---
schema_version: "secwatch.filing_event.v1"
accession: "0000950170-24-072414"
form_type: "8-K"
ticker: "RARE"
cik: "0001515673"
company_name: "Ultragenyx Pharmaceutical Inc."
filed_at: "2024-06-12T23:59:59+00:00"
generated_at: "2026-06-01T04:49:39.428018+00:00"
event_type: "regulatory"
sentiment: "positive"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# FDA agrees CSF heparan sulfate as surrogate endpoint for UX111 accelerated approval BLA in MPS IIIA

## Summary
- FDA agreed cerebral spinal fluid heparan sulfate is a reasonable surrogate endpoint supporting accelerated approval for UX111 gene therapy in Sanfilippo syndrome type A (MPS IIIA).
- Company intends to file BLA late 2024 or early 2025 after a pre-BLA meeting with the FDA.
- BLA filing will rely on data from the ongoing pivotal Transpher A study and long-term follow-up; results were presented at WORLDSymposium.

## SEC filing metadata
- accession: 0000950170-24-072414
- form_type: 8-K
- ticker: RARE
- cik: 0001515673
- company_name: Ultragenyx Pharmaceutical Inc.
- filed_at: 2024-06-12T23:59:59+00:00
- event_type: regulatory
- sentiment: positive
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 8.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1515673/000095017024072414/0000950170-24-072414-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1515673/000095017024072414/rare-20240612.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000950170-24-072414
- JSON: https://secwatch.observer/filing/0000950170-24-072414.json
- Plain text: https://secwatch.observer/filing/0000950170-24-072414.txt

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