---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-026139"
form_type: "8-K"
ticker: "RGNX"
cik: "0001590877"
company_name: "REGENXBIO Inc."
filed_at: "2026-01-28T23:59:59+00:00"
generated_at: "2026-05-16T06:59:46.316829+00:00"
event_type: "regulatory"
sentiment: "negative"
materiality_score: 0.85
calibrated_materiality_score: 0.85
confidence: "high"
source: SEC EDGAR
---

# FDA places clinical hold on REGENXBIO's RGX-111 and RGX-121 gene therapies after neoplasm case

## Summary
- Single neoplasm (intraventricular CNS tumor) found in 5-year-old asymptomatic patient 4 years post-RGX-111 dose; AAV vector integration detected near PLAG1 proto-oncogene.
- RGX-121 placed on hold due to product, population, and risk similarities with RGX-111.
- No neoplasms reported in 9 other RGX-111 or 32 RGX-121 patients.
- CEO surprised by RGX-121 hold while investigation continues; confident in benefit-risk based on positive safety and efficacy data.
- Company has not yet received full clinical hold letter and awaits FDA details.

## SEC filing metadata
- accession: 0001193125-26-026139
- form_type: 8-K
- ticker: RGNX
- cik: 0001590877
- company_name: REGENXBIO Inc.
- filed_at: 2026-01-28T23:59:59+00:00
- event_type: regulatory
- sentiment: negative
- materiality_score: 0.85
- calibrated_materiality_score: 0.85
- confidence: high
- sec_items: 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1590877/000119312526026139/0001193125-26-026139-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1590877/000119312526026139/rgnx-20260123.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-026139
- JSON: https://secwatch.observer/filing/0001193125-26-026139.json
- Plain text: https://secwatch.observer/filing/0001193125-26-026139.txt

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