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): September 13, 2018

ALTIMMUNE, INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number including area code: (240) 654-1450

(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:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (17 CFR §230.405) or Rule 12b-2 of the Securities Exchange Act of 1934 (17 CFR §240.12b-2).

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 September 13, 2018, Altimmune, Inc. (the “Company”) filed a Certificate of Amendment to its Amended and Restated Certificate of Incorporation (the “Certificate of Incorporation”) with the Secretary of State of Delaware to effect a one-for-thirty (1:30) reverse split of the Company’s outstanding common stock, par value $0.0001 per share (the “Reverse Stock Split”). The Reverse Stock Split will reduce the number of the Company’s outstanding shares of common stock from approximately 43 million shares to approximately 1.4 million shares. The number of authorized shares of common stock will remain unadjusted as a result of the Reverse Stock Split. The Reverse Stock Split became effective after the close of market on September 13, 2018 and the consolidated common stock will begin trading on The Nasdaq Global Market on a split-adjusted basis on September 14, 2018.

Additionally, on September 13, 2018, the Company filed a Certificate of Amendment to the Certificate of Incorporation to increase the number of authorized shares of common stock from 100,000,000 to 200,000,000.

Copies of the Certificates of Amendment are attached as Exhibit 3.1 and Exhibit 3.2 to this Current Report on Form 8-K and are incorporated by reference herein.

SIGNATURE

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.

Dated September 13, 2018

Exhibit 3.1

CERTIFICATE OF AMENDMENT TO

AMENDED AND RESTATED

CERTIFICATE OF INCORPORATION

OF

ALTIMMUNE, INC.

The undersigned, being the Chief Executive Officer of Altimmune, Inc., a corporation organized and existing under the laws of the State of Delaware (the “Corporation”), does hereby amend and certify as follows:

1. That the name of the Corporation is Altimmune, Inc., and that the Corporation was originally incorporated pursuant to the GCL on April 25, 2005 under the name Healthcare Acquisition Corp.

2. That this Certificate of Amendment has been duly adopted by the Board of Directors and stockholders in accordance with the provisions of section 242 of the Delaware General Corporation Law.

Article FOURTH of the Amended and Restated Certificate of Incorporation will be amended to add a new Paragraph C. as follows:

“C. Reverse Stock Split. Upon the effectiveness (the “Effective Time”) of this Certificate of Amendment pursuant to Section 242 of the General Corporation Law of the State of Delaware, each thirty (30) shares of the Corporation’s common stock, par value of $0.0001 per share, issued and outstanding immediately prior to the Effective Time (the “Old Common Stock”) shall automatically without further action on the part of the Corporation or any holder of Old Common Stock, be reclassified, combined and changed into one (1) fully paid and nonassessable share of common stock, par value of $0.0001 per share (the “New Common Stock”), subject to the treatment of fractional share interests as described below (the “reverse stock split”). From and after the Effective Time, certificates representing the Old Common Stock shall represent the number of shares of New Common Stock into which such Old Common Stock shall have been combined pursuant to this Certificate of Amendment. Holders who otherwise would be entitled to receive fractional share interests of New Common Stock upon the effectiveness of the reverse stock split shall be entitled to receive a whole share of New Common Stock in lieu of any fractional share created as a result of such reverse stock split.”

3. That this Certificate of Amendment shall be effective as of 5:30 p.m. EDT on September 13, 2018.

4. Except as set forth in this Certificate of Amendment, the Amended and Restated Certificate of Incorporation, as previously amended, remains in full force and effect.

[SIGNATURE PAGE FOLLOWS]

IN WITNESS WHEREOF, this Certificate of Amendment has been executed by a duly authorized officer of the Corporation on this 13^th day of September, 2018.

Exhibit 3.2

CERTIFICATE OF AMENDMENT TO

AMENDED AND RESTATED

CERTIFICATE OF INCORPORATION

OF

ALTIMMUNE, INC.

The undersigned, being the Chief Executive Officer of Altimmune, Inc., a corporation organized and existing under the laws of the State of Delaware (the “Corporation”), does hereby amend and certify as follows:

1. That the name of the Corporation is Altimmune, Inc., and that the Corporation was originally incorporated pursuant to the GCL on April 25, 2005 under the name Healthcare Acquisition Corp.

2. That this Certificate of Amendment has been duly adopted by the Board of Directors and stockholders in accordance with the provisions of section 242 of the Delaware General Corporation Law.

The first paragraph of Article FOURTH of the Amended and Restated Certificate of Incorporation is amended and restated to read as follows:

“FOURTH: The total number of shares of all classes of capital stock which the Corporation shall have authority to issue is 201,000,000 of which 200,000,000 shares shall be Common Stock of the par value of $0.0001 per share and 1,000,000 shares shall be Preferred Stock of the par value of $0.0001 per share.”

3. That this Certificate of Amendment shall be effective as of 5:30 p.m. EDT on September 13, 2018.

4. Except as set forth in this Certificate of Amendment, the Amended and Restated Certificate of Incorporation, as previously amended, remains in full force and effect.

[SIGNATURE PAGE FOLLOWS]

IN WITNESS WHEREOF, this Certificate of Amendment has been executed by a duly authorized officer of the Corporation on this 13^th day of September, 2018.