The Company	6 Months Ended
Jun. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company	1. The Company 4D Molecular Therapeutics, Inc. (the “Company”) was formed as a limited liability company in September 2013 under the name 4D Molecular Therapeutics, LLC. The Company changed its name and converted into a corporation which was incorporated in the state of Delaware in March 2015. The Company is a late-stage biotechnology company advancing durable and disease-targeted therapeutics with potential to transform treatment paradigms and provide benefits to patients. 2025 Offering In November 2025, the Company completed an underwritten offering (the “2025 Offering”) in which 8,385,809 shares of the Company’s common stock were sold at an offering price of $10.51 per share, as well as pre-funded warrants to purchase 1,128,949 shares of the Company’s common stock at an offering price of $10.5099 per underlying share pursuant to an effective Registration Statement on Form S-3. The net proceeds from the 2025 Offering were approximately $93.3 million, after deducting the underwriting discounts and commissions and other offering expenses. Liquidity The Company has incurred significant losses and negative cash flows from operations and had an accumulated deficit of $858.0 million as of June 30, 2026. The Company believes that its cash, cash equivalents and marketable securities as of June 30, 2026 are sufficient for the Company to fund planned operations for at least one year from the issuance date of these condensed financial statements. The Company has funded its operations primarily through the sale and issuance of equity securities, including primary follow-on offerings and use of the Company's "at-the-market" offering program, from borrowings under the Company’s $200.0 million loan facility (the “Loan and Security Agreement”) with Hercules Capital, Inc. (“Hercules”) (see Note 9, Long-Term Debt) and, to a lesser extent, from cash received pursuant to its collaboration and license agreements. To date, none of the Company’s product candidates have been approved for sale, and therefore, the Company has not generated any revenue from product sales. Management expects operating losses and negative cash flows from operations to continue for the foreseeable future. The Company plans to raise additional funding as required based on the status of its clinical trials and projected cash flows. There can be no assurance that, in the event the Company requires additional financing, such financing will be available on terms acceptable to the Company, if at all. Failure to generate sufficient cash flows from operations, raise additional capital and reduce discretionary spending should additional capital not become available could have a material adverse effect on the Company’s ability to achieve its business objectives.

The Company

6 Months Ended

Jun. 30, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

1. The Company

4D Molecular Therapeutics, Inc. (the “Company”) was formed as a limited liability company in September 2013 under the name 4D Molecular Therapeutics, LLC. The Company changed its name and converted into a corporation which was incorporated in the state of Delaware in March 2015. The Company is a late-stage biotechnology company advancing durable and disease-targeted therapeutics with potential to transform treatment paradigms and provide benefits to patients.

2025 Offering

In November 2025, the Company completed an underwritten offering (the “2025 Offering”) in which 8,385,809 shares of the Company’s common stock were sold at an offering price of $10.51 per share, as well as pre-funded warrants to purchase 1,128,949 shares of the Company’s common stock at an offering price of $10.5099 per underlying share pursuant to an effective Registration Statement on Form S-3. The net proceeds from the 2025 Offering were approximately $93.3 million, after deducting the underwriting discounts and commissions and other offering expenses.

Liquidity

The Company has incurred significant losses and negative cash flows from operations and had an accumulated deficit of $858.0 million as of June 30, 2026. The Company believes that its cash, cash equivalents and marketable securities as of June 30, 2026 are sufficient for the Company to fund planned operations for at least one year from the issuance date of these condensed financial statements. The Company has funded its operations primarily through the sale and issuance of equity securities, including primary follow-on offerings and use of the Company's "at-the-market" offering program, from borrowings under the Company’s $200.0 million loan facility (the “Loan and Security Agreement”) with Hercules Capital, Inc. (“Hercules”) (see Note 9, Long-Term Debt) and, to a lesser extent, from cash received pursuant to its collaboration and license agreements. To date, none of the Company’s product candidates have been approved for sale, and therefore, the Company has not generated any revenue from product sales. Management expects operating losses and negative cash flows from operations to continue for the foreseeable future. The Company plans to raise additional funding as required based on the status of its clinical trials and projected cash flows. There can be no assurance that, in the event the Company requires additional financing, such financing will be available on terms acceptable to the Company, if at all. Failure to generate sufficient cash flows from operations, raise additional capital and reduce discretionary spending should additional capital not become available could have a material adverse effect on the Company’s ability to achieve its business objectives.