William D. McCombe - 18 Nov 2025 Form 4 Insider Report for Cytek Biosciences, Inc. (CTKB)

Role: Chief Financial Officer
Signature: /s/ Valerie Barnett, Attorney-in-Fact
Issuer symbol: CTKB
Transactions as of: 18 Nov 2025
Net transactions value: -$34,441
Form type: 4
Filing time: 20 Nov 2025, 19:03:31 UTC
Previous filing: 20 Aug 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
McCombe William D.	Chief Financial Officer	C/O CYTEK BIOSCIENCES, INC., 47215 LAKEVIEW BOULEVARD, FREMONT	/s/ Valerie Barnett, Attorney-in-Fact	20 Nov 2025	0001878824

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	CTKB	Common Stock	Options Exercise		+6,320	+9.4%		73,891	18 Nov 2025	Direct	F1
transaction	CTKB	Common Stock	Tax liability	$11,237	-2,032	-2.7%	$5.53	71,859	18 Nov 2025	Direct	F2
transaction	CTKB	Common Stock	Options Exercise		+13,051	+18%		84,910	18 Nov 2025	Direct	F1
transaction	CTKB	Common Stock	Tax liability	$23,204	-4,196	-4.9%	$5.53	80,714	18 Nov 2025	Direct	F2

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
transaction	CTKB	Restricted Stock Units	Options Exercise	$0	-6,320	-9.1%	$0.000000	63,209	18 Nov 2025	Common Stock	6,320		Direct	F1, F3
transaction	CTKB	Restricted Stock Units	Options Exercise	$0	-13,051	-7%	$0.000000	174,014	18 Nov 2025	Common Stock	13,051		Direct	F1, F4

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	Each Restricted Stock Unit (the "RSU Award") represents a contingent right to receive one share of the Issuer's common stock.
F2	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.
F3	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.
F4	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.