Cytek Biosciences CFO granted options, RSUs

Cytek Biosciences Chief Financial Officer William D. McCombe reported new equity awards and routine vesting-related activity.

Rhea-AI Filing Summary

Cytek Biosciences Chief Financial Officer William D. McCombe reported new equity awards and routine vesting-related activity. He received an employee stock option for 136,205 shares of common stock at an exercise price of $4.23 per share, expiring on March 9, 2036, which vests monthly over four years. He was also granted 256,790 restricted stock units, scheduled to vest over four years under detailed annual vesting schedules. On the same date, 6,320 and 17,401 RSUs converted into common shares, and a total of 9,748 common shares were surrendered at $4.23 per share to cover tax withholding obligations. Following these transactions, he directly holds 94,687 shares of common stock.

Insider Trade Summary

23,721 shares exercised/converted

Exercise 8 txns

Insider McCombe William D.

Role Chief Financial Officer

Type	Security	Shares	Price	Value
Grant/Award	Employee Stock Option (right to buy)	136,205	$0.00	$0.00
Grant/Award	Restricted Stock Units	256,790	$0.00	$0.00
Exercise	Restricted Stock Units	6,320	$0.00	$0.00
Exercise	Restricted Stock Units	17,401	$0.00	$0.00
Exercise	Common Stock	6,320	$0.00	$0.00
Exercise Price or Tax Liability	Common Stock	2,603	$4.23	$11K
Exercise	Common Stock	17,401	$0.00	$0.00
Exercise Price or Tax Liability	Common Stock	7,145	$4.23	$30K

Holdings After Transaction: Employee Stock Option (right to buy) — 136,205 contracts (Direct); Restricted Stock Units — 470,292 contracts (Direct); Common Stock — 94,687 shares (Direct)

Footnotes (6)

1. F1. Each Restricted Stock Unit (the "RSU Award") represents a contingent right to receive one share of the Issuer's common stock.
2. F2. Represents the number of shares withheld by and surrendered to the Issuer on March 10, 2026, to satisfy tax withholding obligations that arose in connection with the vesting of the RSU Award.
3. F3. The shares subject to the stock option shall vest over 4 years with 1/48 of the total shares underlying the stock option vesting on April 10, 2026 and each month thereafter until fully vested.
4. 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, 2026 and each May 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting August 18, 2026 and each August 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting 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.
5. F5. 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.
6. F6. 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.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did Cytek Biosciences (CTKB) CFO William D. McCombe report on this Form 4?

He reported new equity awards and routine vesting activity. The filing shows grants of stock options and restricted stock units, plus RSU conversions into common stock and shares withheld to cover tax obligations tied to those vesting events.

How many stock options did the Cytek Biosciences (CTKB) CFO receive?

He received an employee stock option covering 136,205 shares of common stock. The option has an exercise price of $4.23 per share, expires on March 9, 2036, and vests over four years with equal monthly installments after an initial vesting date.

What restricted stock unit (RSU) awards were granted to the Cytek Biosciences (CTKB) CFO?

He was granted 256,790 restricted stock units tied to Cytek Biosciences common stock. Footnotes describe four-year vesting schedules with different fractions vesting on May 18, August 18, November 18, and March 10 of specified years until the awards are fully vested.

Did the Cytek Biosciences (CTKB) CFO sell any shares in the open market in this Form 4?

The filing shows no open-market sales. Instead, 2,603 and 7,145 common shares, totaling 9,748, were withheld and surrendered to the company at $4.23 per share to satisfy tax withholding obligations from RSU vesting events.

How many Cytek Biosciences (CTKB) common shares does the CFO hold after these transactions?

After the reported transactions, he directly holds 94,687 shares of Cytek Biosciences common stock. This figure reflects RSU conversions into common shares and the shares withheld by the company to cover related tax liabilities on the vesting awards.

Over what period do the Cytek Biosciences (CTKB) CFO’s new equity awards vest?

Both the stock option and RSU awards vest over four-year periods. The option vests monthly starting April 10, 2026, while RSU awards vest on specified May 18, August 18, November 18, and March 10 dates each year according to detailed vesting fractions.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 03/12/2026 - 04:37 PM Learn about SEC filing dates

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^*

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)
03/10/2026

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	03/10/2026		M		6,320	A	(1)	87,034	D
Common Stock	03/10/2026		F		2,603(2)	D	$4.23	84,431	D
Common Stock	03/10/2026		M		17,401	A	(1)	101,832	D
Common Stock	03/10/2026		F		7,145(2)	D	$4.23	94,687	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
Employee Stock Option (right to buy)	$4.23	03/10/2026		A		136,205		(3)	03/09/2036	Common Stock	136,205	$0	136,205	D
Restricted Stock Units	(1)	03/10/2026		A		256,790		(4)	(4)	Common Stock	256,790	$0	256,790	D
Restricted Stock Units	(1)	03/10/2026		M			6,320	(5)	(5)	Common Stock	6,320	$0	56,889	D
Restricted Stock Units	(1)	03/10/2026		M			17,401	(6)	(6)	Common Stock	17,401	$0	156,613	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 March 10, 2026, to satisfy tax withholding obligations that arose in connection with the vesting of the RSU Award.

3. The shares subject to the stock option shall vest over 4 years with 1/48 of the total shares underlying the stock option vesting on April 10, 2026 and each month 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, 2026 and each May 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting August 18, 2026 and each August 18 thereafter; 3/48 of the total shares underlying the RSU Award vesting 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.

5. 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.

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, 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	03/12/2026
	** Signature of Reporting Person	Date
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