PRIMECAP holds 8.54% of MarketAxess Holdings (NASDAQ: MKTX)

Rhea-AI Filing Summary

PRIMECAP Management Co. filed an amended Schedule 13G reporting beneficial ownership of 3,175,425 shares of MarketAxess Holdings Inc., representing 8.54% of the company’s common stock as of December 31, 2025.

PRIMECAP reports sole voting power over 3,162,095 shares and sole dispositive power over all 3,175,425 shares, with no shared voting or dispositive authority. The firm certifies that the securities were acquired and are held in the ordinary course of business and not for the purpose of changing or influencing control of MarketAxess.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

MarketAxess Holdings Inc.

(Name of Issuer)

COM

(Title of Class of Securities)

57060D108

(CUSIP Number)

12/31/2025

(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)

SCHEDULE 13G

CUSIP No. 57060D108

1

Names of Reporting Persons

PRIMECAP MANAGEMENT CO/CA/

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

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 3,162,095.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 3,175,425.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

3,175,425.00

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)

8.54 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: MarketAxess Holdings Inc.
(b)	Address of issuer's principal executive offices: 55 Hudson Yards, New York, NEW YORK 10001
Item 2.
(a)	Name of person filing: PRIMECAP MANAGEMENT CO/CA/
(b)	Address or principal business office or, if none, residence: 177 EAST COLORADO BLVD. 11TH FLOOR PASADENA, California 91105
(c)	Citizenship: PRIMECAP MANAGEMENT CO/CA/ - UNITED STATES
(d)	Title of class of securities: COM
(e)	CUSIP No.: 57060D108
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: 3,175,425
(b)	Percent of class: 8.54 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: PRIMECAP MANAGEMENT CO/CA/ - 3,162,095
	(ii) Shared power to vote or to direct the vote: PRIMECAP MANAGEMENT CO/CA/ - 0
	(iii) Sole power to dispose or to direct the disposition of: PRIMECAP MANAGEMENT CO/CA/ - 3,175,425
	(iv) Shared power to dispose or to direct the disposition of: PRIMECAP MANAGEMENT CO/CA/ - 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.
	Not Applicable
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.

PRIMECAP MANAGEMENT CO/CA/

Signature:	Jorge A. Rodriguez
Name/Title:	Deputy Chief Compliance Officer
Date:	02/10/2026

FAQ

What stake in MarketAxess (MKTX) does PRIMECAP report in this Schedule 13G/A?

PRIMECAP Management Co. reports beneficial ownership of 3,175,425 MarketAxess shares, representing 8.54% of the company’s common stock. This position reflects shares over which PRIMECAP has sole dispositive power, based on holdings as of December 31, 2025.

What voting and dispositive power does PRIMECAP have over MarketAxess (MKTX) shares?

PRIMECAP reports sole voting power over 3,162,095 MarketAxess shares and no shared voting power. It also has sole dispositive power over 3,175,425 shares, with no shared dispositive authority, indicating full decision-making control over voting and disposition for these holdings.

Is PRIMECAP’s MarketAxess (MKTX) position intended to influence control of the company?

PRIMECAP certifies the MarketAxess shares were acquired and are held in the ordinary course of business and not for the purpose or effect of changing or influencing control of the issuer, consistent with a passive institutional investment reported on Schedule 13G.

Who is the reporting person in this MarketAxess (MKTX) Schedule 13G/A filing?

The reporting person is PRIMECAP Management Co., organized in the United States, with its principal business office at 177 East Colorado Blvd., 11th Floor, Pasadena, California 91105. It reports beneficial ownership and control information regarding its MarketAxess Holdings Inc. common stock position.

What key date applies to PRIMECAP’s reported MarketAxess (MKTX) ownership?

The relevant event date for the reported MarketAxess ownership is December 31, 2025. As of this date, PRIMECAP beneficially owned 3,175,425 shares, or 8.54% of the class, with specified sole voting and dispositive powers over nearly all of these shares.

What type of SEC filing is used to report PRIMECAP’s MarketAxess (MKTX) holdings?

PRIMECAP reports its MarketAxess position on Schedule 13G/A (Amendment No. 1). This schedule is used for institutional or other passive investors to disclose significant beneficial ownership stakes, generally when the holdings are not intended to influence or change control of the issuer.