William D. McCombe - 18 Nov 2025 Form 4 Insider Report for Cytek Biosciences, Inc. (CTKB)

Reporting relationship: Chief Financial Officer
Issuer ticker: CTKB
Reported as of: 18 Nov 2025
Net transaction value: -$34,441
SEC form: 4
Accepted by SEC: 20 Nov 2025, 19:03:31 UTC
Prior SEC filing: 20 Aug 2025
Next SEC filing: 12 Mar 2026
Source filing: View source filing
Reporting owner signature: /s/ Valerie Barnett, Attorney-in-Fact

Key filing fact

William D. McCombe filed Form 4 for Cytek Biosciences, Inc. (CTKB) on 20 Nov 2025.

Key facts

This page summarizes William D. McCombe's Form 4 filing for Cytek Biosciences, Inc. (CTKB).
6 reported transactions and 2 derivative rows are listed below.
Accepted by SEC: 20 Nov 2025, 19:03.

Change

Previous filing in this sequence was filed on 20 Aug 2025.
Current net transaction value: -$34,441.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001878824 Primary reporting owner

McCombe William D.

Relationship: Chief Financial Officer
Address: C/O CYTEK BIOSCIENCES, INC., 47215 LAKEVIEW BOULEVARD, FREMONT
Signature: /s/ Valerie Barnett, Attorney-in-Fact
Signature date: 20 Nov 2025

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

CTKB transaction

Common Stock

Options Exercise

Transaction value
Shares: +6,320
Change %: +9.4%
Price
Shares after: 73,891
Date: 18 Nov 2025
Ownership: Direct
Footnotes: F1

CTKB transaction

Common Stock

Tax liability

Transaction value: $11,237
Shares: -2,032
Change %: -2.7%
Price: $5.53
Shares after: 71,859
Date: 18 Nov 2025
Ownership: Direct
Footnotes: F2

CTKB transaction

Common Stock

Options Exercise

Transaction value
Shares: +13,051
Change %: +18%
Price
Shares after: 84,910
Date: 18 Nov 2025
Ownership: Direct
Footnotes: F1

CTKB transaction

Common Stock

Tax liability

Transaction value: $23,204
Shares: -4,196
Change %: -4.9%
Price: $5.53
Shares after: 80,714
Date: 18 Nov 2025
Ownership: Direct
Footnotes: F2

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

CTKB transaction Derivative

Restricted Stock Units

Options Exercise

Transaction value: $0
Shares: -6,320
Change %: -9.1%
Price: $0.000000
Shares after: 63,209
Date: 18 Nov 2025
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 6,320
Exercise price
Footnotes: F1, F3

CTKB transaction Derivative

Restricted Stock Units

Options Exercise

Transaction value: $0
Shares: -13,051
Change %: -7%
Price: $0.000000
Shares after: 174,014
Date: 18 Nov 2025
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 13,051
Exercise price
Footnotes: F1, F4

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 4 footnotes

Footnote F1

Each Restricted Stock Unit (the "RSU Award") represents a contingent right to receive one share of the Issuer's common stock.

Footnote F2

Represents the number of shares withheld by and surrendered to the Issuer on November 18, 2025, to satisfy tax withholding obligations that arose in connection with the vesting of the RSU Award.

Footnote F3

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.

Footnote 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, 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.