Glenn P. Muir - 18 Aug 2026 Form 4 Insider Report for Cytek Biosciences, Inc. (CTKB)

Reporting relationship: Director
Issuer ticker: CTKB
Reported as of: 18 Aug 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 20 Aug 2026, 16:31:29 UTC
Prior SEC filing: 12 Jun 2026
Source filing: View source filing
Reporting owner signature: /s/ Gordon Ho, Attorney-in-Fact

Key filing fact

Glenn P. Muir filed Form 4 for Cytek Biosciences, Inc. (CTKB) on 20 Aug 2026.

Key facts

This page summarizes Glenn P. Muir's Form 4 filing for Cytek Biosciences, Inc. (CTKB).
2 reported transactions and 1 derivative row are listed below.
Accepted by SEC: 20 Aug 2026, 16:31.

Change

Previous filing in this sequence was filed on 12 Jun 2026.
Current net transaction value: $0.

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 0001181190 Primary reporting owner

MUIR GLENN P

Relationship: Director
Address: C/O CYTEK BIOSCIENCES, INC., 47215 LAKEVIEW BOULEVARD, FREMONT
Signature: /s/ Gordon Ho, Attorney-in-Fact
Signature date: 20 Aug 2026

Reported non-derivative transactions

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

CTKB transaction

Common Stock

Options Exercise

Transaction value
Shares: +3,086
Change %
Price
Shares after: 3,086
Date: 18 Aug 2026
Ownership: Direct
Footnotes: F1

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
Shares: -3,086
Change %: -5.6%
Price: $0.000000^*
Shares after: 52,469
Date: 18 Aug 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 3,086
Exercise price
Footnotes: F1, F2

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

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 2 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

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.