# EDGAR Filing Document

**Accession Number:** 0001673772
**File Stem:** 0001635616-26-000001
**Filing Date:** 2026-3
**Character Count:** 11338
**Document Hash:** c22e63aca00a58cc10819014814c3935
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001635616-26-000001.hdr.sgml**: 20260305

**ACCESSION NUMBER**: 0001635616-26-000001

**CONFORMED SUBMISSION TYPE**: 4

**PUBLIC DOCUMENT COUNT**: 1

**CONFORMED PERIOD OF REPORT**: 20260303

**FILED AS OF DATE**: 20260305

**DATE AS OF CHANGE**: 20260305

**REPORTING-OWNER**: 

**OWNER DATA:**
- **COMPANY CONFORMED NAME:** Brockstedt Dirk G.
- **CENTRAL INDEX KEY:** 0001635616

**ORGANIZATION NAME:**

**FILING VALUES:**
- **FORM TYPE:** 4
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-38997
- **FILM NUMBER:** 26724377

**MAIL ADDRESS:**
- **STREET 1:** C/O ADURO BIOTECH, INC.
- **STREET 2:** 740 HEINZ AVENUE
- **CITY:** BERKELEY
- **STATE:** CA
- **ZIP:** 94710
**ISSUER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** RAPT Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001673772
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 473313701
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**BUSINESS ADDRESS:**
- **STREET 1:** 561 ECCLES AVENUE
- **CITY:** SOUTH SAN FRANCISCO
- **STATE:** CA
- **ZIP:** 94080
- **BUSINESS PHONE:** (650) 489-9000

**MAIL ADDRESS:**
- **STREET 1:** 561 ECCLES AVENUE
- **CITY:** SOUTH SAN FRANCISCO
- **STATE:** CA
- **ZIP:** 94080

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** FLX Bio, Inc.
- **DATE OF NAME CHANGE:** 20160504

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## FORM 4

### STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

[x] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

[ ] Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

---

| | | |
|:---|:---|:---|
| **1. Name and Address of Reporting Person**<sup>*</sup><br>Brockstedt Dirk G.<br><sub>(Last) (First) (Middle)</sub><br>C/O RAPT THERAPEUTICS, INC.<br>561 ECCLES AVENUE<br><sub>(Street)</sub><br>SOUTH SAN FRANCISCO, CA 94080<br><sub>(City) (State) (Zip)</sub> | **3. Date of Earliest Transaction (Month/Day/Year)**<br>2026-03-03 | **5. Relationship of Reporting Person(s) to Issuer**<br>(Check all applicable)<br>[ ] Director [ ] 10% Owner<br>[X] Officer (give title below) [ ] Other (specify below)<br>_CHIEF SCIENTIFIC OFFICER_ |
| **2. Issuer Name and Ticker or Trading Symbol**<br>RAPT Therapeutics, Inc. [ RAPT ] | **4. If Amendment, Date of Original Filed (Month/Day/Year)**<br>  | **6. Individual or Joint/Group Filing (Check Applicable Line)**<br>[X] Form filed by One Reporting Person<br>[ ] Form filed by More than One Reporting Person |

---

## Table I - Non-Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | 3. Transaction Code (V) | 3. Transaction Code (V) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 4. Securities Acquired (A) or Disposed of (D) | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| 1. Title of Security | 2. Transaction Date | 2A. Deemed Execution Date | Code | V | Amount | (A) or (D) | Price | 5. Amount of Securities Beneficially Owned | 6. Ownership Form | 7. Nature of Indirect Beneficial Ownership |
| Common Stock | 2026-03-03 |  | U<sup>(1)(2)</sup> |  | 4648<sup>(3)</sup> | D | <sup>(4)</sup> | 0 | D |  |

