UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(D) OF

OF THE SECURITIES EXCHANGE ACT OF 1934

January 6 7, 2026

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

~~001-38042~~

~~46-0408024~~

(State or other jurisdictionof incorporation)

(CommissionFile Number)

(IRS EmployerIdentification No.)

(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

☐	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 71.01 ~~Regulation~~Entry FDinto ~~Disclosure.~~a Material Definitive Agreement

OnEquity ~~January~~Offering 6, 2026, Arrowhead Pharmaceuticals, Inc. (the “Company”) issued a press release announcing interim results from its two Phase 1/2a clinical trials of ARO-INHBE and ARO-ALK7, the Company’s investigational RNA interference (“RNAi”) therapeutics being developed as potential treatments for obesity. In addition, the Company made publicly available a data presentation announcing interim results from its Phase 1/2a clinical trials of ARO-INHBE and ARO-ALK7. The Company hosted a conference call and webcast today, Tuesday, January 6, 2026, at 11:30 a.m., Eastern Time, to discuss the data results.

~~The~~On ~~information in Item~~ January 7~~.01~~, of2026, ~~this~~Arrowhead ~~Current Report on Form 8-K~~Pharmaceuticals, ~~including~~Inc. (the ~~information~~“Company”) inentered ~~the~~into ~~press~~an ~~release~~underwriting ~~and~~agreement (the ~~presentation~~“Equity ~~attached~~Underwriting asAgreement”) ~~Exhibit~~with ~~99.1~~Jefferies LLC and ~~Exhibit 99~~J.2,P. ~~respectively,~~Morgan toSecurities ~~this Current Report on Form 8-K~~LLC, isas ~~furnished~~representatives ~~pursuant to Item 7.01~~ of ~~Form~~the ~~8-K~~several ~~and~~underwriters ~~shall~~named ~~not~~therein be(collectively, ~~deemed~~the “~~filed~~Equity Underwriters”), ~~for~~to ~~the~~issue ~~purposes~~and ofsell ~~Section~~3,100,776 18shares of the ~~Securities~~Company’s ~~Exchange~~common ~~Act~~stock, of$0.001 ~~1934,~~par asvalue ~~amended,~~per orshare ~~otherwise~~(“Common ~~subject~~Stock”), toat ~~the~~a ~~liabilities~~public ofoffering ~~that~~price ~~section~~of $64.50 ~~Furthermore,~~per ~~the~~share ~~information~~or, in ~~Item~~lieu ~~7.01~~of shares of ~~this~~Common ~~Current~~Stock ~~Report~~to oncertain ~~Form~~investors, 8pre-K,funded ~~including~~warrants (the ~~information~~“Pre-Funded inWarrants”) ~~the~~to ~~press~~purchase ~~release~~up ~~and~~to ~~the presentation attached as Exhibit 99.~~1,550,387 ~~and~~shares ~~Exhibit~~of ~~99.2,~~Common ~~respectively~~Stock, toat ~~this~~a ~~Current~~public ~~Report~~offering onprice ~~Form~~of ~~8-K~~$64.499, ~~shall~~which ~~not~~represents bethe ~~deemed~~per toshare bepublic ~~incorporated~~offering byprice ~~reference~~for in the ~~filings~~common ofstock less the ~~Company~~$0.001 ~~under~~per ~~the~~share ~~Securities~~exercise ~~Act~~price offor ~~1933,~~each asPre-Funded ~~amended~~Warrant (the “Equity Offering”).

The Pre-Funded Warrants will be exercisable, at the option of each holder, in whole or in part, by delivering to us a duly executed exercise notice accompanied by payment in full for the number of shares of our common stock purchased upon such exercise (except in the case of a cashless exercise). A holder (together with its affiliates) may not exercise any portion of such holder’s Pre-Funded Warrant to the extent that the holder would own more than 9.99% of the outstanding shares of common stock immediately after exercise, except that upon at least 61 days’ written prior notice from the holder to us, the holder may increase or decrease the amount of ownership of outstanding shares of common stock after exercising the holder’s Pre-Funded Warrants up to 9.99% of the number of shares of common stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the Pre-Funded Warrants.

In addition, the Company granted the Equity Underwriters a 30-day option to purchase up to an additional 456,116 shares of Common Stock, on the same terms and conditions, which the Equity Underwriters exercised in full on January 8, 2026. The net proceeds from the Equity Offering are expected to be approximately $216.6 million, after deducting customary underwriting discounts and offering expenses.

The shares of Common Stock and the Pre-Funded Warrants described above are offered pursuant to an automatic shelf registration statement (File No. 333-292061) filed with the U.S. Securities and Exchange Commission (the “SEC”) on December 11, 2025. A final prospectus supplement dated January 7, 2026 relating to and describing the terms of the Equity Offering was filed with the SEC on January 8, 2026.

