---
schema_version: "secwatch.filing_event.v1"
accession: "0000950170-25-100918"
form_type: "8-K"
ticker: "RARE"
cik: "0001515673"
company_name: "Ultragenyx Pharmaceutical Inc."
filed_at: "2025-07-31T23:59:59+00:00"
generated_at: "2026-05-17T22:18:19.429078+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.65
calibrated_materiality_score: 0.65
confidence: "high"
source: SEC EDGAR
---

# Ultragenyx fully enrolls Phase 3 Aspire study (129 patients) for GTX-102 in Angelman Syndrome

## Summary
- Phase 3 Aspire study fully enrolled with ~129 patients ages 4-17 with maternal UBE3A deletion.
- Participants randomized 1:1 to GTX-102 intrathecal injection or sham comparator for 48 weeks; sham can cross over after Week 48.
- Primary endpoint: Bayley-4 cognitive raw score improvement; key secondary: MDRI across five domains.
- Study completion expected H2 2026; company plans to move to topline data and regulatory submission.

## SEC filing metadata
- accession: 0000950170-25-100918
- form_type: 8-K
- ticker: RARE
- cik: 0001515673
- company_name: Ultragenyx Pharmaceutical Inc.
- filed_at: 2025-07-31T23:59:59+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.65
- calibrated_materiality_score: 0.65
- confidence: high
- sec_items: 8.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1515673/000095017025100918/0000950170-25-100918-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1515673/000095017025100918/rare-20250731.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000950170-25-100918
- JSON: https://secwatch.observer/filing/0000950170-25-100918.json
- Plain text: https://secwatch.observer/filing/0000950170-25-100918.txt

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