IRONWOOD PHARMACEUTICALS INC

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User’s Guide

Our board of directors is soliciting proxies for the 2026 annual meeting of stockholders. This proxy statement explains the agenda, voting information and procedures for the meeting. Please read it carefully. This proxy statement and related materials are first being made available to stockholders on or about April 28, 2026, and the notice of internet availability of proxy materials is first being sent to our stockholders on the same day. All stockholders will also have the ability to access the proxy materials online through the Investors & Media section of our website atwww.ironwoodpharma.com, under the heading Financials — SEC Filings.

Who can vote

Only stockholders of record of our Class A common stock at the close of business on April 21, 2026, can vote at the meeting.

Quorum

In order to hold and complete the business of the annual meeting, we must have a majority of the votes entitled to be cast present at the meeting or represented by proxy. On our record date, April 21, 2026, we had 164,613,406 shares of our Class A common stock outstanding and entitled to vote. With respect to all matters that will come before the meeting, each share is entitled to one vote.

Notice of internet availability of proxy materials

Pursuant to rules adopted by the SEC, we have elected to provide access to our proxy materials via the internet. Accordingly, we are sending a notice of internet availability of proxy materials to our stockholders. All stockholders will have the ability to access the proxy materials on the website referenced in the notice and to request to receive a printed set of the proxy materials by mail. Instructions on how to access the proxy materials over the internet and how to request a printed copy may be found in the notice. In addition, stockholders may request to receive proxy materials in printed form by mail or electronically by email on an ongoing basis. We encourage stockholders to take advantage of the availability of the proxy materials on the internet or through email to help reduce the environmental impact of our annual meetings.

Voting procedures — stockholders of record and beneficial owners

You are a stockholder of record if your shares of our stock are registered directly in your own name with our transfer agent, Computershare Trust Company, N.A., or Computershare. You are a beneficial owner if a brokerage firm, bank, trustee or other agent, called a “nominee,” holds your stock. This is often called ownership in “street name” because your name does not appear in the records of Computershare. If you hold your shares in street name, you should receive a voting instruction form from your nominee.

How to vote your shares.

If you are a stockholder of record, there are four ways to vote:

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Online Before the Meeting. You may vote by proxy via the internet by following the instructions provided on the notice of internet availability of proxy materials or the proxy card. You must have the 16-digit control number that is on either the notice of internet availability of proxy materials or the proxy card when voting.

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Online During the Meeting. You may vote online during the annual meeting through the link The 16-digit control number provided on your notice of internet availability of proxy materials or proxy card is necessary to access the website. The meeting will begin at 9:00 a.m. Eastern Time (with log-in beginning at 8:45 a.m. Eastern Time) on Tuesday, June 16, 2026.

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By Telephone. If you request printed copies of the proxy materials by mail and you live in the United States or Canada, you may vote by proxy by calling the toll-free number found on the proxy card. You must have the control number that is on the proxy card when voting.

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By Mail. If you request printed copies of the proxy materials by mail, you may vote by proxy by filling out the proxy card and sending it back in the envelope provided.

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If you are a beneficial owner of shares held in street name, there are four ways to provide voting instructions:

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Online Before the Meeting. You may provide voting instructions via the internet by following the instructions provided on your voting instruction form. You must have the 16-digit control number that is on the voting instruction form when voting.

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Online During the Meeting. You may vote online during the annual meeting through the linkwww.virtualshareholdermeeting.com/IRWD2026. The 16-digit control number provided on your voting instruction form is necessary to access the website. The meeting will begin at 9:00 a.m. Eastern Time (with log-in beginning at 8:45 a.m. Eastern Time) on Tuesday, June 16, 2026.

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By Telephone. You may provide voting instructions by calling the toll-free number found on your voting instruction form. You must have the control number that is on the voting instruction form when voting.

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By Mail. You may provide voting instructions by filling out the voting instruction form and sending it back in the envelope provided.

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How you may revoke your proxy or voting instructions. If you are a stockholder of record, you may revoke or amend your proxy before it is voted at the annual meeting by writing to us directly in a timely manner “revoking” your earlier proxy, submitting a new proxy in a timely manner with a later date by mail, over the telephone or on the internet, or by attending the meeting and voting. Your last dated proxy timely received prior to or vote cast at the annual meeting will be counted.

