REGENXBIO (RGNX) says FDA puts RGX-111 and RGX-121 MPS trials on hold

Rhea-AI Filing Summary

REGENXBIO Inc. reported that the U.S. Food and Drug Administration has placed clinical holds on two of its gene therapy programs. On January 28, 2026, the FDA put the Company’s Investigational New Drug applications for the Phase I/II trial of RGX-111 for Mucopolysaccharidosis type I and the Phase I/II/III trial of RGX-121 for Mucopolysaccharidosis type II on clinical hold. The Company disclosed this development and filed the related press release as an exhibit.

Positive

• None.

Negative

• FDA clinical holds on two key programs: The FDA placed the Phase I/II RGX-111 trial for Mucopolysaccharidosis type I and the Phase I/II/III RGX-121 trial for Mucopolysaccharidosis type II on clinical hold, creating meaningful uncertainty for these development programs.

Insights

Biotech regulatory and clinical-stage analyst

FDA clinical holds on two MPS trials create significant development risk.

REGENXBIO disclosed that the FDA placed clinical holds on its Phase I/II RGX-111 program for Mucopolysaccharidosis type I and Phase I/II/III RGX-121 program for Mucopolysaccharidosis type II. A clinical hold pauses study activities under the Investigational New Drug applications.

This affects two rare disease gene therapy programs simultaneously, which can be material for a company focused on these indications. The specific reasons for the holds, any requested actions, or timing for resolution are not described in the excerpt.

The company attached a press release dated January 28, 2026 as an exhibit, which may provide additional detail. The future path for these trials will depend on FDA feedback and the company’s responses, which are not outlined here.

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, and exhibit attachments filed with this report.

Understanding 8-K Material Events →

0001590877false00015908772026-01-232026-01-23

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): January 23, 2026

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 January 28, 2026, REGENXBIO Inc. (the “Company”) announced that it received communication from the U.S. Food and Drug Administration (“FDA”) that the Company’s Investigational New Drug applications for both its Phase I/II trial evaluating RGX-111 for Mucopolysaccharidosis type I and its Phase I/II/III trial of RGX-121 for Mucopolysaccharidosis type II were placed on clinical hold.

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 January 28, 2026.
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:	January 28, 2026	By:	/s/ Patrick J. Christmas II
			Patrick J. Christmas II Executive Vice President, Chief Strategy & Legal Officer

FAQ

What did REGENXBIO Inc. (RGNX) disclose in this 8-K filing?

REGENXBIO disclosed that the FDA placed clinical holds on two gene therapy programs, RGX-111 and RGX-121. These holds affect Phase I/II and Phase I/II/III trials in Mucopolysaccharidosis types I and II, and the company filed a related press release as an exhibit.

Which REGENXBIO (RGNX) clinical trials are on FDA clinical hold?

The FDA placed clinical holds on REGENXBIO’s Phase I/II trial of RGX-111 for Mucopolysaccharidosis type I and its Phase I/II/III trial of RGX-121 for Mucopolysaccharidosis type II. Both holds apply to the company’s Investigational New Drug applications for these programs.

When did REGENXBIO (RGNX) receive notice of the FDA clinical holds?

REGENXBIO stated that on January 28, 2026, it received communication from the FDA that its Investigational New Drug applications for RGX-111 and RGX-121 were placed on clinical hold. The company also issued a press release dated the same day, filed as Exhibit 99.1.

What is the subject of REGENXBIO’s Exhibit 99.1 in this 8-K?

Exhibit 99.1 is a press release dated January 28, 2026. The press release addresses the FDA’s decision to place clinical holds on REGENXBIO’s RGX-111 Phase I/II trial and RGX-121 Phase I/II/III trial for Mucopolysaccharidosis types I and II, respectively.

Does the REGENXBIO (RGNX) filing explain why the FDA imposed clinical holds?

The excerpt notes that the FDA placed the RGX-111 and RGX-121 trials on clinical hold but does not describe the reasons. It references a January 28, 2026 press release, filed as Exhibit 99.1, which may contain further details beyond this summarized text.