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): October 24, 2017

Idera Pharmaceuticals, Inc.

(Exact Name of Registrant as Specified in Charter)

167 Sidney Street

Cambridge, Massachusetts 02139

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (617) 679-5500

(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):

o    Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o    Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

o    Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o    Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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

Emerging growth company o

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. o

Item 2.02. Results of Operations and Financial Condition

On October 24, 2017, Idera Pharmaceuticals, Inc. (the “Company”) filed a prospectus supplement with the Securities and Exchange Commission in connection with a proposed offering of shares of its common stock, as described in the press release filed under Item 8.01 of this Current Report on Form 8-K, that included estimated information about the Company’s cash, cash equivalents and investments as of September 30, 2017. As of September 30, 2017, the Company estimates its cash, cash equivalents and investments was approximately $65.3 million. This estimate was prepared by management in good faith based upon internal reporting and expectations as of and for the three months ended September 30, 2017. This estimate is preliminary, and unaudited, and may be revised as a result of management’s further review of the Company’s results. The Company and its auditors have not completed the normal quarterly review procedures as of and for the period ended September 30, 2017, and there can be no assurance that the Company’s final results for this quarterly period will not differ from this estimate.

The information in this Item 2.02 of this Current Report on Form 8-K shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934 (the “Exchange Act”) or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933 or the Exchange Act, except as expressly set forth by specific reference in such a filing.

Item 5.02. Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

On October 24, 2017, Mr. Youssef El Zein resigned from the Board of Directors of the Company (the “Board”), effective immediately. Mr. El Zein’s decision to resign did not result from any disagreement with the Company on any matter relating to the Company’s operations, policies or practices.

Item 8.01. Other Events.

On October 24, 2017, the Company issued a press release announcing its intention to offer and sell $60 million of shares of its common stock in an underwritten public offering, subject to market conditions and other factors, pursuant to the Company’s effective Registration Statement on Form S-3 (File No. 333-219851). The full text of the press release issued in connection with the announcement is attached to this Current Report on Form 8-K as Exhibit 99.1 and is incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits.

2

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

3

Exhibit 99.1

Idera Pharmaceuticals Announces Proposed Public Offering of Common Stock

CAMBRIDGE, Mass. and EXTON, Pa. — (GLOBE NEWSWIRE) — October 24, 2017 — Idera Pharmaceuticals, Inc. (NASDAQ: IDRA) (“Idera” or the “Company”) today announced that it intends to offer and sell up to $60 million of shares of its common stock in an underwritten public offering. In connection with this offering, Idera expects to grant the underwriters a 30-day option to purchase additional shares of common stock, in an amount equal to up to 15% of the number of shares of common stock sold in the offering. All of the shares in the offering are to be sold by Idera. Idera intends to use the net proceeds from this offering, together with existing cash, cash equivalents and investments, to advance the development of IMO-2125 in its immuno-oncology program and for working capital and other general corporate purposes. J.P. Morgan and Goldman Sachs are acting as joint bookrunning managers on the transaction.  Barclays is also acting as a joint bookrunning manager on the transaction.

The shares are being offered by the Company pursuant to a shelf registration statement initially filed with the Securities and Exchange Commission (the “SEC”) on August 10, 2017 and declared effective by the SEC on September 8, 2017. A preliminary prospectus supplement describing the terms of the offering will be filed with the SEC and will form a part of the effective registration statement. The offering will be made only by means of the written prospectus and prospectus supplement that form a part of the registration statement. Copies of the preliminary prospectus supplement and the accompanying prospectus relating to the securities being offered may also be obtained from J.P. Morgan Securities LLC, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717 (telephone: 866-803-9204); from Goldman Sachs & Co. LLC, Attention: Prospectus Department, 200 West Street, New York, NY 10282, or by telephone at (866) 471-2526 or e-mail at prospectus-ny@ny.email.gs.com; or from Barclays Capital Inc., c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717, or by telephone at (888) 603-5847 or email at barclaysprospectus@broadridge.com.

This press release shall not constitute an offer to sell or the solicitation of an offer to buy the securities being offered, nor shall there be any sale of the securities being offered in any state or other jurisdiction in which such offer, solicitation or sale would be unlawful prior to the registration or qualification under the securities laws of any such state or other jurisdiction.

About Idera Pharmaceuticals, Inc.

Harnessing the approach of the earliest researchers in immunotherapy and the company’s vast experience in developing proprietary immunology platforms, Idera’s lead development program is focused on priming the immune system to play a more powerful role in fighting cancer, ultimately increasing the number of people who can benefit from immunotherapy. Idera continues to invest in research and development, and is committed to working with investigators

and partners who share the common goal of addressing the unmet needs of patients suffering from rare, life-threatening diseases.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. All statements, other than statements of historical fact, included or incorporated in this press release are forward-looking statements. The words “believes,” “anticipates,” “estimates,” “plans,” “expects,” “intends,” “may,” “could,” “should,” “potential,” “likely,” “projects,” “continue,” “will,” and “would” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Idera cannot guarantee that it will actually achieve the plans, intentions or expectations disclosed in its forward-looking statements and you should not place undue reliance on the Company’s forward-looking statements. There are a number of important factors that could cause Idera’s actual results to differ materially from those indicated or implied by its forward-looking statements. Factors that may cause such a difference include, without limitation, risks and uncertainties related to whether or not Idera will be able to raise capital through the sale of shares of common stock, the final terms of the proposed offering, market and other conditions, the satisfaction of customary closing conditions related to the proposed public offering, the impact of general economic, industry or political conditions in the United States or internationally, and such other important factors as are set forth under the caption “Risk Factors” in the Company’s Annual Report on Form 10-K for the period ended December 31, 2016. Although Idera may elect to do so at some point in the future, the Company does not assume any obligation to update any forward-looking statements and it disclaims any intention or obligation to update or revise any forward-looking statement, whether as a result of new information, future events or otherwise.

Source: Idera Pharmaceuticals, Inc.

Investor Contact

Robert Doody

Vice President, Investor Relations & Corporate Communications

617-679-5515 (office)

484-639-7235 (mobile)

rdoody@iderapharma.com