[8-K] IONIS PHARMACEUTICALS INC Reports Material Event

Rhea-AI Filing Summary

Ionis Pharmaceuticals, Inc. completed a private offering of $770.0 million aggregate principal amount of 0.00% Convertible Senior Notes due 2030. The zero-coupon notes are unsecured, mature on December 1, 2030, and can be converted into cash, Ionis common stock, or a combination, at the company’s election. The initial conversion rate is 10.1932 shares per $1,000 principal (about $98.10 per share), a roughly 35.0% premium to the November 12, 2025 stock price, with potential rate increases after certain corporate events.

Ionis estimates net proceeds of about $751.2 million. It used approximately $267.6 million to repurchase for cash $200.0 million principal amount of its 0% Convertible Senior Notes due 2026 and plans to use the remaining proceeds for additional repurchases of the 2026 notes and general corporate purposes. Based on the initial maximum conversion rate of 13.7608 shares per $1,000, up to 10,595,816 shares of common stock may initially be issuable upon conversion.

Insights

Capital structure and credit analyst

Ionis refinances 2026 converts with a large 0% 2030 issue, adding non‑cash debt with potential dilution.

Ionis issued $770.0 million of 0.00% Convertible Senior Notes due 2030, a sizable unsecured financing that extends its debt maturity profile beyond the existing 0% notes due 2026. The notes carry no regular interest and no accretion, so cash interest outflows are minimized, while investors receive value primarily through conversion rights tied to the equity.

The initial conversion rate of 10.1932 shares per $1,000 (about $98.10 per share) reflects a roughly 35.0% premium to the common stock price on November 12, 2025. If anti-dilution adjustments and maximum conversion features are triggered, up to 10,595,816 shares could initially be issued based on a maximum rate of 13.7608 shares per $1,000, which would represent meaningful potential dilution relative to the current equity base.

Net proceeds are estimated at $751.2 million, with $267.6 million already used to repurchase $200.0 million of the 2026 notes. Remaining proceeds are earmarked for further 2026 note repurchases, including repayment at maturity, and general corporate purposes. The overall effect is a shift from nearer-term 2026 obligations to a longer-dated 2030 convertible structure, balancing reduced near-term cash demands against future equity dilution risk if conversion conditions are met.

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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

Date of report (Date of earliest event reported): November 11, 2025

IONIS PHARMACEUTICALS, INC.

(Exact Name of Registrant as Specified in Charter)

Delaware

(State or Other Jurisdiction of Incorporation)

000-19125		33-0336973
(Commission File No.)		(IRS Employer Identification No.)

2855 Gazelle Court

Carlsbad, CA 92010

(Address of Principal Executive Offices and Zip Code)

Registrant’s telephone number, including area code: (760) 931-9200

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		Name of each exchange on which registered
Common Stock, $.001 Par Value		“IONS”		The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (Section 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (Section 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 1.01 Entry into a Material Definitive Agreement.

On November 17, 2025, Ionis Pharmaceuticals, Inc. (the “Company”) completed its previously announced private offering (the “Offering”) of $770.0 million aggregate principal amount of 0.00% Convertible Senior Notes due 2030 (the “Notes”), including the exercise in full of the initial purchasers’ option to purchase up to an additional $70.0 million principal amount of Notes. The Notes were issued pursuant to an indenture, dated November 17, 2025 (the “Indenture”), between the Company and U.S. Bank Trust Company, National Association, as trustee.

The Notes are general unsecured obligations of the Company and will mature on December 1, 2030, unless earlier converted, redeemed or repurchased. The Notes will not bear regular interest, and the principal amount of the Notes will not accrete. Special interest, if any, will be payable semiannually in arrears on June 1 and December 1 of each year, beginning on June 1, 2026 (if and to the extent that special interest is then payable on the Notes). The Notes are convertible at the option of the holders at any time prior to the close of business on the business day immediately preceding September 1, 2030 only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on March 31, 2026 (and only during such calendar quarter), if the last reported sale price of the Company’s common stock, par value $0.001 per share (“Common Stock”), for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price for the Notes on each applicable trading day; (2) during the five business day period after any ten consecutive trading day period (the “measurement period”) in which the trading price (as defined in the Indenture) per $1,000 principal amount of the Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Common Stock and the conversion rate on each such trading day; (3) if the Company calls such Notes for redemption, at any time prior to the close of business on the second scheduled trading day immediately preceding the redemption date, but only with respect to the Notes called (or deemed called) for redemption; or (4) upon the occurrence of specified corporate events as set forth in the Indenture. On or after September 1, 2030 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert all or any portion of their Notes at any time, regardless of the foregoing circumstances. Upon conversion, the Company will pay or deliver, as the case may be, cash, shares of Common Stock or a combination of cash and shares of Common Stock, at the Company’s election, in the manner and subject to the terms and conditions provided in the Indenture.

