Ultragenyx Faces Setbacks While Advancing Gene Therapy

Ultragenyx Pharmaceutical has cut 10% of its workforce following a Phase III failure of setrusumab. Despite this, its gene therapy DTX301 for Ornithine Transcarbamylase Deficiency showed positive interim Phase III results.

In the Enh3ance study, DTX301 achieved an 18% reduction in 24-hour ammonia levels versus placebo, with levels remaining normal up to 36 weeks. Most patients with elevated baseline ammonia reached normal levels after treatment. Patient-reported outcomes were also favorable, with 71% reporting significant improvement.

The therapy demonstrated a manageable safety profile, with one treatment-related serious adverse event that resolved. Fewer hyperammonaemia crises and no deaths occurred in the treatment group compared to placebo.

The study will continue to evaluate reduction in treatment burden, with further results expected in 2027. Meanwhile, the company is working with the U.S. Food and Drug Administration to advance other gene therapy programs.

17-03-2026