---

## Table II - Derivative Securities

---

|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | 4. Transaction Code (V) | 4. Transaction Code (V) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 5. Number of Derivative Securities Acquired (A) or Disposed of (D) | 6. Date Exercisable and Expiration Date | 6. Date Exercisable and Expiration Date | 7. Title and Amount of Underlying Securities | 7. Title and Amount of Underlying Securities | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| 1. Title of Derivative Security | 2. Conversion or Exercise Price | 3. Transaction Date | 3A. Deemed Execution Date | Code | V | (A) | (D) | Date Exercisable | Expiration Date | Title | Amount or Number of Shares | 8. Price of Derivative Security | 9. Number of Derivative Securities Beneficially Owned | 10. Ownership Form | 11. Nature of Indirect Beneficial Ownership |
| Employee Stock Option (right to buy)<sup>(5)</sup> | $49.44 | 2026-03-03 |  | D<sup>(1)(2)</sup> |  |  | 1225 | <sup>(6)</sup> | <sup>(6)</sup> | Common Stock | 1225 | <sup>(6)</sup> | 0 | D |  |
| Employee Stock Option (right to buy)<sup>(5)</sup> | $50.40 | 2026-03-03 |  | D<sup>(1)(2)</sup> |  |  | 1035 | <sup>(6)</sup> | <sup>(6)</sup> | Common Stock | 1035 | <sup>(6)</sup> | 0 | D |  |
| Employee Stock Option (right to buy)<sup>(5)</sup> | $108.96 | 2026-03-03 |  | D<sup>(1)(2)</sup> |  |  | 3125 | <sup>(6)</sup> | <sup>(6)</sup> | Common Stock | 3125 | <sup>(6)</sup> | 0 | D |  |
| Employee Stock Option (right to buy)<sup>(5)</sup> | $12.56 | 2026-03-03 |  | D<sup>(1)(2)</sup> |  |  | 2500 | <sup>(6)</sup> | <sup>(6)</sup> | Common Stock | 2500 | <sup>(6)</sup> | 0 | D |  |
| Employee Stock Option (right to buy)<sup>(5)</sup> | $12.56 | 2026-03-03 |  | D<sup>(1)(2)</sup> |  |  | 6250 | <sup>(6)</sup> | <sup>(6)</sup> | Common Stock | 6250 | <sup>(6)</sup> | 0 | D |  |
| Employee Stock Option (right to buy)<sup>(5)</sup> | $12.56 | 2026-03-03 |  | D<sup>(1)(2)</sup> |  |  | 6876 | <sup>(6)</sup> | <sup>(6)</sup> | Common Stock | 3876 | <sup>(6)</sup> | 0 | D |  |
| Employee Stock Option (right to buy)<sup>(5)</sup> | $12.56 | 2026-03-03 |  | D<sup>(1)(2)</sup> |  |  | 7000 | <sup>(6)</sup> | <sup>(6)</sup> | Common Stock | 7000 | <sup>(6)</sup> | 0 | D |  |
| Employee Stock Option (right to buy)<sup>(5)</sup> | $12.56 | 2026-03-03 |  | D<sup>(1)(2)</sup> |  |  | 9375 | <sup>(6)</sup> | <sup>(6)</sup> | Common Stock | 9375 | <sup>(6)</sup> | 0 | D |  |
| Employee Stock Option (right to buy)<sup>(5)</sup> | $9.12 | 2026-03-03 |  | D<sup>(1)(2)</sup> |  |  | 64375 | <sup>(6)</sup> | <sup>(6)</sup> | Common Stock | 64375 | <sup>(6)</sup> | 0 | D |  |
| Employee Stock Option (right to buy) | $7.43 | 2026-03-03 |  | D<sup>(1)(2)</sup> |  |  | 58333 | <sup>(7)(8)</sup> | <sup>(7)(8)</sup> | Common Stock | 58333 | <sup>(7)(8)</sup> | 41667 | D |  |

---

### Footnotes:

(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 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. 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, with the 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 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 (a) 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, and (b) greater than the Offer Price, was cancelled for no consideration.

(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 to the 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 Option Consideration shall immediately vest and become payable without any further action on the part of Parent or any other person.

**Signature:** /s/ Rodney Young, Attorney-in-Fact  
**Date:** 2026-03-05

### Remarks:

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

**Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.**