The conversion rate for the Notes will initially be 10.1932 shares of Common Stock per $1,000 principal amount of Notes (equivalent to an initial conversion price of approximately $98.10 per share of Common Stock). The initial conversion price of the Notes represents a premium of approximately 35.0% to the last reported sale price of the Common Stock on the Nasdaq Global Select Market on November 12, 2025. The conversion rate for the Notes is subject to adjustment in some events in accordance with the terms of the Indenture but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date of the Notes or if the Company delivers a notice of redemption, the Company will, in certain circumstances, increase the conversion rate of the Notes for a holder who elects to convert its Notes in connection with such a corporate event or convert its Notes called (or deemed called) for redemption during the related redemption period (as defined in the Indenture), as the case may be.

The Company may not redeem the Notes prior to December 6, 2028. The Company may redeem for cash all or any portion of the Notes (subject to the partial redemption limitation described in the Indenture), at its option, on a redemption date on or after December 6, 2028 if the last reported sale price of the Common Stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period (including the last trading day of such period) ending on, and including, the trading day immediately preceding the date on which the Company provides notice of redemption, at a redemption price equal to 100% of the principal amount of the Notes to be redeemed, plus accrued and unpaid special interest, if any, to, but excluding, the redemption date. No sinking fund is provided for the Notes.

If the Company undergoes a fundamental change (as defined in the Indenture), then, subject to certain conditions and except as described in the Indenture, holders may require the Company to repurchase for cash all or any portion of their Notes at a fundamental change repurchase price equal to 100% of the principal amount of the Notes to be repurchased, plus accrued and unpaid special interest, if any, to, but excluding, the fundamental change repurchase date.

The Indenture includes customary covenants and sets forth certain events of default after which the Notes may be declared immediately due and payable and sets forth certain types of bankruptcy or insolvency events of default involving the Company after which the Notes become automatically due and payable. The following events are considered “events of default” under the Indenture:

• default in any payment of special interest on any Note when due and payable and the default continues for a period of 30 days;

• default in the payment of principal of any Note when due and payable at its stated maturity, upon any optional redemption, upon any required repurchase, upon declaration of acceleration or otherwise;

• the Company’s failure to comply with its obligation to convert the Notes in accordance with the Indenture upon exercise of a holder’s conversion right and such failure continues for three business days;

• the Company’s failure to give (i) a fundamental change notice or notice of a make-whole fundamental change, in either case when due and such failure continues for five business days, or (ii) notice of a specified corporate event, when due and such failure continues for three business days;

• the Company’s failure to comply with its obligations in respect of any consolidation, merger or sale of assets;

• the Company’s failure to comply with any of the Company’s other agreements contained in the Notes or the Indenture for 60 days after its receipt of written notice of such failure from the trustee or the holders of at least 25% in principal amount of the Notes then outstanding;

• default by the Company or any of the Company’s significant subsidiaries (as defined in the Indenture) with respect to any mortgage, agreement or other instrument under which there may be outstanding, or by which there may be secured or evidenced, any indebtedness for money borrowed with a principal amount in excess of $100.0 million (or its foreign currency equivalent) in the aggregate of the Company and/or any such significant subsidiary, whether such indebtedness now exists or shall hereafter be created (i) resulting in such indebtedness becoming or being declared due and payable prior to its stated maturity date or (ii) constituting a failure to pay the principal of any such debt when due and payable (after the expiration of all applicable grace periods) at its stated maturity, upon required repurchase, upon declaration of acceleration or otherwise, and in the cases of clauses (i) and (ii), such acceleration shall not have been rescinded or annulled or such failure to pay or default shall not have been cured or waived, or such indebtedness is not paid or discharged, as the case may be, within 45 days after written notice to the Company by the trustee or to the Company and the trustee by holders of at least 25% in aggregate principal amount of the Notes then outstanding in accordance with the Indenture; and

• certain events of bankruptcy, insolvency, or reorganization of the Company or any of the Company’s significant subsidiaries.

