Gossamer Bio, Inc. (NASDAQ:GOSS) (the "Company" or "Gossamer"), a clinical-stage biopharmaceutical company focused on the development and commercialization of seralutinib for the treatment of pulmonary arterial hypertension and pulmonary hypertension associated with interstitial lung disease, today announced that its board of directors (the "Board") has selected a 1-for-80 reverse stock split of the Company’s common stock and a proportionate reduction in the number of authorized shares of common stock (and a corresponding decrease in the total number of authorized shares of capital stock). At a special meeting held on July 14, 2026, the Company’s stockholders approved thirty alternate amendments to the Company’s amended and restated certificate of incorporation to effect a reverse stock split at one of thirty reverse stock split ratios, with the exact ratio to be determined by the Board.

The reverse stock split is intended to help the Company regain compliance with the minimum bid price requirement for continued listing on the Nasdaq Global Select Market.

The reverse stock split is expected to become effective at 11:59 p.m. Eastern Time on September 10, 2026. Shares of the Company’s common stock are expected to begin trading on a split-adjusted basis on the Nasdaq Global Select Market at market open on September 11, 2026 under the existing trading symbol "GOSS" and a new CUSIP number of 38341P 201.

In connection with the reverse stock split, every 80 shares of the Company’s common stock issued and outstanding immediately prior to the effective time will be automatically reclassified and combined into 1 share of common stock.

No fractional shares of common stock will be issued as a result of the reverse stock split. Instead, the Company will issue to holders of record who are entitled to a fraction of a share as a result of the Reverse Stock Split, a fraction of a share of common stock as is necessary to round up to the nearest whole share. For shares held through The Depository Trust Company ("DTC"), fractions of shares will be issued as is necessary to round up to the nearest whole share at the DTC participant level. Brokers, banks or other nominees holding shares in "street name" will be instructed to effect the reverse stock split for their beneficial holders; however, such brokers, banks or other nominees may apply their own specific procedures for processing the reverse stock split.

In connection with the authorized share reduction, the number of authorized shares of common stock will be reduced from 4,000,000,000 to 50,000,000, and the total number of authorized shares of capital stock will be correspondingly reduced from 4,070,000,000 to 120,000,000.

Upon the effectiveness of the reverse stock split, the conversion rates of the Company’s outstanding convertible notes, the number of shares of common stock issuable upon exercise of outstanding warrants and prefunded warrants and the exercise prices thereof, and the number of shares subject to outstanding equity awards under the Company’s equity incentive plans (and the applicable exercise prices thereof), will each be proportionately adjusted pursuant to their respective terms and as determined by the Board to reflect the 1-for-80 reverse stock split ratio. In addition, the number of shares reserved for future issuance under the Company’s equity incentive plans will be proportionately reduced.