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 22, 2017

G1 THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

79 T.W. Alexander Drive

4501 Research Commons, Suite 100

Research Triangle Park, NC 27709

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (919) 213-9835

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:

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

Emerging Growth Company  ☒

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

As previously disclosed in the Registration Statement for the initial public offering (the “IPO”) of the common stock of G1 Therapeutics, Inc. (the “Company”), in connection with the closing of the IPO, which occurred on May 22, 2017, Timothy E. Sullivan and Peter Kolchinsky, Ph.D. resigned as members of the Company’s board of directors effective immediately prior to the closing of the IPO.

Amendment and Restatement of Certificate of Incorporation

On May 22, 2017, the Company filed an amended and restated certificate of incorporation (the “Restated Certificate”) with the Secretary of State of the State of Delaware in connection with the closing of the IPO. The Company’s board of directors and stockholders previously approved the Restated Certificate effective as of and contingent upon the closing of the IPO.

A copy of the Restated Certificate is furnished herewith as Exhibit 3.1 and is incorporated herein by reference.

Amendment and Restatement of Bylaws

The Company also adopted amended and restated bylaws (the “Restated Bylaws”) in connection with the closing of the IPO. The Company’s board of directors and stockholders previously approved the Restated Bylaws effective as of and contingent upon the closing of the IPO.

A copy of the Restated Bylaws is furnished herewith as Exhibit 3.2 and is incorporated herein by reference.

On May 22, 2017, we closed our initial public offering of 7,781,564 shares of our common stock at a price of $15.00 per share, less underwriting discounts and commissions. The initial public offering included the sale of 781,564 shares pursuant to the underwriters’ over-allotment option. A copy of the press release announcing the information contained in this Item 8.01 is being filed herewith as Exhibit 99.1 and the information contained therein is incorporated by reference into this Current Report on Form 8-K.

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 thereunto duly authorized.

Date: May 26, 2017

INDEX TO EXHIBITS