The Company	9 Months Ended
Sep. 30, 2023
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 clinical-stage biotherapeutics company harnessing the power of directed evolution for targeted genetic medicines. Initial Public Offering In December 2020, the Company sold and issued 9,660,000 shares of common stock at a price to the public of $23.00 per share, which included shares sold upon the underwriters’ exercise of their overallotment option to purchase 1,260,000 additional shares. The Company received an aggregate of $204.7 million in net proceeds, after deducting underwriting discounts and commissions and offering costs. Upon the closing of the Company's initial public offering in December 2020 (the "IPO"), all outstanding shares of redeemable convertible preferred stock automatically converted into 11,575,984 shares of common stock. Subsequent to the closing of the IPO, there were no shares of redeemable convertible preferred stock outstanding. 2021 Follow On Public Offering In November 2021, the Company completed an underwritten public offering ("2021 Offering") in which 4,750,000 shares of the Company's common stock were sold at an offering price of $25.00 per share pursuant to an effective Registration Statement on Form S-1. The net proceeds from the 2021 Offering were $111.1 million, after deducting underwriting discounts and commissions and estimated offering expenses. 2023 Follow On Public Offering In May 2023, the Company completed its third underwritten public offering (the “2023 Offering”) in which 8,625,000 shares of the Company’s common stock were sold at an offering price of $16.00 per share pursuant to an effective Registration Statement on Form S-3. The net proceeds from the 2023 Offering were $129.2 million, after deducting underwriting discounts and commissions and offering expenses. Liquidity The Company has incurred significant losses and negative cash flows from operations and had an accumulated deficit of $383.0 million as of September 30, 2023. The Company believes that its cash and cash equivalents and marketable securities as of September 30, 2023 are sufficient for the Company to fund planned operations for at least one year from the issuance date of these unaudited condensed financial statements. The Company has historically financed its operations primarily through the sale of equity securities, 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

9 Months Ended

Sep. 30, 2023

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 clinical-stage biotherapeutics company harnessing the power of directed evolution for targeted genetic medicines.

Initial Public Offering

In December 2020, the Company sold and issued 9,660,000 shares of common stock at a price to the public of $23.00 per share, which included shares sold upon the underwriters’ exercise of their overallotment option to purchase 1,260,000 additional shares. The Company received an aggregate of $204.7 million in net proceeds, after deducting underwriting discounts and commissions and offering costs.

Upon the closing of the Company's initial public offering in December 2020 (the "IPO"), all outstanding shares of redeemable convertible preferred stock automatically converted into 11,575,984 shares of common stock. Subsequent to the closing of the IPO, there were no shares of redeemable convertible preferred stock outstanding.

2021 Follow On Public Offering

In November 2021, the Company completed an underwritten public offering ("2021 Offering") in which 4,750,000 shares of the Company's common stock were sold at an offering price of $25.00 per share pursuant to an effective Registration Statement on Form S-1. The net proceeds from the 2021 Offering were $111.1 million, after deducting underwriting discounts and commissions and estimated offering expenses.

2023 Follow On Public Offering

In May 2023, the Company completed its third underwritten public offering (the “2023 Offering”) in which 8,625,000 shares of the Company’s common stock were sold at an offering price of $16.00 per share pursuant to an effective Registration Statement on Form S-3. The net proceeds from the 2023 Offering were $129.2 million, after deducting underwriting discounts and commissions and offering expenses.

Liquidity

The Company has incurred significant losses and negative cash flows from operations and had an accumulated deficit of $383.0 million as of September 30, 2023. The Company believes that its cash and cash equivalents and marketable securities as of September 30, 2023 are sufficient for the Company to fund planned operations for at least one year from the issuance date of these unaudited condensed financial statements. The Company has historically financed its operations primarily through the sale of equity securities, 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.