---
schema_version: "secwatch.filing_event.v1"
accession: "0000950170-24-066553"
form_type: "8-K"
ticker: "RARE"
cik: "0001515673"
company_name: "Ultragenyx Pharmaceutical Inc."
filed_at: "2024-05-30T23:59:59+00:00"
generated_at: "2026-06-01T07:22:58.218642+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.85
calibrated_materiality_score: 0.85
confidence: "high"
source: SEC EDGAR
---

# Ultragenyx Phase 3 DTX401 gene therapy meets primary endpoint in GSDIa

## Summary
- DTX401 reduced daily cornstarch intake by 41.3% vs 10.3% for placebo at Week 48 (p<0.0001).
- 68% of DTX401 patients achieved ≥30% reduction; 37% achieved ≥50% reduction.
- Secondary endpoint met: 1.1 fewer cornstarch doses/day vs 0.2 for placebo (p=0.0011).
- Safety profile acceptable; no dorsal root ganglion toxicity or thrombotic microangiopathy observed.
- Company plans to discuss results with regulators and submit marketing application in 2025.

## SEC filing metadata
- accession: 0000950170-24-066553
- form_type: 8-K
- ticker: RARE
- cik: 0001515673
- company_name: Ultragenyx Pharmaceutical Inc.
- filed_at: 2024-05-30T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.85
- calibrated_materiality_score: 0.85
- confidence: high
- sec_items: 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1515673/000095017024066553/0000950170-24-066553-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1515673/000095017024066553/rare-20240530.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000950170-24-066553
- JSON: https://secwatch.observer/filing/0000950170-24-066553.json
- Plain text: https://secwatch.observer/filing/0000950170-24-066553.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.