Insider filing report for Changes in Beneficial Ownership
- Schedule 13G & 13D forms are used to report a party's ownership of stock which exceeds 5% of a company's total stock issue.
- Schedule 13G is a shorter version of Schedule 13D with fewer reporting requirements.
"Insiders might sell their shares for any number of reasons, but they buy them for only one: they think the price will rise"
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- Peter Lynch
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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549 |
SCHEDULE 13D
Under the Securities Exchange Act of 1934
(Amendment No. 4)*
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IRONWOOD PHARMACEUTICALS INC (Name of Issuer) |
Class A Common Stock, $0.001 par value (Title of Class of Securities) |
46333X108 (CUSIP Number) |
Patrice Bonfiglio Sarissa Capaital Management LP, 500 West Putnam Ave, Suite 400 Greenwich, CT, 06830 (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) |
If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.


The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the
Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other
provisions of the Act (however, see the Notes).
SCHEDULE 13D
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| CUSIP No. | 46333X108 |
| 1 |
Name of reporting person
Sarissa Capital Management LP | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
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| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
WC | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
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| 6 | Citizenship or place of organization
DELAWARE
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| Number of Shares Beneficially Owned by Each Reporting Person With: |
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| 11 | Aggregate amount beneficially owned by each reporting person
9,188,635.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
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| 13 | Percent of class represented by amount in Row (11)
5.6 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
PN |
Comment for Type of 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.
SCHEDULE 13D
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| CUSIP No. | 46333X108 |
| 1 |
Name of reporting person
Alexander J. Denner | ||||||||
| 2 | Check the appropriate box if a member of a Group (See Instructions)
(a)
(b)
| ||||||||
| 3 | SEC use only | ||||||||
| 4 |
Source of funds (See Instructions)
WC | ||||||||
| 5 |
Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)
![]() | ||||||||
| 6 |
Citizenship or place of organization
UNITED STATES
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| Number of Shares Beneficially Owned by Each Reporting Person With: |
| ||||||||
| 11 | Aggregate amount beneficially owned by each reporting person
9,444,944.00 | ||||||||
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)
![]() | ||||||||
| 13 | Percent of class represented by amount in Row (11)
5.8 % | ||||||||
| 14 | Type of Reporting Person (See Instructions)
IN |
Comment for Type of 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.
SCHEDULE 13D
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| 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,
MASSACHUSETTS
, 02110. | |
Item 1 Comment:
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 2. | Identity and Background | |
| (b) | Item 2(b) of the Initial Schedule 13D is hereby amended to include the following: The principal business address of each Reporting Person is c/o Sarissa Capital Management LP, 500 West Putnam Ave, Suite 400, Greenwich, CT 06830. | |
| 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.
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