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 23, 2017

ACHAOGEN, INC.

(Exact name of registrant as specified in its charter)

1 Tower Place, Suite 300

South San Francisco, CA 94080

(Address of principal executive offices, including Zip Code)

7000 Shoreline Court, Suite 371

South San Francisco, CA 94080

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

Registrant’s telephone number, including area code: (650) 800-3636

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:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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 financing accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☒

On May 23, 2017, Achaogen, Inc. announced that the U.S. Food and Drug Administration granted Breakthrough Therapy designation for plazomicin for the treatment of bloodstream infections caused by certain Enterobacteriaceae, Klebsiella pneumoniae and Enterobacter aerogenes. A Breakthrough Therapy drug must show preliminary clinical evidence of a substantial improvement on a clinically significant endpoint over available therapies. Breakthrough Therapy designation is a process designed to expedite the development and review of designated drugs. Should the clinical development program not continue to meet the criteria for Breakthrough Therapy designation, however, the designation may be rescinded.

SIGNATURES

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