If certain bankruptcy and insolvency-related events of default with respect to the Company (and not just any of its significant subsidiaries) occur, 100% of the principal of and accrued and unpaid special interest, if any, on the Notes will automatically become immediately due and payable. If an event of default with respect to the Notes, other than certain bankruptcy and insolvency-related events of default with respect to the Company, occurs and is continuing, the trustee, by notice to the Company, or the holders of at least 25% in principal amount of the outstanding Notes by notice to the Company and the trustee, may, and the trustee at the request of such holders shall, declare 100% of the principal of and accrued and unpaid special interest, if any, on all the outstanding Notes to be immediately due and payable. Notwithstanding the foregoing, the Indenture provides that, to the extent the Company so elects, the sole remedy for an event of default relating to certain failures by the Company to comply with certain reporting covenants in the Indenture will, for the first 365 days after the occurrence of such an event of default, consist exclusively of the right to receive special interest on the Notes as set forth in the Indenture.

The Indenture provides that the Company shall not consolidate with or merge with or into, or sell, convey, transfer or lease the consolidated properties and assets of the Company and its subsidiaries substantially as an entirety to another person (other than any such sale, conveyance, transfer or lease to one or more of the Company’s direct or indirect wholly owned subsidiaries), unless: (i) the resulting, surviving or transferee person (if not the Company) is a “qualified successor entity” (as defined in the Indenture) organized and existing under the laws of the United States of America, any State thereof or the District of Columbia, and such successor entity (if not the Company) expressly assumes by supplemental indenture all of the Company’s obligations under the Notes and the Indenture; and (ii) immediately after giving effect to such transaction, no default or event of default has occurred and is continuing under the Indenture.

A copy of the Indenture is attached hereto as Exhibit 4.1 (including the form of the Notes attached hereto as Exhibit 4.2) and this description is qualified in its entirety by reference to such document.

The Company’s estimated net proceeds from the Offering will be approximately $751.2 million, after deducting the initial purchasers’ discounts and commissions and the estimated offering expenses payable by the Company. The Company used approximately $267.6 million of the net proceeds from the Offering to repurchase for cash $200.0 million in aggregate principal amount of its 0% Convertible Senior Notes due 2026 (the “2026 Notes”) pursuant to the concurrent note repurchase transactions. The Company expects to use the remaining net proceeds from the Offering for additional repurchases of the 2026 Notes from time to time following the Offering, including the repayment of any remaining 2026 Notes at maturity, and for general corporate purposes.

Item 2.03 Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.

The information set forth under Item 1.01 of this Current Report on Form 8-K is incorporated herein by reference.

Item 3.02 Unregistered Sale of Equity Securities.

The information set forth under Item 1.01 of this Current Report on Form 8-K is incorporated herein by reference.

The Company offered and sold the Notes to the initial purchasers in reliance on the exemption from registration provided under the Securities Act, and for resale by the initial purchasers to qualified institutional buyers pursuant to the exemption from registration provided by Section 4(a)(2) and Rule 144A under the Securities Act. The Company relied on these exemptions from registration based in part on representations made by the initial purchasers in the purchase agreement dated November 12, 2025 by and among the Company and the initial purchasers.

The Notes and the shares of Common Stock issuable upon conversion of the Notes, if any, have not been registered under the Securities Act and may not be offered or sold in the United States absent registration or an applicable exemption from registration requirements.

To the extent that any shares of Common Stock are issued upon conversion of the Notes, they will be issued in transactions anticipated to be exempt from registration under the Securities Act by virtue of Section 3(a)(9) thereof because no commission or other remuneration is expected to be paid in connection with conversion of the Notes and any resulting issuance of shares of Common Stock. Initially, a maximum of 10,595,816 shares of Common Stock may be issued upon conversion of the Notes based on the initial maximum conversion rate of 13.7608 shares of Common Stock per $1,000 principal amount of the Notes, which is subject to customary anti-dilution adjustment provisions.

Item 8.01 Other Events.

On November 11, 2025, the Company issued a press release announcing the proposed Offering. A copy of the press release is attached hereto as Exhibit 99.1.

