Sarissa Capital (IRWD) cuts Ironwood stake with 6.7M-share sale, keeps 5.8%

Rhea-AI Filing Summary

Sarissa Capital Management LP and Alexander J. Denner filed Amendment No. 4 to their Schedule 13D for Ironwood Pharmaceuticals. The filing reports that Sarissa Capital may be deemed to beneficially own 9,188,635 shares, or approximately 5.6% of Ironwood’s Class A common stock.

Dr. Denner may be deemed to beneficially own 9,444,944 shares, representing about 5.8% of the outstanding shares, including those held through Sarissa-managed funds and those he holds directly as a director. On March 17, 2026, Sarissa Funds sold 6,725,000 shares at a weighted average price of $3.0501 per share and 5,800 shares at $3.3084 per share, for aggregate proceeds of $20,511,923 and $19,189, respectively.

On the same date, Dr. Denner was granted 4,451 shares in his capacity as a director of Ironwood. The filing states that, other than these transactions, no other transactions in the shares were effected by the reporting persons during the prior 60 days as of the afternoon of March 19, 2026.

Positive

• None.

Negative

• Sarissa Funds executed large open-market sales, disposing of 6,725,000 shares at a weighted average price of $3.0501 and 5,800 shares at $3.3084 on March 17, 2026, reducing the activist group’s exposure while it still holds a significant stake.

Insights

Activist & ownership structure analyst

Large holder sells ~6.7M Ironwood shares but retains a 5.8% stake.

The filing shows Sarissa Capital and Alexander J. Denner remain significant Ironwood shareholders but after sizable open-market sales. Sarissa Capital is deemed to own 9,188,635 shares (about 5.6% of the class), while Denner is deemed to own 9,444,944 shares (5.8%).

On March 17, 2026, Sarissa Funds sold 6,725,000 shares at a weighted average price of $3.0501 and 5,800 shares at $3.3084, totaling about $20.53M in proceeds. At the same time, Denner received 4,451 shares as director compensation, a routine governance-related grant.

The combined picture is a notable reduction in position size by a historically active holder while maintaining a meaningful stake. Subsequent ownership disclosures in future company filings will provide clarity on whether this level stabilizes or continues to change.

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)

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).

schemaVersion:

SCHEDULE 13D

CUSIP Number(s): 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)

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 9,188,635.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 9,188,635.00

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)

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

CUSIP Number(s): 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

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 256,309.00
8	Shared Voting Power 9,188,635.00
9	Sole Dispositive Power 256,309.00
10	Shared Dispositive Power 9,188,635.00

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

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.

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

Alexander J. Denner

Signature:	/s/Alexander J. Denner, Ph.D.
Name/Title:	Alexander J. Denner, Ph.D., Chief Investment Officer
Date:	03/19/2026

FAQ

What stake in Ironwood Pharmaceuticals (IRWD) does Sarissa Capital now report?

Sarissa Capital may be deemed to beneficially own 9,188,635 Ironwood shares, representing approximately 5.6% of the outstanding Class A common stock, based on 163,058,316 shares outstanding as of January 31, 2026, as disclosed in Ironwood’s Form 10-K.

How many Ironwood (IRWD) shares does Alexander J. Denner beneficially own after this amendment?

Alexander J. Denner may be deemed to beneficially own 9,444,944 Ironwood shares, or about 5.8% of the outstanding Class A common stock. This total includes shares held directly by him as a director and shares that may be deemed owned through Sarissa Capital and related funds.

What Ironwood (IRWD) share sales did Sarissa Funds report on March 17, 2026?

On March 17, 2026, Sarissa Funds sold 6,725,000 Ironwood shares at a weighted average price of $3.0501 per share and 5,800 shares at $3.3084 per share, for aggregate proceeds of $20,511,923 and $19,189, respectively, in open-market transactions.

Did Alexander J. Denner receive any new Ironwood (IRWD) shares as a director?

Yes. On March 17, 2026, Alexander J. Denner was granted 4,451 Ironwood shares in his capacity as a director of the company. This director grant is included in his reported 9,444,944 beneficially owned shares and reflects routine board-related equity compensation.

What is the total Ironwood (IRWD) share count used to calculate Sarissa’s ownership percentages?

Both Sarissa Capital and Alexander J. Denner calculate their ownership percentages using 163,058,316 Ironwood shares outstanding as of January 31, 2026. This outstanding share figure comes from Ironwood’s Form 10-K filed with the Securities and Exchange Commission on February 26, 2026.

Were there any other recent Ironwood (IRWD) share transactions by Sarissa or Denner?

The filing states that, other than the March 17, 2026 sales by Sarissa Funds and the 4,451-share director grant to Dr. Denner, no other transactions in Ironwood shares were effected by the reporting persons during the 60 days prior to 4:00 p.m. Eastern on March 19, 2026.