Ionis Prices Convertible Notes Offering to Refinance 2026 Convertible Notes

Ionis Pharmaceuticals, Inc. (NASDAQ: IONS) announced today the pricing of $700.0 million aggregate principal amount of 0.00% Convertible Senior Notes due 2030 (the “notes”) in a private placement (the “offering”) to qualified institutional buyers pursuant to Rule 144A under the Securities Act of 1933, as amended (the “Securities Act”). Ionis also granted the initial purchasers of the notes an option to purchase, within the 13-day period beginning on, and including, the date on which the notes are first issued, up to an additional $70.0 million aggregate principal amount of notes from Ionis. The sale of the notes is expected to close on November 17, 2025, subject to customary closing conditions.

The notes will be general unsecured obligations of Ionis, and will not bear regular interest and the principal amount of the notes will not accrete. The notes will mature on December 1, 2030, unless earlier converted, redeemed or repurchased.

Ionis estimates that the net proceeds from the offering will be approximately $682.8 million (or approximately $751.2 million if the initial purchasers exercise their option to purchase additional notes in full), after deducting the initial purchasers’ discounts and commissions and estimated offering expenses payable by Ionis.

Ionis expects to use 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 described below. Ionis 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.

Before September 1, 2030, holders will have the right to convert their notes only upon the satisfaction of specified conditions and during certain periods. 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. Upon conversion, Ionis will pay or deliver, as the case may be, cash, shares of its common stock or a combination of cash and shares of its common stock, at its election. The conversion rate for the notes will initially be 10.1932 shares of Ionis’ common stock per $1,000 principal amount of notes (equivalent to an initial conversion price of approximately $98.10 per share of Ionis’ common stock). The initial conversion price represents a premium of approximately 35.0% over the last reported sale price of $72.67 per share of Ionis’ common stock on November 12, 2025. The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued or unpaid special interest, if any.