RGNX / REGENXBIO Inc. - SEC-arkiveringar, Årsredovisning, Fullmaktsutlåtande

REGENXBIO INC. TERMS OF ELECTION

Exhibit (a)(1)(D) REGENXBIO INC. TERMS OF ELECTION BY PARTICIPATING, YOU AGREE TO ALL TERMS OF THE OPTION EXCHANGE AS SET FORTH IN THE OFFER TO EXCHANGE ELIGIBLE OPTIONS FOR REPLACEMENT OPTIONS, DATED JUNE 3, 2026 (AS IT MAY BE AMENDED AND SUPPLEMENTED FROM TIME TO TIME, THE “OFFER TO EXCHANGE”). ALL CAPITALIZED TERMS USED AND NOT DEFINED HEREIN SHALL HAVE THE MEANINGS GIVEN TO THEM IN THE OFFER T

How do I make my elections? You will log into the exchange website, www.myoptionexchange.com, where you can use the modeling tool to evaluate your options and make your exchange elections. Why were there two proposals in the proxy? There was one prop

Why did REGENXBIO decide to offer an option exchange program? We have a large number of underwater stock options, many of which are approaching expiration.

FORM 8-K Item 5.07 Submission of Matters to a Vote of Security Holders. Proposal 4: By the following vote, the stockholders approved, the Stock Option Exchange Program for the Company’s non-executive employees: Proposal 5: By the following vote, th

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): May 29, 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

Calculation of Filing Fee Tables SCHEDULE TO (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1 - Transaction Valuation

Exhibit 107 Calculation of Filing Fee Tables SCHEDULE TO (Form Type) REGENXBIO Inc.

First reminder email to Eligible Employees

Exhibit (a)(1)(F) 1) First reminder email to Eligible Employees • To be sent June 10th • From Infinite Equity system • To Eligible Employees Subject: The Stock Option Exchange window is now open! The voluntary Stock Option Exchange Program is currently open.

Disclaimer This presentation is provided for informational purposes only and is a summary of certain key terms of the Stock Option Exchange Program. It does not constitute a complete description of the program or its terms. The Stock Option Exchange

Stock Option Exchange Program June 2026 Exhibit (a)(1)(I) Disclaimer This presentation is provided for informational purposes only and is a summary of certain key terms of the Stock Option Exchange Program.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO (Rule 13a-4) Tender Offer Statement Under Section 14(d)(1) or 13(e)(1) of the Securities Exchange Act of 1934 REGENXBIO Inc. (Name of Subject Company (Issuer) and Fil

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE TO (Rule 13a-4) Tender Offer Statement Under Section 14(d)(1) or 13(e)(1) of the Securities Exchange Act of 1934 REGENXBIO Inc. (Name of Subject Company (Issuer) and Filing Person (Offeror)) Options to Purchase Common Stock, Par Value $0.0001 per share (Title of Class of Securities) 75901B107 (CUSIP Number of Class of

OFFER TO EXCHANGE ELIGIBLE OPTIONS FOR REPLACEMENT OPTIONS REGENXBIO INC. THIS OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 11:59 P.M., EASTERN TIME, ON JULY 1, 2026 UNLESS THIS OFFER IS EXTENDED Unless the context requires otherwise, references in this Off

Table of Contents Exhibit (a)(1)(A) OFFER TO EXCHANGE ELIGIBLE OPTIONS FOR REPLACEMENT OPTIONS   REGENXBIO INC.

Confirmation Email

Exhibit (a)(1)(E) Confirmation Email To: Eligible Employee From: [email protected] Subject: Confirmation of Election to Participate in Offer to Exchange We strongly encourage you to print this email and keep it for your records. REGENXBIO OPTION EXCHANGE PROGRAM REGENXBIO Inc. ("REGENXBIO") has received your election via the offer website, by which you elected to accept or reject REGENX

Election Form:

Exhibit (a)(1)(G) Welcome: Election Form: Confirm Election: Confirmed Election: Election Confirmation: Resources: Value Calculator:

Subject: Stock Option Exchange Program Approved and Launching Today

Exhibit (a)(1)(B) Subject: Stock Option Exchange Program Approved and Launching Today Date: 6/3/26 at 8a Dear Team, I’m pleased to share that the Stock Option Exchange Program proposal covering eligible employees below the EVP level was approved, allowing us to move forward with the program as planned.

SUBJECT: REGENXBIO Offer to Exchange Eligible Options for Replacement Options

Exhibit (a)(1)(C) SUBJECT: REGENXBIO Offer to Exchange Eligible Options for Replacement Options TO: Eligible Employees FROM: Infinite Equity We are offering you the opportunity to exchange some or all of your eligible options, as described in the Offer to Exchange Eligible Options for Replacement Options (the "Offer to Exchange"), for a number of new replacement options.

REGENXBIO Announces Positive Topline Results from Pivotal Phase III AFFINITY DUCHENNE® Study of RGX-202

EXHIBIT 99.2 REGENXBIO Announces Positive Topline Results from Pivotal Phase III AFFINITY DUCHENNE® Study of RGX-202 • Achieved primary endpoint with high statistical significance; 93% of patients achieved microdystrophin expression above 10% (p<0.0001) • Statistically significant correlation between RGX-202 microdystrophin expression and functional improvement (NSAA n=9), supporting validity of s

REGENXBIO Reports First Quarter 2026 Financial Results and Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports First Quarter 2026 Financial Results and Operational Highlights • Company announced positive topline results from pivotal Phase III AFFINITY DUCHENNE® study of RGX-202 o Primary endpoint achieved with high statistical significance o Statistically significant correlation between RGX-202 microdystrophin expression and functional improvement (NSAA, n=9), supporting vali

LICENSE AGREEMENT EMORY UNIVERSITY

EXHIBIT 10.2 Certain identified information has been excluded from this exhibit because such information both (i) is not material and (ii) is customarily and actually treated as private or confidential. Excluded information is indicated with brackets and asterisks. LICENSE AGREEMENT between EMORY UNIVERSITY and REGENXBIO INC. LIC.18.023 TABLE OF CONTENTS ARTICLE 1. DEFINITIONS 3 ARTICLE 2. GRANT O

SETTLEMENT AND RELEASE AGREEMENT

EXHIBIT 10.1 Certain identified information has been excluded from this exhibit because such information both (i) is not material and (ii) would likely cause competitive harm if publicly disclosed. Excluded information is indicated with brackets and asterisks. EXECUTION VERSION SETTLEMENT AND RELEASE AGREEMENT This Settlement and Release Agreement (the "2026 Settlement Agreement" or "Agreement") i

FORM 8-K

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): May 14, 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

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2026 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 00

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Defin

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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ցց ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2025 or տտ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-37553 REGENXBIO In

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☐ Defin

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a party other than the Registrant ☐ Check the appropriate box: ☒ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6

FORM 8-K

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): March 18, 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 Numb

AMENDED AND RESTATED BYLAWS OF REGENXBIO INC. A DELAWARE CORPORATION EFFECTIVE: March 4, 2026 TABLE OF CONTENTS

EXHIBIT 3.2 AMENDED AND RESTATED BYLAWS OF REGENXBIO INC. A DELAWARE CORPORATION EFFECTIVE: March 4, 2026 TABLE OF CONTENTS Page ARTICLE I OFFICES AND RECORDS 2 Section 1.1 Delaware Office 2 Section 1.2 Other Offices 2 Section 1.3 Books and Records 2 ARTICLE II STOCKHOLDERS 2 Section 2.1 Annual Meeting 2 Section 2.2 Special Meeting 3 Section 2.3 Place of Meeting 3 Section 2.4 Notice of Meeting 3 S

Subsidiaries of REGENXBIO Inc.

EXHIBIT 21.1 Subsidiaries of REGENXBIO Inc. Name of Subsidiary Jurisdiction of Incorporation or Organization REGENXBIO EU Limited Ireland REGENXBIO RS LLC Delaware

Overview AAV Therapeutics Our NAV Technology Platform Our AAV Platform Discovery and Development AAV Therapeutic Manufacturing Collaborations, Licensing and Company Formation

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2025 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-37

FORM 8-K

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): March 05, 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 Numb

REGENXBIO Reports Fourth Quarter and Full Year 2025 Financial Results and Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports Fourth Quarter and Full Year 2025 Financial Results and Operational Highlights • Late-stage gene therapy pipeline for rare and retinal diseases advancing toward key catalysts o RGX-202 for Duchenne muscular dystrophy: New Phase I/II data at MDA, topline pivotal results expected early Q2 2026 - Robust patient enrollment continues in confirmatory trial o Surabgene lomp

Up to $150,000,000 Common Stock

424B5 Table of Contents Filed Pursuant to Rule 424(b)(5) Registration Number 333-291816 PROSPECTUS SUPPLEMENT (To prospectus dated December 12, 2025) Up to $150,000,000 Common Stock We have entered into a sales agreement (the “Sales Agreement”) with Leerink Partners LLC, dated December 9, 2024, relating to shares of our common stock, par value $0.

