Sec Form 4 Filing - Feuchtwang Ilan @ Cytek Biosciences, Inc. - 2026-08-10

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Feuchtwang Ilan 2. Issuer Name and Ticker or Trading Symbol Cytek Biosciences, Inc. [ CTKB] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) Chief Legal Officer, Secretary (Last) (First) (Middle) C/O CYTEK BIOSCIENCES, INC., 47215 LAKEVIEW BOULEVARD 3. Date of Earliest Transaction (MM/DD/YY) 08/10/2026 (Street) FREMONT, CA94538 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: 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 ) 08/10/2026 A 241,416 ( 2 ) ( 2 ) Common Stock 241,416 $ 0 241,416 D Employee Stock Option (right to buy) $ 4.66 08/10/2026 A 127,118 ( 3 ) 08/09/2036 Common Stock 127,118 $ 0 127,118 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Feuchtwang Ilan C/O CYTEK BIOSCIENCES, INC. 47215 LAKEVIEW BOULEVARD FREMONT, CA94538 Chief Legal Officer, Secretary Signatures /s/ Wenbin Jiang, Attorney-in-Fact 08/12/2026 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Each restricted stock unit (the "RSU") represents a contingent right to receive one share of the Issuer's common stock. ( 2 )The RSUs shall vest and settle into common stock over 4 years, with 12/48 of the RSUs vesting on August 18, 2027; 3/48 of the RSUs vesting on November 18, 2027 and each November 18 thereafter; 4/48 of the RSUs vesting on March 10, 2028 and each March 10 thereafter; 2/48 of the RSUs vesting on May 18, 2028 and each May 18 thereafter; and 3/48 of the RSUs vesting on August 18, 2028 and each August 18 thereafter, until fully vested (in each case, subject to the Reporting Person's Continuous Service (as defined in the Issuer's 2021 Equity Invesntive Plan (the "2021 Plan"))). ( 3 )The shares subject to the option shall vest over 4 years with 25% vesting on August 10, 2027 and 1/48 of the shares vesting each month thereafter, until fully vested (in each case, subject to the Reporting Person's Continuous Service (as defined in the 2021 Plan)).

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).

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