---
schema_version: "secwatch.filing_event.v1"
accession: "0000950170-24-124458"
form_type: "8-K"
ticker: "RARE"
cik: "0001515673"
company_name: "Ultragenyx Pharmaceutical Inc."
filed_at: "2024-11-12T23:59:59+00:00"
generated_at: "2026-05-30T01:49:42.247559+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.85
calibrated_materiality_score: 0.85
confidence: "high"
source: SEC EDGAR
---

# Ultragenyx reports positive Phase 1/2 data for GTX-102 in Angelman syndrome; Phase 3 Aspire study well powered

## Summary
- Week 48 Bayley-4 Cognition GSV mean change +6.7 vs minimally important difference +5 (n=40).
- Phase 3 primary endpoint Bayley-4 Raw score mean change +10.9 from baseline.
- Study >95% powered to detect treatment effect even with up to 3x higher sham response.
- MDRI net response +2.0 (p<0.0001); 80% of patients achieved net improvement in at least one domain.
- Phase 3 Aspire will enroll ~120 patients with full maternal UBE3A deletion; 48-week primary analysis.

## SEC filing metadata
- accession: 0000950170-24-124458
- form_type: 8-K
- ticker: RARE
- cik: 0001515673
- company_name: Ultragenyx Pharmaceutical Inc.
- filed_at: 2024-11-12T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.85
- calibrated_materiality_score: 0.85
- confidence: high
- sec_items: 8.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1515673/000095017024124458/0000950170-24-124458-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1515673/000095017024124458/rare-20241109.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000950170-24-124458
- JSON: https://secwatch.observer/filing/0000950170-24-124458.json
- Plain text: https://secwatch.observer/filing/0000950170-24-124458.txt

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