---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-043342"
form_type: "8-K"
ticker: "RGNX"
cik: "0001590877"
company_name: "REGENXBIO Inc."
filed_at: "2026-02-10T23:59:59+00:00"
generated_at: "2026-05-16T03:35:48.374061+00:00"
event_type: "regulatory"
sentiment: "negative"
materiality_score: 0.85
calibrated_materiality_score: 0.85
confidence: "high"
source: SEC EDGAR
---

# FDA rejects REGENXBIO's RGX-121 BLA for MPS II; company plans resubmission

## Summary
- FDA issued CRL on Feb 7, 2026 for RGX-121 (clemidsogene lanparvovec) to treat MPS II (Hunter syndrome).
- CRL cites uncertainty in defining neuronopathic population, external control comparability, and surrogate endpoint CSF HS D2S6.
- FDA suggests new study, additional patients, longer follow-up, or untreated control arm; company calls it 'devastating'.
- REGENXBIO plans to request Type A meeting and aim for BLA resubmission with additional data.
- Company had believed it addressed FDA's concerns during BLA review; independent experts supported data.

## SEC filing metadata
- accession: 0001193125-26-043342
- form_type: 8-K
- ticker: RGNX
- cik: 0001590877
- company_name: REGENXBIO Inc.
- filed_at: 2026-02-10T23:59:59+00:00
- event_type: regulatory
- sentiment: negative
- materiality_score: 0.85
- calibrated_materiality_score: 0.85
- confidence: high
- sec_items: 7.01, 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1590877/000119312526043342/0001193125-26-043342-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1590877/000119312526043342/rgnx-20260207.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-043342
- JSON: https://secwatch.observer/filing/0001193125-26-043342.json
- Plain text: https://secwatch.observer/filing/0001193125-26-043342.txt

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