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):

June 16, 2026

IRONWOOD PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

(617) 621-7722

(Registrant’s telephone number,

including area code)

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:

Securities registered pursuant to Section 12(b) of the Act:

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 ¨

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. ¨

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

On June 16, 2026, Ironwood Pharmaceuticals, Inc. (the “Company”) held its 2026 Annual Meeting of Stockholders (the “Annual Meeting”). As described in Item 5.07 below, at the Annual Meeting, the stockholders of the Company voted to approve an amendment (the “Plan Amendment”) to the Company’s Amended and Restated 2019 Equity Incentive Plan (the “Plan”, as amended by the Plan Amendment, the “Amended Plan”). The Plan Amendment, which had previously been adopted by the Company’s Board of Directors (the “Board”) subject to stockholder approval, increases the number of shares of Company’s Class A common stock available for issuance under the Amended Plan by 10,000,000 shares.

The terms of the Amended Plan are described on pages 53 to 58 in the Company’s Definitive Proxy Statement on Schedule 14A , filed with the Securities and Exchange Commission on April 28, 2026 (the “Proxy Statement”).

The foregoing description of the Plan Amendment is a summary only and is qualified in its entirety by reference to the full text of the Plan Amendment, a copy of which is attached as Exhibit 10.1 hereto.

Item 5.07 Submission of Matters to a Vote of Security Holders.

The final voting results for the Annual Meeting are as follows:

Item 9.01 Financial Statements and Exhibits.

(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.