Material Agreement (Form 8-K)

On September 9, 2025, Rapport Therapeutics, Inc. (the "Company") entered into an Underwriting Agreement (the "Underwriting Agreement") with Goldman Sachs & Co. LLC, Jefferies LLC, TD Securities (USA) LLC and Stifel, Nicolaus & Company, Incorporated (collectively, the "Underwriters"), related to an underwritten public offering (the "Offering") of 9,615,385 shares (the "Firm Shares") of the Company's common stock, par value $0.001 per share ("Common Stock"), at a public offering price of $26.00 per share. In addition, the Company has granted the Underwriters an option, exercisable in whole or in part at any time for a period of 30 days from the date of the Underwriting Agreement, to purchase, at the public offering price, less the underwriting discounts and commissions, up to an additional 1,442,307 shares of Common Stock (such shares, together with the Firm Shares, the "Shares").

The Company estimates that the net proceeds from the Offering, after deducting the underwriting discounts and commissions and estimated offering expenses payable by the Company, will be approximately $234.7 million, excluding any proceeds from exercise of the underwriters' option to purchase additional shares. The Company intends to use the net proceeds from the Offering, together with its existing cash, cash equivalents and short-term investments, to primarily fund its ongoing and planned clinical trials advancing RAP-219,other research and development, and for working capital and general corporate purposes. The Offering is expected to close on or about September 11, 2025, subject to the satisfaction of customary closing conditions. All of the Shares in the Offering are being sold by the Company.

The Company made certain customary representations, warranties and covenants concerning the Company and the registration statement in the Underwriting Agreement and also agreed to indemnify the Underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended (the "Securities Act"). The Offering was made pursuant to the Company's shelf registration statement on Form S-3(File No. 333-288444),filed with the Securities and Exchange Commission (the "SEC") on July 1, 2025 and declared effective by the SEC on July 9, 2025, including the base prospectus therein, as supplemented by a final prospectus supplement, dated September 9, 2025 and filed with the SEC on September 10, 2025. This Current Report on Form 8-Kdoes not constitute an offer to sell or a solicitation of an offer to buy any of the shares of Common Stock.

The foregoing description of certain terms of the Underwriting Agreement and the transactions contemplated thereby does not purport to be complete and is subject to, and qualified in its entirety by, the full text of the Underwriting Agreement, which is filed as Exhibit 1.1 to this Current Report on Form 8-Kand is incorporated by reference herein.

A copy of the legal opinion of Goodwin Procter LLP, relating to the legality of the issuance and sale of shares of Common Stock in the Offering, is filed as Exhibit 5.1 to this Current Report on Form 8-Kand is incorporated by reference herein.