The Equity Offering is expected to close on January 9, 2026, subject to customary closing conditions.

In the Equity Underwriting Agreement, the Company agreed to indemnify the Equity Underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended (the “Securities Act”), or to contribute payments that the Equity Underwriters may be required to make because of such liabilities.

A copy of the Equity Underwriting Agreement and the form of Pre-Funded Warrant are filed as Exhibit 1.1 and 4.1, respectively, and are incorporated herein by reference. The foregoing descriptions of the Equity Underwriting Agreement and the Pre-Funded Warrants do not purport to be complete and are qualified in their entirety by reference to such exhibit.

A copy of the opinion of Gibson, Dunn & Crutcher LLP relating to the validity of the issuance and sale of the shares of Common Stock and the Pre-Funded Warrants in the Equity Offering is filed herewith as Exhibit 5.1.

Notes Offering

On January 7, 2026, the Company entered into an underwriting agreement (the “Convertible Notes Underwriting Agreement”) with J.P. Morgan Securities LLC and Jefferies LLC, as representatives of the several underwriters named therein (the “Convertible Notes Underwriters”), to issue and sell (the “Convertible Notes Offering”) $625,000,000 aggregate principal amount of its 0.00% convertible senior notes due 2032 (the “Convertible Notes”).

In addition, the Company granted the Convertible Notes Underwriters a 30-day option to purchase up to an additional $75,000,000 aggregate principal amount of Convertible Notes, solely to cover over-allotments in the Convertible Notes Offering, which the Convertible Notes Underwriters exercised in full on January 8, 2026. The net proceeds from the Convertible Notes Offering are expected to be approximately $681.3 million, after deducting customary underwriting discounts and offering expenses.

The Convertible Notes are offered pursuant to an automatic shelf registration statement (File No. 333-292061) filed with the SEC on December 11, 2025. A final prospectus supplement dated January 7, 2026 relating to and describing the terms of the Convertible Notes Offering was filed with the SEC on January 8, 2026.

The Convertible Notes Offering is expected to close on January 12, 2026, subject to customary closing conditions.

In the Convertible Notes Underwriting Agreement, the Company agreed to indemnify the Convertible Notes Underwriters against certain liabilities, including liabilities under the Securities Act, or to contribute payments that the Convertible Notes Underwriters may be required to make because of such liabilities.

A copy of the Convertible Notes Underwriting Agreement is filed as Exhibit 1.2 and is incorporated herein by reference. The foregoing description of the Convertible Notes Underwriting Agreement does not purport to be complete and is qualified in its entirety by reference to such exhibit.

Item 8.01

Other Events.

On January 6 7, 2026, the Company ~~announced~~issued ~~interim~~a ~~results~~press ~~from~~release ~~its~~announcing ~~Phase~~that ~~1/2a~~it ~~clinical~~priced ~~trials~~the Equity Offering and the Convertible Notes Offering. A copy of ~~ARO-INHBE~~this press release is filed as Exhibit 99.1 hereto and ~~ARO-ALK7~~is incorporated herein by reference.

~~Select~~Item ~~ARO-INHBE~~9.01 ~~Phase~~Financial ~~1/2a~~Statements ~~Results~~and Exhibits.

A single dose of ARO-INHBE in adult volunteers with obesity (n= 4 per dose level) achieved a dose dependent reduction in serum Activin E with a mean maximum reduction of -85% after a single 400 mg dose and a maximum observed reduction of -94%.

Single dose ARO-INHBE monotherapy at week 16 led to:

•Mean visceral fat reduction of -9.9%

•Mean liver fat relative reduction of -38%

•Increased total lean tissue of 3.6%

Two doses of ARO-INHBE monotherapy at Week 24 achieved:

•Mean visceral fat reduction of -15.6%, adjusted for placebo.

ARO-INHBE enhanced weight loss and fat reduction versus tirzepatide alone in obese patients with type 2 diabetes mellitus. Two doses of ARO-INHBE (400 mg) in combination with tirzepatide (n = 4) achieved approximately two-fold weight loss at week 16 and an approximately three-fold reduction in fat, based on the week 12 MRI, versus tirzepatide alone in these patients. Results include the following, measured by mean percent change from baseline:

	Tirzepatide + Placebo	ARO-INHBE (400 mg) Tirzepatide Combination
Weight Loss (week 16 weight)	-4.8 % (n=5)	-9.4% (n=4)
Visceral Fat (week 12 MRI)	-7.4% (n=5)	-23.2% (n=3)
Total Fat (week 12 MRI)	-5.3% (n=5)	-15.4% (n=3)
Liver Fat (relative reduction on (week 12 MRI))	-20% (n=5)	-76.7% (n=3)

