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 8, 2018

REGENXBIO INC.

(Exact Name of Registrant as Specified in its Charter)

(240) 552-8181

(Registrant’s telephone number, including area code)

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 (see General Instruction A.2. below):

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 under the Securities Act of 1933 (17 CFR 230.405) or Rule 12b-2 under the Securities Exchange Act of 1934 (17 CFR 240.12b-2).

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.  ☒

On August 8, 2018, REGENXBIO Inc. (the “Company”) issued a press release regarding its results of operations and financial condition for the quarter ended June 30, 2018. The press release is furnished as Exhibit 99.1 to this Current Report on Form 8‑K and is incorporated by reference herein.

The Company expects to discuss certain presentation materials (the “Presentation Materials”) during its conference call and webcast scheduled to begin at 8:00 a.m. Eastern Time on August 8, 2018. The Presentation Materials are furnished as Exhibit 99.2 to this Current Report on Form 8-K. The Presentation Materials include selected financial information relating to the Company, and the portion of the Presentation Materials including such financial information is incorporated by reference herein.

Item 7.01.Regulation FD Disclosure.

The Presentation Materials described in Item 2.02 above are incorporated by reference herein.

The information in Items 2.02 and 7.01 of this Current Report on Form 8‑K and Exhibits 99.1 and 99.2 attached hereto shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to liability under that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing.

(d)Exhibits

SIGNATURE

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.