Cytek Biosciences (CTKB) CEO reports RSU vesting and tax share withholding

Rhea-AI Filing Summary

Cytek Biosciences, Inc. President and CEO Wenbin Jiang reported routine equity compensation activity involving restricted stock units that vested into common stock. On May 18, 2026, he exercised RSU awards to acquire 80,062 shares of common stock and had 25,542 shares withheld to cover tax obligations at $3.55 per share.

Following these transactions, Jiang directly held about 5.43 million shares of Cytek common stock and continued to hold 39,275 restricted stock units that will vest over time under multi-year schedules described in the RSU footnotes. No open-market purchases or sales were reported.

Insights

Equity compensation analyst

CEO’s Form 4 shows RSU vesting with tax withholding, not market selling.

Cytek Biosciences’ CEO Wenbin Jiang reported RSU vesting and related transactions on May 18, 2026. He exercised restricted stock units into 80,062 common shares. To satisfy tax obligations, 25,542 shares were withheld at a reference price of $3.55 per share.

These are coded as M (derivative exercise) and F (tax-withholding disposition), which are compensation mechanics rather than open-market buys or sells. After the activity, Jiang directly held about 5,430,537 common shares and 39,275 remaining RSUs, indicating a substantial continuing stake.

The RSU footnotes detail four-year vesting patterns with specific tranches each May 18, August 18, November 18, and March 10. Future vesting events will depend on continued service and will be reflected in subsequent filings if additional RSUs convert into shares.

Insider Trade Summary

80,062 shares exercised/converted

Mixed 12 txns

Insider Jiang Wenbin

Role PRESIDENT AND CEO

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units	7,854	$0.00	--
Exercise	Restricted Stock Units	14,733	$0.00	--
Exercise	Restricted Stock Units	19,334	$0.00	--
Exercise	Restricted Stock Units	38,141	$0.00	--
Exercise	Common Stock	7,854	$0.00	--
Tax Withholding	Common Stock	1,913	$3.55	$7K
Exercise	Common Stock	14,733	$0.00	--
Tax Withholding	Common Stock	3,588	$3.55	$13K
Exercise	Common Stock	19,334	$0.00	--
Tax Withholding	Common Stock	5,032	$3.55	$18K
Exercise	Common Stock	38,141	$0.00	--
Tax Withholding	Common Stock	15,009	$3.55	$53K

Holdings After Transaction: Restricted Stock Units — 39,275 shares (Direct, null); Common Stock — 5,430,537 shares (Direct, null)

Footnotes (1)

1. Each Restricted Stock Unit (the "RSU Award") represents a contingent right to receive one share of the Issuer's common stock. Represents the number of shares withheld by and surrendered to the Issuer on May 18, 2026, to satisfy tax withholding obligations that arose in connection with the vesting of the RSU Award. 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, 2023 and each May 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on August 18, 2023 and each August 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on November 18, 2023 and each November 18 thereafter; and 4/48 of the total shares underlying the RSU Award vesting on March 10, 2024 and each March 10 thereafter, until fully vested. 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. 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. 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, 2026 and each May 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on August 18, 2026 and each August 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on November 18, 2026 and each November 18 thereafter; and 4/48 of the total shares underlying the RSU Award vesting on March 10, 2027 and each March 10 thereafter, until fully vested.

Key Figures

RSUs exercised into common stock: 80,062 shares Shares withheld for taxes: 25,542 shares Reference share price: $3.55 per share +4 more

7 metrics

RSUs exercised into common stock 80,062 shares Derivative exercises on May 18, 2026

Shares withheld for taxes 25,542 shares Tax-withholding dispositions at $3.55 on May 18, 2026

Reference share price $3.55 per share Used for tax withholding transactions coded F

Common shares held after transactions 5,430,537 shares Direct ownership following May 18, 2026 activity

Remaining RSU balance 39,275 units Restricted stock units outstanding after conversions

Exercise transactions count 4 transactions M-coded derivative exercises summarized in filing

Tax-withholding transactions count 4 transactions F-coded dispositions for tax obligations

Key Terms

Restricted Stock Unit, tax withholding obligations, derivative security, vesting, +1 more

5 terms

Restricted Stock Unit financial

"Each Restricted Stock Unit (the "RSU Award") represents a contingent right"

A restricted stock unit is a promise from a company to give an employee shares of stock after certain conditions are met, like staying with the company for a set amount of time. It’s like earning a bonus that turns into company stock once you’ve proven your commitment, making it a way to motivate and reward employees.

tax withholding obligations financial

"shares withheld by and surrendered to the Issuer ... to satisfy tax withholding obligations"

derivative security financial

"Exercise or conversion of derivative security"

A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.

vesting financial

"obligations that arose in connection with the vesting of the RSU Award"

Vesting is the process by which you earn full ownership of something, like company stock or a retirement benefit, over time. It’s like earning the right to keep a gift piece by piece the longer you stay with a company, making sure employees stay committed before they receive all the benefits.

contingent right financial

"represents a contingent right to receive one share of the Issuer's common stock"

Form 4 Insider Transactions: What Each Field Means →

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
Estimated average burden
hours per response:			0.5

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^*

Jiang Wenbin

(Last) (First) (Middle)

C/O CYTEK BIOSCIENCES, INC.

