144/A: Filer Information

Filer CIK

0001838539

Filer CCC

XXXXXXXX

Previous Accession Number Of The Filing

0001972481-26-000114

Is this a LIVE or TEST Filing?

LIVE

TEST

Submission Contact Information

Name

Phone

E-Mail Address

144/A: Issuer Information

Name of Issuer

IONIS PHARMACEUTICALS INC

SEC File Number

000-19125

Address of Issuer

2855 GAZELLE COURT
CARLSBAD
CALIFORNIA
92010

Phone

7609319200

Name of Person for Whose Account the Securities are To Be Sold

Schneider Eugene

See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.

Relationship to Issuer

Officer

144/A: Securities Information

Title of the Class of Securities To Be Sold

Name and Address of the Broker

Number of Shares or Other Units To Be Sold

Aggregate Market Value

Number of Shares or Other Units Outstanding

Approximate Date of Sale

Name the Securities Exchange

Common Stock

Stifel Nicolaus & Company Inc
501 N Broadway
St. Louis � MO � 63102

5812

412486.00

165190000

03/19/2026

Nasdaq

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144/A: Securities To Be Sold

Title of the Class

Date you Acquired

Nature of Acquisition Transaction

Name of Person from Whom Acquired

Is this a Gift?

Date Donor Acquired

Amount of Securities Acquired

Date of Payment

Nature of Payment *

Common Stock

01/15/2026

Performance Stock Units

Issuer

5812

01/15/2026

Equity Compensation

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144/A: Securities Sold During The Past 3 Months

Name and Address of Seller

Title of Securities Sold

Date of Sale

Amount of Securities Sold

Gross Proceeds

Eugene Schneider
2855 Gazelle Ct
Carlsbad � CA � 92010

Common Stock

01/30/2026

6179

512906.00

Eugene Schneider
2855 Gazelle Ct
Carlsbad � CA � 92010

Common Stock

01/16/2026

9302

703138.00

144/A: Remarks and Signature

Remarks

Date of Notice

03/24/2026

Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1

11/19/2025

ATTENTION:

The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.

Signature

/s/ James Weimer, as a duly authorized representative of STIFEL, as attorney-in-fact for Eugene Schneider

144/A: Filer Information

Submission Contact Information

144/A: Issuer Information

144/A: Securities Information

144/A: Securities To Be Sold

144/A: Securities Sold During The Past 3 Months

144/A: Remarks and Signature

ATTENTION:

ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)

Amendment: SEC Form 144/A filed by Ionis Pharmaceuticals Inc.