# EDGAR Filing Document

**Accession Number:** 0001446847
**File Stem:** 0000899140-26-000333
**Filing Date:** 2026-3
**Character Count:** 11228
**Document Hash:** 8f9967ef00e743b6dc64240e481e7fd1
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0000899140-26-000333.hdr.sgml**: 20260319

**ACCESSION NUMBER**: 0000899140-26-000333

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13D/A

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20260319

**DATE AS OF CHANGE**: 20260319

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** IRONWOOD PHARMACEUTICALS INC
- **CENTRAL INDEX KEY:** 0001446847
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 043404176
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-85292
- **FILM NUMBER:** 26775552

**BUSINESS ADDRESS:**
- **STREET 1:** 100 SUMMER STREET, SUITE 2300
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02110
- **BUSINESS PHONE:** 617-621-7722

**MAIL ADDRESS:**
- **STREET 1:** 100 SUMMER STREET, SUITE 2300
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02110
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Sarissa Capital Management LP
- **CENTRAL INDEX KEY:** 0001577524

**ORGANIZATION NAME:**
- **EIN:** 900924432
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D/A

**BUSINESS ADDRESS:**
- **STREET 1:** 500 WEST PUTNAM AVENUE, SUITE 400
- **CITY:** GREENWICH
- **STATE:** CT
- **ZIP:** 06830
- **BUSINESS PHONE:** 203-302-2330

**MAIL ADDRESS:**
- **STREET 1:** 500 WEST PUTNAM AVENUE, SUITE 400
- **CITY:** GREENWICH
- **STATE:** CT
- **ZIP:** 06830

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## SCHEDULE 13D

### Under the Securities Exchange Act of 1934

**(Amendment No. 4)**

**IRONWOOD PHARMACEUTICALS INC**

*(Name of Issuer)*

**Class A Common Stock, $0.001 par value**

*(Title of Class of Securities)*

**—**

*(CUSIP Number)*

**Patrice Bonfiglio**<br>Sarissa Capaital Management LP<br>500 West Putnam Ave, Suite 400<br>Greenwich CT 06830<br>(203) 302-2330

*(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)*

**03/17/2026**

*(Date of Event Which Requires Filing of this Statement)*

| **CUSIP No.** | **—** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Sarissa Capital Management LP** | Name of reporting person<br>**Sarissa Capital Management LP** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**WC** | Source of funds (See Instructions)<br>**WC** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**9188635.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**9188635.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**9188635.00** | Aggregate amount beneficially owned by each reporting person<br>**9188635.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**5.6%** | Percent of class represented by amount in Row (11)<br>**5.6%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**PN** | Type of Reporting Person (See Instructions)<br>**PN** | |

---

**Comment for Reporting Person:** Calculations of the percentage set forth in Row 13 are based upon the 163,058,316 Shares stated to be outstanding as of January 31, 2026 by the Issuer in the Issuer's Form 10-K filed with the Securities and Exchange Commission on February 26, 2026.

| **CUSIP No.** | **—** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Alexander J. Denner** | Name of reporting person<br>**Alexander J. Denner** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**WC** | Source of funds (See Instructions)<br>**WC** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**X1** | Citizenship or place of organization<br>**X1** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**256309.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**9188635.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**256309.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**9188635.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**9444944.00** | Aggregate amount beneficially owned by each reporting person<br>**9444944.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**5.8%** | Percent of class represented by amount in Row (11)<br>**5.8%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

**Comment for Reporting Person:** The amount set forth in each of Rows 7 and 9 represents shares acquired by Dr. Denner in his capacity as a director of the Issuer. Calculations of the percentage set forth in Row 13 are based upon the 163,058,316 Shares stated to be outstanding as of January 31, 2026 by the Issuer in the Issuer's Form 10-K filed with the Securities and Exchange Commission on February 26, 2026.

