Ultragenyx’s DTX301 Achieves 18% Ammonia Reduction and 27% Scavenger Med Cut at Week 36
Ultragenyx’s DTX301 Phase 3 study showed an 18% reduction in 24-hour plasma ammonia (p=0.018) at Week 36, maintaining normal ammonia levels with a 27% cut in ammonia scavenger medications. Treated patients reported 71% much-improved global symptoms and experienced only one hyperammonemic crisis versus five in placebo.
1. Phase 3 Enh3ance Efficacy Results
DTX301-treated patients (n=18) achieved an 18% reduction in 24-hour plasma ammonia (p=0.018) at Week 36 versus placebo (n=19), maintaining mean ammonia AUC0-24 within normal range through the randomized control period.
2. Patient-Reported Improvements
At Week 24, 71% of treated patients reported being much improved on the Patient Global Impression Scale for overall OTC symptoms, while 64% showed moderate or much improvement in OTC deficiency symptoms and daily living impact versus 0–19% in placebo.
3. Safety and Tolerability
DTX301 was well tolerated with mostly mild-to-moderate transient hepatic reactions managed with steroids; one treatment-related acute hepatitis resolved with steroids. Hyperammonemic crises occurred once in the treated group (no deaths) versus five events and one death in placebo.
4. Study Continuation and Financial Impact
The Enh3ance study will progress to assess reduction in treatment burden through 64 weeks of follow-up, with data expected in the first half of 2027. This program aligns with Ultragenyx’s February 2026 spend guidance and 2027 profitability goals.