REGENXBIO FDA extends RGX-121 PDUFA to Feb 2026

Rhea-AI Filing Summary

REGENXBIO Inc. reported that the U.S. Food and Drug Administration has extended the review timeline for its biologics license application seeking accelerated approval of clemidsogene lanparvovec (RGX-121), a treatment for Mucopolysaccharidosis II (Hunter syndrome). The FDA moved the Prescription Drug User Fee Act (PDUFA) action date from November 9, 2025 to February 8, 2026 to allow additional time to review new data submitted for the application.

Insights

Biotech regulatory and drug development analyst

FDA pushes RGX-121 decision about three months to review more data.

The update centers on the FDA extending the PDUFA action date for REGENXBIO's biologics license application for RGX-121, an accelerated approval candidate for Mucopolysaccharidosis II. The decision date shifts from November 9, 2025 to February 8, 2026 so regulators can evaluate additional data.

In drug development, an extension typically means regulators see value in new information but need more time to assess it. While this does not indicate an approval or rejection outcome, it does delay any potential regulatory decision and the associated timing of possible commercialization for RGX-121.

Investors will likely focus on how RGX-121 fits into REGENXBIO's broader rare disease portfolio and whether future disclosures around the submission and data package provide more clarity before the updated February 8, 2026 action date.

8-K Event Classification

2 items: 8.01, 9.01

2 items

Item 8.01 Other Events Other

Voluntary disclosure of events the company deems important to shareholders but not covered by other items.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, or exhibit attachments filed with this report.

FAQ

What did REGENXBIO (RGNX) announce regarding its RGX-121 program?

REGENXBIO announced that the FDA has extended the Prescription Drug User Fee Act (PDUFA) action date for its biologics license application for clemidsogene lanparvovec (RGX-121), which seeks accelerated approval to treat Mucopolysaccharidosis II (Hunter syndrome).

How much did the FDA extend the RGX-121 PDUFA date for REGENXBIO (RGNX)?

The FDA extended the PDUFA action date for RGX-121 from November 9, 2025 to February 8, 2026 to allow time for review of additional data submitted with the application.

What indication is REGENXBIO (RGNX) seeking for clemidsogene lanparvovec (RGX-121)?

REGENXBIO is seeking accelerated approval of clemidsogene lanparvovec (RGX-121) for the treatment of Mucopolysaccharidosis II (MPS II), also known as Hunter syndrome.

Did REGENXBIO (RGNX) say why the FDA extended the RGX-121 PDUFA date?

Yes. REGENXBIO stated that the FDA extended the PDUFA action date for RGX-121 to February 8, 2026 in order to allow for the review of additional data related to the biologics license application.

Where can investors find more details on the REGENXBIO (RGNX) RGX-121 update?

Additional details are provided in a REGENXBIO press release dated August 18, 2025, which is included as Exhibit 99.1 and incorporated by reference in the report.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 08/18/2025 - 05:10 PM Learn about SEC filing dates

0001590877false00015908772025-08-182025-08-18

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): August 18, 2025

REGENXBIO Inc.

(Exact name of Registrant as Specified in Its Charter)

Delaware			001-37553	47-1851754
(State or Other Jurisdiction of Incorporation)			(Commission File Number)	(IRS Employer Identification No.)
9804 Medical Center Drive
Rockville, Maryland				20850
(Address of Principal Executive Offices)				(Zip Code)

Registrant’s Telephone Number, Including Area Code: (240) 552-8181

N/A

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, par value $0.0001 per share		RGNX		The Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01. Other Events.

On August 18, 2025, REGENXBIO Inc. (the “Company”) issued a press release announcing that the U.S. Food and Drug Administration (“FDA”) has extended the Prescription Drug User Fee Act (“PDUFA”) date for the Company’s Biologics License Application seeking accelerated approval of clemidsogene lanparvovec (RGX-121) for the treatment of Mucopolysaccharidosis II (MPS II), also known as Hunter syndrome. The FDA extended the PDUFA action date from November 9, 2025 to February 8, 2026 to allow for the review of additional data.

A copy of the press release is filed herewith as Exhibit 99.1 to this Current Report on Form 8-K and incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits

Exhibit No.		Description
99.1		Press release dated August 18, 2025.
104		The cover page from this Current Report on Form 8-K, formatted in Inline XBRL.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

			REGENXBIO INC.
Date:	August 18, 2025	By:	/s/ Patrick J. Christmas II
			Patrick J. Christmas II Executive Vice President, Chief Strategy & Legal Officer