On November 12, 2025, the Company issued a press release announcing the pricing of the Offering. A copy of the press release is attached hereto as Exhibit 99.2.

Forward-Looking Statements

This Current Report on Form 8-K contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995 that involve risks and uncertainties. All forward-looking statements included in this report, including statements regarding the Company’s expected uses of the net proceeds from the Offering, are based upon information available to the Company as of the date of this report, which may change, and the Company assumes no obligation to update any such forward-looking statements. Although the Company’s forward-looking statements reflect the good faith judgment of its management, these statements are based only on facts and factors currently known by the Company. These statements are not guarantees of future performance and actual results could differ materially from the Company’s current expectations. As a result, you are cautioned not to rely on these forward-looking statements. Factors that could cause or contribute to such differences include the risks and uncertainties discussed in the “Risk Factors” section of the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2025, filed with the Securities and Exchange Commission on October 29, 2025, and other subsequent filings the Company makes with the Securities and Exchange Commission from time to time, as well as market risks, trends and conditions, and unanticipated uses of the net proceeds from the Offering. The Company assumes no obligation and does not intend to update the forward-looking statements provided, whether as a result of new information, future events or otherwise.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No.		Description
4.1		Indenture, dated as of November 17, 2025, by and between the Company and U.S. Bank Trust Company, National Association, as Trustee.
4.2		Form of Global Note, representing the Company’s 0.00% Convertible Senior Notes due 2030 (included as Exhibit A to the Indenture filed as Exhibit 4.1).
99.1		Press release entitled “Ionis Announces Proposed Convertible Offering to Refinance 2026 Convertible Notes,” dated November 11, 2025.
99.2		Press release entitled “Ionis Prices Convertible Notes Offering to Refinance 2026 Convertible Notes,” dated November 12, 2025.
104		Cover Page Interactive Data File (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 hereunto duly authorized.

				Ionis Pharmaceuticals, Inc.
Date: November 17, 2025				By:		/s/ Patrick R. O’Neil
						PATRICK R. O’NEIL
						Executive Vice President, Chief Legal Officer and General Counsel

FAQ

What did Ionis Pharmaceuticals (IONS) announce in this Form 8-K?

Ionis Pharmaceuticals announced it completed a private offering of $770.0 million aggregate principal amount of 0.00% Convertible Senior Notes due 2030, along with related terms, intended use of proceeds, and associated refinancing of its existing 0% Convertible Senior Notes due 2026.

What are the key terms of Ionis Pharmaceuticals 0.00% Convertible Senior Notes due 2030?

The notes are general unsecured obligations maturing on December 1, 2030, bear no regular interest and have no accretion of principal. They are convertible at specified times and conditions into cash, Ionis common stock, or a combination, at the companys election, and are redeemable for cash by Ionis on or after December 6, 2028 if certain stock price triggers are met.

What is the conversion rate and conversion price for the new Ionis 2030 convertible notes?

The initial conversion rate is 10.1932 shares of common stock per $1,000 principal amount of notes, which equals an initial conversion price of approximately $98.10 per share. This represents a conversion premium of about 35.0% to the last reported Ionis stock price on the Nasdaq Global Select Market on November 12, 2025.

How will Ionis use the net proceeds from the $770.0 million convertible notes offering?

Ionis expects net proceeds of about $751.2 million. It has already used approximately $267.6 million of those proceeds to repurchase for cash $200.0 million in aggregate principal amount of its 0% Convertible Senior Notes due 2026 and plans to use the remaining proceeds for additional repurchases of the 2026 notes, including repayment of any remaining notes at maturity, and for general corporate purposes.

How many Ionis common shares could be issued upon conversion of the 2030 notes?

Based on the initial maximum conversion rate of 13.7608 shares of common stock per $1,000 principal amount of notes, up to 10,595,816 shares of Ionis common stock may initially be issued upon conversion, subject to customary anti-dilution adjustments described in the indenture.

Under what conditions can Ionis redeem the 2030 convertible notes early?

Ionis may not redeem the notes before December 6, 2028. On or after that date, it may redeem for cash all or part of the notes if the last reported sale price of its common stock is at least 130% of the then-applicable conversion price for at least 20 trading days in any 30 consecutive trading day period, at a redemption price equal to 100% of principal plus any accrued and unpaid special interest.