Cytek director converts 3,086 RSUs into shares

Cytek Biosciences, Inc. (CTKB) director Glenn P. Muir reported an automatic conversion of 3,086 Restricted Stock Units into 3,086 shares of Common Stock on August 18, 2026.

Rhea-AI Filing Summary

Cytek Biosciences, Inc. (CTKB) director Glenn P. Muir reported an automatic conversion of 3,086 Restricted Stock Units into 3,086 shares of Common Stock on August 18, 2026. The RSU conversion price was $0.00 per share.

Following this transaction, Muir’s directly held RSU balance tied to this award is reported as 52,469 units, and his directly held Common Stock position from this transaction is 3,086 shares3 years in multiple tranches, including 2/36 of the total shares vesting on August 18, 2026, and additional 3/36 and 4/36 installments on specified dates thereafter, as long as the vesting conditions are met.

Insider Trade Summary

3,086 shares exercised/converted

Exercise 2 txns

Insider MUIR GLENN P

Role Director

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units F1, F2	3,086	$0.00	$0.00
Exercise	Common Stock F1	3,086	--	--

Holdings After Transaction: Restricted Stock Units — 52,469 contracts (Direct); Common Stock — 3,086 shares (Direct)

Footnotes (2)

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. The shares underlying the RSU Award shall vest over 3 years, with 2/36 of the total shares underlying the RSU Award vesting on August 18, 2026; 3/36 of the total shares underlying the RSU Award vesting on November 18, 2026 and each November 18 thereafter; 4/36 of the total shares underlying the RSU Award vesting on March 10, 2027 and each March 10 thereafter; 3/36 of the total shares underlying the RSU Award vesting on May 18, 2027 and each May 18 thereafter; and 3/36 of the total shares underlying the RSU Award vesting on August 18, 2027 and each August 18 thereafter.

Key Figures

RSUs converted: 3,086 units Common Stock acquired: 3,086 shares Conversion price: $0.00 per share +2 more

5 metrics

RSUs converted 3,086 units Restricted Stock Units converted into common stock on August 18, 2026

Common Stock acquired 3,086 shares Shares of Cytek common stock received from RSU conversion on August 18, 2026

Conversion price $0.00 per share Exercise or conversion price for the RSU-to-common stock transaction

RSUs following transaction 52,469 units Total RSU balance for this award after the derivative transaction

Vesting period 3 years Total time over which the RSU Award vests in multiple tranches

Key Terms

Restricted Stock Units, contingent right, vest, derivative security

4 terms

Restricted Stock Units financial

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

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

contingent right financial

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

vest financial

"The shares underlying the RSU Award shall vest over 3 years"

A vest is the process by which an employee earns the right to receive certain benefits or ownership interests, such as stock or retirement funds, over time. It’s similar to earning a reward gradually, ensuring that the benefit becomes fully yours only after a set period or meeting specific conditions. This makes it important for investors because it determines when they can actually claim or use those benefits.

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.

FAQ

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

What insider transaction did CTKB director Glenn P. Muir report?

Glenn P. Muir reported the conversion of 3,086 Restricted Stock Units into 3,086 shares of Cytek Biosciences, Inc. common stock on August 18, 2026, through an M-code derivative exercise/conversion transaction.

How many Cytek Biosciences (CTKB) RSUs does Glenn P. Muir hold after this Form 4?

After the reported transaction, Glenn P. Muir holds 52,469 Restricted Stock Units related to this RSU Award, as shown by the derivative security’s total shares following the transaction.

How many CTKB common shares did Glenn P. Muir acquire in this transaction?

Glenn P. Muir acquired 3,086 shares of Cytek Biosciences, Inc. common stock upon conversion of Restricted Stock Units on August 18, 2026. His total directly held common shares from this reported line are 3,086 after the transaction.

What was the exercise or conversion price for Glenn P. Muir’s CTKB RSUs?

The Restricted Stock Units converted into Cytek Biosciences, Inc. common stock at an exercise or conversion price of $0.00 per share, meaning no cash price per share was paid in the reported transaction.

How does Glenn P. Muir’s CTKB RSU Award vest over time?

The RSU Award vests over 3 years, with 2/36 of the total shares vesting on August 18, 2026; 3/36 vesting on November 18, 2026 and each November 18 thereafter; 4/36 vesting on March 10, 2027 and each March 10 thereafter; and additional 3/36 tranches on May 18 and August 18, 2027 and annually thereafter.

Was Glenn P. Muir’s CTKB transaction under a Rule 10b5-1 trading plan?

The filing’s Rule 10b5-1 checkbox is not marked, and there is no footnote indicating the use of a Rule 10b5-1 trading plan for this transaction.

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

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Available on EDGAR 08/20/2026 - 04:32 PM Accepted by SEC EDGAR 08/20/2026 - 04:31 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^*

MUIR GLENN P

(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
	Officer (give title below)		Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
08/18/2026

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	08/18/2026		M		3,086	A	(1)	3,086	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)	08/18/2026		M			3,086	(2)	(2)	Common Stock	3,086	$0	52,469	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. The shares underlying the RSU Award shall vest over 3 years, with 2/36 of the total shares underlying the RSU Award vesting on August 18, 2026; 3/36 of the total shares underlying the RSU Award vesting on November 18, 2026 and each November 18 thereafter; 4/36 of the total shares underlying the RSU Award vesting on March 10, 2027 and each March 10 thereafter; 3/36 of the total shares underlying the RSU Award vesting on May 18, 2027 and each May 18 thereafter; and 3/36 of the total shares underlying the RSU Award vesting on August 18, 2027 and each August 18 thereafter.

	/s/ Gordon Ho, Attorney-in-Fact	08/20/2026
	** 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)