Ultragenyx reported a positive mid‑trial readout from its Phase 3 program testing a gene therapy for ornithine transcarbamylase (OTC) deficiency, meeting one of two co‑primary endpoints. The company said the treatment reduced blood ammonia levels in a 37‑patient study, a direct biomarker of urea cycle function. Ultragenyx framed the result as an important clinical signal while the program continues to mature toward regulatory filings. The data were disclosed by Ultragenyx in company statements and trial briefings; full datasets and the second co‑primary endpoint remain pending. OTC deficiency is an ultra‑rare, life‑threatening metabolic disorder in which correcting ammonia handling can translate to meaningful clinical benefit. Sponsors and investors will watch the second endpoint and safety follow‑up ahead of any submission planning.