REGENXBIO Announces Regulatory Update on RGX-121 BLA for MPS II

EXHIBIT 99.1 REGENXBIO Announces Regulatory Update on RGX-121 BLA for MPS II • FDA issues Complete Response Letter for RGX-121 (clemidsogene lanparvovec) for treatment of Mucopolysaccharidosis II (MPS II) • REGENXBIO plans to work with FDA on a path forward with the goal of resubmitting the BLA ROCKVILLE, Md., February 9, 2026 – REGENXBIO Inc. (Nasdaq: RGNX) today announced that the U.S. Food and

FORM 8-K

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): February 07, 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 N

FORM 8-K

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 Nu

REGENXBIO Announces Regulatory Update on Ultra Rare MPS Programs

EXHIBIT 99.1 REGENXBIO Announces Regulatory Update on Ultra Rare MPS Programs ROCKVILLE, Md., January 28, 2026 – REGENXBIO Inc. (Nasdaq: RGNX) today announced that the U.S. Food and Drug Administration (FDA) placed a clinical hold on its investigational gene therapy, RGX-111, for the treatment of MPS I, also known as Hurler syndrome, following preliminary analysis of a single case of neoplasm (int

December 9, 2025

CORRESP December 9, 2025 Via EDGAR U.S. Securities and Exchange Commission Division of Corporation Finance 100 F Street, N.E. Washington, D.C. 20549 Attn: Tim Buchmiller Re: REGENXBIO Inc. (the “Company”) Registration Statement Filed on Form S-3 (the “Registration Statement”) File No. 333-291816 Ladies and Gentlemen: Pursuant to Rule 461 under the Securities Act of 1933, as amended, the Company he

Security Type

Calculation of Filing Fee Tables S-3 REGENXBIO Inc. Table 1: Newly Registered and Carry Forward Securities ☐Not Applicable Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry Forward Form Type Carry Forward File Number Carry Forward Initial Effe

As filed with the Securities and Exchange Commission on November 26, 2025

S-3 Table of Contents As filed with the Securities and Exchange Commission on November 26, 2025 Registration No.

FORM 8-K

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): November 06, 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 N

REGENXBIO Reports Third Quarter 2025 Financial Results and Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports Third Quarter 2025 Financial Results and Operational Highlights • RGX-202 program for Duchenne muscular dystrophy advancing rapidly, topline results expected early Q2 2026 and BLA submission mid-2026 o Pivotal trial enrollment completed in October; confirmatory trial open and enrolling o New 12-month analysis shows all participants demonstrate improved functional out

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Numbe

First Amendment to Collaboration and License Agreement dated September 10, 2021 between the Registrant and AbbVie Global Enterprises Ltd.

EXHIBIT 10.1 EXECUTION COPY Certain identified information has been excluded from this exhibit because such information both (i) is not material and (ii) is customarily and actually treated as private or confidential. Excluded information is indicated with brackets and asterisks. FIRST AMENDMENT TO COLLABORATION AND LICENSE AGREEMENT This First Amendment to the Collaboration and License Agreement

144

144 0001346164 XXXXXXXX LIVE 0001590877 REGENXBIO INC 001-37553 9804 Medical Center Drive Rockville MD 20850 2405528181 CURRAN M SIMPSON Director Officer Common Morgan Stanley Smith Barney LLC Executive Financial Services 1 New York Plaza 8th Floor New York NY 10004 20811 254310.

144

144 0001346164 XXXXXXXX LIVE 0001590877 REGENXBIO INC 001-37553 9804 Medical Center Drive Rockville MD 20850 2405528181 CURRAN M SIMPSON Director Officer Common Morgan Stanley Smith Barney LLC Executive Financial Services 1 New York Plaza 8th Floor New York NY 10004 15358 151890.

REGENXBIO Announces FDA Review Extension of BLA for RGX-121 to Treat Patients with MPS II

EXHIBIT 99.1 REGENXBIO Announces FDA Review Extension of BLA for RGX-121 to Treat Patients with MPS II - RGX-121 would be the first and only potential one-time commercially-available therapy designed to directly address the underlying genetic cause of Hunter syndrome, if approved - Commercial launch plans remain on track - REGENXBIO plans to present updated pivotal data during the ICIEM meeting in

FORM 8-K

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 Num

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001

Form of Restricted Stock Unit Award Agreement for the 2025 Equity Incentive Plan

EXHIBIT 10.2 REGENXBIO INC. 2025 EQUITY INCENTIVE PLAN NOTICE OF RESTRICTED STOCK UNIT AWARD REGENXBIO Inc. (the “Company”) has granted you (the “Grantee”) Stock Units (this “Award”) with respect to shares of the common stock of the Company on the following terms: Name of Grantee: [Participant Name] Total Number of Stock Units Granted: [Number of Stock Units] Date of Grant: [Grant Date] Vesting Sc

Loan Agreement dated May 16, 2025 between REGENXBIO RS LLC and affiliate of HealthCare Royalty Management, LLC

EXHIBIT 10.4 Execution Version Certain identified information has been excluded from this exhibit because such information both (i) is not material and (ii) would likely cause competitive harm if publicly disclosed. Excluded information is indicated with brackets and asterisks. LOAN AGREEMENT Dated as of May 16, 2025 Between REGENXBIO RS LLC, as Borrower, and HCR RGNX ROYALTY SPV, LP, as Lender TA

Form of Stock Option Award Agreement for the 2025 Equity Incentive Plan

EXHIBIT 10.3 REGENXBIO INC. 2025 EQUITY INCENTIVE PLAN NOTICE OF STOCK OPTION GRANT REGENXBIO Inc. (the “Company”) has granted you (the “Optionee”) the following option (the “Option”) to purchase shares of the common stock of the Company: Name of Optionee: [Participant Name] Total Number of Common Shares: [Number of Options] Type of Option: [ISO or NSO] Exercise Price per Common Share: [Exercise P

FORM 8-K

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 05, 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 Num

REGENXBIO Announces Pivotal Program for Surabgene Lomparvovec in Diabetic Retinopathy

EXHIBIT 99.2 REGENXBIO Announces Pivotal Program for Surabgene Lomparvovec in Diabetic Retinopathy - A pivotal Phase IIb/III clinical trial using suprachoroidal delivery for treatment of diabetic retinopathy will be initiated - New Phase II ALTITUDE® trial data demonstrate a durable safety and efficacy profile observed through two years with a single, in-office injection of surabgene lomparvovec i

REGENXBIO Reports Second Quarter 2025 Financial Results and Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports Second Quarter 2025 Financial Results and Operational Highlights • RGX-202 in Duchenne muscular dystrophy on track for topline results 1H 2026 and BLA submission mid-2026 o Pivotal trial enrollment accelerated, expected to complete in October 2025 ahead of previous guidance • Clemidsogene lanparvovec (RGX-121) on track to be first gene therapy and one-time treatment

Up to 268,096 Shares of Common Stock

Table of Contents Filed Pursuant to Rule 424(b)(3) Registration No. 333-288053 PROSPECTUS Up to 268,096 Shares of Common Stock This prospectus relates to the resale of up to 268,096 shares of common stock, par value $0.0001 per share (the “Shares”), of REGENXBIO Inc. (the “Company,” “we,” “our” or “us”) by the selling stockholder named in this prospectus (the “Selling Stockholder”). The Shares are

June 23, 2025

CORRESP June 23, 2025 Via EDGAR U.S. Securities and Exchange Commission Division of Corporation Finance 100 F Street, N.E. Washington, D.C. 20549 Attn: Doris Stacey Gama Re: REGENXBIO Inc. (the “Company”)   Registration Statement Filed on Form S-3 (the “Registration Statement”)   File No. 333-288053 Ladies and Gentlemen: Pursuant to Rule 461 under the Securities Act of 1933, as amended, the Compan

LETTER

June 20, 2025 Curran Simpson Chief Executive Officer REGENXBIO Inc. 9804 Medical Center Drive Rockville, MD 20850 Re: REGENXBIO Inc. Registration Statement on Form S-3 Filed June 13, 2025 File No. 333-288053 Dear Curran Simpson: This is to advise you that we have not reviewed and will not review your registration statement. Please refer to Rules 460 and 461 regarding requests for acceleration. We

REGENXBIO Inc. 2025 Equity Incentive Plan

EXHIBIT 99.1 REGENXBIO INC. 2025 EQUITY INCENTIVE PLAN ARTICLE 1. INTRODUCTION. 1.1 Purpose. The purpose of the Plan is to promote the long-term success of the Company and the creation of stockholder value by (a) encouraging Service Providers to focus on critical long-range corporate objectives, (b) encouraging the attraction and retention of Service Providers with exceptional qualifications and (

Filing Fee Table.

