RAPT Therapeutics (RAPT) CSO details equity payout in GSK merger

Rhea-AI Filing Summary

RAPT Therapeutics chief scientific officer Dirk G. Brockstedt reported dispositions of common stock and employee stock options tied to the company’s acquisition by a GlaxoSmithKline subsidiary. All transactions occurred on March 3, 2026, when Redrose Acquisition Co. merged with RAPT.

Under a January 19, 2026 Merger Agreement, a tender offer acquired all RAPT common shares at $58.00 per share in cash. At the merger’s effective time, each share of common stock held by the reporting person was exchanged for the cash offer price. All outstanding stock options became fully vested immediately before closing.

In-the-money options were cancelled and converted into a right to receive cash equal to the number of option shares multiplied by the excess of the $58.00 offer price over the applicable exercise price, while out-of-the-money options were cancelled for no consideration. Certain unvested options granted after March 1, 2025 were instead converted into cash-based awards of GlaxoSmithKline LLC, preserving prior vesting terms.

SEC Form 4

FORM 4

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

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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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^*

Brockstedt Dirk G.

(Last) (First) (Middle)

C/O RAPT THERAPEUTICS, INC.

561 ECCLES AVENUE

(Street)

SOUTH SAN FRANCISCO CA 94080

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
RAPT Therapeutics, Inc. [ RAPT ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	CHIEF SCIENTIFIC OFFICER

3. Date of Earliest Transaction (Month/Day/Year)
03/03/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	03/03/2026		U(1)(2)		4,648(3)	D	(4)	0	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Employee Stock Option (right to buy)(5)	$49.44	03/03/2026		D(1)(2)			1,225	(6)	(6)	Common Stock	1,225	(6)	0	D
Employee Stock Option (right to buy)(5)	$50.4	03/03/2026		D(1)(2)			1,035	(6)	(6)	Common Stock	1,035	(6)	0	D
Employee Stock Option (right to buy)(5)	$108.96	03/03/2026		D(1)(2)			3,125	(6)	(6)	Common Stock	3,125	(6)	0	D
Employee Stock Option (right to buy)(5)	$12.56	03/03/2026		D(1)(2)			2,500	(6)	(6)	Common Stock	2,500	(6)	0	D
Employee Stock Option (right to buy)(5)	$12.56	03/03/2026		D(1)(2)			6,250	(6)	(6)	Common Stock	6,250	(6)	0	D
Employee Stock Option (right to buy)(5)	$12.56	03/03/2026		D(1)(2)			6,876	(6)	(6)	Common Stock	3,876	(6)	0	D
Employee Stock Option (right to buy)(5)	$12.56	03/03/2026		D(1)(2)			7,000	(6)	(6)	Common Stock	7,000	(6)	0	D
Employee Stock Option (right to buy)(5)	$12.56	03/03/2026		D(1)(2)			9,375	(6)	(6)	Common Stock	9,375	(6)	0	D
Employee Stock Option (right to buy)(5)	$9.12	03/03/2026		D(1)(2)			64,375	(6)	(6)	Common Stock	64,375	(6)	0	D
Employee Stock Option (right to buy)	$7.43	03/03/2026		D(1)(2)			58,333	(7)(8)	(7)(8)	Common Stock	58,333	(7)(8)	41,667	D

Explanation of Responses:

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.

	/s/ Rodney Young, Attorney-in-Fact	03/05/2026
	** Signature of Reporting Person	Date
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FAQ

What insider activity did RAPT (RAPT) report in this Form 4?

The filing reports that chief scientific officer Dirk G. Brockstedt disposed of RAPT common stock and employee stock options on March 3, 2026. These transactions reflect how his equity awards were treated when RAPT was acquired by a GlaxoSmithKline subsidiary under a previously signed Merger Agreement.

How were RAPT Therapeutics (RAPT) shares treated in the GSK tender offer?

All issued and outstanding RAPT common shares were acquired in a tender offer at $58.00 per share in cash. At the merger’s effective time, each share held by the reporting person was exchanged for this cash offer price, subject to applicable tax withholding as described in the agreement.

What happened to RAPT (RAPT) stock options held by the CSO in the merger?

All outstanding RAPT stock options became fully vested and exercisable immediately before the merger’s effective time. In-the-money options were cancelled and converted into a cash right based on $58.00 per share, while options with an exercise price above $58.00 were cancelled without any cash consideration.

How were unvested 2025 RAPT (RAPT) options converted in the GSK deal?

Unvested stock options granted after March 1, 2025 were converted into cash-based awards of GlaxoSmithKline LLC. These Converted Options follow the same vesting and forfeiture terms but pay 50% at closing and 50% nine months later, with full acceleration upon certain involuntary terminations after closing.

Did RAPT (RAPT) adjust share and option counts before the merger?

Yes. The number of RAPT common shares and option shares in the filing reflects a 1-for-8 reverse stock split effective June 16, 2025. Both the underlying share counts and option exercise prices were adjusted to account for this reverse split ahead of the merger transactions.

What corporate structure resulted for RAPT (RAPT) after the GSK transaction?

After the merger, Redrose Acquisition Co., a wholly owned subsidiary of GlaxoSmithKline LLC, merged with and into RAPT Therapeutics. RAPT survived the transaction as an indirect wholly owned subsidiary of GlaxoSmithKline LLC, aligning its equity under the acquirer’s corporate structure.