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 12, 2018

G1 THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

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.  ☒

(d) Election of Director

On September 12, 2018, the Board of Directors (the “Board”) of G1 Therapeutics, Inc. (the “Company”), following the recommendation of the Nominating and Governance Committee of the Board appointed Garry Nicholson as an independent director to the Board to serve immediately as a Class III Director with a term expiring at the Company’s 2020 annual meeting of stockholders.

Mr. Nicholson has more than 30 years of pharmaceutical and biotech oncology experience. He led the global oncology franchise at Pfizer in the role of President, Pfizer Oncology from May 2008 through April 2015. Earlier in his career, Mr. Nicholson held various leadership positions in the oncology division of Eli Lilly and Company. Most recently, he served as President and Chief Executive Officer of XTuit Pharmaceuticals, where he also was a member of the board of directors. Mr. Nicholson began his career in healthcare as a staff pharmacist at Emory University. He also currently serves on the boards of directors of Five Prime Therapeutics, Inc., TESARO, Inc., and SQZ Biotechnologies. Mr. Nicholson holds an MBA from the University of South Carolina and earned his B.S. in Pharmacy at the University of North Carolina, Chapel Hill.

In connection with Mr. Nicholson’s election to the Board, and pursuant to the Company’s Non-Employee Director Compensation Policy (the “Director Compensation Policy”), the Board granted to Mr. Nicholson a non-statutory stock option to purchase up to 20,000 shares of the Company’s common stock. The stock option will have an exercise price per share of $65.75, the closing price of the Company’s common stock on The NASDAQ Global Select Market on the date of grant. The stock option will vest in equal monthly installments through the third anniversary of the date of grant, subject to Mr. Nicholson’s continued service as a director.

In addition, Mr. Nicholson is entitled to receive an annual cash retainer of $38,500 for his service as a non-employee director of the Company pursuant to the Director Compensation Policy, prorated for the portion of the year that Mr. Nicholson serves as a director.

Also in connection with Mr. Nicholson’s election to the Board, Mr. Nicholson and the Company will enter into an indemnification agreement in the form the Company has entered into with its other non-employee directors, which form is filed as Exhibit 10.1 to the Company’s Amendment No. 2 to its Registration Statement on Form S-1 (File No. 333-217285) filed by the Company on May 8, 2017. Under this agreement, the Company will agree, among other things, to indemnify Mr. Nicholson for certain expenses, including attorneys’ fees, judgments, fines and settlement amounts incurred by him in any action or proceeding arising out of his service as one of the Company’s directors.

There are no arrangements or understandings between Mr. Nicholson and any other person pursuant to which Mr. Nicholson was appointed as a director. There are no transactions to which the Company is a party and in which Mr. Nicholson has a material interest that are required to be disclosed under Item 404(a) of Regulation S-K. Mr. Nicholson has not previously held any positions with the Company and has no family relations with any directors or executive officers of the Company.

(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 thereunto duly authorized.

Date: September 13, 2018

Exhibit 99.1

G1 Therapeutics Announces Appointment of Garry Nicholson to Board of Directors

RESEARCH TRIANGLE PARK, NC, September 13, 2018 – G1 Therapeutics, Inc. (Nasdaq: GTHX), a clinical-stage oncology company, today announced that Garry Nicholson has been appointed to its board of directors, effective September 12, 2018.

“We are pleased to welcome Garry as an independent director to our board. He has a breadth of experience in oncology development and commercialization, including leading the global regulatory and launch strategy for the first CDK4/6 inhibitor approved in the U.S. and Europe. We look forward to his contributions as we advance our pipeline of innovative therapies to improve the lives of those affected by cancer,” said Mark Velleca, M.D., Ph.D., Chief Executive Officer.

“I am excited to be joining the G1 board of directors as the company moves toward commercialization of its lead program. Trilaciclib is a first-in-class therapy that could benefit millions of people living with cancer,” added Mr. Nicholson.

Mr. Nicholson has more than 30 years of pharmaceutical and biotech oncology experience. He led the global oncology franchise at Pfizer in the role of President, Pfizer Oncology. His responsibilities included global commercialization and sales, clinical development and regulatory strategy, and business development. Mr. Nicholson also served on the board of directors of the Pfizer Foundation. Earlier in his career, he held various leadership positions in the oncology division of Eli Lilly and Company. Most recently, Mr. Nicholson served as President and Chief Executive Officer of XTuit Pharmaceuticals.

Mr. Nicholson currently serves on the board of directors of Five Prime Therapeutics, Inc., TESARO, Inc., and SQZ Biotechnologies.

About G1 Therapeutics

G1 Therapeutics, Inc. is a clinical-stage biopharmaceutical company focused on the discovery, development and delivery of innovative therapies that improve the lives of those affected by cancer. The company is advancing three clinical-stage programs, trilaciclib, lerociclib and G1T48, that are designed to enable more effective combination treatment strategies and improve patient outcomes across multiple oncology indications.

G1 is based in Research Triangle Park, NC. For additional information, please visit www.g1therapeutics.com and follow us on Twitter @G1Therapeutics.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Words such as “may,” “will,” “expect,” “plan,” “anticipate,” “estimate,” “intend” and similar expressions (as well as other words or expressions referencing future events, conditions or circumstances) are intended to identify forward-looking statements. Forward-looking statements in this news release include, but are not limited to, the therapeutic potential of trilaciclib,

lerociclib and G1T48, and are based on G1 Therapeutics’ expectations and assumptions as of the date of this press release. Each of these forward-looking statements involves risks and uncertainties. Factors that may cause G1 Therapeutics’ actual results to differ from those expressed or implied in the forward-looking statements in this press release are discussed in G1 Therapeutics’ filings with the U.S. Securities and Exchange Commission, including the “Risk Factors” sections contained therein and include, but are not limited to, G1 Therapeutics’ ability to recruit and enroll patients in its studies; G1 Therapeutics’ initial success in ongoing clinical trials may not be indicative of results obtained when these trials are completed or in later stage trials; the inherent uncertainties associated with developing new products or technologies and operating as a development-stage company; G1 Therapeutics’ ability to complete clinical trials for, obtain approvals for and commercialize any of its product candidates; competition in the industry in which G1 Therapeutics operates; and market conditions, including future legislation that may increase the difficulty and cost for G1 Therapeutics to obtain marketing approval of and commercialize its product candidates. Except as required by law, G1 Therapeutics assumes no obligation to update any forward-looking statements contained herein to reflect any change in expectations, even as new information becomes available.

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Contact:

Jeff Macdonald

Head of Investor Relations / Public Relations

917-371-0940

jmacdonald@g1therapeutics.com