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): February 28, 2014

OPEXA THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (281) 272-9331

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:

On March 5, 2014, Opexa Therapeutics, Inc. (the “Company”), entered into a First Amendment to Sales Agreement (the “First Amendment”) with Meyers Associates, L.P. (doing business as Brinson Patrick, a division of Meyers Associates, L.P.) (the “New Sales Manager”) and Brinson Patrick Securities Corporation (the “Original Sales Manager”). Pursuant to the First Amendment, the Sales Agreement dated September 6, 2012 by and between the Company and the Original Sales Manager was assigned by the Original Sales Manager to the New Sales Manager. The Sales Agreement, as amended, is referred to herein as the “ATM Agreement.”

Under the ATM Agreement, the Company may offer and sell shares of its common stock from time to time depending upon market demand, with the New Sales Manager acting as an agent for the sale of shares in transactions deemed to be an “at the market” offering as defined in Rule 415 of the Securities Act of 1933.

The Company will pay the New Sales Manager a commission equal to 3% of the gross proceeds from the sale of shares of common stock by it as agent under the ATM Agreement. The ATM Agreement provides that the Company will provide customary indemnification rights to the New Sales Manager as well as the Original Sales Manager. The Company has no obligation to sell any shares of common stock pursuant to the ATM Agreement and may at any time suspend sales pursuant to the ATM Agreement. Either party may terminate the ATM Agreement at any time without liability of any party.

The shares of common stock will be sold pursuant to a shelf registration statement on Form S-3 (Registration No. 333-185001), declared effective by the Securities and Exchange Commission on December 5, 2012. A prospectus supplement relating to the offer and sale of up to 2,500,000 shares of common stock pursuant to the ATM Agreement will be filed with the Securities and Exchange Commission as part of the registration statement. Interested investors should read the registration statement and prospectus supplement and all documents incorporated therein by reference. This Current Report shall not constitute an offer to sell or the solicitation of an offer to buy 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 laws of any such state.

The First Amendment is attached to this Current Report on Form 8-K as Exhibit 10.1 and incorporated herein by reference. The Sales Agreement was filed as Exhibit 10.1 to the Company’s Current Report on Form 8-K filed on September 7, 2012 and is incorporated herein by reference. The foregoing description of the First Amendment and ATM Agreement does not purport to be complete and is qualified in its entirety by reference to the First Amendment and ATM Agreement.

As a result of the foregoing, the continuous offering through the Original Sales Manager pursuant to a prospectus supplement dated January 18, 2013 is deemed terminated and no further shares will be offered or sold by the Company through the Original Sales Manager.

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On February 28, 2014, the Board of Directors of the Company approved discretionary cash bonuses for fiscal year 2013 performance for the Company’s executive officers. This resulted in cash bonuses payable in the amounts shown below for the Company’s named executive officers.

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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, thereunto duly authorized.

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