EXHIBIT 107 Calculation of Filing Fee Tables Form S-8 (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1)(2) Proposed Maximum Offering Price Per Unit(3) Maximum Aggregate Offering Price(3) Fee Rate Amount of Registration Fee Equity Common Stock, par value

As filed with the Securities and Exchange Commission on June 13, 2025

As filed with the Securities and Exchange Commission on June 13, 2025 Registration No.

As filed with the Securities and Exchange Commission on June 13, 2025

S-3 Table of Contents As filed with the Securities and Exchange Commission on June 13, 2025 Registration No.

Form of Warrant.

EX-4.5 Exhibit 4.5 REGENXBIO INC. WARRANT TO PURCHASE COMMON STOCK Number of Warrant Shares: 268,096 (subject to adjustment) Warrant No. 1 Original Issue Date: May 16, 2025 REGENXBIO Inc., a Delaware corporation (the “Company”), hereby certifies that, for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, HCR RGNX ROYALTY SPV, LP. or its permitted regist

Filing Fee Table.

EX-FILING FEES Exhibit 107 Calculation of Filing Fee Tables Form S-3 (Form Type) REGENXBIO Inc.

FORM 8-K Item 5.07 Submission of Matters to a Vote of Security Holders. Proposal 4: By the following vote, the stockholders voted, on an advisory basis, to hold future advisory votes on the Company’s executive compensation every year: Proposal 5: B

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): May 30, 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

Regulation FD Disclosure

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): May 16, 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

REGENXBIO Announces Strategic Royalty Monetization Agreement for Up to $250 Million

EXHIBIT 99.1 REGENXBIO Announces Strategic Royalty Monetization Agreement for Up to $250 Million • $150 million secured at closing extends cash runway into early 2027 • REGENXBIO retains additional potential non-dilutive funding opportunities, including monetization of Priority Review Voucher (PRV) and milestones from AbbVie ROCKVILLE, Md., May 19, 2025 (PRNewswire) — REGENXBIO Inc. (Nasdaq: RGNX)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 00

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): May 12, 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

Collaboration and License Agreement dated January 14, 2025 between the Registrant and Nippon Shinyaku Co., Ltd.

EXHIBIT 10.1 Confidential Executed Version Certain identified information has been excluded from this exhibit because such information both (i) is not material and (ii) is customarily and actually treated as private or confidential. Excluded information is indicated with brackets and asterisks. COLLABORATION AND LICENSE AGREEMENT BETWEEN REGENXBIO INC. AND NIPPON SHINYAKU CO., LTD. DATED AS OF JAN

REGENXBIO Reports First Quarter 2025 Financial Results and Recent Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports First Quarter 2025 Financial Results and Recent Operational Highlights • RGX-202 in Duchenne muscular dystrophy on track for BLA submission mid-2026 o Pivotal trial more than half enrolled, with completion expected in 2025 o Additional Phase I/II functional data expected 1H 2025 o Initiating commercial supply manufacturing in Q3 2025 • FDA acceptance of Biologics Lic

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6

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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One)  ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2024 or  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-37553 REGENXBIO Inc.

Filing Fee Table.

Exhibit 107 Calculation of Filing Fee Tables Form S-3 (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1) Proposed Maximum Offering Price Per Unit(1) Maximum Aggregate Offering Price(1) Fee Rate Amount of Registration Fee Fees to be Paid Equity Common Stoc

REGENXBIO Reports Fourth Quarter and Full Year 2024 Financial Results and Recent Operational Updates

EXHIBIT 99.1 REGENXBIO Reports Fourth Quarter and Full Year 2024 Financial Results and Recent Operational Updates • Biologics Licensing Application (BLA) for clemidsogene lanparvovec (RGX-121) submitted and on track for potential FDA approval 2H 2025; strategic partnership with Nippon Shinyaku aims to expand potential access and commercial opportunity in MPS II and MPS I • Pivotal trial of RGX-202

Subsidiaries of the Registrant

EXHIBIT 21.1 Subsidiaries of REGENXBIO Inc. Name of Subsidiary Jurisdiction of Incorporation or Organization REGENXBIO EU Limited Ireland

As filed with the Securities and Exchange Commission on March 13, 2025

Table of Contents As filed with the Securities and Exchange Commission on March 13, 2025 Registration No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2024 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-37553 REGENXBIO Inc.

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): March 13, 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 Numb

Insider Trading Policy

EXHIBIT 19.1 REGENXBIO INC. INSIDER TRADING POLICY (as adopted by the Board of Directors on February 23, 2024) Background The Board of Directors of REGENXBIO Inc. (the “Company”) has adopted this Insider Trading Policy (the “Policy”) for our directors, officers, employees and consultants. It applies to the trading of the Company’s securities as well as the securities of any other publicly traded c

Description of Common Stock (incorporated herein by reference to Exhibit 4.2 to the Company’s Annual Report on Form 10-K for the year ended December 31, 2024).

EXHIBIT 4.2 Description of Registrant’s Securities Registered Pursuant to Section 12 of the Securities Exchange Act of 1934 REGENXBIO Inc. has one class of securities registered under Section 12 of the Securities Exchange Act of 1934, as amended: our common stock, par value $0.0001 per share. The following is a general summary of the terms of shares of our common stock. The description below does

Filing Fee Table.

EXHIBIT 107 Calculation of Filing Fee Tables Form S-8 (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1)(2) Proposed Maximum Offering Price Per Unit(3) Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, par value $0.

As filed with the Securities and Exchange Commission on March 13, 2025

POS AM Table of Contents As filed with the Securities and Exchange Commission on March 13, 2025 Registration No.

As filed with the Securities and Exchange Commission on March 13, 2025

As filed with the Securities and Exchange Commission on March 13, 2025 Registration No.

REGENXBIO Announces Closing of Strategic Partnership with Nippon Shinyaku for MPS

EXHIBIT 99.1 REGENXBIO Announces Closing of Strategic Partnership with Nippon Shinyaku for MPS Diseases ROCKVILLE, Md., March 4, 2025 /PRNewswire/ — REGENXBIO Inc. (Nasdaq: RGNX) today announced the closing of its previously announced strategic partnership with Nippon Shinyaku. Under the terms of the agreement, REGENXBIO and Nippon Shinyaku will develop and commercialize RGX-121 (clemidsogene lanp

Regulation FD Disclosure

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): March 3, 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 Numbe

REGENXBIO and Nippon Shinyaku Announce Exclusive Partnership to Develop and Commercialize RGX-121 and RGX-111 for MPS Diseases

EX-99.1 Exhibit 99.1 REGENXBIO and Nippon Shinyaku Announce Exclusive Partnership to Develop and Commercialize RGX-121 and RGX-111 for MPS Diseases • REGENXBIO to receive $110 million upfront, potential milestone payments of up to $700 million and meaningful double-digit royalties on net sales, and lead manufacturing • Nippon Shinyaku to lead commercialization of first potential gene therapies for

Current Report

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 14, 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 Nu

RGNX / REGENXBIO Inc. / BlackRock, Inc. - POWER OF ATTORNEY

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Sales Agreement, dated as of December 9, 2024, between Leerink Partners LLC and REGENXBIO Inc.

Exhibit 1.1 REGENXBIO INC. Common Stock (par value $0.0001 per share) SALES AGREEMENT December 9, 2024 LEERINK PARTNERS LLC 1301 Avenue of the Americas, 5th Floor New York, New York 10019 Ladies and Gentlemen: REGENXBIO Inc., a Delaware corporation (the “Company”), proposes, subject to the terms and conditions stated herein, to issue and sell from time to time to or through Leerink Partners LLC, a

Up to $150,000,000 Common Stock

Filed Pursuant to Rule 424(b)(5) Registration Number 333-269086 PROSPECTUS SUPPLEMENT (To prospectus dated December 30, 2022) Up to $150,000,000 Common Stock We have entered into a sales agreement (the “Sales Agreement”) with Leerink Partners LLC, dated December 9, 2024, relating to shares of our common stock, par value $0.