Safety and Tolerability

ARO-INHBE has been generally well tolerated to date as monotherapy and in combination with tirzepatide in participants with obesity with and without type 2 diabetes. Most treatment emergent adverse events (“TEAE”) were mild in severity. No TEAEs led to study or study drug discontinuation. Injection site reactions were generally mild and self-limited. One serious adverse effect (“SAE”) of “limb abscess” was reported, managed with bedside drainage, and assessed as unrelated to study treatment by both sponsor and site investigator. Frequency of gastrointestinal (GI) adverse events was similar in

combination and tirzepatide monotherapy groups. There were no clinically significant adverse laboratory trends including liver enzymes, glycemic indices, or lipid parameters.

Select ARO-ALK7 Phase 1/2a Results

ARO-ALK7 is the first RNAi-therapeutic to show adipocyte gene target silencing in a clinical trial. ARO-ALK7 achieved dose dependent reductions in adipose ALK7 mRNA with a mean reduction of -88% at the 200 mg dose at week 8 with a maximum reduction of -94% (n = 4).

In addition, a single dose of ARO-ALK7 led to rapid dose dependent reductions in mean visceral fat with a -14.1% reduction, adjusted for placebo, already observed at Week 8.

Safety and Tolerability

ARO-ALK7 has been generally well tolerated to date as monotherapy in participants with obesity. No clinically significant adverse laboratory trends, including in liver enzymes and glycemic parameters, were identified. Most TEAEs were mild in severity. No TEAEs led to study or study drug discontinuation. No SAEs were reported.

Safe Harbor Statement under the Private Securities Litigation Reform Act

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 release 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. In addition, any statements that refer to projections of the Company’s future financial performance, trends in the Company’s business, expectations for the Company’s product pipeline or product candidates, including anticipated regulatory submissions and clinical program results, prospects or benefits of the Company’s collaborations with other companies, or other characterizations of future events or circumstances are forward-looking statements. These forward-looking statements include, but are not limited to, statements about: the potential therapeutic benefits and safety of ARO-INHBE and ARO-ALK7; the potential to advance multiple novel RNAi-based therapies for cardiometabolic diseases; the initiation, timing, progress and results of the Company’s preclinical studies and clinical trials, and the Company’s research and development programs; the Company’s expectations regarding the potential benefits of the partnership, licensing and/or collaboration arrangements and other strategic arrangements and transactions the Company has entered into or may enter into in the future; the Company’s beliefs and expectations regarding milestone, royalty or other payments that could be due to or from third parties under existing agreements; and the Company’s estimates regarding future revenues, research and development expenses, capital requirements and payments to third parties. These statements are based upon the Company’s current expectations and speak only as of the date hereof. The Company’s actual results may differ materially and adversely from those expressed in any forward-looking statements as a result of numerous factors and uncertainties, including interim results of a clinical trial are not necessarily indicative of final results and one or more of the clinical outcomes may materially change as patient enrollment continues, following more comprehensive reviews of the data and as more patient data becomes available, the safety and efficacy of the Company’s product candidates, decisions of regulatory authorities and the timing thereof, the duration and impact of regulatory delays in the Company’s clinical programs, the Company’s ability to finance the Company’s operations, the likelihood and timing of the receipt of future milestone and licensing fees, the future success of the Company’s scientific studies, the Company’s ability to successfully develop and commercialize drug candidates, the timing for starting and completing clinical trials, rapid technological change in the Company’s markets, the enforcement of the Company’s intellectual property rights, and the other risks and uncertainties described in the Company’s 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. The Company assumes 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
ExhibitNo.	Description
99.1		Press Release, dated January 6, 2026
1.1	Equity Underwriting Agreement, dated as of January 7, 2026, between Arrowhead Pharmaceuticals, Inc. and the representatives of the underwriters named therein.
99.2		Presentation, dated January 6, 2026
1.2	Convertible Notes Underwriting Agreement, dated as of January 7, 2026, between Arrowhead Pharmaceuticals, Inc. and the representatives of the underwriters named therein.
104		Cover Page Interactive Data File (embedded within the Inline XBRL document).
4.1	Form of Pre-Funded Warrant
5.1	Opinion of Gibson, Dunn & Crutcher LLP
23.1	Consent of Gibson, Dunn & Crutcher LLP (included in Exhibit 5.1)
99.1	Press release dated January 7, 2026
104	The cover page from the Company’s Current Report on Form 8-K formatted in Inline XBRL

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~~hereunto duly authorized.

Date: September 11, 2025

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

Date: January 8, 2026

ARROWHEAD PHARMACEUTICALS, INC.

/s/ Daniel Apel

Daniel Apel

Chief Financial Officer

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