Item 1.01 Entry into a Material Definitive Agreement.

(a) Registered Direct Offering

On October 23, 2025, Tango Therapeutics, Inc. (the "Company") entered into an underwriting agreement (the "Underwriting Agreement") with Leerink Partners LLC, as representative to the several underwriters named in the Underwriting Agreement (collectively, the "Underwriters"), relating to an underwritten offering (the "Registered Direct Offering") of (i) 21,023,337 shares (the "Shares") of the Company's common stock, $0.001 par value per share (the "Common Stock") and (ii) pre-fundedwarrants (the "Pre-FundedWarrants") to purchase up to 3,226,458 shares of Common Stock (such shares issuable upon exercise of the Pre-FundedWarrants, the "Pre-FundedWarrant Shares", and together with the Shares and the Pre-FundedWarrants, the "Securities"). All of the Shares and the Pre-FundedWarrants in the Offering were sold by the Company. Each Share was offered and sold at an offering price of $8.66 before deducting underwriting discounts and commissions and each Pre-Funded Warrantwas offered and sold at an offering price of $8.659 which is equal to the offering price per share less the $0.001 exercise price of each Pre-Funded Warrant,before deducting underwriting discounts and commissions.

Each Pre-Funded Warranthas an initial exercise price per share of $0.001, subject to certain adjustments. The Pre-Funded Warrantsare exercisable immediately and may be exercised at any time until all of the Pre-Funded Warrantsare exercised in full. The pre-funded warrants do not expire.

Under the Pre-FundedWarrants, the Company may not effect the exercise of any Pre-FundedWarrant, and a holder will not be entitled to exercise any portion of any Warrant (i) if immediately prior to the exercise, a holder (together with its affiliates), beneficially owns an aggregate number of shares of Common Stock greater than 4.99% or 9.99%, as applicable (the "Maximum Percentage") of the total number of issued and outstanding shares of Common Stock of the Company without taking into account any Pre-FundedWarrant Shares, or (ii) to the extent that immediately following the exercise, the holder (together with its affiliates) would beneficially own in excess of the Maximum Percentage of the number of shares of Common Stock outstanding immediately after giving effect to the issuance of such shares of Common Stock, which such percentage may be changed at the holder's election to a higher or lower percentage not in excess of 19.99% upon 61 days' notice to the Company.

The Registered Direct Offering is expected to close on October 24, 2025, and is subject to the satisfaction of customary closing conditions. The Company estimates that the net proceeds to the Company from the Registered Direct Offering, after deducting underwriting discounts and commissions and estimated offering expenses payable by the Company are approximately $197 million. The Company intends to use the net proceeds from the Registered Direct Offering to advance its pipeline and for working capital and general corporate purposes. Based upon the Company's current operating plan, it believes that the net proceeds from this Registered Direct Offering and the Private Placement (defined below), together with its existing cash, cash equivalents and investments, will enable it to fund its operating expenses and capital expenditure requirements into 2028.

The Underwriting Agreement contains customary representations, warranties and agreements by the Company, customary conditions to closing, indemnification obligations of the Company and the Underwriters, including for liabilities under the Securities Act of 1933, as amended (the "Securities Act"), other 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.

The Securities were issued pursuant to the Company's Registration Statement on Form S-3(File No. 333-287202)(the "Registration Statement"), as supplemented by a prospectus supplement dated October 23, 2025.

A copy of the legal opinion of Goodwin Procter LLP relating to the legality of the issuance and sale of the Securities issued in the Registered Direct Offering is filed as Exhibit 5.1 to this Current Report on Form 8-Kand incorporated by reference into the Registration Statement.

(b) Private Placement

On October 23, 2025, the Company also entered into a securities purchase agreement (the "Purchase Agreement") with a certain accredited investor (the "Purchaser"), for the private investment in public equity (the "Private Placement") of 1,732,101 shares (the "PIPE Shares") of the Company's Common Stock, at a purchase price of $8.66 per share. The aggregate gross proceeds for the Private Placement will be approximately $15 million, before deducting offering commissions and estimated offering expenses payable by the Company.

The closing of the Private Placement is anticipated to occur on October 24, 2025, subject to the satisfaction of customary closing conditions. Pursuant to the Purchase Agreement, the Company also agreed to file a registration statement with the Commission no later than 30 calendar days following the date of the agreement to register the resale of the PIPE Shares, to use its commercially reasonable efforts to have such registration statement to be declared effective within the time period set forth in the Purchase Agreement and to keep such registration statement effective for up to three years. The Company will also agree among other things, to indemnify the Purchasers and the Purchaser's affiliates under the registration statement from certain liabilities and pay all fees and expenses (excluding any legal fees of the selling holder(s), and any underwriting discounts and selling commissions) incident to the Company's obligation to file such registration statement.

The Private Placement is exempt from registration pursuant to Section 4(a)(2) of the Securities Act of 1933, as amended (the "Securities Act") and Rule 506(b) of Regulation D promulgated by the SEC thereunder, as a transaction by an issuer not involving a public offering. The Purchasers will acquire the securities for investment only and not with a view to or for sale in connection with any distribution thereof, and appropriate legends will be affixed to the securities issued in this transaction.

The foregoing descriptions of the Underwriting Agreement, the Pre-FundedWarrants and the Purchase Agreement, are subject to, and qualified in their entirety by, such documents (or forms thereof), which are attached hereto as Exhibits 1.1, 4.1 and 10.1, respectively, and incorporated herein by reference.

Item 3.02 Unregistered Sales of Equity Securities.