Calculation of Filing Fee Tables (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities

Exhibit 107 Calculation of Filing Fee Tables 424(b)(5) (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered  Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry

REGENXBIO INITIATES PIVOTAL PHASE OF AFFINITY DUCHENNE® TRIAL OF RGX-202 GENE THERAPY AND REPORTS POSITIVE FUNCTIONAL DATA

Exhibit 99.1       REGENXBIO INITIATES PIVOTAL PHASE OF AFFINITY DUCHENNE® TRIAL OF RGX-202 GENE THERAPY AND REPORTS POSITIVE FUNCTIONAL DATA • Alignment achieved with FDA on AFFINITY DUCHENNE® pivotal program and access to accelerated approval; BLA expected in 2026 • Pivotal trial of RGX-202 is enrolling ambulatory patients aged 1 and above with first patient dosed • Phase I/II data show RGX-202

Current Report

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): December 9, 2024 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File Nu

Joint Filing Agreement

EX-99.1 2 tm2427858d8ex99-1.htm EXHIBIT 99.1 Exhibit 99.1 Joint Filing Agreement In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), the undersigned hereby agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto, the “Schedule 13G”) relating to the Common Stock, par valu

RGNX / REGENXBIO Inc. / Redmile Group, LLC - SC 13G/A Passive Investment

SC 13G/A 1 tm2427858d8sc13ga.htm SC 13G/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 2) REGENXBIO Inc. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 75901B107 (CUSIP Number) September 30, 2024 (Date of Event Which Requires Filing of this Statement) Check th

RGNX / REGENXBIO Inc. / VANGUARD GROUP INC Passive Investment

SC 13G/A 1 UnitedStates13GREGENXBIOI.txt 240.13d-102 Schedule 13G - Information to be included in statements filed pursuant to 240.13d-1(b), (c), and (d) and amendments thereto filed pursuant to 240.13d-2. Securities and Exchange Commission, Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No. 8)* (Name of Issuer) REGENXBIO Inc (Title of Class of Securities)

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): November 06, 2024 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File N

REGENXBIO INC. CONSOLIDATED BALANCE SHEETS (in thousands)

EXHIBIT 99.1 REGENXBIO Reports Third Quarter 2024 Financial Results and Recent Operational Updates • Advancement in Phase I/II AFFINITY DUCHENNE® trial of RGX-202 for Duchenne Muscular Dystrophy; pivotal trial initiation and first functional data expected this month • BLA submission for RGX-121 initiated and expected to complete in Q1 2025 • Positive Phase II data support bilateral administration

Consulting Agreement, effective as of September 16, 2024, between the Registrant and Vittal Vasista

EXHIBIT 10.2 Consulting Agreement This Consulting Agreement (the “Agreement”) is entered into as of September 16, 2024, by and between REGENXBIO Inc. (“REGENXBIO”), a Delaware corporation with offices at 9804 Medical Center Drive, Rockville, Maryland 20850, and Vittal Vasista (“Consultant”), an individual with an address at 1218 Harve Lafitte Drive, Austin, TX 78746 each a “Party” and collectively

Employment Separation Agreement effective as of September 21, 2024 between the Registrant and Vittal Vasista

EXHIBIT 10.1 September 14, 2024 Vittal Vasista 1218 Harve Lafitte Drive Austin, TX 78746 Dear Vit: This letter (“Agreement”) confirms the details of your separation from REGENXBIO Inc. (“REGENXBIO” or the “Company”), and all subsidiaries, successors, affiliated and/or related entities (collectively referred to as “REGENXBIO” or the “Company”). While these matters are never easy, we hope that your

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Numbe

RGNX / REGENXBIO Inc. / VANGUARD GROUP INC Passive Investment

SC 13G/A 1 UnitedStates13GREGENXBIOI.txt 240.13d-102 Schedule 13G - Information to be included in statements filed pursuant to 240.13d-1(b), (c), and (d) and amendments thereto filed pursuant to 240.13d-2. Securities and Exchange Commission, Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No. 7)* (Name of Issuer) REGENXBIO Inc (Title of Class of Securities)

RGNX / REGENXBIO Inc. / JPMORGAN CHASE & CO - FILING REGENXBIO INC. Passive Investment

SC 13G/A 1 REGENXBIOInc.htm FILING REGENXBIO INC. UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 05)* REGENXBIO Inc. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 75901B107 (CUSIP Number) September 30, 2024 (Date of Event Which Requires Filing of this Statement

REGENXBIO Appoints Mitchell Chan as Chief Financial Officer

EXHIBIT 99.1 REGENXBIO Appoints Mitchell Chan as Chief Financial Officer • Life sciences veteran Mitchell Chan joins the company ahead of multiple catalysts across late-stage gene therapy programs • Vit Vasista steps down following more than 15 years at the Company ROCKVILLE, Md. - September 17, 2024 - REGENXBIO Inc. (Nasdaq: RGNX) today announced that Mitchell Chan has been appointed as Executive

Regulation FD Disclosure, Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits

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): September 16, 2024 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File

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 1, 2024 REGENXBIO Inc. (Ex

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 1, 2024 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File Numb

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001

Employment Agreement effective as of July 1, 2024 between the Registrant and Curran Simpson

EXHIBIT 10.1 This Employment Agreement (this "Agreement") is entered into and made effective as of July 1. 2024, by and between Curran Simpson (the "Employee") and REGENXBIO Inc., a Delaware corporation (the "Company"). 1. Position. (a) During your employment with the Company pursuant to this Agreement, you will hold the title of President & Chief Executive Officer (CEO). As CEO you shall report d

REGENXBIO Reports Second Quarter 2024 Financial Results and Recent Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports Second Quarter 2024 Financial Results and Recent Operational Highlights • Company remains on track for its first BLA filing in 2024 and is accelerating progress toward pivotal trial initiation for Duchenne (H2 2024) and diabetic retinopathy (H1 2025) o New, positive data from Phase II AFFINITY DUCHENNE® trial of RGX-202 demonstrates consistent high expression of micr

Consulting and Employment Separation Agreement effective as of July 1, 2024 between the Registrant and Kenneth T. Mills

EXHIBIT 10.2 Agreement This Consulting and Employment Separation Agreement (the “Agreement”) is entered into as of June 12, 2024, by and between REGENXBIO Inc. (“REGENXBIO”), a Delaware corporation with offices at 9804 Medical Center Drive, Rockville, Maryland 20850, and Ken Mills (“Mr. Mills”), (each a “Party” and collectively the “Parties”). WHEREAS, Mr. Mills will voluntarily resign from his ro

Financial Statements and Exhibits, Results of Operations and Financial Condition

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 01, 2024 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File Num

Regulation FD Disclosure

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): June 12, 2024 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

REGENXBIO Announces Leadership Transition

Exhibit 99.1 REGENXBIO Announces Leadership Transition - Curran Simpson, Chief Operating Officer, Appointed as President and CEO - Co-Founder Kenneth T. Mills to Step Down as President and CEO; Named Chairman of the Board ROCKVILLE, Md. — June 12, 2024 — REGENXBIO Inc. (Nasdaq: RGNX) today announced that Curran Simpson, Chief Operating Officer, has been appointed as President, Chief Executive Offi

Financial Statements and Exhibits, Submission of Matters to a Vote of Security Holders

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): May 31, 2024 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

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 00

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): May 08, 2024 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

REGENXBIO Reports First Quarter 2024 Financial Results and Recent Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports First Quarter 2024 Financial Results and Recent Operational Highlights • Company remains on track for its first BLA filing in 2024 and is accelerating progress toward pivotal trial initiation for Duchenne (H2 2024) and diabetic retinopathy (H1 2025) • Dose level 2 selected as pivotal dose for RGX-202 treatment of Duchenne o New positive interim efficacy and safety da

ARS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2023 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-37553 REGENXBIO Inc.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6

Underwriting Agreement, dated March 6, 2024, among REGENXBIO Inc. and Morgan Stanley & Co. LLC, Goldman Sachs & Co. LLC, Barclays Capital Inc. and Stifel, Nicolaus & Company, Incorporated, as representatives of the Underwriters.

