Ultragenyx UX111 gene therapy shows significant cognitive benefit in MPS IIIA; BLA resubmitted with PDUFA Q3 2026

Ultragenyx Pharmaceutical Inc.

Children under 2 treated with UX111 showed +23.2 point improvement in Bayley-III cognitive raw score vs natural history (p<0.0001).
81.5% of overall efficacy set achieved ≥50% reduction in CSF heparan sulfate; median reduction 63.98% (p<0.001).
Functional retention observed: all older children retained communication; 9/10 retained ambulation and self-feeding.
UX111 well-tolerated with median follow-up 4.8 years; no TMA, myocarditis, DRG toxicity, or malignancy.
BLA resubmitted to FDA seeking accelerated approval; PDUFA date expected in Q3 2026.

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