---
schema_version: "secwatch.filing_event.v1"
accession: "0000950170-25-095334"
form_type: "8-K"
ticker: "RARE"
cik: "0001515673"
company_name: "Ultragenyx Pharmaceutical Inc."
filed_at: "2025-07-11T23:59:59+00:00"
generated_at: "2026-05-18T06:54:59.019966+00:00"
event_type: "regulatory"
sentiment: "negative"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# FDA issues Complete Response Letter for Ultragenyx UX111 BLA; resubmission planned with 6-month review

## Summary
- FDA CRL received July 11, 2025, for UX111 (ABO-102) AAV gene therapy for Sanfilippo syndrome type A.
- CRL requests additional CMC documentation and addresses observations from manufacturing facility inspections.
- Company states observations are readily addressable and unrelated to product quality; clinical data package not cited.
- FDA acknowledged robust neurodevelopmental outcome data and supportive biomarker evidence; updated clinical data requested.
- Ultragenyx plans to resubmit BLA within months, expecting up to 6-month FDA review period.

## SEC filing metadata
- accession: 0000950170-25-095334
- form_type: 8-K
- ticker: RARE
- cik: 0001515673
- company_name: Ultragenyx Pharmaceutical Inc.
- filed_at: 2025-07-11T23:59:59+00:00
- event_type: regulatory
- sentiment: negative
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 8.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1515673/000095017025095334/0000950170-25-095334-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1515673/000095017025095334/rare-20250711.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0000950170-25-095334
- JSON: https://secwatch.observer/filing/0000950170-25-095334.json
- Plain text: https://secwatch.observer/filing/0000950170-25-095334.txt

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