What if you receive more than one notice of internet availability of proxy materials, proxy card or voting instruction form? This means that you may have more than one account at Computershare and/or with a nominee. Your notice of internet availability of proxy materials, proxy card or voting instruction form lists the number of shares you are voting. Please vote the shares on all notices of internet availability of proxy materials, proxy cards and voting instruction forms that you receive.

We recommend you consolidate your holdings under the same name, address and tax identification number, if possible. This will eliminate some duplication of mailings and reduce costs. Please contact your nominee to consolidate accounts, or our transfer agent, Computershare, at (800) 368-5948, as applicable.

Householding of proxy materials. SEC rules concerning the delivery of proxy materials allow us or your nominee to send a single notice or, if applicable, a single set of our proxy materials to any household at which two or more of our stockholders reside, if we or your nominee believe that the stockholders are members of the same family, unless we have received contrary instructions from one or more of the stockholders. This practice, referred to as “householding,” benefits both you and us. It reduces the volume of duplicate information received at your household and helps to reduce our expenses. The rule applies to our notices, annual reports, proxy statements and information statements.

We will undertake to deliver promptly, upon written request, a separate copy to a stockholder at a shared address to which a single copy of the notice of internet availability of proxy materials was delivered. You may make a written request by sending a notification to our Secretary at the address below, providing your name, your shared address, and the address to which we should direct the additional copy of the notice of internet availability of proxy materials. Multiple

2026 Proxy Statement 65 stockholders sharing an address who have received one copy of a mailing and would prefer us to mail each stockholder a separate copy of future mailings should contact us at the below address, as well. Additionally, if current stockholders with a shared address received multiple copies of a mailing and would prefer us to mail one copy of future mailings to stockholders at the shared address, notification of that request may also be sent to us at the below address. Stockholders who participate in householding will continue to have access to and utilize separate proxy voting instructions.

Any request relating to receipt of proxy materials should be sent to: Secretary, Ironwood Pharmaceuticals, Inc., 100 Summer Street, Suite 2300, Boston, Massachusetts 02110, or by telephone: (617) 621 7722.

Abstentions and “broker non-votes.” If you are a stockholder of record and you vote “abstain” or “withhold” on any matter, your shares will not be voted on that matter and will not be counted as votes cast in the final tally of votes on that matter. However, your shares will be counted for purposes of determining whether a quorum is present. If you are a beneficial owner holding shares through a broker nominee, you may instruct your broker nominee that you wish to abstain from voting on a proposal or withhold authority to vote for one or more nominees for director.

A broker nominee generally may not vote on “non-discretionary” matters without receiving your specific voting instructions. A “broker non-vote” occurs when a broker nominee holding shares in street name votes shares on some matters at the meeting but not others. Like abstentions, broker non-votes are counted as present and entitled to vote for quorum purposes, but are not counted as votes cast. Broker nominees who hold shares for the accounts of their clients have discretionary authority to vote shares if specific instructions are not given with respect to discretionary matters. Although the determination of whether a broker nominee will have discretionary voting power for a particular item is typically determined only after proxy materials are filed with the SEC, we expect that at the annual meeting of stockholders your broker nominee will not be able to submit a vote on the election of directors, the advisory vote on named executive officer compensation and the amendment to our A&R 2019 Plan unless it receives your specific instructions, but will be able to vote on the ratification of the selection of our independent auditors even if it does not receive your instructions. As a result, if your broker nominee does not receive your specific instructions for these proposals, it will submit a broker non-vote. The broker nominee may, however, vote on the ratification of the selection of our independent auditors even if it does not receive your instructions.

Discretionary authority. If you are a stockholder of record and you properly submit your proxy card without making any specific selections, your shares will be voted on each matter before the annual meeting in the manner recommended by our board of directors. If other matters not included in this proxy statement properly come before the annual meeting, the persons named on the proxy card, or otherwise designated, will have the authority to vote on those matters for you as they determine, to the extent permitted by Rule 14a-4(c)(1) of the Exchange Act. If you are a beneficial owner of shares held in street name, please see the discussion above regarding broker non-votes and the rules related to voting by broker nominees.

Vote required

The required vote for each of the proposals expected to be acted upon at the annual meeting is described below.