Exhibit 1.1 REGENXBIO INC. 4,565,260 SHARES OF COMMON STOCK (PAR VALUE $0.0001 PER SHARE) AND PRE- FUNDED WARRANTS TO PURCHASE 1,521,740 SHARES OF COMMON STOCK UNDERWRITING AGREEMENT March 6, 2024 March 6, 2024 Morgan Stanley & Co. LLC Goldman Sachs & Co. LLC Barclays Capital Inc. Stifel, Nicolaus & Company, Incorporated c/o Morgan Stanley & Co. LLC 1585 Broadway New York, New York 10036 c/o Goldm

REGENXBIO Announces Pricing of Upsized Public Offering of Common Stock and Pre-funded Warrants

Exhibit 99.1 REGENXBIO Announces Pricing of Upsized Public Offering of Common Stock and Pre-funded Warrants ROCKVILLE, Md., March 6, 2024 /PRNewswire/ — REGENXBIO Inc. (Nasdaq: RGNX) a leading clinical-stage biotechnology company seeking to improve lives through the curative potential of gene therapy, today announced the pricing of an underwritten upsized public offering of 4,565,260 shares of its

Form of Pre-funded Warrant

Exhibit 4.1 REGENXBIO INC. FORM OF WARRANT TO PURCHASE COMMON STOCK Number of Shares: [●] (subject to adjustment) Warrant No. [●] Original Issue Date: March [ ], 2024 REGENXBIO Inc., a Delaware corporation (the “Company”), hereby certifies that, for good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, [●] or its permitted registered assigns (the “Holder”),

Current Report

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): March 6, 2024 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

Calculation of Filing Fee Tables (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security  Type  Security Class Title Fee Calculation or Carry Forward Rule Amount  Registered  Pro

Exhibit 107 Calculation of Filing Fee Tables 424(b)(5) (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security  Type  Security Class Title Fee Calculation or Carry Forward Rule Amount  Registered  Proposed  Maximum  Offering  Price Per  Unit  Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee(1) Fees to Be Pa

4,565,260 shares of Common Stock 1,521,740 Pre-funded Warrants to Purchase Shares of Common Stock

Table of Contents Filed pursuant to Rule 424(b)(5) Registration No. 333-269086 Prospectus Supplement (To Prospectus dated December 30, 2022) 4,565,260 shares of Common Stock 1,521,740 Pre-funded Warrants to Purchase Shares of Common Stock We are offering 4,565,260 shares of our common stock and, in lieu of common stock to certain investors, pre-funded warrants to purchase shares of our common stoc

REGENXBIO INC. Common Stock Pre-funded Warrants to Purchase Shares of Common Stock

FWP 1 d764729dfwp.htm FWP Issuer Free Writing Prospectus Filed Pursuant to Rule 433 Dated March 6, 2024 Relating to Preliminary Prospectus Supplement Dated March 6, 2024 Registration Statement No. 333-269086 REGENXBIO INC. Common Stock Pre-funded Warrants to Purchase Shares of Common Stock This free writing prospectus relates only to the public offering of shares of common stock and pre-funded war

Subject to completion, dated March 6, 2024

Table of Contents Filed pursuant to Rule 424(b)(5) Registration No. 333-269086 The information in this preliminary prospectus supplement and the accompanying prospectus is not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where

Subsidiaries of the Registrant

EXHIBIT 21.1 Subsidiaries of REGENXBIO Inc. Name of Subsidiary Jurisdiction of Incorporation or Organization REGENXBIO EU Limited Ireland

Form of Employment Agreement for Executive Vice Presidents

EXHIBIT 10.9 [Letterhead of REGENXBIO Inc.] This Employment Agreement (this "Agreement") is entered into and made effective as of , by and between (the "Employee") and REGENXBIO Inc., a Delaware corporation (the "Company"). 1. Position. (a) During your employment with the Company pursuant to this Agreement, you will hold the title of . As the you shall report directly to the. By signing this Agree

Compensation Clawback Policy

EXHIBIT 97.1 REGENXBIO INC. COMPENSATION CLAWBACK POLICY Adopted November 30, 2023 Purpose The Board of Directors (the “Board”) of REGENXBIO Inc. (the “Company”) has adopted this compensation clawback policy (the “Policy”) which provides for the recoupment of Incentive-Based Compensation (as defined below) in the event of an Accounting Restatement (as defined below). This Policy is intended to com

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): February 27, 2024 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File N

Filing Fee Table.

EXHIBIT 107 Calculation of Filing Fee Tables Form S-8 (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1)(2) Proposed Maximum Offering Price Per Unit(3) Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, par value $0.

As filed with the Securities and Exchange Commission on February 27, 2024

As filed with the Securities and Exchange Commission on February 27, 2024 Registration No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2023 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-37

REGENXBIO Reports Fourth Quarter and Full Year 2023 Financial Results and Recent Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports Fourth Quarter and Full Year 2023 Financial Results and Recent Operational Highlights • Focus on clinical stage AAV Therapeutic product candidates addressing large commercial opportunities and value generation • Prioritized pipeline is expected to further progress to pivotal stage and first BLA filing in 2024 • New updates planned for Duchenne and in-office delivery

Joint Filing Agreement

EX-99.1 2 tm245846d9ex99-1.htm EXHIBIT 99.1 Exhibit 99.1 Joint Filing Agreement In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), the undersigned hereby agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto, the “Schedule 13G”) relating to the Common Stock, par value

RGNX / REGENXBIO Inc. / Redmile Group, LLC - SC 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1) REGENXBIO Inc. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 75901B107 (CUSIP Number) December 31, 2023 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pur

RGNX / REGENXBIO Inc. / VANGUARD GROUP INC - SCHEDULE 13G/A Passive Investment

SC 13G/A 1 tv01801-regenxbioinc.htm SCHEDULE 13G/A SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 6)* Name of issuer: REGENXBIO Inc Title of Class of Securities: Common Stock CUSIP Number: 75901B107 Date of Event Which Requires Filing of this Statement: December 29, 2023 Check the appropriate box to designate the rul

RGNX / REGENXBIO Inc. / GIC Private Ltd - SC 13G/A Passive Investment

SC 13G/A 1 ef20020646sc13ga.htm SC 13G/A UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1) * REGENXBIO Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 75901B107 (CUSIP Number) December 31, 2023 (Date of the Event Which Requires Filing of this Statement) Chec

RGNX / REGENXBIO Inc. / JPMORGAN CHASE & CO - FILING REGENXBIO INC. Passive Investment

Schedule 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 04)* REGENXBIO Inc. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 75901B107 (CUSIP Number) December 29, 2023 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designa

RGNX / REGENXBIO Inc. / JPMORGAN CHASE & CO - FILING REGENXBIO INC. Passive Investment

Schedule 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 04)* REGENXBIO Inc. (Name of Issuer) Common Stock, par value $0.0001 per share (Title of Class of Securities) 75901B107 (CUSIP Number) December 29, 2023 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designa

RGNX / REGENXBIO Inc. / STATE STREET CORP Passive Investment

SC 13G/A 1 REGENXBIOInc.txt UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 AMENDED FILING REGENXBIO INC (NAME OF ISSUER) COMMON STOCK (TITLE OF CLASS OF SECURITIES) 75901B107 (CUSIP NUMBER) 12/31/2023 (DATE OF EVENT WHICH REQUIRES FILING OF THIS STATEMENT) CHECK THE APPROPRIATE BOX TO DESIGNATE THE RULE PURSUANT TO WHI

RGNX / REGENXBIO Inc. / BlackRock Inc. Passive Investment

SC 13G/A 1 us75901b1070011924.txt us75901b1070011924.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: 9) REGENXBIO INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 75901B107 - (CUSIP Number) December 31, 2023 - (Date of Event Which Requires Filing of this Statement) Check the appropriate box to d

RGNX / Regenxbio Inc / Redmile Group, LLC - SC 13G Passive Investment

SC 13G 1 tm2331039d1sc13g.htm SC 13G     UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549   SCHEDULE 13G   Under the Securities Exchange Act of 1934 (Amendment No. )   REGENXBIO Inc.     (Name of Issuer)   Common Stock, $0.0001 per share     (Title of Class of Securities)   75901B107     (CUSIP Number)   November 9, 2023     (Date of Event Which Requires Filing of this State

Joint Filing Agreement

EX-99.1 2 tm2331039d1ex99-1.htm EXHIBIT 99.1 Exhibit 99.1   Joint Filing Agreement   In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), the undersigned hereby agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto, the “Schedule 13G”) relating to the Common Stock, $0.0

REGENXBIO INC. CONSOLIDATED BALANCE SHEETS (in thousands)

EXHIBIT 99.1 REGENXBIO Announces Updated Strategic Plans and Third Quarter 2023 Financial Results • Announces pipeline prioritization and corporate restructuring to focus on clinical stage AAV Therapeutic product candidates addressing large commercial opportunities and value generation • Highest priority programs are ABBV-RGX-314 for the treatment of wet AMD and diabetic retinopathy, being develop

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Numbe

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

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): November 08, 2023 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File N

Calculation of Filing Fee Tables (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount

EX-FILING FEES Exhibit 107 Calculation of Filing Fee Tables 424(b)(5) (Form Type) REGENXBIO Inc.

