UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K/A

(Amendment No. 2)

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 22, 2016

Eiger BioPharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (650) 272-6138

(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 obligations of the registrant under any of the following provisions:

Explanatory Note

As previously reported in the Current Report on Form 8-K, initially filed with the Securities and Exchange Commission on March 23, 2016, and as amended May 13, 2016 (the “Amended Report”), on March 22, 2016, Eiger BioPharmaceuticals, Inc. (the “Company”), formerly known as Celladon Corporation, completed its merger with what was then known as “Eiger BioPharmaceuticals, Inc.” (“Private Eiger”). This Amendment No. 2 to Current Report on Form 8-K is being filed solely to file the Interactive Data files relating to the audited financial statements of Private Eiger as of December 31, 2015 and 2014 and for each of the three years ended December 31, 2015, 2014 and 2013, in accordance with Rule 405 of Regulation S-T. No other changes have been made to the Amended Report.

(a) Financial statements of businesses acquired.

The audited financial statements of Private Eiger as of December 31, 2015 and 2014 and for each of the three years ended December 31, 2015, 2014, and 2013, are filed herewith as Exhibit 99.2 and are incorporated herein by reference. The consent of KPMG LLP, Private Eiger’s independent registered public accounting firm, is attached as Exhibit 23.1 to this Amendment No. 2 to Current Report on Form 8-K.

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

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 INDEX