Proposal No. 1 — Election of Directors:

The election of the board of director nominees will be determined by a plurality of the votes cast, meaning that board of director nominees with the greatest number of votes cast for election, even if less than a majority, will be elected as directors to serve for one-year terms and until his or her successor is duly elected and qualified or until their death, resignation or removal. We expect that broker nominees will not have discretion to vote on this proposal without your instruction; if you do not instruct your broker nominee how to vote on this proposal, your broker nominee will deliver a broker non-vote. Votes withheld and broker non-votes will not affect the outcome of this proposal.

Proposal No. 2 — Advisory (non-binding) Vote on Named Executive Officer Compensation, or “Say-on-Pay”:

The approval of this proposal requires the affirmative vote of a majority of the votes cast for or against the proposal. As an advisory vote, this proposal is not binding. The outcome of this advisory vote does not overrule any decision by

66 Ironwood the company or the board (or any committee thereof), create or imply any change to the fiduciary duties of the company or the board (or any committee thereof), or create or imply any additional fiduciary duties for the company or the board (or any committee thereof).

However, our board of directors, including our compensation and HR committee, values the opinions of our stockholders and, to the extent there are a substantial number of votes cast against the named executive officer compensation disclosed in this proxy statement, we will consider our stockholders’ concerns and evaluate what actions may be appropriate to address those concerns. We expect that broker nominees will not have discretion to vote on this proposal without your instruction; if you do not instruct your broker nominee how to vote on this proposal, your broker nominee will deliver a broker non-vote. Any shares that are not voted, whether by abstention, broker non-votes or otherwise, will not affect the outcome of this proposal.

Proposal No. 3 — Approve an Amendment to the Ironwood Pharmaceuticals, Inc. Amended and Restated 2019 Equity Incentive Plan to Increase the Number of Shares Available for Issuance Thereunder by 10,000,000 Shares:

The approval of this proposal requires the affirmative vote of a majority of the votes cast for or against the proposal. Abstentions and broker non-votes will not affect the outcome of this proposal. We expect that broker nominees will not have discretion to vote on this proposal without your instruction; if you do not instruct your broker nominee how to vote on this proposal, your broker nominee will deliver a broker non-vote. Any shares that are not voted, whether by abstention, broker non-votes or otherwise, will not affect the outcome of this proposal.

Proposal No. 4 — Ratification of Auditors:

The approval of this proposal requires a the affirmative vote of majority of the votes cast for or against the proposal. Abstentions and any broker non-votes will not affect the outcome of this proposal. Further, because we believe this matter to be discretionary, a broker nominee may vote on your behalf if you do not otherwise provide instructions. As a result, we do not expect there will be any broker non-votes on this matter.

Results of the voting. We expect to announce the preliminary voting results at the annual meeting. The final voting results will be tallied by the inspector of election and published in a Current Report on Form 8-K, which we are required to file with the SEC, within four business days following the annual meeting.

Costs of solicitation and solicitation participants. We will pay the costs of soliciting proxies. These costs also include support for the hosting of the virtual meeting. We will solicit proxies by email from stockholders who are our employees or who previously requested to receive proxy materials electronically. Our directors, our officers and our employees also may solicit proxies on our behalf, personally, electronically or by telephone, facsimile or mail or other means, without additional compensation. We may request that brokerage firms, banks and other agents forward proxy materials to beneficial owners and we would reimburse such institutions for their out-of-pocket expenses incurred.

We may also utilize the assistance of third parties in connection with our proxy solicitation efforts and we would compensate such third parties for their efforts. We have engaged one such third party, MacKenzie Partners, to assist in the solicitation of proxies and provide related advice and informational support, for service fees of up to $14,000 and the reimbursement of certain expenses.

Additional Meeting Information

We encourage you to access the meeting prior to the start time. Please allow sufficient time for online log-in, which begins at 8:45 a.m. Eastern Time. You may check your browser’s compatibility any time prior to the meeting atwww.virtualshareholdermeeting.com/IRWD2026. If you want to submit a question you may do so electronically starting at the time of check-in or during the meeting.

If you have technical difficulties or trouble accessing the virtual meeting, there will be technicians ready to assist you. If you encounter any technical difficulties accessing the virtual meeting during the check-in or meeting time, please call the technical support number that will be posted on the virtual stockholder meeting log in page.

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