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): September 1, 2023 REGENXBIO Inc.

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): September 1, 2023 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File N

ATM Equity OfferingSM Sales Agreement, dated as of September 1, 2023, between BofA Securities, Inc. and REGENXBIO Inc.

Exhibit 1.1 REGENXBIO INC. Common Stock (par value $0.0001 per share) ATM EQUITY OFFERINGSM SALES AGREEMENT September 1, 2023 BofA Securities, Inc. One Bryant Park New York, New York 10036 Ladies and Gentlemen: REGENXBIO Inc., a Delaware corporation (the “Company”), proposes, subject to the terms and conditions stated herein, to issue and sell from time to time to or through BofA Securities, Inc.,

$150,000,000 Common Stock

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration Number 333-269086 PROSPECTUS SUPPLEMENT (To prospectus dated December 30, 2022) $150,000,000 Common Stock We have entered into an ATM Equity OfferingSM Sales Agreement (the “Sales Agreement”) with BofA Securities, Inc.

As filed with the Securities and Exchange Commission on August 4, 2023

S-3ASR Table of Contents As filed with the Securities and Exchange Commission on August 4, 2023 Registration No.

Filing Fee Table.

Exhibit 107 Calculation of Filing Fee Tables Form S-3 (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered(1) Proposed Maximum Offering Price Per Unit(2) Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Ca

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001

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

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 02, 2023 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File Num

REGENXBIO Reports Second Quarter 2023 Financial Results and Recent Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports Second Quarter 2023 Financial Results and Recent Operational Highlights • Continued progress on ‘5x’25’ strategy to advance five AAV Therapeutics from REGENXBIO’s internal pipeline and licensed programs into pivotal-stage or commercial products by 2025 • ABBV-RGX-314 program for the treatment of wet AMD and diabetic retinopathy, being developed in collaboration with

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

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): June 02, 2023 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File Numbe

RGNX / Regenxbio Inc / VANGUARD GROUP INC - SCHEDULE 13G/A Passive Investment

SC 13G/A 1 tv0005-regenxbioinc.htm SCHEDULE 13G/A SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 5)* Name of issuer: REGENXBIO Inc. Title of Class of Securities: Common Stock CUSIP Number: 75901B107 Date of Event Which Requires Filing of this Statement: April 28, 2023 Check the appropriate box to designate the rule p

REGENXBIO Reports First Quarter 2023 Financial Results and Recent Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports First Quarter 2023 Financial Results and Recent Operational Highlights - Continued progress on ‘5x’25’ strategy to advance five AAV Therapeutics from REGENXBIO’s internal pipeline and licensed programs into pivotal-stage or commercial products by 2025 - Announced Updates to Eye Care Collaboration with AbbVie o Investigational gene therapy renamed ABBV-RGX-314 o IND s

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

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): May 03, 2023 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

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 00

RGNX / Regenxbio Inc / GIC Private Ltd - SC 13G Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. ) * REGENXBIO Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 75901B107 (CUSIP Number) March 31, 2023 (Date of the Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule p

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6

Definitive Proxy Statement on Schedule 14A, as filed with the SEC on April 6, 2023;

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6

ARS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2022 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-37553 REGENXBIO Inc.

Filing Fee Table.

EXHIBIT 107 Calculation of Filing Fee Tables Form S-8 (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1)(2) Proposed Maximum Offering Price Per Unit(3) Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, par value $0.

Annual Report on Form 10-K for the year ended December 31, 2022, filed with the SEC on February 28, 2023;

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2022 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-37

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

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): February 28, 2023 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File N

REGENXBIO Reports Fourth Quarter 2022 and Full-Year 2022 Financial Results and Recent Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports Fourth Quarter 2022 and Full-Year 2022 Financial Results and Recent Operational Highlights - Continued progress on ‘5x’25’ strategy to advance five AAV Therapeutics from REGENXBIO’s internal pipeline and licensed programs into pivotal-stage or commercial products by 2025 - RGX-314 program for the treatment of wet AMD and diabetic retinopathy, being developed in colla

As filed with the Securities and Exchange Commission on February 28, 2023

As filed with the Securities and Exchange Commission on February 28, 2023 Registration No.

Subsidiaries of the Registrant

EXHIBIT 21.1 Subsidiaries of REGENXBIO Inc. Name of Subsidiary Jurisdiction of Incorporation or Organization REGENXBIO EU Limited Ireland

RGNX / Regenxbio Inc / VANGUARD GROUP INC - SCHEDULE 13G/A Passive Investment

SC 13G/A 1 tv01774-regenxbioinc.htm SCHEDULE 13G/A SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 4)* Name of issuer: REGENXBIO Inc. Title of Class of Securities: Common Stock CUSIP Number: 75901B107 Date of Event Which Requires Filing of this Statement: December 30, 2022 Check the appropriate box to designate the ru

RGNX / Regenxbio Inc / STATE STREET CORP Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 AMENDED FILING REGENXBIO INC (NAME OF ISSUER) COMMON STOCK (TITLE OF CLASS OF SECURITIES) 75901B107 (CUSIP NUMBER) 12/31/2022 (DATE OF EVENT WHICH REQUIRES FILING OF THIS STATEMENT) CHECK THE APPROPRIATE BOX TO DESIGNATE THE RULE PURSUANT TO WHICH THIS SCHEDULE IS FILED: (

RGNX / Regenxbio Inc / JPMORGAN CHASE & CO - FILING REGENXBIO INC. Passive Investment

Schedule 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 03)* REGENXBIO Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 75901B107 (CUSIP Number) December 30, 2022 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designa

RGNX / Regenxbio Inc / BlackRock Inc. Passive Investment

SC 13G/A 1 us75901b1070012323.txt us75901b1070012323.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: 8) REGENXBIO INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 75901B107 - (CUSIP Number) December 31, 2022 - (Date of Event Which Requires Filing of this Statement) Check the appropriate box to d

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 09, 2023 REGENXBIO Inc. (

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 09, 2023 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File Nu

REGENXBIO ANNOUNCES SENIOR LEADERSHIP PROMOTIONS

Exhibit 99.1 REGENXBIO ANNOUNCES SENIOR LEADERSHIP PROMOTIONS • Curran Simpson has been appointed Chief Operating Officer • Shiva Fritsch assumes the role of Chief Communications Officer ROCKVILLE, Md., Jan. 9, 2023, REGENXBIO Inc. (Nasdaq: RGNX) today announced the promotion of Curran Simpson from Chief Technology and Operations Officer to Chief Operating Officer. In addition, Shiva Fritsch has b

Filing Fee Table.

EX-FILING FEES 4 d439458dexfilingfees.htm EX-FILING FEES Exhibit 107 Calculation of Filing Fee Tables Form S-3 (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Of

As filed with the Securities and Exchange Commission on December 30, 2022

Table of Contents As filed with the Securities and Exchange Commission on December 30, 2022 Registration No.

REGENXBIO Reports Third Quarter 2022 Financial Results and Recent Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports Third Quarter 2022 Financial Results and Recent Operational Highlights - Continued progress on 5x25 strategy to advance five AAV Therapeutics from our internal pipeline and licensed programs into pivotal-stage or commercial products by 2025 - RGX-314 program for the treatment of wet AMD and diabetic retinopathy, being developed in collaboration with AbbVie, remains o

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): November 03, 2022 REGENXBIO Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-37553 47-1851754 (State or Other Jurisdiction of Incorporation) (Commission File N

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2022 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Numbe

Financial Statements and Exhibits, Results of Operations and Financial Condition

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 3, 2022 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File Numb

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2022 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001

REGENXBIO Reports Second Quarter 2022 Financial Results and Recent Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports Second Quarter 2022 Financial Results and Recent Operational Highlights - RGX-314 program for the treatment of wet AMD and diabetic retinopathy, being developed in collaboration with AbbVie, remains on track for first BLA filing in 2024 o Enrollment ongoing in the pivotal ATMOSPHERE? and ASCENT? clinical trials of RGX-314 for the treatment of wet AMD using subretinal

Compensation Program for Non-Employee Directors

EXHIBIT 10.1 REGENXBIO INC. COMPENSATION PROGRAM FOR NON-EMPLOYEE DIRECTORS (as amended on June 3, 2022) A. Cash Compensation 1. Board retainer: $45,000 per year for each non-employee director, paid in quarterly installments in arrears. 2. Chairman of the Board retainer: $35,000 per year, paid in quarterly installments in arrears. 3. Lead Independent Director retainer: $25,000 per year, paid in qu

