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 8, 2020

SIGILON THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

(Registrant’s telephone number, including area code): 617-336-7540

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2. below):

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

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

Emerging growth company x

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

Item 5.03 Amendments to Articles of Incorporation or Bylaws; Change in Fiscal Year.

On December 8, 2020, in connection with the consummation of the initial public offering of the common stock (the “IPO”) of Sigilon Therapeutics, Inc. (the “Company”), the Company filed a fifth amended and restated certificate of incorporation (the “Restated Certificate”) with the Secretary of State of the State of Delaware, which became effective upon filing. The Company’s board of directors and stockholders previously approved the Restated Certificate to be filed in connection with the consummation of the IPO. The Restated Certificate amends and restates the Company’s certificate of incorporation in its entirety to, among other things, (i) authorize 175 million shares of common stock, (ii) eliminate all references to previously existing series of preferred stock, (iii) authorize 25 million shares of undesignated preferred stock that may be issued from time to time with the approval of the Company’s board of directors in one or more series, and (iv) eliminate the ability of the Company’s stockholders to take action by written consent in lieu of a meeting.

The foregoing description of the Restated Certificate is qualified by reference to the Restated Certificate, a copy of which is attached hereto as Exhibit 3.1 and is incorporated herein by reference.

Also on December 8, 2020, in connection with the consummation of the IPO, the amended and restated bylaws of the Company (the “Amended and Restated Bylaws”), previously approved by the Company’s board of directors and stockholders, became effective. The Amended and Restated Bylaws amend and restate the Company’s bylaws in their entirety to, among other things, (i) establish procedures relating to the presentation of stockholder proposals at stockholder meetings, (ii) establish procedures relating to the nomination of directors, (iii) modify the indemnification provisions for the Company’s directors and officers, and (iv) conform to the amended provisions of the Restated Certificate.

The foregoing description of the Amended and Restated Bylaws is qualified by reference to the Amended and Restated Bylaws, a copy of which is attached hereto as Exhibit 3.2 and is incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

SIGNATURES

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

Date: December 8, 2020