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 16, 2018

Tetraphase Pharmaceuticals, Inc.

(Exact name of registrant as specified in charter)

Registrant’s telephone number, including area code: (617) 715-3600

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):

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  ☐

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 5.02 (b). Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

Effective March 16, 2018, the Company’s Board of Directors elected Christopher Watt the Company’s principal financial officer and principal accounting officer until a chief financial officer is named. On February 26, 2018, the Company filed a Current Report on Form 8-K announcing that Kamalam Unninayar submitted her resignation as chief financial officer of the Company effective March 16, 2018.

Mr. Watt, 53, has served as the Company’s senior vice president, finance since January 2017. He previously served as our vice president, finance from July 2015 to January 2017. Prior to joining the Company, Mr. Watt spent ten years at Biogen, Inc., a publicly traded pharmaceutical company, most recently serving as senior director, global commercial finance. From 2009 to 2011, Mr. Watt served as the finance director for Biogen’s UK/Ireland affiliate and from 2006 to 2009 as director of business planning, international. Mr. Watt received a B.A. from Colby College and an M.B.A. from the University of Michigan.

SIGNATURE

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