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

Rhea-AI Filing Summary

Cytek Biosciences, Inc. (CTKB) reported insider equity activity by its Chief Financial Officer on 11/18/2025. The filing shows the vesting and settlement of restricted stock units (RSUs) into common stock, along with shares withheld to cover taxes. The CFO acquired 6,320 shares of common stock upon RSU vesting, then had 2,032 shares withheld and surrendered to the company at $5.53 per share for tax obligations. A second RSU vesting added 13,051 shares, followed by 4,196 shares withheld at the same price for taxes. After these transactions, the CFO directly owned 80,714 shares of common stock and continued to hold additional unvested RSUs, reflecting ongoing equity-based compensation rather than an open-market sale.

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^*

McCombe William D.

(Last) (First) (Middle)

C/O CYTEK BIOSCIENCES, INC.

47215 LAKEVIEW BOULEVARD

(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)
	Chief Financial Officer

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		6,320	A	(1)	73,891	D
Common Stock	11/18/2025		F		2,032(2)	D	$5.53	71,859	D
Common Stock	11/18/2025		M		13,051	A	(1)	84,910	D
Common Stock	11/18/2025		F		4,196(2)	D	$5.53	80,714	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			6,320	(3)	(3)	Common Stock	6,320	$0	63,209	D
Restricted Stock Units	(1)	11/18/2025		M			13,051	(4)	(4)	Common Stock	13,051	$0	174,014	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 4 years with 12/48 of the total shares underlying the RSU Award vesting on May 18, 2025; 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 3/48 of the total shares underlying the RSU Award vesting on March 10, 2026 and each March 10 thereafter; and 3/48 of the total shares underlying the RSU Award vesting on May 18, 2026 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, 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).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
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FAQ

What insider transaction did CTKB disclose in this Form 4?

The Form 4 discloses that Cytek Biosciences' Chief Financial Officer had restricted stock units vest on 11/18/2025, converting into shares of common stock, with a portion of the shares withheld to satisfy tax obligations.

How many CTKB shares were acquired through RSU vesting on 11/18/2025?

On 11/18/2025, the CFO acquired 6,320 shares and an additional 13,051 shares of Cytek Biosciences common stock upon the vesting and settlement of RSU awards.

How were taxes handled for the CTKB CFO's RSU vesting?

To cover tax withholding from the RSU vesting, the CFO had 2,032 shares and 4,196 shares withheld and surrendered to Cytek Biosciences at a price of $5.53 per share.

How many CTKB common shares does the CFO own after these transactions?

Following the reported transactions on 11/18/2025, the CFO directly owned 80,714 shares of Cytek Biosciences common stock.

What RSU positions does the CTKB CFO hold after the reported transactions?

After the activity on 11/18/2025, the CFO beneficially owned 63,209 and 174,014 restricted stock units, each RSU representing a contingent right to receive one share of common stock.

How do the CTKB CFO's RSU awards vest over time?

The RSU awards vest over 4 years on specified schedules, with different fractions of the total shares vesting on May 18, August 18, November 18 and March 10 of various years until fully vested.