47215 LAKEVIEW BOULEVARD

(Street)

FREMONT CALIFORNIA 94538

(City) (State) (Zip)

UNITED STATES

(Country)

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

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

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	PRESIDENT AND CEO

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/18/2026

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

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

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

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	05/18/2026		M		7,854	A	(1)	5,430,537	D
Common Stock	05/18/2026		F		1,913(2)	D	$3.55	5,428,624	D
Common Stock	05/18/2026		M		14,733(2)	A	(1)	5,443,357	D
Common Stock	05/18/2026		F		3,588(2)	D	$3.55	5,439,769	D
Common Stock	05/18/2026		M		19,334(2)	A	(1)	5,459,103	D
Common Stock	05/18/2026		F		5,032(2)	D	$3.55	5,454,071	D
Common Stock	05/18/2026		M		38,141	A	(1)	5,492,212	D
Common Stock	05/18/2026		F		15,009(2)	D	$3.55	5,477,203	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)	05/18/2026		M			7,854	(3)	(3)	Common Stock	7,854	$0	39,275	D
Restricted Stock Units	(1)	05/18/2026		M			14,733	(4)	(4)	Common Stock	14,733	$0	162,073	D
Restricted Stock Units	(1)	05/18/2026		M			19,334	(5)	(5)	Common Stock	19,334	$0	328,696	D
Restricted Stock Units	(1)	05/18/2026		M			38,141	(6)	(6)	Common Stock	38,141	$0	877,266	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 May 18, 2026, 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 2/48 of the total shares underlying the RSU Award vesting on May 18, 2023 and each May 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on August 18, 2023 and each August 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on November 18, 2023 and each November 18 thereafter; and 4/48 of the total shares underlying the RSU Award vesting on March 10, 2024 and each March 10 thereafter, until fully vested.

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.

6. 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, 2026 and each May 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on August 18, 2026 and each August 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting on November 18, 2026 and each November 18 thereafter; and 4/48 of the total shares underlying the RSU Award vesting on March 10, 2027 and each March 10 thereafter, until fully vested.

	/s/ Valerie Barnett, Attorney-in-Fact	05/20/2026
	** 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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

FAQ

What insider transactions did Cytek Biosciences (CTKB) CEO Wenbin Jiang report?

Wenbin Jiang reported equity compensation activity on May 18, 2026. He exercised restricted stock units into 80,062 shares of Cytek common stock, with 25,542 shares withheld to cover tax obligations, and reported no open-market purchases or sales.

How many Cytek Biosciences (CTKB) shares does the CEO hold after this Form 4?

After the reported transactions, CEO Wenbin Jiang directly held about 5,430,537 shares of Cytek common stock. He also retained 39,275 restricted stock units that may convert into additional shares over time under the specified multi-year vesting schedules.

Were the Cytek Biosciences (CTKB) CEO’s Form 4 transactions open-market sales?

No, the Form 4 shows no open-market sales. The F-code transactions represent 25,542 shares withheld and surrendered to Cytek Biosciences on May 18, 2026 to satisfy tax withholding obligations arising from RSU vesting, rather than discretionary market sales.

What does the RSU vesting schedule look like for Cytek Biosciences (CTKB) CEO?

The RSU awards vest over four years in tranches. Portions vest each May 18, August 18, November 18, and March 10, with different fractions (such as 2/48, 3/48, and 4/48) of the total RSU awards becoming vested on those recurring dates until fully vested.

How many restricted stock units remain for the Cytek Biosciences (CTKB) CEO?

Following the May 18, 2026 vesting and conversions, Wenbin Jiang reported 39,275 restricted stock units remaining. Each RSU represents a contingent right to receive one share of Cytek common stock, subject to the continued vesting schedule and service conditions.

What do the M and F transaction codes mean in the Cytek Biosciences (CTKB) Form 4?

M-coded entries show exercises or conversions of derivative securities, here restricted stock units converting into common stock. F-coded entries show shares withheld and surrendered to Cytek to pay tax liabilities tied to that vesting, not voluntary open-market sales by the CEO.