Description of Business	6 Months Ended
Jun. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Gossamer Bio, Inc. (including its subsidiaries, referred to as "we," "us," "our,", or the “Company”) is a clinical-stage biopharmaceutical company focused on the development and commercialization of seralutinib for the treatment of pulmonary hypertension ("PH") including pulmonary arterial hypertension ("PAH") and PH associated with interstitial lung disease ("PH-ILD"). The Company was incorporated in the state of Delaware on October 25, 2015 (originally as FSG Bio, Inc.) and is based in San Diego, California. The unaudited condensed consolidated financial statements include the accounts of Gossamer Bio, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions among the consolidated entity have been eliminated in consolidation. Liquidity and Going Concern The Company has incurred significant operating losses since its inception. As of June 30, 2026, the Company had an accumulated deficit of $1,468.7 million. From the Company’s inception through June 30, 2026, the Company has funded its operations primarily through equity financings, convertible senior notes and the Chiesi Collaboration Agreement (as defined in Note 10 below). The Company’s existing cash and cash equivalents are not sufficient to fund operating plans for at least one year from the issuance date of these financial statements. Accordingly, these conditions raise substantial doubt about the Company’s ability to continue as a going concern. The consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and settlement of liabilities, in the normal course of business, and does not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or amounts and classification of liabilities that may result from the outcome of this uncertainty. If the Company is not able to obtain the required funding, through equity or debt financings, license agreements for seralutinib in domestic or foreign markets, or other means, or is unable to obtain funding on terms favorable to the Company, or there is an event of default affecting the Company’s 2027 Notes and 2030 Notes (each as defined below), there will be a material adverse effect on commercialization and development operations, and the Company's ability to execute its strategic development plan for future growth. If the Company cannot successfully raise additional funding and implement its strategic development plan, the Company may be forced to make further reductions in spending, including spending in connection with our clinical development, pre-commercialization activities, extend payment terms with suppliers, suspend or curtail planned operations or cease operations entirely. The Company has concluded that these circumstances and the uncertainties associated with the Company’s ability to obtain additional equity or debt financing on terms that are favorable to the Company, or at all, and otherwise succeed in its future operations raise substantial doubt about the Company’s ability to continue as a going concern. Management believes that it has sufficient working capital on hand to fund operations into the first quarter of 2027. On March 16, 2026, the Company commenced a workforce reduction of 73 individuals, constituting approximately 46% of its workforce, to reduce its operating expenses. The Company's remaining management and employees will continue the development of seralutinib and explore potential regulatory paths forward. This workforce reduction is expected to be completed by the end of September 2026. The Company recognized $6.1 million of charges associated with the workforce reduction in the first quarter of 2026.

Gossamer Bio, Inc. (including its subsidiaries, referred to as "we," "us," "our,", or the “Company”) is a clinical-stage biopharmaceutical company focused on the development and commercialization of seralutinib for the treatment of pulmonary hypertension ("PH") including pulmonary arterial hypertension ("PAH") and PH associated with interstitial lung disease ("PH-ILD"). The Company was incorporated in the state of Delaware on October 25, 2015 (originally as FSG Bio, Inc.) and is based in San Diego, California.

The Company has incurred significant operating losses since its inception. As of June 30, 2026, the Company had an accumulated deficit of $1,468.7 million. From the Company’s inception through June 30, 2026, the Company has funded its operations primarily through equity financings, convertible senior notes and the Chiesi Collaboration Agreement (as defined in Note 10 below).

The Company’s existing cash and cash equivalents are not sufficient to fund operating plans for at least one year from the issuance date of these financial statements. Accordingly, these conditions raise substantial doubt about the Company’s ability to continue as a going concern. The consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and settlement of liabilities, in the normal course of business, and does not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or amounts and classification of liabilities that may result from the outcome of this uncertainty.

If the Company is not able to obtain the required funding, through equity or debt financings, license agreements for seralutinib in domestic or foreign markets, or other means, or is unable to obtain funding on terms favorable to the Company, or there is an event of default affecting the Company’s 2027 Notes and 2030 Notes (each as defined below), there will be a material adverse effect on commercialization and development operations, and the Company's ability to execute its strategic development plan for future growth. If the Company cannot successfully raise additional funding and implement its strategic development plan, the Company may be forced to make further reductions in spending, including spending in connection with our clinical development, pre-commercialization activities, extend payment terms with suppliers, suspend or curtail planned operations or cease operations entirely. The Company has concluded that these circumstances and the uncertainties associated with the Company’s ability to obtain additional equity or debt financing on terms that are favorable to the Company, or at all, and otherwise succeed in its future operations raise substantial doubt about the Company’s ability to continue as a going concern. Management believes that it has sufficient working capital on hand to fund operations into the first quarter of 2027.

On March 16, 2026, the Company commenced a workforce reduction of 73 individuals, constituting approximately 46% of its workforce, to reduce its operating expenses. The Company's remaining management and employees will continue the development of seralutinib and explore potential regulatory paths forward. This workforce reduction is expected to be completed by the end of September 2026. The Company recognized $6.1 million of charges associated with the workforce reduction in the first quarter of 2026.