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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

X0202 SCHEDULE 13D/A 0000899140-19-000402 0001577524 XXXXXXXX LIVE 4 Class A Common Stock, $0.001 par value 03/17/2026 false 0001446847 46333X108 IRONWOOD PHARMACEUTICALS INC 100 Summer Street Suite 2300 Boston MA 02110 Patrice Bonfiglio (203) 302-2330 Sarissa Capaital Management LP 500 West Putnam Ave, Suite 400 Greenwich CT 06830 0001577524 Sarissa Capital Management LP WC DE 0 9188635 0 9188635 9188635 N 5.6 PN 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. Y Alexander J. Denner WC X1 256309 9188635 256309 9188635 9444944 N 5.8 IN 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. Class A Common Stock, $0.001 par value IRONWOOD PHARMACEUTICALS INC 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 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. 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. 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. 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. Sarissa Capital Management LP /s/Alexander J. Denner, Ph.D. Alexander J. Denner, Ph.D., Chief Investment Officer 03/19/2026 Alexander J. Denner /s/Alexander J. Denner, Ph.D. Alexander J. Denner, Ph.D., Chief Investment Officer 03/19/2026