Spyre Therapeutics, Inc. Announces Closing of Public Offering and Full Exercise of the Underwriters’ Option to Purchase Additional Shares for Gross Proceeds of $463.5 Million

Spyre Therapeutics, Inc. (“Spyre” or the “Company”) (Nasdaq: SYRE), a clinical-stage biotechnology company pioneering long-acting antibodies and antibody combinations to redefine the standard of care for inflammatory bowel disease (IBD) and rheumatic diseases, today announced the closing of its previously announced underwritten public offering of 7,475,000 shares of its common stock, including the full exercise of the underwriters’ option to purchase up to 975,000 additional shares, at a public offering price per share of $62.00. The gross proceeds to Spyre from the offering were approximately $463.5 million before deducting underwriting discounts and commissions and other offering expenses payable by Spyre.

Jefferies LLC, Goldman Sachs & Co. LLC, Evercore ISI, and Guggenheim Securities, LLC acted as the joint book-running managers for the offering. LifeSci Capital LLC acted as passive bookrunner for the offering.

A registration statement on Form S-3 (File No. 333-293600) relating to these securities has been filed with the Securities and Exchange Commission (the “SEC”) and became effective on February 27, 2026. This offering was solely by means of a prospectus supplement and accompanying prospectus. A final prospectus supplement dated April 14, 2026 and accompanying base prospectus relating to and describing the terms of the offering were filed with the SEC on April 16, 2026 and are available on the SEC’s website located at http://www.sec.gov. Copies of the final prospectus supplement and the accompanying prospectus relating to the offering may be obtained from Jefferies LLC, Attention: Equity Syndicate Prospectus Department, 520 Madison Avenue, New York, NY 10022, by telephone at (877) 821-7388 or by email at [email protected]; Goldman Sachs & Co. LLC, Attention: Prospectus Department, 200 West Street, New York, NY 10282, by telephone at (866) 471-2526 or by email at [email protected]; Evercore Group L.L.C., Attention: Equity Capital Markets, 55 East 52nd Street, 35th Floor, New York, NY 10055, by telephone at (888) 474-0200 or by email at [email protected]; Guggenheim Securities, LLC, Attention: Equity Syndicate Department, 330 Madison Avenue, New York, NY 10017, by telephone at (212) 518-9544 or by email at [email protected]; or LifeSci Capital LLC at 1700 Broadway, 40th Floor, New York, New York 10019, or by email at [email protected].

This press release shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation, or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

About Spyre Therapeutics

Spyre Therapeutics is a clinical-stage biotechnology company pioneering long-acting antibodies and antibody combinations to redefine the standard of care for IBD and rheumatic diseases. Spyre's pipeline includes investigational extended half-life antibodies targeting α4β7, TL1A, and IL-23.

For Investors: Eric McIntyre VP of Finance and Investor Relations Spyre Therapeutics [email protected]

For Media: Josie Butler, 1AB [email protected]