**Item 1. Security and Issuer**

**(a) Title of Class of Securities:**
Class A Common Stock, $0.001 par value

**(b) Name of Issuer:**
IRONWOOD PHARMACEUTICALS INC

**(c) Address of Issuer's Principal Executive Offices:**
100 Summer Street, Suite 2300, Boston, MA, 02110

This statement constitutes Amendment No. 4 to the Schedule 13D (this "Amendment No. 4") relating to the Class A Common Stock, par value $0.001 (the "Shares"), issued by Ironwood Pharmaceuticals, Inc. (the "Issuer"), and hereby amends the Schedule 13D filed with the Securities and Exchange Commission (the "SEC") on May 16, 2019, as amended by Amendment No. 1 filed with the SEC on February 26, 2020, Amendment No. 2 filed with the SEC on November 11, 2020, and Amendment No. 3 filed with the SEC on March 1, 2021 (as amended, the "Initial Schedule 13D"), on behalf of the Reporting Persons (as defined in the Initial Schedule 13D), to furnish the additional information set forth herein. All capitalized terms contained herein but not otherwise defined shall have the meanings ascribed to such terms in the Initial Schedule 13D.

**Item 5. Interest in Securities of the Issuer**

**(a)**
Items 5 (a) and (b) of the Initial Schedule 13D are hereby amended by replacing them in their entirety with the following:

(a) Sarissa Capital Management LP ("Sarissa Capital") may be deemed to beneficially own, in the aggregate, 9,188,635 Shares representing approximately 5.6% of the Issuer's outstanding Shares (based upon the 163,058,316  Shares stated to be outstanding as of January 31, 2026 by the Issuer in the Issuer's Form 10-K filed with the Securities and Exchange Commission on February 26, 2026).  Dr. Denner may be deemed to beneficially own, in the aggregate, 9,444,944 Shares (inclusive of the Shares held directly by Dr. Denner and the Shares that may be deemed to be beneficially owned by Sarissa Capital) representing approximately 5.8% of the Issuer's outstanding Shares.

**(b)**
For purposes of this Schedule 13D:

Other than the Shares held directly by Dr. Denner, all of the Shares for which Dr. Denner and Sarissa Capital may be deemed to have beneficial ownership are held directly by either Sarissa Capital or by funds and other investment vehicles (the "Sarissa Funds") for which Sarissa Capital serves as the investment advisor.  As the investment advisor to the Sarissa Funds, Sarissa Capital has the power to vote or direct the vote of (and the power to dispose or direct the disposition of) the Shares held by the Sarissa Funds.  By virtue of his position as the Chief Investment Officer of Sarissa Capital and as the managing member, general partner or other control party of the Sarissa Funds, Dr. Denner may be deemed to have the shared power to vote or direct the vote of (and the shared power to dispose or direct the disposition of) the Shares held by Sarissa Capital and the Sarissa Funds.

**(c)**
On March 17, 2026, the Sarissa Funds sold 6,725,000 Shares at a weighted average price of $3.0501 per Share in open market transactions, for an aggregate price of $20,511,923.
On March 17, 2026, the Sarissa Funds sold 5,800 Shares at a weighted average price of $3.3084 per Share in open market transactions, for an aggregate price of $19,189.
On March 17, 2026, Dr. Denner was granted 4,451 Shares in his capacity as a director of the Issuer.
The Reporting Persons undertake to provide, upon request by the Staff of the SEC, full information regarding the number of Shares sold at each separate price.
Other than as set forth above, as of 4:00 p.m., Eastern Time, on March 19, 2026, no transactions with respect to Shares were effected during the past sixty (60) days by any of the Reporting Persons.

### SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Sarissa Capital Management LP

**Signature:** /s/Alexander J. Denner, Ph.D.

**Name/Title:** Alexander J. Denner, Ph.D., Chief Investment Officer

**Date:** 03/19/2026

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

**Reporting Person:** Alexander J. Denner

**Signature:** /s/Alexander J. Denner, Ph.D.

**Name/Title:** Alexander J. Denner, Ph.D., Chief Investment Officer

**Date:** 03/19/2026