RAPT Therapeutics, Inc.

Item 1.01 Entry into a Material Definitive Agreement. Agreement and Plan of Merger On January 19, 2026, RAPT Therapeutics, Inc., a Delaware corporation (the “Company” or “RAPT Therapeutics”), entered into an Agreement and Plan of Merger (the “Merger Agreement”) by and among the Company, GlaxoSmithKline LLC, a Delaware limited liability company (“Parent”), Redrose Acquisition Co., a Delaware corporation and a wholly owned subsidiary of Parent (“Purchaser”) and, solely for purposes of providing a guaranty pursuant to Section 8.11 of the Merger Agreement, GSK plc, a public limited company organized under the laws of England and Wales (“Ultimate Parent” or “GSK”). Pursuant to the Merger Agreement, upon the terms and subject to the conditions thereof, Parent will cause Purchaser to commence a cash tender offer (the “Offer”) no later than ten business days after the date of the Merger Agreement. The Offer will consist of an offer to purchase all of the outstanding shares of common stock of the Company, par value $0.0001 per share (the “Shares”), at a price of $58.00 per Share (the “Offer Price”), in cash, without interest and subject to any applicable withholding of taxes. The obligation of Purchaser to accept for payment, and pay for, Shares validly tendered (and not validly withdrawn) pursuant to the Offer is subject solely to the satisfaction or waiver, to the extent permitted under applicable legal requirements, of certain conditions set forth in the Merger Agreement, including, among other things, (i) there being validly tendered and not validly withdrawn Shares that, considered together with all other Shares (if any) beneficially owned by Parent or any of its wholly owned subsidiaries (but excluding Shares tendered pursuant to guaranteed delivery procedures, if permitted by the terms of the Offer, that have not yet been “received” by the “depositary”, as such terms are defined by Section 251(h)(6) of the General Corporation Law of the State of Delaware (the “DGCL”)), would represent a majority of Shares outstanding at the time of the expiration of the Offer, and (ii) any applicable waiting period (and any extension thereof) imposed under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, and the rules and regulations promulgated thereunder (the “HSR Act”), and any timing agreement mutually entered by Parent and the Company with a governmental body to not consummate the Offer or Merger, shall have expired or been terminated. Parent’s and Purchaser’s obligations to consummate the Offer are not subject to a condition that any financing be received by Parent or Purchaser for the consummation of the transactions contemplated by the Merger Agreement (the “Transactions”). As soon as practicable following consummation of the Offer, subject to the terms and conditions of the Merger Agreement and in accordance with Section 251(h) of the DGCL, Purchaser will merge with and into the Company (the “Merger”), with the Company surviving the Merger as a wholly owned subsidiary of Parent in accordance with the DGCL. At the effective time of the Merger (the “Effective Time”), each Share then outstanding (other than Shares (a) held by the Company or held in the Company’s treasury (other than, in each case, Shares that are held in a fiduciary or agency capacity and are beneficially owned by third parties), (b) held by the Parent, Purchaser or any other direct or indirect wholly owned subsidiary of Parent, (c) held by stockholders of the Company who have properly exercised and perfected their statutory rights of appraisal under Section 262 of the DGCL, or (d) irrevocably accepted for purchase in the Offer) will be converted into the right to receive the Offer Price (the “Merger Consideration”), without interest and subject to any applicable withholding of taxes. In addition, as of the Effective Time, except as otherwise provided below, (a) each option to purchase Shares (an “Option”) that is outstanding immediately prior to the Effective Time, whether vested or unvested, other than a 2025 Option (as defined below), will accelerate and become fully vested and be cancelled and entitle the holder thereof to receive for each Share underlying such Option a cash amount equal to the excess of (x) the Merger Consideration over (y) the exercise price payable per Share under such Option, if any (the “Option Consideration”); (b) each restricted stock unit of the Company (an “RSU”) that is outstanding immediately prior to the Effective Time, whether vested or unvested, other than any 2025 RSU (as defined below), will be cancelled and entitle the holder thereof to receive a cash amount equal to the Merger Consideration for each Share underlying such RSU (the “RSU Consideration”); (c) each Option that is unvested as of immediately prior to the Effective Time and was granted to an employee of the Company after March 1, 2025 (a “2025 Option”) will be cancelled and entitle the holder thereof to receive an amount in cash equal to the Option Consideration (the “Converted Option Cash Consideration”). Each holder’s right to receive the Converted Option Cash Consideration will be subject to the same terms and conditions (including vesting, forfeiture and acceleration provision... ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── (d) each RSU that is unvested as of immediately prior to the Effective Time and was granted to an employee after March 1, 2025 (a “2025 RSU”) will be cancelled and entitle the holder thereof to receive an amount in cash equal to the RSU Consideration (the “Converted RSU Cash Consideration”). Each holder’s right to receive the Converted RSU Cash Consideration will be subject to the same terms and conditions (including vesting, forfeiture and acceleration provisions) applicable to the correspon... ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── At the Effective Time, each outstanding warrant to purchase Shares (a “Warrant”) that is outstanding and unexercised as of immediately prior to the Effective Time (excluding, for the avoidance of doubt, any Warrant to the extent the holder thereof has elected a cashless exercise of such Warrant prior to the Effective Time) will be converted into the right to receive cash, without any interest thereon, in an amount equal to (i) the total number of Shares subject to such Warrant immediately prior to the Effective Time, multiplied by (ii) the excess of (x) the Merger Consideration over (y) the exercise price per Share under such Warrant. The Merger Agreement includes representations, warranties and covenants of the parties customary for a transaction of this nature. From the date of the Merger Agreement until the earlier of the Effective Time and the termination of the Merger Agreement, the Company has agreed, subject to certain exceptions, to use commercially reasonable efforts to operate its business and operations in all material respects in the ordinary course and has agreed to certain other interim operating covenants, as set forth more fully in the Merger Agreement. The Company has also agreed to customary “no-shop” restrictions on its ability to, directly or indirectly, solicit alternative acquisition proposals from third parties and engage in discussions or negotiations with third parties regarding alternative acquisition proposals. Notwithstanding these restrictions, the Company may under certain circumstances provide, pursuant to an acceptable confidentiality agreement, information to and engage in or otherwise participate in discussions or negotiations with third parties with respect to a written alternative acquisition proposal that the board of directors of the Company (the “Company Board”) has determined in good faith, after consultation with its financial advisors and outside legal counsel, constitutes or would reasonably be expected to lead to a Superior Proposal (as defined in the Merger Agreement) and the failure to take such action would reasonably be expected to be inconsistent with fiduciary duties of the Company Board under applicable law. The Merger Agreement also requires that the Company Board recommend that the stockholders of the Company accept the Offer and tender their Shares pursuant to the Offer (the “Company Board Recommendation”) and not, among other things, (i) (A) withdraw or qualify (or modify in a manner adverse to Parent or Purchaser), or publicly propose to withdraw or qualify (or modify in a manner adverse to Parent or Purchaser), the Company Board Recommendation, (B) approve, recommend or declare advisable, or publicly propose to approve, recommend or declare advisable, any alternative acquisition proposal, (C) fail to include the Company Board Recommendation in the Company’s Solicitation/Recommendation Statement on Schedule 14D-9 (discussed below), (D) if any acquisition proposal is structured as a tender offer or exchange offer for the outstanding Shares and is commenced pursuant to Rule 14d-2 under the Exchange Act (other than by Parent or an affiliate of Parent), fail to recommend, within 10 business days after such commencement, rejection of such tender offer or exchange offer, or (E) publicly propose to do any of the foregoing (any such action in (i), a “Company Adverse Change Recommendation”), or (ii) approve, recommend or declare advisable, or propose to approve, recommend or declare advisable, or allow the Company to execute or enter into any Company Acquisition Agreement (as defined in the Merger Agreement) (other than an acceptable confidentiality agreement) with respect to any alternative acquisition proposal. Notwithstanding these restrictions, the Company Board is permitted, subject to the terms and conditions set forth in the Merger Agreement, to make a Company Adverse Change Recommendation or terminate the Merger Agreement to enter into a definitive agreement with respect to a Superior Proposal or make a Company Adverse Change Recommendation in response to a Change in Circumstance (as defined in the Merger Agreement), subject in each case to certain notice and matching rights in favor of Parent and payment of the termination fee described below in certain circumstances. The Merger Agreement includes a remedy of specific performance for the Company, Parent and Purchaser. The Merger Agreement also includes customary termination provisions for both the Company and Parent and provides that, in connection with the termination of the Merger Agreement under specified circumstances, including (i) termination by the Company to accept and enter into a definitive agreement with respect to a Superior Proposal or (ii) termination by Parent due to a Company Adverse Change Recommendation, the Company will be required to pay to Parent a termination fee (the “Company Termination Fee”) of an amount in cash equal to $78.4 million. The Company Termination Fee is also payable if: (x) the Merger Agreement is terminated in certain circumstances, (y) after the date of the Merger Agreement and prior to such termination (or the End Date (as defined below), if such termination is due to the occurrence of the End Date) a bona fide proposal for an alternative acquisition transaction has been publicly disclosed and not withdrawn, and (z) within 12 months of such termination, the Company enters into a definitive agreement with respect to, or consummates, an alternative acquisition transaction. Any such termination of the Merger Agreement by the Company is subject to certain conditions, including the Company’s compliance with certain procedures set forth in the Merger Agreement. The Merger Agreement further provides that Parent will be required to pay the Company a reverse termination fee of an amount in cash equal to $100.8 million in the event the Merger Agreement is terminated under certain specified circumstances, including if the Merger Agreement is terminated by Parent or the Company either (A) due to the existence of a permanent legal restraint under the HSR Act, or (B) due to the Offer not being consummated by July 19, 2026 (“End Date”) (provided that the End Date may be extended by either Parent or the Company by written notice to the other on or prior to the initial End Date for an additional 90 days each pursuant to the Merger Agreement), when, at the time of termination, the applicable regulatory conditions to the Offer, as such relate to the HSR Act, have not been satisfied, and all other Offer Conditions (other than the Offer Conditions that are by their nature to be satisfied at the Offer Acceptance Time) have been satisfied or waived. The foregoing description of the Merger Agreement and the Transactions does not purport to be complete and is qualified in its entirety by reference to the Merger Agreement, which is filed as Exhibit 2.1 hereto and which is incorporated herein by reference. The Merger Agreement has been filed to provide information to investors regarding its terms. The Merger Agreement is not intended to provide any other factual information about the Company, Parent, Purchaser or Ultimate Parent, their respective businesses, or the actual conduct of their respective businesses during the period prior to the consummation of the Offer, the Merger or the other Transactions. The Merger Agreement and this summary should not be relied upon as disclosure about the Company or Parent. None of the Company’s stockholders or any other third parties should rely on the representations, warranties and covenants or any descriptions thereof as characterizations of the actual state of facts or conditions of the Company, Parent, Purchaser, Ultimate Parent or any of their respective subsidiaries or affiliates. The Merger Agreement contains representations and warranties that are the product of negotiations among the parties thereto and that the parties made to, and solely for the benefit of, each other as of specified dates. The assertions embodied in those representations and warranties are subject to qualifications and limitations agreed to by the respective parties and are also qualified in important part by confidential disclosure schedules delivered by the Company to Parent and Purchaser in connection with the Merger Agreement. The representations and warranties may have been made for the purpose of allocating contractual risk among the parties to the Merger Agreement instead of establishing these matters as facts and may be subject to standards of materiality applicable to the contracting parties that differ from those applicable to stockholders or investors. Accordingly, investors should consider the information in the Merger Agreement in conjunction with the entirety of the factual disclosure about the Company in the Company’s public reports filed with the Securities and Exchange Commission (the “SEC”). Information concerning the subject matter of the representations and warranties may change after the date of the Merger Agreement, which subsequent information may or may not be fully reflected in the Company’s public disclosures. Tender and Support Agreements On January 19, 2026, in connection with the execution of the Merger Agreement, certain stockholders of the Company (collectively, the “Supporting Stockholders”) entered into tender and support agreements with Parent and Purchaser (the “Tender and Support Agreements”). The Supporting Stockholders held an aggregate of approximately 0.25% of the outstanding Shares as of January 16, 2026. Each Tender and Support Agreement provides that each Supporting Stockholder, solely in such Supporting Stockholder’s capacity as a holder of Shares, will tender all of the Shares held by such Supporting Stockholder (the “Subject Shares”) in the Offer. Each Tender and Support Agreement also provides that, in connection with any meeting of stockholders of the Company, or any action by written consent, in which the vote, consent or other approval of the stockholders of the Company is sought with respect to the Offer, the Merger, the Merger Agreement or any alternative acquisition proposal, the applicable Supporting Stockholder will, among other matters, vote all of the Subject Shares (i) against any alternative acquisition proposal, (ii) against any change in membership of the Company Board that is not recommended or approved by the Company Board, and (iii) against any other proposed action, agreement or transaction involving the Company that is intended, or would reasonably be expected, to impede, interfere with, delay, adversely affect or prevent the consummation of the Offer, the Merger or the other Transactions. Each Tender and Support Agreement terminates upon the earliest to occur of the termination of the Merger Agreement, the Effective Time and certain other specified events. The foregoing description of the Tender and Support Agreements does not purport to be complete and is subject to, and qualified in its entirety by reference to, the full text of the form of Tender and Support Agreement, which is attached as Exhibit 10.1 to this Current Report on Form 8-K and is incorporated herein by reference.

Item 7.01 Regulation FD Disclosure. On January 20, 2026, Ultimate Parent and the Company issued a joint press release announcing the execution of the Merger Agreement as described above. A copy of the joint press release is attached as Exhibit 99.1 and incorporated herein by reference. The information contained in this Item 7.01 of this report, including Exhibit 99.1 attached hereto, is furnished pursuant to Item 7.01 of Form 8-K and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or subject to the liabilities of that section. The information shall not be deemed incorporated by reference into any other filing with the SEC made by the Company regardless of any general incorporation language in such filing, except as shall be expressly set forth by specific reference in such filing.