Ultragenyx gene therapy hits a primary endpoint in rare ammonia disorder trial

Ultragenyx reported that its gene therapy candidate for ornithine transcarbamylase (OTC) deficiency met one of two primary endpoints in a Phase 3 trial involving 37 patients with blood ammonia dysregulation. The company said the readout represents a key efficacy signal for a rare urea‑cycle disorder that causes life‑threatening hyperammonemia. While the second primary endpoint remains outstanding, the hit advances Ultragenyx’s regulatory and commercial positioning for a genetic metabolic indication with high unmet need.