clinical fracture rate, with participants moving into an open-label extension period after the primary analysis [7] - The Cosmic study targets a younger population aged two to under seven years, comparing UX143 to intravenous bisphosphonates for fracture reduction, with 69 patients enrolled [8] Partnership and Market Context - Ultragenyx Pharmaceuticals and Mereo BioPharma entered a licensing agreement in 2020 for the joint development of UX143, with RARE holding exclusive rights in several regions [9] - The partnership was expanded in 2024 through a manufacturing and supply agreement, with RARE responsible for supplying setrusumab to MREO [9] - OI affects approximately 60,000 individuals in commercially accessible geographies, and there are currently no approved treatments available [11]