---
schema_version: "secwatch.filing_event.v1"
accession: "0000950170-24-138467"
form_type: "8-K"
ticker: "RARE"
cik: "0001515673"
company_name: "Ultragenyx Pharmaceutical Inc."
filed_at: "2024-12-19T23:59:59+00:00"
generated_at: "2026-05-29T01:36:05.873976+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# First patient dosed in Ultragenyx Phase 3 Aspire study of GTX-102 for Angelman syndrome

## Summary
- Global Phase 3 Aspire study will enroll ~120 children ages 4-17 with full maternal UBE3A deletion.
- Patients randomized 1:1 to GTX-102 intrathecal injections or sham comparator for 48-week primary analysis.
- Primary endpoint: cognition improvement (Bayley-4 cognitive raw score); key secondary: Multi-domain Responder Index.
- Active group receives three monthly 8 mg loading doses then quarterly maintenance up to 14 mg; sham crossover after Week 48.

## SEC filing metadata
- accession: 0000950170-24-138467
- form_type: 8-K
- ticker: RARE
- cik: 0001515673
- company_name: Ultragenyx Pharmaceutical Inc.
- filed_at: 2024-12-19T23:59:59+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 8.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1515673/000095017024138467/0000950170-24-138467-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1515673/000095017024138467/rare-20241219.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000950170-24-138467
- JSON: https://secwatch.observer/filing/0000950170-24-138467.json
- Plain text: https://secwatch.observer/filing/0000950170-24-138467.txt

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