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Cytek Biosciences (CTKB) CFO exercises shares, surrenders stock for taxes

(Neutral)
(Neutral)
Form Type
4

Rhea-AI Filing Summary

Cytek Biosciences, Inc. (CTKB) reported that Chief Financial Officer William D. McCombe exercised restricted stock units (RSUs) into 35,420 shares of common stock on August 18, 2026, through three RSU awards. In connection with these vestings, 11,904 shares of common stock were withheld and surrendered to Cytek to satisfy tax withholding obligations at a price of $4.67 per share. Each RSU represents a contingent right to receive one share of common stock, and the related awards vest over four years in specified installment schedules tied to May 18, August 18, November 18 and March 10 of various years.

Positive

  • None.

Negative

  • None.
Insider McCombe William D.
Role Chief Financial Officer
Type Security Shares Price Value
Exercise Restricted Stock Units F1, F3 6,320 $0.00 $0.00
Exercise Restricted Stock Units F1, F4 13,051 $0.00 $0.00
Exercise Restricted Stock Units F1, F5 16,049 $0.00 $0.00
Exercise Common Stock F1 6,320 -- --
Tax Withholding Common Stock F2 2,111 $4.67 $10K
Exercise Common Stock F1 13,051 -- --
Tax Withholding Common Stock F2 4,392 $4.67 $21K
Exercise Common Stock F1 16,049 -- --
Tax Withholding Common Stock F2 5,401 $4.67 $25K
Holdings After Transaction: Restricted Stock Units — 409,153 shares (Direct); Common Stock — 134,693 shares (Direct)
Footnotes (5)
  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 August 18, 2026 to satisfy tax withholding obligations that arose in connection with the vesting of the RSU Award.
  3. F3. The shares underlying 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; 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.
  4. F4. The shares underlying 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.
  5. F5. The shares underlying 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.
Shares acquired via RSU exercises 35,420 shares Total underlying shares from three RSU exercises reported on August 18, 2026
Shares withheld for taxes 11,904 shares Shares surrendered to Cytek to satisfy tax withholding obligations on August 18, 2026
Tax-withholding share price $4.67 per share Per‑share value for common stock withheld to pay tax liability
Derivative exercises (count) 3 Number of RSU-related derivative exercises (code M) in this filing
Code F dispositions (count) 3 Number of tax-withholding dispositions of common stock (code F)
Exercise shares detail 6,320; 13,051; 16,049 shares Underlying common shares for each of the three RSU exercises
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"
tax withholding obligations financial
"to satisfy tax withholding obligations that arose in connection with the vesting"
vest over 4 years financial
"The shares underlying the RSU Award shall vest over 4 years, with 12/48"

FAQ

What did Cytek Biosciences (CTKB) disclose about William D. McCombe’s Form 4 transactions?

Cytek Biosciences disclosed that CFO William D. McCombe exercised restricted stock units into 35,420 shares of common stock on August 18, 2026, with part of the resulting shares withheld to cover tax obligations related to the RSU vesting.

How many Cytek (CTKB) shares were withheld for taxes in this Form 4?

A total of 11,904 shares of Cytek common stock were withheld and surrendered to the company on August 18, 2026 to satisfy tax withholding obligations arising from the vesting of restricted stock unit awards, at a price of $4.67 per share.

How many restricted stock units did the Cytek (CTKB) CFO exercise?

The Cytek CFO exercised restricted stock units that converted into 35,420 shares of common stock. These exercises were reported under transaction code M as derivative exercises or conversions of RSUs, each RSU representing a contingent right to receive one share.

What price is associated with the tax-withholding share dispositions in the CTKB Form 4?

The shares withheld for tax obligations were valued at $4.67 per share. In total, 11,904 shares of Cytek common stock were surrendered at this per‑share value to satisfy tax withholding related to the vesting of restricted stock unit awards.

How do the Cytek (CTKB) RSU awards for the CFO vest over time?

The RSU awards vest over four years in staged installments. Footnotes describe vesting fractions such as 12/48, 2/48, 3/48, and 4/48 of total RSU shares on recurring dates including May 18, August 18, November 18, and March 10 in successive years.

Were the CTKB Form 4 transactions made under a Rule 10b5-1 plan?

The filing’s Rule 10b5‑1 checkbox is not checked, and the footnotes do not state that the transactions were made under a trading plan. The disclosure therefore does not indicate use of a pre‑arranged Rule 10b5‑1 trading plan.

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

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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*
McCombe William D.

(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)
Director10% Owner
XOfficer (give title below)Other (specify below)
Chief Financial Officer
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
08/18/2026
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 Stock08/18/2026M6,320A(1)117,497D
Common Stock08/18/2026F2,111(2)D$4.67115,386D
Common Stock08/18/2026M13,051A(1)128,437D
Common Stock08/18/2026F4,392(2)D$4.67124,045D
Common Stock08/18/2026M16,049A(1)140,094D
Common Stock08/18/2026F5,401(2)D$4.67134,693D
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)08/18/2026M6,320 (3) (3)Common Stock6,320$044,249D
Restricted Stock Units(1)08/18/2026M13,051 (4) (4)Common Stock13,051$0134,862D
Restricted Stock Units(1)08/18/2026M16,049 (5) (5)Common Stock16,049$0230,042D
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 August 18, 2026 to satisfy tax withholding obligations that arose in connection with the vesting of the RSU Award.
3. The shares underlying 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; 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.
4. The shares underlying 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.
5. The shares underlying 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.
/s/ Gordon Ho, Attorney-in-Fact08/20/2026
** 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)