Boston Partners reports 5.91% stake in Cytek Biosciences

Boston Partners, a Delaware entity, reports beneficial ownership of Cytek Biosciences, Inc. common stock on a Schedule 13G. It reports holding 7,635,145 shares of common stock, representing 5.91% of the class as of June 30, 2026.

Rhea-AI Filing Summary

Boston Partners, a Delaware entity, reports beneficial ownership of Cytek Biosciences, Inc. common stock on a Schedule 13G. It reports holding 7,635,145 shares of common stock, representing 5.91% of the class as of June 30, 2026. Boston Partners has sole voting power and sole dispositive power over all 7,635,145 shares, with no shared voting or dispositive power.

The shares are held in discretionary accounts for certain clients, and Boston Partners may be deemed a beneficial owner under Rule 13d-3. To its knowledge, no other person has rights to dividends or sale proceeds relating to more than 5% of the outstanding common stock referenced.

Key Figures

Shares beneficially owned: 7,635,145 shares Percent of class: 5.91% Sole voting power: 7,635,145 shares +5 more

8 metrics

Shares beneficially owned 7,635,145 shares Amount beneficially owned by Boston Partners as of 06/30/2026

Percent of class 5.91% Percent of Cytek Biosciences common stock class held by Boston Partners

Sole voting power 7,635,145 shares Shares over which Boston Partners has sole power to vote

Shared voting power 0 shares Shares over which Boston Partners has shared power to vote

Sole dispositive power 7,635,145 shares Shares over which Boston Partners has sole power to dispose

Shared dispositive power 0 shares Shares over which Boston Partners has shared power to dispose

Reporting date of holdings 06/30/2026 Date as of which the reported holdings are stated

Signature date 08/04/2026 Date the Schedule 13G was signed by Senior Compliance Manager

Key Terms

beneficial owner, Schedule 13G, sole voting power, sole dispositive power, +1 more

5 terms

beneficial owner regulatory

"By reason of rule 13d-3 under the act Boston Partners may be deemed to be a beneficial owner"

A beneficial owner is the person who ultimately owns or controls a financial asset or property, even if their name isn't directly on official documents. Think of it like someone who secretly holds the keys to a safe deposit box—others may appear to have access, but the true owner is the one who benefits from what's inside. Identifying beneficial owners helps ensure transparency and prevent illegal activities like money laundering or fraud.

Schedule 13G regulatory

"This Schedule is being filed with respect to 7,635,145 shares of Cytek Biosciences, Inc."

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

sole voting power financial

"Sole Voting Power 7,635,145.00"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

sole dispositive power financial

"Sole Dispositive Power 7,635,145.00"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

discretionary account financial

"held by Boston Partners on 06/30/2026 for the discretionary account of certain clients"

An account in which the account holder gives a broker or advisor authority to buy and sell securities on their behalf without asking for permission for each trade. Like handing someone the keys to your car to run errands, it lets a professional act quickly and make ongoing decisions for you; this matters to investors because it changes who controls trade timing, affects fees and tax reporting, and shifts responsibility for execution and record-keeping.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What percentage of Cytek Biosciences (CTKB) shares does Boston Partners report owning?

Boston Partners reports beneficial ownership of 5.91% of Cytek Biosciences, Inc. common stock, based on 7,635,145 shares held as of June 30, 2026 under Rule 13d-3.

How many Cytek Biosciences (CTKB) shares does Boston Partners control?

Boston Partners reports beneficial ownership of 7,635,145 shares of Cytek Biosciences common stock, with sole voting power and sole dispositive power over all of these shares and no shared power.

Does Boston Partners share voting or dispositive power over Cytek Biosciences (CTKB) stock?

No. Boston Partners reports 0 shares with shared voting power and 0 shares with shared dispositive power, and 7,635,145 shares with both sole voting and sole dispositive power.

On whose behalf does Boston Partners hold Cytek Biosciences (CTKB) shares?

Boston Partners states that the 7,635,145 shares of Cytek Biosciences common stock are held for the discretionary accounts of certain clients, making Boston Partners a deemed beneficial owner under Rule 13d-3.

Does any other person have rights to more than 5% of Cytek Biosciences (CTKB) through Boston Partners’ holdings?

Boston Partners states that, to its knowledge, no person has the right to receive dividends or sale proceeds from the reported common stock representing more than 5% of the outstanding class.

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

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Available on EDGAR 08/04/2026 - 05:16 PM Accepted by SEC EDGAR 08/04/2026 - 05:15 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Cytek Biosciences, Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

23285D109

(CUSIP Number)

06/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 23285D109

1

Names of Reporting Persons

Boston Partners

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 7,635,145.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 7,635,145.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

7,635,145.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.91 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Cytek Biosciences, Inc.
(b)	Address of issuer's principal executive offices: 47215 LAKEVIEW BOULEVARD, FREMONT, CALIFORNIA 94538
Item 2.
(a)	Name of person filing: Boston Partners
(b)	Address or principal business office or, if none, residence: ONE BEACON STREET 30TH FLOOR BOSTON, Massachusetts 02108
(c)	Citizenship: Boston Partners - DELAWARE
(d)	Title of class of securities: Common Stock
(e)	CUSIP Number(s): 23285D109
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 7,635,145
(b)	Percent of class: 5.91 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: Boston Partners - 7,635,145
	(ii) Shared power to vote or to direct the vote: Boston Partners - 0
	(iii) Sole power to dispose or to direct the disposition of: Boston Partners - 7,635,145
	(iv) Shared power to dispose or to direct the disposition of: Boston Partners - 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. This Schedule is being filed with respect to 7,635,145 shares of Cytek Biosciences, Inc. (the Common Stock) held by Boston Partners on 06/30/2026 for the discretionary account of certain clients. By reason of rule 13d-3 under the act Boston Partners may be deemed to be a beneficial owner of such Common Stock. To the knowledge of Boston Partners no person has the right to receive or the power to direct the receipt of dividends from or the proceeds from the sale of such Common Stock which represents more than 5% of the outstanding shares of the Common Stock referred to in item 4(b) hereof.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Boston Partners

Signature:	/s/ Ali Farooqi
Name/Title:	Ali Farooqi / Senior Compliance Manager
Date:	08/04/2026