T. Rowe Price holds 5.6% of Ionis (NASDAQ: IONS) stock

Rhea-AI Filing Summary

T. Rowe Price Investment Management, Inc. filed an amended Schedule 13G reporting beneficial ownership of 9,108,019 shares of Ionis Pharmaceuticals common stock, representing 5.6% of the outstanding class as of the event date.

The firm reports sole voting power over 9,083,319 shares and sole dispositive power over 9,108,019 shares, with no shared voting or dispositive authority. It certifies the shares were acquired and are held in the ordinary course of business, not for the purpose of changing or influencing control of Ionis Pharmaceuticals, and includes a legal disclaimer that it is not admitting beneficial ownership.

Insights

Equity ownership and governance analyst

Large institutional holder reports a 5.6% passive stake in Ionis.

T. Rowe Price Investment Management discloses beneficial ownership of 9,108,019 Ionis Pharmaceuticals shares, or 5.6% of the common stock. It holds sole voting power over 9,083,319 shares and sole dispositive power over the full 9,108,019 shares, with no shared authority.

The filing is on Schedule 13G/A, which is used for investors characterizing themselves as passive. The firm explicitly states the position was acquired and is held in the ordinary course of business and not to change or influence control of Ionis Pharmaceuticals.

The disclosure confirms the presence of a sizable institutional investor but does not itself signal strategic activity or governance pressure. Future ownership updates in later beneficial ownership filings would show whether this percentage meaningfully increases or declines from the reported 12/31/2025 level.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 4)

IONIS PHARMACEUTICALS INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

462222100

(CUSIP Number)

12/31/2025

(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)

SCHEDULE 13G

CUSIP No. 462222100

1

Names of Reporting Persons

T. Rowe Price Investment Management, Inc.

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

MARYLAND

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 9,083,319.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 9,108,019.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

9,108,019.00

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)

5.6 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: IONIS PHARMACEUTICALS INC
(b)	Address of issuer's principal executive offices: 2855 GAZELLE COURT, CARLSBAD, CA, 92010
Item 2.
(a)	Name of person filing: T. Rowe Price Investment Management, Inc.
(b)	Address or principal business office or, if none, residence: 1307 Point Street, Baltimore, MD 21231
(c)	Citizenship: Maryland
(d)	Title of class of securities: COMMON STOCK
(e)	CUSIP No.: 462222100
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: 9108019
(b)	Percent of class: 5.6 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 9083319
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 9108019
	(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.
	Not Applicable
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. T. Rowe Price Investment Management, Inc. hereby declares and affirms that the filing of Schedule 13G shall not be construed as an admission that Price Investment Management is the beneficial owner of the securities referred to, which beneficial ownership is expressly denied.

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.

T. Rowe Price Investment Management, Inc.

Signature:	Ellen York
Name/Title:	Vice President
Date:	02/17/2026

FAQ

What percentage of Ionis Pharmaceuticals (IONS) does T. Rowe Price hold?

T. Rowe Price Investment Management reports beneficial ownership of 5.6% of Ionis Pharmaceuticals’ common stock. This corresponds to 9,108,019 shares, making it a significant institutional holder while still below typical control thresholds for public companies.

How many Ionis Pharmaceuticals (IONS) shares does T. Rowe Price control for voting?

T. Rowe Price Investment Management reports sole voting power over 9,083,319 Ionis shares. It indicates no shared voting authority, meaning voting decisions on these shares are made solely by the firm, consistent with a centralized institutional ownership structure.

Is T. Rowe Price’s stake in Ionis Pharmaceuticals (IONS) considered passive or activist?

The filing characterizes T. Rowe Price’s stake as passive. It certifies the Ionis shares were acquired and are held in the ordinary course of business, and not for the purpose of changing or influencing control of the company.

What type of SEC filing did T. Rowe Price submit for its Ionis (IONS) position?

T. Rowe Price submitted an amended Schedule 13G/A (Amendment No. 4) for its Ionis Pharmaceuticals holdings. Schedule 13G is typically used by institutional investors claiming passive ownership rather than seeking to influence corporate control.

Does T. Rowe Price share dispositive power over Ionis Pharmaceuticals (IONS) shares?

No. The firm reports sole dispositive power over 9,108,019 Ionis shares and zero shared dispositive power. This means T. Rowe Price alone decides if and when these shares are sold or otherwise disposed of on behalf of its clients.

What event date applies to T. Rowe Price’s Ionis Pharmaceuticals (IONS) ownership report?

The beneficial ownership information is reported as of the event date of 12/31/2025. This date anchors the 9,108,019 shares and 5.6% ownership figure disclosed in the amended Schedule 13G/A filing for Ionis Pharmaceuticals.