Cytek (CTKB) Insider Filing: RSU Conversions Increase Ownership, Shares Withheld

Rhea-AI Filing Summary

Insider Form 4 for Cytek Biosciences, Inc. (CTKB) reports that Philippe Busque, SVP, Global Sales and Services and a director, had multiple restricted stock unit (RSU) vesting events on 08/18/2025 that increased his beneficial ownership. A series of RSU awards converted into common shares: 1,536; 2,210; and 3,625 RSUs became vested and reflected as acquired shares. The filing also shows withholding/surrender of shares to satisfy tax obligations related to the vesting, reducing net share additions.

Positive

• RSU vesting increased insider beneficial ownership by the conversion of 1,536, 2,210, and 3,625 RSUs into common shares on 08/18/2025

Negative

• Shares were withheld/surrendered to satisfy tax obligations (599, 861, and 1,412 shares), reducing the net increase in shares held

Insights

Corporate Governance Expert

TL;DR: Routine executive RSU vesting increased insider ownership while some shares were withheld for taxes.

This Form 4 documents scheduled vesting of multiple RSU awards for a senior officer/director, resulting in the conversion of RSUs into common stock on 08/18/2025. Vesting events are standard compensation fulfillment rather than open-market purchases or sales. The filing discloses shares withheld and surrendered to the issuer to cover tax withholding obligations, which is a common practice and reduces net share additions. There is no indication of open-market trading or changes in control.

Securities Analyst

TL;DR: The transactions are procedurally material for share count but carry no new operational or financial information.

The reported transactions show RSU-to-share settlements increasing the reporting person’s beneficial ownership in measured increments: 1,536, 2,210, and 3,625 shares credited from RSU vesting. Offsetting these, the filer surrendered 599, 861, and 1,412 shares to satisfy tax withholdings at a price of $4.06 per share as disclosed. These entries affect insider ownership disclosures and outstanding share composition but do not convey company performance updates.

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

OMB Number:			3235-0287
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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)
08/18/2025

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	08/18/2025		M		1,536	A	(1)	20,453	D
Common Stock	08/18/2025		F		599(2)	D	$4.06	19,854	D
Common Stock	08/18/2025		M		2,210	A	(1)	22,064	D
Common Stock	08/18/2025		F		861(2)	D	$4.06	21,203	D
Common Stock	08/18/2025		M		3,625	A	(1)	24,828	D
Common Stock	08/18/2025		F		1,412(2)	D	$4.06	23,416	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)	08/18/2025		M			1,536	(3)	(3)	Common Stock	1,536	$0	10,250	D
Restricted Stock Units	(1)	08/18/2025		M			2,210	(4)	(4)	Common Stock	2,210	$0	22,838	D
Restricted Stock Units	(1)	08/18/2025		M			3,625	(5)	(5)	Common Stock	3,625	$0	51,963	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 August 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	08/20/2025
	** 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 transactions did Philippe Busque report on Form 4 for CTKB?

He reported RSU vesting on 08/18/2025 that converted to common shares (1,536; 2,210; 3,625) and related share withholdings for taxes (599; 861; 1,412).

Did the Form 4 show any open-market purchases or sales for CTKB?

No; the filing reflects restricted stock unit vesting and shares withheld for tax purposes, not open-market trades.

How did the tax withholding affect net shares acquired on this Form 4?

Shares withheld and surrendered (total 2,872 shares) reduced the net increase in beneficially owned shares resulting from the RSU vesting.

What is the execution date of the reported transactions on the Form 4?

The transactions are reported with a transaction date of 08/18/2025 and the form was signed on 08/20/2025.

What is the price reported for the shares surrendered for tax withholding?

The filing lists $4.06 per share as the price associated with the surrendered shares.