Vanguard Portfolio Management (NASDAQ: ARWR) reports 5.19% stake in Arrowhead

Rhea-AI Filing Summary

Arrowhead Pharmaceuticals Inc ownership disclosure: Vanguard Portfolio Management reports beneficial ownership of 7,269,957 shares of common stock, representing 5.19% of the class. The filing states Vanguard has sole dispositive power over these shares and sole voting power over 123,821 shares. The holdings include securities held for Vanguard funds and managed accounts.

Insights

Institutional Ownership Analyst

Vanguard reports a 5.19% passive stake in Arrowhead; dispositive control lies with the manager.

Vanguard Portfolio Management discloses beneficial ownership of 5.19% totaling 7,269,957 shares with sole dispositive power. Voting power is limited to 123,821 shares, indicating that voting and economic interests are held across managed funds.

Cash‑flow treatment and trading intentions are not included; subsequent filings may disclose changes in holdings. The filing ties holdings to Vanguard funds and managed accounts under the Investment Company Act structure.

Key Figures

Beneficial ownership: 7,269,957 shares Percent of class: 5.19% Sole voting power: 123,821 shares +2 more

5 metrics

Beneficial ownership 7,269,957 shares reported on Schedule 13G

Percent of class 5.19% percent of common stock beneficially owned

Sole voting power 123,821 shares shares with sole power to vote

Sole dispositive power 7,269,957 shares shares with sole power to dispose

Signature date 04/28/2026 filing signed by Ashley Grim

Key Terms

Schedule 13G, dispositive power, Investment Company Act

3 terms

Schedule 13G regulatory

"Vanguard Portfolio Management reports beneficial ownership on Schedule 13G"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

dispositive power financial

"sole dispositive power over 7,269,957 shares"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

Investment Company Act regulatory

"investment companies registered under the Investment Company Act of 1940"

The Investment Company Act is a law that sets rules for businesses whose main activity is managing and selling pooled money, such as mutual funds and other investment funds. It matters to investors because it requires clear reporting, limits managers from putting their own interests ahead of clients, and mandates safekeeping and oversight of assets—similar to safety inspections and traffic rules that help keep shared vehicles reliable and trustworthy.

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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Arrowhead Pharmaceuticals Inc

(Name of Issuer)

Common Stock

(Title of Class of Securities)

04280A100

(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): 04280A100

1

Names of Reporting Persons

Vanguard Portfolio Management

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

PENNSYLVANIA

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 123,821.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 7,269,957.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

7,269,957.00

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)

5.19 %

12

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person: In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by Vanguard Portfolio Management LLC and the following affiliates of Vanguard Portfolio Management LLC or business divisions of such affiliates: Vanguard Fiduciary Trust Company and Vanguard Global Advisers, LLC. This Schedule 13G includes securities held by Vanguard funds, or sleeves thereof, over which Vanguard Portfolio Management LLC exercises dispositive power, in addition to securities held by clients over which the affiliates or business divisions of such affiliates indicated above exercise dispositive and/or voting power. This Schedule 13G does not include securities, if any, beneficially owned by other subsidiaries or affiliates of Vanguard Portfolio Management LLC, or business divisions of such subsidiaries whose ownership of securities is disaggregated from that of the reporting business unit in accordance with such release.

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Arrowhead Pharmaceuticals Inc
(b)	Address of issuer's principal executive offices: 177 East Colorado Blvd, Suite 700, Pasadena, CA, 91105
Item 2.
(a)	Name of person filing: Vanguard Portfolio Management
(b)	Address or principal business office or, if none, residence: 100 Vanguard Blvd,, Malvern, PA, 19355
(c)	Citizenship: PA
(d)	Title of class of securities: Common Stock
(e)	CUSIP Number(s): 04280A100
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: 7269957
(b)	Percent of class: 5.19 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 123821
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 7269957
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
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. Vanguard Portfolio Management, including investment companies registered under the Investment Company Act of 1940 and other managed accounts, have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the securities reported herein.No one other person's interest in the securities reported herein is more than 5%.
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.

Vanguard Portfolio Management

Signature:	Ashley Grim
Name/Title:	Head of Global Fund Administration
Date:	04/28/2026

FAQ

What stake does Vanguard hold in Arrowhead (ARWR)?

Vanguard Portfolio Management reports beneficial ownership of 7,269,957 shares, equal to 5.19% of Arrowhead's common stock, showing a sizable institutional position disclosed on the Schedule 13G.

Does Vanguard control voting for all its Arrowhead shares?

No; Vanguard reports sole voting power for 123,821 shares while holding sole dispositive power over 7,269,957 shares, indicating voting and dispositive authorities differ across accounts.

Are these Arrowhead shares held for Vanguard funds or clients?

Yes; the filing states the shares include securities held by Vanguard funds and managed accounts over which Vanguard Portfolio Management or affiliates exercise dispositive power, per the Schedule 13G disclosure language.

When was the Schedule 13G signed for Vanguard's Arrowhead holdings?

The Schedule 13G was signed by Ashley Grim, Head of Global Fund Administration, on 04/28/2026, reflecting the reported beneficial ownership figures as set out in the filing.