[8-K] Arrowhead Research Corporation Reports Material Event

Rhea-AI Filing Summary

Arrowhead Research Corporation (ARWR) filed an 8-K reporting a material event that primarily contains forward-looking statement disclosures and a brief litigation update. The company states it intends to vigorously pursue its claims in an ongoing lawsuit and refers to planned commercialization efforts for its investigational drug plozasiran. The filing cites uncertainties tied to the Ionis letter, the validity and enforceability of the '333 Patent, the company’s broader patent portfolio, and the outcome of the lawsuit. It emphasizes that forward-looking statements are based on current expectations and that actual results may differ materially due to risks described in prior SEC filings.

Insights

Securities Litigation Analyst

TL;DR: Routine 8-K legal disclosure noting active litigation and patent dispute; signals ongoing legal risk without new financial details.

The filing is primarily boilerplate forward-looking language combined with a statement that the company will vigorously pursue its claims in litigation. It references specific intellectual property issues—an Ionis letter and the '333 Patent—which indicate an active patent dispute that could affect Arrowhead's rights around plozasiran. No financial impacts, timelines, settlements, or court decisions are disclosed, so materiality cannot be assessed beyond confirming litigation risk is present.

Biotech Corporate Strategy Specialist

TL;DR: Company reiterates commercialization intent for plozasiran while disclosing patent contention; strategic risk exists but remains undefined.

From a commercial standpoint, the mention of planned commercialization of plozasiran indicates a continued strategic focus on advancing the asset. However, the reference to patent validity and an external letter from Ionis suggests potential IP headwinds. Without details on the scope of the dispute, potential injunctions, or licensing outcomes, the disclosure stops short of quantifying program risk or likely strategic adjustments.

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(D) OF

THE SECURITIES EXCHANGE ACT OF 1934

September 10, 2025

Date of Report

(Date of earliest event reported)

Arrowhead Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Delaware

001-38042

46-0408024

(State or other jurisdiction of incorporation)

(Commission File Number)

(IRS Employer Identification No.)

177 E. Colorado Blvd, Suite 700, Pasadena, CA 91105

(Address of principal executive offices, including Zip Code)

(626) 304-3400

(Registrant’s telephone number, including area code)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐			Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)
☐			Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)
☐			Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))
☐			Pre-commencement communications pursuant to Rule 13e-4 (c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading Symbol(s)

Name of each exchange on which registered

Common Stock, par value $0.001 per share

ARWR

The Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01 Other Events

On September 10, 2025, Arrowhead Pharmaceuticals, Inc. (the “Company” or the “Plaintiff”) filed a Complaint for Declaratory Judgment in the United States District Court for the District of Delaware against Ionis Pharmaceuticals, Inc. (the “Defendant”) to declare that Ionis’s United States Patent Number 9,593,333 (“the ’333 patent”) is invalid and/or not infringed by the Company’s planned commercialization of investigational plozasiran. A copy of the complaint is attached hereto as Exhibit 99.1 (the “Complaint”).

The Company intends to vigorously pursue its claims in this litigation.

Forward-Looking Statements

This Current Report on Form 8-K contains forward-looking statements within the meaning of the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995. Any statements contained in this report except for historical information may be deemed to be forward-looking statements. Without limiting the generality of the foregoing, words such as “may,” “will,” “expect,” “believe,” “anticipate,” “hope,” “intend,” “plan,” “project,” “could,” “estimate,” “continue,” “target,” “forecast” or “continue” or the negative of these words or other variations thereof or comparable terminology are intended to identify such forward-looking statements. These forward-looking statements include, but are not limited to, statements about our planned commercialization of investigational plozasiran and beliefs and expectations regarding the merit of the Ionis letter, the validity and enforceability of the ‘333 Patent, the Company’s patent portfolio, and the Company’s claims and lawsuit against the Defendant. These statements are based upon our current expectations and speak only as of the date hereof. Our actual results or outcomes may differ materially and adversely from those expressed in any forward-looking statements as a result of numerous factors and uncertainties, including the risks and uncertainties described in our most recent Annual Report on Form 10-K, subsequent Quarterly Reports on Form 10-Q and other documents filed with the Securities and Exchange Commission from time to time. We assume no obligation to update or revise forward-looking statements to reflect new events or circumstances.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits

Exhibit No.						Description
99.1						Complaint for Declaratory Judgment dated September 10, 2025
99.2						Press Release, dated September 11, 2025.
104						Cover Page Interactive Data File (the cover page tags are embedded within the Inline XBRL document).

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

Date: September 11, 2025

ARROWHEAD PHARMACEUTICALS, INC.
By:						/s/ Daniel Apel
						Daniel Apel
						Chief Financial Officer

FAQ

What did Arrowhead (ARWR) disclose in this 8-K about litigation?

Arrowhead stated it intends to vigorously pursue its claims in the referenced litigation but provided no details on timing, remedies, or financial impact.

Does the filing mention Arrowhead's plans for plozasiran?

Yes. The filing references the company’s planned commercialization of investigational plozasiran.

What patent issues are referenced in the 8-K?

The company mentions concerns regarding the validity and enforceability of the '333 Patent and its broader patent portfolio.

Did Arrowhead provide any financial impact or guidance related to this disclosure?

No. The excerpt contains forward-looking statements and risks but does not include financial figures, guidance, or quantified impacts.

What should investors take away from the forward-looking statements?

The company warns that actual results may differ materially from expectations due to numerous risks described in its SEC filings; no updates or obligations to revise statements were provided.