Jennifer Zachary Joins REGENXBIO Board of Directors

Exhibit 99.1 Jennifer Zachary Joins REGENXBIO Board of Directors ROCKVILLE, Md., June 7, 2022 (PRNewswire) ? REGENXBIO Inc. (Nasdaq: RGNX) today announced the appointment of Jennifer Zachary to its Board of Directors, effective June 3, 2022. Ms. Zachary will serve as a member of REGENXBIO?s Audit Committee and brings 20 years of legal and regulatory experience working in the pharmaceutical and med

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits, Submission of Matters to a Vote of Security Holders

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): June 3, 2022 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

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2022 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 00

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): May 4, 2022 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)

Letter Agreement dated March 21, 2022 between the Company and the Trustees of the University of Pennsylvania

EXHIBIT 10.1 Certain identified information has been excluded from this exhibit because such information both (i) is not material and (ii) would likely cause competitive harm if publicly disclosed. Excluded information is indicated with brackets and asterisks. [Letterhead of Penn Center for Innovation] March 21, 2022 VIA ELECTRONIC MAIL CONFIDENTIAL Ken Mills, President and CEO REGENXBIO Inc. 9804

REGENXBIO Reports First Quarter 2022 Financial Results and Recent Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports First Quarter 2022 Financial Results and Recent Operational Highlights - Continues to advance RGX-314 program for the treatment of wet AMD and diabetic retinopathy; remains on track for first BLA filing in 2024 o Enrollment ongoing in the pivotal ATMOSPHERE? and ASCENT? clinical trials of RGX-314 for the treatment of wet AMD using subretinal delivery o Enrollment ong

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ? Filed by a party other than the Registrant ? Check the appropriate box: ?Preliminary Proxy Statement ?Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ? Filed by a party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6

Entry into a Material Definitive Agreement

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): March 21, 2022 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File Numb

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

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): March 14, 2022 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File Numb

REGENXBIO Reports Fourth Quarter and Full-Year 2021 Financial Results and Recent Operational Highlights

EX-99.1 2 rgnx-ex99124.htm EX-99.1 EXHIBIT 99.1 REGENXBIO Reports Fourth Quarter and Full-Year 2021 Financial Results and Recent Operational Highlights - Closed eye care collaboration agreement with AbbVie to develop and commercialize RGX-314 o Received upfront payment of $370 million and eligible to receive up to $1.38 billion in additional development, regulatory and commercial milestones - Cont

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ? ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2021 or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-37

description of our common stock set forth in Exhibit 4.2 to our Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 1, 2022

EXHIBIT 4.2 Description of Registrant?s Securities Registered Pursuant to Section 12 of the Securities Exchange Act of 1934 REGENXBIO Inc. has one class of securities registered under Section 12 of the Securities Exchange Act of 1934, as amended: our common stock, par value $0.0001 per share. The following is a general summary of the terms of shares of our common stock. The description below does

As filed with the Securities and Exchange Commission on March 1, 2022

As filed with the Securities and Exchange Commission on March 1, 2022 Registration No.

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): March 1, 2022 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File Numbe

Subsidiaries of the Registrant

EXHIBIT 21.1 Subsidiaries of REGENXBIO Inc. Name of Subsidiary Jurisdiction of Incorporation or Organization REGENXBIO EU Limited Ireland

Filing Fee Table.

EXHIBIT 107 Calculation of Filing Fee Tables Form S-8 (Form Type) REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered(1) Proposed Maximum Offering Price Per Unit(3) Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, par value $0.000

Settlement Agreement and Mutual Release dated November 12, 2021 between the Registrant and Abeona Therapeutics Inc.

EXHIBIT 10.40 Certain identified information has been excluded from this exhibit pursuant to Item 601(b)(10)(iv) of Regulation S-K because such information both (i) is not material and (ii) would likely cause competitive harm if publicly disclosed. Excluded information is indicated with brackets and asterisks. SETTLEMENT AGREEMENT AND MUTUAL RELEASE This Settlement Agreement and Mutual Release (?S

RGNX / Regenxbio Inc / Redmile Group, LLC - SCHEDULE 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G/A Under the Securities Exchange Act of 1934 (Amendment No. 2) REGENXBIO Inc. (Name of Issuer) Common Stock, $0.0001 per share (Title of Class of Securities) 75901B107 (CUSIP Number) December 31, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to

Joint Filing Agreement

Exhibit 99.1 Joint Filing Agreement In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended (the ?Exchange Act?), the undersigned hereby agree to the joint filing on behalf of each of them of a Statement on Schedule 13G (including any and all amendments thereto, the ?Schedule 13G?) relating to the Common Stock, $0.0001 par value per share, of REGENXBIO Inc., which

REGENXBIO Presents Positive Interim Data from Phase II ALTITUDE™ Trial of RGX-314 for the Treatment of Diabetic Retinopathy Using Suprachoroidal Delivery

Exhibit 99.1 REGENXBIO Presents Positive Interim Data from Phase II ALTITUDE? Trial of RGX-314 for the Treatment of Diabetic Retinopathy Using Suprachoroidal Delivery ? 47% of patients in Cohort 1 treated with RGX-314 demonstrated a ?2 step improvement from baseline on the ETDRS-DRSS at six months, compared to 0% of patients in observational control; increase from 33% of patients at three months ?

Regulation FD Disclosure, Financial Statements and Exhibits, Other Events

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): February 12, 2022 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File N

RGNX / Regenxbio Inc / STATE STREET CORP Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 13G UNDER THE SECURITIES EXCHANGE ACT OF 1934 AMENDED FILING REGENXBIO INC (NAME OF ISSUER) COMMON STOCK (TITLE OF CLASS OF SECURITIES) 75901B107 (CUSIP NUMBER) 12/31/2021 (DATE OF EVENT WHICH REQUIRES FILING OF THIS STATEMENT) CHECK THE APPROPRIATE BOX TO DESIGNATE THE RULE PURSUANT TO WHICH THIS SCHEDULE IS FILED: (

RGNX / Regenxbio Inc / GIC Private Ltd - SC 13G/A Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 2) * REGENXBIO Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 75901B107 (CUSIP Number) December 31, 2021 (Date of the Event Which Requires Filing of this Statement) Check the appropriate box to designate the ru

RGNX / Regenxbio Inc / VANGUARD GROUP INC - SCHEDULE 13G/A Passive Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 3)* Name of issuer: REGENXBIO Inc. Title of Class of Securities: Common Stock CUSIP Number: 75901B107 Date of Event Which Requires Filing of this Statement: December 31, 2021 Check the appropriate box to designate the rule pursuant to which this Schedule is filed: ☒ Rule

REGENXBIO Presents Additional Positive Interim Data from Phase I/II Trial of RGX-121 for the Treatment of MPS II (Hunter Syndrome) at 18th Annual WORLDSymposiumTM 2022

EXHIBIT 99.1 REGENXBIO Presents Additional Positive Interim Data from Phase I/II Trial of RGX-121 for the Treatment of MPS II (Hunter Syndrome) at 18th Annual WORLDSymposiumTM 2022 ? RGX-121, a one-time gene therapy for MPS II, continues to be well-tolerated with no drug-related SAEs across three dose levels ? Dose-dependent reductions in CSF biomarkers observed; Cohort 3 patients approach normal

REGENXBIO Presents Positive Initial Data from Phase I/II Trial of RGX-111 for the Treatment of Severe MPS I at 18th Annual WORLDSymposiumTM 2022

EXHIBIT 99.2 REGENXBIO Presents Positive Initial Data from Phase I/II Trial of RGX-111 for the Treatment of Severe MPS I at 18th Annual WORLDSymposiumTM 2022 ? RGX-111, a potential one-time gene therapy for MPS I, is well-tolerated across two dose levels, with no drug-related serious adverse events ? Biomarker and neurodevelopmental assessments indicate encouraging CNS profile in patients dosed wi

Regulation FD Disclosure, Financial Statements and Exhibits, Other Events

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): February 9, 2022 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File Nu

RGNX / Regenxbio Inc / BlackRock Inc. Passive Investment

us75901b1070012722.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: 7) REGENXBIO INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 75901B107 - (CUSIP Number) December 31, 2021 - (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to whic

RGNX / Regenxbio Inc / BlackRock Inc. Passive Investment

us75901b1070012622.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: 6) REGENXBIO INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 75901B107 - (CUSIP Number) December 31, 2021 - (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to whic

RGNX / Regenxbio Inc / JPMORGAN CHASE & CO - FILING REGENXBIO INC. Passive Investment

