---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-380165"
form_type: "8-K"
ticker: "RARE"
cik: "0001515673"
company_name: "Ultragenyx Pharmaceutical Inc."
filed_at: "2026-09-02T20:04:05+00:00"
generated_at: "2026-09-02T20:06:37.238772+00:00"
event_type: "other_material"
sentiment: "negative"
materiality_score: 1.0
calibrated_materiality_score: 1.0
confidence: "high"
source: SEC EDGAR
---

# Ultragenyx Phase 3 Aspire fails primary and key secondary endpoints in Angelman syndrome

## Summary
- Apazunersen (GTX-102) did not meet primary endpoint (Bayley-4 cognitive raw score change) nor key secondary (MDRI net response).
- No differences vs control on Bayley Cognition raw scores or MDRI mean changes across five individual endpoints.
- Safety profile in Aspire consistent with Phase 1/2; randomized groups comparable at baseline.
- Company will evaluate apazunersen program disposition and implement significant expense reductions while supporting commercial business.

## SEC filing metadata
- accession: 0001193125-26-380165
- form_type: 8-K
- ticker: RARE
- cik: 0001515673
- company_name: Ultragenyx Pharmaceutical Inc.
- filed_at: 2026-09-02T20:04:05+00:00
- event_type: other_material
- sentiment: negative
- materiality_score: 1.0
- calibrated_materiality_score: 1.0
- confidence: high
- sec_items: 8.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1515673/000119312526380165/0001193125-26-380165-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1515673/000119312526380165/rare-20260902.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-380165
- JSON: https://secwatch.observer/filing/0001193125-26-380165.json
- Plain text: https://secwatch.observer/filing/0001193125-26-380165.txt

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