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Cytek Biosciences (CTKB) SVP nets shares after RSU vesting and tax withholding

Filing Impact
(Neutral)
Filing Sentiment
(Neutral)
Form Type
4

Rhea-AI Filing Summary

Cytek Biosciences SVP Philippe Busque reported compensation-related stock activity. On May 18, 2026, he exercised awards covering 10,464 shares of common stock, converting vested restricted stock units into shares. To cover tax withholding obligations, 2,685 shares were surrendered back to the company at $3.55 per share rather than sold on the open market.

Following these transactions, Busque directly holds 36,448 shares of Cytek Biosciences common stock and 5,641 unvested restricted stock units that may convert into shares as they vest over time under multi-year vesting schedules.

Positive

  • None.

Negative

  • None.
Insider Busque Philippe
Role SVP, GLOBAL SALES AND SERVICES
Type Security Shares Price Value
Exercise Restricted Stock Units 1,024 $0.00 --
Exercise Restricted Stock Units 1,473 $0.00 --
Exercise Restricted Stock Units 2,416 $0.00 --
Exercise Restricted Stock Units 5,551 $0.00 --
Exercise Common Stock 1,024 $0.00 --
Tax Withholding Common Stock 263 $3.55 $933.65
Exercise Common Stock 1,473 $0.00 --
Tax Withholding Common Stock 378 $3.55 $1K
Exercise Common Stock 2,416 $0.00 --
Tax Withholding Common Stock 620 $3.55 $2K
Exercise Common Stock 5,551 $0.00 --
Tax Withholding Common Stock 1,424 $3.55 $5K
Holdings After Transaction: Restricted Stock Units — 5,641 shares (Direct, null); Common Stock — 36,711 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 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. 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 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.
Shares from RSU exercises 10,464 shares Common stock acquired via RSU conversion on May 18, 2026
Shares withheld for taxes 2,685 shares Surrendered to issuer at $3.55 per share for tax withholding
Post-transaction common shares 36,448 shares Direct holdings after May 18, 2026 transactions
Remaining RSUs 5,641 units Unvested restricted stock units after reported vesting events
Tax withholding price $3.55 per share Value used for shares surrendered to cover tax obligations
Restricted Stock Unit financial
"Each Restricted Stock Unit (the "RSU Award") represents a contingent right to receive one share"
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"
vest over four years financial
"The shares subject to the RSU Award shall vest over four years with 13/48 of the total shares"
derivative security financial
"transaction_code_description: 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.
contingent right financial
"represents a contingent right to receive one share of the Issuer's common stock"
SEC Form 4
FORM 4UNITED 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*
Busque Philippe

(Last)(First)(Middle)
C/O CYTEK BIOSCIENCES, INC.
47215 LAKEVIEW BLVD.

(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)
Director10% Owner
XOfficer (give title below)Other (specify below)
SVP, GLOBAL SALES AND SERVICES
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
05/18/2026
6. Individual or Joint/Group Filing (Check Applicable Line)
XForm 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)
CodeVAmount(A) or (D)Price
Common Stock05/18/2026M1,024A(1)36,711D
Common Stock05/18/2026F263(2)D$3.5536,448D
Common Stock05/18/2026M1,473A(1)37,921D
Common Stock05/18/2026F378(2)D$3.5537,543D
Common Stock05/18/2026M2,416A(1)39,959D
Common Stock05/18/2026F620(2)D$3.5539,339D
Common Stock05/18/2026M5,551A(1)44,890D
Common Stock05/18/2026F1,424(2)D$3.5543,466D
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)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Restricted Stock Units(1)05/18/2026M1,024 (3) (3)Common Stock1,024$05,641D
Restricted Stock Units(1)05/18/2026M1,473 (4) (4)Common Stock1,473$016,209D
Restricted Stock Units(1)05/18/2026M2,416 (5) (5)Common Stock2,416$041,089D
Restricted Stock Units(1)05/18/2026M5,551 (6) (6)Common Stock5,551$0127,675D
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 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.
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 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-Fact05/20/2026
** Signature of Reporting PersonDate
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) report for Philippe Busque?

Cytek Biosciences reported that SVP Philippe Busque exercised equity awards for 10,464 shares of common stock. He used 2,685 of those shares to satisfy tax withholding obligations, with no open-market purchases or sales disclosed in these transactions.

Did the Cytek Biosciences (CTKB) SVP buy or sell shares on the open market?

The filing shows no open-market buying or selling. Instead, shares were acquired through vesting and exercise of restricted stock units, and some were surrendered back to the company solely to cover tax withholding obligations at a stated price of $3.55 per share.

How many Cytek Biosciences (CTKB) shares does Philippe Busque hold after these transactions?

After the reported transactions, Philippe Busque directly holds 36,448 shares of Cytek Biosciences common stock. This reflects his position after exercising equity awards and surrendering 2,685 shares to the company for tax withholding obligations on May 18, 2026.

What restricted stock unit activity did Cytek Biosciences (CTKB) disclose for its SVP?

Cytek Biosciences disclosed that multiple restricted stock unit awards vested, converting into 10,464 common shares at a conversion price of $0.00 per share. These RSUs vest over four-year schedules with fractional installments on specified May, August, November, and March vesting dates.

How many unvested restricted stock units does the Cytek Biosciences (CTKB) SVP retain?

Following the May 18, 2026 vesting events, the filing shows Philippe Busque retaining 5,641 restricted stock units. These RSUs represent additional potential shares of Cytek Biosciences common stock that will be delivered only as the awards continue to vest over time.

What does the $3.55 price mean in the Cytek Biosciences (CTKB) Form 4?

The Form 4 lists a price of $3.55 per share for 2,685 shares surrendered. This amount reflects the value used when shares were withheld and returned to Cytek Biosciences to satisfy tax withholding obligations arising from the vesting of restricted stock unit awards.