RAPT Therapeutics, Inc.

1. The Issuer entered into an Agreement and Plan of Merger, dated January 19, 2026 (the "Merger Agreement") with GlaxoSmithKline LLC, a Delaware limited liability company ("Parent"), Redrose Acquisition Co., a Delaware corporation and a wholly owned subsidiaryof 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. Pursuant to the Merger Agreement, Purchaser completed a tender offer to acquire all of the issued and outstanding shares of common stock of the Issuer, for $58.00 per share (the "Offer Price"), in cash, without interest and subject to any applicable withholding of taxes. On March 3, 2026, Purchaser merged with and into the Issuer, withthe Issuer surviving as an indirect wholly owned subsidiary of Parent (the effective time of such merger, the "Effective Time").

2. This Form 4 reports securities transacted pursuant to the Merger Agreement.

3. The number of shares was adjusted to reflect the 1-for-8 reverse stock split effected by the Issuer on June 16, 2025.

4. Pursuant to the terms of the Merger Agreement, at the Effective Time, each share of common stock held by the Reporting Person was tendered in exchange for the Offer Price.

5. The number of shares underlying this option and the exercise price were adjusted to reflect the 1-for-8 reverse stock split effected by the Issuer on June 16, 2025.

6. Pursuant to the terms of the Merger Agreement, each stock option Pursuant to the terms of the Merger Agreement, each stock option that was outstanding as of immediately prior to the Effective Time, whether vested or unvested, was accelerated and became fully vested and exercisable as of immediately prior to the Effective Time. At the Effective Time, each stock option that was outstanding and unexercised as of immediately before the Effective Time and which had a per share exercise price that was less than Offer Price was cancelled and converted solely into the right to receive cash in an amount equal to the product of (i) the total number of shares subject to such stock option immediately prior to the Effective Time, multiplied by (ii) the excess of (x) the Offer Price, over (y) the exercise price payable per share under such stock option.

7. Pursuant to the terms of the Merger Agreement, each stock option that is unvested as of immediately prior to the Effective Time and was granted after March 1, 2025 (a "2025 Option") was cancelled and converted into a cash-based award of Parent (a "Converted Option"), which shall entitle the holder thereof to receive an amount in cash equal to the Option Consideration (the "Converted Option Consideration").

8. Each Converted Option (and the right to receive the Converted Option Consideration) shall be subject to the same terms and conditions (including vesting, forfeiture and acceleration provisions) that were applicable to the corresponding 2025 Option immediately prior tothe Effective Time; provided, that (i) the Converted Option Consideration shall vest and become payable 50% upon the date that closing occurs pursuant to the Merger Agreement (the "Closing Date") and 50% upon the date that is nine months following the Closing Date and (ii) in the event that the holder of a Converted Option experiences an Involuntary Termination (as defined in the Merger Agreement) following the Closing Date but prior to the date that is nine months following the Closing Date, such holder's Converted OptionConsideration shall immediately vest and become payable without any further action on the part of Parent or any other person.