Ironwood: Renaissance reports 4.90% stake

Ironwood Pharmaceuticals files Amendment No. 1 to a Schedule 13G/A disclosing that Renaissance Technologies LLC and Renaissance Technologies Holdings Corporation beneficially own 8,061,073 shares of Class A common stock, representing 4.90% of the class.

Rhea-AI Filing Summary

Ironwood Pharmaceuticals files Amendment No. 1 to a Schedule 13G/A disclosing that Renaissance Technologies LLC and Renaissance Technologies Holdings Corporation beneficially own 8,061,073 shares of Class A common stock, representing 4.90% of the class. The filing lists sole voting and sole dispositive power over those shares.

Insights

Institutional Ownership Analyst

Renaissance reports a passive 8,061,073-share stake, equal to 4.90%.

The amendment records beneficial ownership by Renaissance Technologies LLC and its parent, with sole voting and sole dispositive power over 8,061,073 Class A shares. The filing is a disclosure of stake size under Schedule 13G/A.

Holder composition and any trading intent are not disclosed; subsequent filings would show changes in position or status.

Key Figures

Beneficial ownership: 8,061,073 shares Percent of class: 4.90% CUSIP: 46333X108 +2 more

5 metrics

Beneficial ownership 8,061,073 shares Amount beneficially owned as reported in Item 4

Percent of class 4.90% Percent of Class A common stock reported in Item 4(b)

CUSIP 46333X108 CUSIP for Class A common stock listed on the cover

Header date 03/31/2026 Date shown near the top of the filing excerpt

Signature date 05/14/2026 Dates on the signing blocks for the filing

Key Terms

Schedule 13G/A, beneficially owned, sole dispositive power, sole voting power

4 terms

Schedule 13G/A regulatory

"files Amendment No. 1 to a Schedule 13G/A disclosing"

A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.

beneficially owned financial

"Amount beneficially owned: 8061073"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole dispositive power financial

"Sole Dispositive Power 8,061,073.00"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

sole voting power financial

"Sole Voting Power 8,061,073.00"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What stake does Renaissance Technologies report in IRWD?

Renaissance Technologies reports beneficial ownership of 8,061,073 shares, equal to 4.90% of Ironwood's Class A common stock as stated in the amendment.

Which entities filed the Schedule 13G/A for IRWD?

The filing was made by Renaissance Technologies LLC and Renaissance Technologies Holdings Corporation, both identified as Delaware-organized entities in the amendment.

Does the Schedule 13G/A indicate voting or dispositive power?

Yes. The amendment reports sole voting power of 8,061,073 shares and sole dispositive power of 8,061,073 shares for the reporting entities.

What dates are shown in the IRWD amendment filing?

The header includes 03/31/2026 and the signatures are dated 05/14/2026, both appearing in the amendment text.

Is Renaissance’s ownership reported above or below 5% of IRWD Class A shares?

The amendment states Renaissance beneficially owns 4.90% of the Class A common stock, which is below the 5% filing threshold for certain reporting categories.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 05/14/2026 - 04:45 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

IRONWOOD PHARMACEUTICALS INC

(Name of Issuer)

Class A common stock, $0.001 par value

(Title of Class of Securities)

46333X108

(CUSIP Number)

03/31/2026

(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)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 46333X108

1

Names of Reporting Persons

Renaissance Technologies LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 8,061,073.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 8,061,073.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,061,073.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

4.90 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

CUSIP Number(s): 46333X108

1

Names of Reporting Persons

Renaissance Technologies Holdings Corporation

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 8,061,073.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 8,061,073.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

8,061,073.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

4.90 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: IRONWOOD PHARMACEUTICALS INC
(b)	Address of issuer's principal executive offices: 100 SUMMER STREET, SUITE 2300, BOSTON, MA 02110
Item 2.
(a)	Name of person filing: This Schedule 13G is being filed by Renaissance Technologies LLC ("RTC") and Renaissance Technologies Holdings Corporation ("RTHC").
(b)	Address or principal business office or, if none, residence: 800 Third Avenue New York, New York 10022
(c)	Citizenship: RTC is a Delaware limited liability company, and RTHC is a Delaware corporation.
(d)	Title of class of securities: Class A common stock, $0.001 par value
(e)	CUSIP No.: 46333X108
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 8061073
(b)	Percent of class: 4.90 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 8061073
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 8061073
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Ownership of 5 percent or less of a class
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. Certain funds managed by RTC have the right to receive dividends and proceeds from the sale of the securities which are the subject of this report.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

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.

Renaissance Technologies LLC

Signature:	Brian Felczak
Name/Title:	Chief Financial Officer
Date:	05/14/2026

Renaissance Technologies Holdings Corporation

Signature:	Brian Felczak
Name/Title:	Vice President
Date:	05/14/2026

Exhibit Information

In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, each of the undersigned agrees to the filing on behalf of each of a Statement on Schedule 13G, and all amendments thereto, with respect to the Class A common stock, $0.001 par value of IRONWOOD PHARMACEUTICALS INC.