Material Event (Form 8-K)

On November 6, 2025, 4D Molecular Therapeutics, Inc. (the "Company") entered into an underwriting agreement (the "Underwriting Agreement") with Leerink Partners LLC and Evercore Group L.L.C., as representatives of the several underwriters named therein (the "Underwriters"), pursuant to which the Company agreed to issue and sell (the "Offering") 8,385,809 shares of its common stock (the "Shares"), par value $0.0001 per share ("Common Stock"), at an offering price of $10.51 per share, and, with respect to certain investors, pre-fundedwarrants to purchase 1,128,949 shares of Common Stock (the "Pre-FundedWarrants") at a price of $10.5099 per Pre-FundedWarrant, which is the price per share at which shares of Common Stock are being sold in the Offering, minus the $0.0001 exercise price per Pre-FundedWarrant. The Underwriters agreed to purchase the Shares from the Company pursuant to the Underwriting Agreement at a price of $9.8794 per share and the Pre-FundedWarrants at a price of $9.8793 per Pre-FundedWarrant.

The net proceeds from the Offering were approximately $93.3 million, after deducting the underwriting discounts and commissions and other estimated offering expenses payable by the Company. The Offering closed on November 7, 2025.

The Offering was made under a prospectus supplement and related prospectus filed with the Securities and Exchange Commission (the "SEC") pursuant to the Company's registration statement on Form S-3(Registration No. 333-273845),which was declared effective by the SEC on August 15, 2023.

Pursuant to the Underwriting Agreement, the Company agreed to indemnify the Underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended, or to contribute to payments that the Underwriters may be required to make because of such liabilities. In addition, the Underwriting Agreement also contains customary representations, warranties and agreements by the Company and customary conditions to closing, obligations of the parties and termination provisions. The representations, warranties and covenants contained in the Underwriting Agreement were made only for purposes of such agreement and as of specific dates, were solely for the benefit of the parties to such agreement, and may be subject to limitations agreed upon by such parties.

In connection with the Offering, the Company and the Company's directors and executive officers agreed not to sell or transfer any Common Stock without first obtaining the written consent of Leerink Partners LLC and Evercore Group L.L.C., on behalf of the Underwriters, subject to certain exceptions, until January 6, 2026.

A copy of the Underwriting Agreement and the form of the Pre-FundedWarrant are attached as Exhibit 1.1 and Exhibit 4.1 hereto, respectively and are incorporated herein by reference. The foregoing descriptions of the Underwriting Agreement, lock-uparrangements and the form of the Pre-FundedWarrant do not purport to be complete and are qualified in their entirety by reference to such exhibits.

A copy of the opinion of Latham & Watkins LLP relating to the validity of the securities issued in the Offering is filed herewith as Exhibit 5.1.