Schedule 13G UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 02)* REGENXBIO Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 75901B107 (CUSIP Number) December 31, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designa

Entry into a Material Definitive Agreement

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): November 12, 2021 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File N

Regulation FD Disclosure, Financial Statements and Exhibits, Other Events

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): November 12, 2021 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File N

REGENXBIO Presents Additional Positive Interim Data from Trials of RGX-314 in Wet AMD and Diabetic Retinopathy Using Suprachoroidal Delivery at AAO 2021

Exhibit 99.1 REGENXBIO Presents Additional Positive Interim Data from Trials of RGX-314 in Wet AMD and Diabetic Retinopathy Using Suprachoroidal Delivery at AAO 2021 ? Suprachoroidal delivery of RGX-314 in Phase II AAVIATE? trial for the treatment of wet AMD continues to be well tolerated in 50 patients from Cohorts 1-3 with no drug-related serious adverse events ? Positive initial data from Cohor

Regulation FD Disclosure, Financial Statements and Exhibits, Other Events

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): November 8, 2021 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File Nu

RGNX / Regenxbio Inc / JPMORGAN CHASE & CO - FILING REGENXBIO INC. Passive Investment

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 01)* REGENXBIO Inc. (Name of Issuer) Common Stock, $0.0001 par value per share (Title of Class of Securities) 75901B107 (CUSIP Number) October 29, 2021 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pu

REGENXBIO Announces Closing of Eye Care Collaboration Agreement with AbbVie

Exhibit 99.1 REGENXBIO Announces Closing of Eye Care Collaboration Agreement with AbbVie ROCKVILLE, Md., November 9, 2021 ? REGENXBIO Inc. (Nasdaq: RGNX) today announced the closing of its Collaboration and License Agreement with AbbVie to develop and commercialize RGX-314, a potential one-time gene therapy for the treatment of wet age-related macular degeneration (wet AMD), diabetic retinopathy (

Collaboration and License Agreement dated September 10, 2021 between the Registrant and AbbVie Global Enterprises Ltd.

EXHIBIT 10.1 EXECUTED VERSION Certain identified information has been excluded from this exhibit because such information both (i) is not material and (ii) would likely cause competitive harm if publicly disclosed. Excluded information is indicated with brackets and asterisks. COLLABORATION AND LICENSE AGREEMENT BETWEEN regenxbio inc. AND ABBVIE GLOBAL ENTERPRISES LTD. DATED AS OF September 10, 20

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2021 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Numbe

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): November 2, 2021 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File Nu

REGENXBIO Reports Third Quarter 2021 Financial Results and Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports Third Quarter 2021 Financial Results and Operational Highlights ? Announced eye care collaboration with AbbVie to develop and commercialize RGX-314 o AbbVie and REGENXBIO form a strategic partnership combining eye care and gene therapy expertise o REGENXBIO to receive $370 million upfront payment o Transaction expected to close by end of 2021, subject to satisfaction

Regulation FD Disclosure, Financial Statements and Exhibits, Other Events

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): October 9, 2021 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File Num

REGENXBIO Presents Positive Initial Data from Phase II ALTITUDE™ Trial of RGX-314 for the Treatment of Diabetic Retinopathy Using Suprachoroidal Delivery at American Society of Retina Specialists Annual Meeting

Exhibit 99.1 REGENXBIO Presents Positive Initial Data from Phase II ALTITUDE? Trial of RGX-314 for the Treatment of Diabetic Retinopathy Using Suprachoroidal Delivery at American Society of Retina Specialists Annual Meeting ? Suprachoroidal delivery of RGX-314 well tolerated in 15 patients in Cohort 1 with no drug-related serious adverse events ? No intraocular inflammation observed ? Positive int

Regulation FD Disclosure, Financial Statements and Exhibits, Other Events

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): October 1, 2021 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File Num

REGENXBIO Presents Positive Initial Data from Phase II AAVIATE® Trial of RGX-314 for the Treatment of Wet AMD Using Suprachoroidal Delivery and Provides Trial Update at Retina Society 54th Annual Scientific Meeting

Exhibit 99.1 REGENXBIO Presents Positive Initial Data from Phase II AAVIATE? Trial of RGX-314 for the Treatment of Wet AMD Using Suprachoroidal Delivery and Provides Trial Update at Retina Society 54th Annual Scientific Meeting ? Suprachoroidal delivery of RGX-314 well tolerated in 50 patients in Cohorts 1-3 with no drug-related serious adverse events ? Positive initial data from Cohort 1 at six m

###

Exhibit 99.1 PRESS RELEASE AbbVie and REGENXBIO Announce Eye Care Collaboration ? AbbVie and REGENXBIO form a strategic partnership combining eye care and gene therapy expertise ? Companies will develop and commercialize RGX-314, an investigational gene therapy for wet age-related macular degeneration, diabetic retinopathy and other chronic retinal diseases ? REGENXBIO to receive $370 million upfr

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): September 10, 2021 REGENXBIO Inc.

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): September 10, 2021 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File

Dr. Jean Bennett and George Migausky Join REGENXBIO Board of Directors

EXHIBIT 99.1 Dr. Jean Bennett and George Migausky Join REGENXBIO Board of Directors ? Renowned gene therapy pioneer and biotechnology executive bring extensive R&D leadership and financial and operational expertise to the Board ROCKVILLE, Md., September 7, 2021 ? REGENXBIO Inc. (Nasdaq: RGNX) today announced the appointment of Jean Bennett, M.D., Ph.D., and George Migausky to its Board of Director

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Financial Statements and Exhibits

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): September 3, 2021 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File N

REGENXBIO Reports Second Quarter 2021 Financial Results and Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports Second Quarter 2021 Financial Results and Operational Highlights ? Enrollment in RGX-314 programs is on-track, including the pivotal program for the treatment of wet AMD utilizing subretinal delivery, and the Phase II trials for the treatment of wet AMD and DR utilizing in-office suprachoroidal delivery ? Interim data from RGX-314 Phase II trial for the treatment of

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2021 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001

Financial Statements and Exhibits, Results of Operations and Financial Condition

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 9, 2021 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File Numb

Other Events

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): July 13, 2021 REGENXBIO Inc. (Exact Name of Registrant as Specified in its Charter) Delaware 001-37553 47-1851754 (State or other jurisdiction of incorporation) (Commission File Numbe

Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year, Financial Statements and Exhibits

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): June 4, 2021 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

Restated Certificate of Incorporation (incorporated herein by reference to Exhibit 3.1 to the Company’s Current Report on Form 8-K filed on January 7, 2021).

Exhibit 3.1 RESTATED CERTIFICATE OF INCORPORATION OF REGENXBIO INC. (Pursuant to Sections 242 and 245 of the Delaware General Corporation Law) REGENXBIO Inc., a corporation organized and existing under and by virtue of the provisions of the Delaware General Corporation Law, DOES HEREBY CERTIFY: FIRST:That the name of the corporation is REGENXBIO Inc. and that this corporation was originally incorp

Financial Statements and Exhibits, Results of Operations and Financial Condition

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): May 5, 2021 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)

Quarterly Report - 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2021 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 00

REGENXBIO Reports First Quarter 2021 Financial Results and Operational Highlights

EXHIBIT 99.1 REGENXBIO Reports First Quarter 2021 Financial Results and Operational Highlights ? Enrollment ongoing in ATMOSPHERE?, the first of two planned pivotal trials for the subretinal delivery of RGX-314 for the treatment of wet AMD ? Continued progress and expansion of Phase II AAVIATE? trial of RGX-314 utilizing in-office suprachoroidal delivery for the treatment of wet AMD ? Began dosing

definitive proxy statement on Schedule 14A for the 2021 Annual Meeting of Stockholders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ? Filed by a party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6

- DEFA14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ?Filed by a party other than the Registrant ? Check the appropriate box: ?Preliminary Proxy Statement ?Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)

- PRE 14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A (Rule 14a-101) Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ? Filed by a party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6

-

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Form of Restricted Stock Unit Award Agreement for the 2015 Equity Incentive Plan (incorporated by reference from Exhibit 10.4 to the Company’s Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on March 1, 2021).

EXHIBIT 10.4 REGENXBIO Inc. 2015 Equity Incentive Plan Notice of Restricted Stock Unit Award You have been granted units representing shares of Common Stock of REGENXBIO Inc. (the ?Company?) on the following terms: Name of Recipient: [Participant Name] Total Number of Units Granted: [Number of Units] Date of Grant: [Grant Date] Vesting Schedule: [Vesting Schedule] You and the Company agree that th

Annual Report - 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark One) ? ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2020 or ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-37