REGENXBIO Inc. Reports FDA Clinical Hold on RGX-121 (MPS II)

What Happened

• On August 24, 2026, REGENXBIO Inc. (RGNX) announced it received communication from the U.S. Food and Drug Administration that the company’s Investigational New Drug (IND) application for its Phase I/II/III trial of RGX-121 (for Mucopolysaccharidosis type II, aka Hunter Syndrome) was placed on clinical hold. The company also stated it does not expect to resubmit the RGX-121 Biologics License Application (BLA) in the near term. The announcement was filed on Form 8-K (Items 7.01 and 8.01) and a press release was furnished as Exhibit 99.1.

Key Details

• Date of notice: August 24, 2026.
• Program impacted: RGX-121 for Mucopolysaccharidosis type II (Hunter Syndrome).
• Regulatory status: IND placed on clinical hold by the FDA; company does not expect to resubmit the BLA soon.
• Filing: Announcement furnished as Exhibit 99.1 to the Form 8-K (Items 7.01, 8.01, 9.01).

Why It Matters

• A clinical hold pauses the company’s ability to proceed under the RGX-121 IND, delaying clinical development and any near-term pathway to FDA approval for this program.
• Because REGENXBIO has stated it does not expect to resubmit the RGX-121 BLA in the near term, this creates increased regulatory uncertainty and potential delays to future revenue from this candidate.
• Investors should watch for subsequent updates from REGENXBIO about the reasons for the hold, planned next steps, timing for any resubmission, and any impacts to company guidance or resource allocation.