[Form 4] Cytek Biosciences, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Cytek Biosciences (CTKB) senior executive reports RSU vesting and share withholding transactions. On November 18, 2025, the SVP, Global Sales and Services converted multiple batches of restricted stock units (RSUs) into common stock and had shares withheld to cover taxes.

Form 4 data shows RSU exercises adding 1,536, 2,210, and 3,625 shares of common stock, with tax withholding sales of 393, 565, and 927 shares at $5.53 per share. After these transactions, the executive directly owned 28,902 shares of Cytek common stock.

The filing also reports remaining unvested or unsettled RSUs, with derivative holdings of 8,714, 20,628, and 48,338 RSUs, each tied to multi-year vesting schedules that allocate specific fractions of each award to vest on set dates in May, August, November, and March until fully vested.

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

OMB APPROVAL

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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^*

Busque Philippe

(Last) (First) (Middle)

C/O CYTEK BIOSCIENCES, INC.

47215 LAKEVIEW BLVD.

(Street)

FREMONT CA 94538

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Cytek Biosciences, Inc. [ CTKB ]

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

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	SVP, GLOBAL SALES AND SERVICES

3. Date of Earliest Transaction (Month/Day/Year)
11/18/2025

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	11/18/2025		M		1,536	A	(1)	24,952	D
Common Stock	11/18/2025		F		393(2)	D	$5.53	24,559	D
Common Stock	11/18/2025		M		2,210	A	(1)	26,769	D
Common Stock	11/18/2025		F		565(2)	D	$5.53	26,204	D
Common Stock	11/18/2025		M		3,625	A	(1)	29,829	D
Common Stock	11/18/2025		F		927(2)	D	$5.53	28,902	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
Restricted Stock Units	(1)	11/18/2025		M			1,536	(3)	(3)	Common Stock	1,536	$0	8,714	D
Restricted Stock Units	(1)	11/18/2025		M			2,210	(4)	(4)	Common Stock	2,210	$0	20,628	D
Restricted Stock Units	(1)	11/18/2025		M			3,625	(5)	(5)	Common Stock	3,625	$0	48,338	D

Explanation of Responses:

1. Each Restricted Stock Unit (the "RSU Award") represents a contingent right to receive one share of the Issuer's common stock.

2. Represents the number of shares withheld by and surrendered to the Issuer on November 18, 2025, to satisfy tax withholding obligations that arose in connection with the vesting of the RSU Award.

3. The shares subject to the RSU Award shall vest over four years with 13/48 of the total shares underlying the RSU Award vesting on May 18, 2024; 3/48 of the total shares underlying the RSU Award vesting on August 18, 2024 and each August 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on November 18, 2024 and each November 18 thereafter; 4/48 of the total shares underlying the RSU Award vesting on March 10, 2025 and each March 10 thereafter; and 2/48 of the total shares underlying the RSU Award vesting on May 18, 2025 and each May 18 thereafter.

4. The shares subject to the RSU Award shall vest over 4 years with 2/48 of the total shares underlying the RSU Award vesting on May 18, 2024 and each May 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on August 18, 2024 and each August 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on November 18, 2024 and each November 18 thereafter; and 4/48 of the total shares underlying the RSU Award vesting on March 10, 2025 and each March 10 thereafter.

5. The shares subject to the RSU Award shall vest over 4 years with 2/48 of the total shares underlying the RSU Award vesting on May 18, 2025 and each May 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on August 18, 2025 and each August 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on November 18, 2025 and each November 18 thereafter; and 4/48 of the total shares underlying the RSU Award vesting on March 10, 2026 and each March 10 thereafter, until fully vested.

	/s/ Valerie Barnett, Attorney-in-Fact	11/20/2025
	** Signature of Reporting Person	Date
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).
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FAQ

What insider transaction did Cytek Biosciences (CTKB) report in this Form 4?

The Form 4 reports that the SVP, Global Sales and Services of Cytek Biosciences (CTKB) had several restricted stock unit (RSU) awards vest on November 18, 2025, converting into common stock with some shares withheld for taxes.

How many Cytek (CTKB) shares does the reporting person own after the transactions?

Following the reported transactions on November 18, 2025, the executive directly owned 28,902 shares of Cytek Biosciences common stock.

What was the tax withholding price on the Cytek (CTKB) shares?

The filing shows that to satisfy tax withholding obligations related to the RSU vesting, the issuer withheld and surrendered shares at a price of $5.53 per share.

How many Cytek Biosciences RSUs vested and converted to common stock?

On November 18, 2025, RSU awards representing 1,536, 2,210, and 3,625 shares of Cytek common stock were exercised (coded "M"), each at an exercise price of $0.

How many RSUs remain outstanding for the Cytek (CTKB) executive after this Form 4?

After the reported transactions, the executive still held derivative positions of 8,714, 20,628, and 48,338 restricted stock units, each convertible into an equal number of Cytek common shares subject to vesting.

What is the vesting schedule of the Cytek Biosciences RSU awards in this filing?

The RSU awards vest over four years, with specified fractions (such as 13/48, 3/48, 4/48, and 2/48) of each award vesting on recurring dates in May, August, November, and March until each award is fully vested.