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): November 30, 2015

Celladon Corporation

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (858) 350-4355

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligations of the registrant under any of the following provisions:

As previously announced, on November 18, 2015, Celladon Corporation (“Celladon”), Celladon Merger Sub, Inc. (“Merger Sub”) and Eiger BioPharmaceuticals, Inc. (“Eiger”) entered into an Agreement and Plan of Merger and Reorganization (“Merger Agreement”), pursuant to which, among other things, subject to the satisfaction or waiver of the conditions set forth in the Merger Agreement, Merger Sub will merge with and into Eiger, with Eiger becoming a wholly-owned subsidiary of Celladon and the surviving corporation of the merger.

Attached hereto and incorporated herein by reference as Exhibit 99.1 is a press release issued by Eiger on November 30, 2015 entitled “Eiger BioPharmaceuticals Granted Orphan Drug Status for Ubenimex in Pulmonary Arterial Hypertension.”

Additional Information about the Merger and Where to Find It

In connection with the proposed merger, Celladon and Eiger intend to file relevant materials with the Securities and Exchange Commission, or the SEC, including a registration statement on Form S-4 that will contain a prospectus and a proxy statement/information statement. Investors and security holders of Celladon and Eiger are urged to read these materials when they become available because they will contain important information about Celladon, Eiger and the proposed merger. The proxy statement/information statement, prospectus and other relevant materials (when they become available), and any other documents filed by Celladon with the SEC, may be obtained free of charge at the SEC web site at www.sec.gov. In addition, investors and security holders may obtain free copies of the documents filed with the SEC by Celladon by directing a written request to: Celladon Corporation, 12707 High Bluff Dr #200, San Diego, CA 92130, Attention: Investor Relations. Investors and security holders are urged to read the proxy statement/information statement, prospectus and the other relevant materials when they become available before making any voting or investment decision with respect to the proposed merger.

This communication shall not constitute an offer to sell or the solicitation of an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. No offering of securities in connection with the proposed merger shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended.

Reference is made to the Exhibit Index included with this Current Report on Form 8-K.

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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.

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EXHIBIT INDEX