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 12, 2020

AKEBIA THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (617) 871-2098

N/A

(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:

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  ☐

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.  ☐

On March 12, 2020, Akebia Therapeutics, Inc. (the “Company”) registered up to $65,000,000 of the Company’s common stock, par value $0.00001 per share (the “Shares”), pursuant to a prospectus supplement under its automatic shelf registration statement on Form S-3 (File No. 333-223585), filed with the Securities and Exchange Commission on March 12, 2018 (the “Registration Statement”). The Shares will be sold from time to time pursuant to the Amended and Restated Controlled Equity Offering^TM Sales Agreement with Cantor Fitzgerald & Co., as sales agent, dated November 12, 2019. The opinion and consent of Wilmer Cutler Pickering Hale and Dorr LLP as to the validity of the Shares, filed as Exhibits 5.1 and 23.1 to this Current Report on Form 8-K, respectively, are incorporated by reference into the Registration Statement.

The Shares are registered pursuant to an effective shelf Registration Statement on Form S-3 (File No. 333-223585) and the base prospectus contained therein, and offerings for the Shares will be made only by means of the Prospectus Supplement. This Current Report on Form 8-K shall not constitute an offer to sell or solicitation of an offer to buy these securities, nor shall there be any sale of these securities in any state in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities law of such state or jurisdiction.

(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.

Exhibit 5.1

March 12, 2020

Akebia Therapeutics, Inc.

245 First Street

Cambridge, MA 02142

Ladies and Gentlemen:

This opinion is being furnished to you in connection with (i) the Registration Statement on Form S-3 (File No. 333-223585) (the “Registration Statement”) filed by Akebia Therapeutics, Inc., a Delaware corporation (the “Company”), with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”), for the registration of, among other things, an indeterminate number of shares of Common Stock, $0.00001 par value per share, of the Company, which may be issued from time to time on a delayed or continuous basis pursuant to Rule 415 under the Securities Act, as set forth in the Registration Statement and the prospectus contained therein (the “Base Prospectus”) and (ii) the prospectus supplement, dated March 12, 2020 (the “Prospectus Supplement” and, together with the Base Prospectus, the “Prospectus”) relating to the issuance and sale from time to time by the Company of shares of Common Stock with an aggregate offering price of up to $65,000,000 (the “Shares”).

The Shares are to be issued and sold by the Company pursuant to an Amended and Restated Controlled Equity Offering^SM Sales Agreement, dated November 12, 2019 (the “Sales Agreement”), between the Company and Cantor Fitzgerald & Co. We are acting as counsel for the Company in connection with the issue and sale by the Company of the Shares. We have examined copies of the Registration Statement and the Prospectus as filed with the Commission. We have also examined and relied upon the Sales Agreement, minutes of meetings of the stockholders and the Board of Directors of the Company, including committees thereof as provided to us by the Company, stock record books of the Company as provided to us by the Company, the Certificate of Incorporation and Bylaws of the Company, each as restated and/or amended to date, and such other documents as we have deemed necessary for purposes of rendering the opinions hereinafter set forth.

In our examination of the foregoing documents, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as copies, the authenticity of the originals of such latter documents and the legal competence of all signatories to such documents. Further, we have assumed that the Company will not issue and sell pursuant to the Sales Agreement such number of Shares that would cause the Company not to satisfy the eligibility requirements for Form S-3 (including Instruction I.B.6. thereof).

Wilmer Cutler Pickering Hale and Dorr LLP, 60 State Street, Boston, Massachusetts 02109

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Akebia Therapeutics, Inc.

March 12, 2020

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We express no opinion herein as to the laws of any state or jurisdiction other than the General Corporation Law of the State of Delaware and the federal laws of the United States of America.

Based upon and subject to the foregoing, we are of the opinion that the Shares have been duly authorized for issuance and, when the Shares are issued and paid for in accordance with the terms and conditions of the Sales Agreement, the Shares will be validly issued, fully paid and nonassessable.

Please note that we are opining only as to the matters expressly set forth herein, and no opinion should be inferred as to any other matters. This opinion is based upon currently existing statutes, rules, regulations and judicial decisions, and we disclaim any obligation to advise you of any change in any of these sources of law or subsequent legal or factual developments which might affect any matters or opinions set forth herein.

We hereby consent to the filing of this opinion with the Commission in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act as an exhibit to the Current Report on Form 8-K to be filed by the Company on the date hereof in connection with the issuance and sale of the Shares and to the use of our name therein and in the related Prospectus Supplement under the caption “Legal Matters.” In giving such consent, we do not hereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act or the rules and regulations of the Commission.

[Signature Page Follows]

Akebia Therapeutics, Inc.

March 12, 2020

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