UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 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): April 2, 2015

CONATUS PHARMACEUTICALS INC.

(Exact Name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (858) 376-2600

(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):

On April 2, 2015, Conatus Pharmaceuticals Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with Stifel, Nicolaus & Company, Incorporated and Roth Capital Partners, LLC, as representatives of the several underwriters named therein (collectively, the “Underwriters”), relating to the issuance and sale of 3,500,000 shares of the Company’s common stock, par value $0.0001 per share (the “Common Stock”). The price to the public in this offering is $5.75 per share. The Underwriters have agreed to purchase the shares from the Company pursuant to the Underwriting Agreement at a price of $5.405 per share. The net proceeds to the Company from the offering are expected to be approximately $18.6 million, after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company. The offering is expected to close on or about April 8, 2015, subject to customary closing conditions. In addition, under the terms of the Underwriting Agreement, the Company has granted the Underwriters a 30-day option to purchase up to 525,000 additional shares of Common Stock.

The offering is being made pursuant to the Company’s effective registration statement on Form S-3 (Registration Statement No. 333-198142) previously filed with and declared effective by the Securities and Exchange Commission (the “SEC”) and a prospectus supplement and accompanying prospectus filed with the SEC.

The Underwriting Agreement contains customary representations, warranties and agreements by the Company, customary conditions to closing, indemnification obligations of the Company and the Underwriters, including for liabilities under the Securities Act of 1933, as amended, other obligations of the parties and termination provisions. The representations, warranties and covenants contained in the Underwriting Agreement were made only for purposes of such agreement and as of specific dates, were solely for the benefit of the parties to such agreement, and may be subject to limitations agreed upon by the contracting parties.

The foregoing description of the Underwriting Agreement is not complete and is qualified in its entirety by reference to the full text of the Underwriting Agreement, a copy of which is filed as Exhibit 1.1 to this report and is incorporated by reference herein. A copy of the opinion of Latham & Watkins LLP relating to the legality of the issuance and sale of Common Stock in the offering is attached as Exhibit 5.1 to this report.

The Company issued press releases on April 1, 2015 and April 2, 2015 announcing the commencement of the offering and the pricing of the offering, respectively, which press releases are attached as Exhibits 99.1 and 99.2, respectively, to this report.

* * *

This report contains forward-looking statements within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended. All statements other than statements of historical facts contained in this report are forward looking statements, including statements regarding: the completion of the offering and the expected net proceeds therefrom. In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplates,” “believes,” “estimates,” “predicts,” “potential” or “continue” or the negative of these terms or other similar expressions. These forward-looking statements speak only as of the date of this report and are subject to a number of risks, uncertainties and assumptions, including: the risks and uncertainties associated with market conditions and the satisfaction of customary closing conditions related to the offering, as well risks and uncertainties inherent in Conatus’ business, including those risks described in Conatus’ periodic reports it files with the SEC. The events and circumstances reflected in Conatus’ forward-looking statements may not be achieved or occur and actual results could differ materially from those projected in the forward-looking statements. Except as required by applicable law, Conatus does not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances or otherwise.

(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.