Sec Form 4 Filing - MITSUI SUMITOMO INSURANCE CO LTD @ BERKLEY W R CORP - 2026-01-29

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 MITSUI SUMITOMO INSURANCE CO LTD 2. Issuer Name and Ticker or Trading Symbol BERKLEY W R CORP [ WRB] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 9, KANDA-SURUGADAI 3-CHOME, CHIYODA-KU, 3. Date of Earliest Transaction (MM/DD/YY) 01/29/2026 (Street) TOKYO, M0 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ 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 Common Stock 01/29/2026 P( 1 ) 262,282 A $ 68.0816 ( 2 ) 55,880,717 D ( 3 ) Common Stock 01/29/2026 P( 1 ) 27,718 A $ 68.5605 ( 4 ) 55,908,435 D ( 3 ) Common Stock 01/30/2026 P( 1 ) 195,000 A $ 68.3611 ( 5 ) 56,103,435 D ( 3 )

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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MITSUI SUMITOMO INSURANCE CO LTD 9, KANDA-SURUGADAI 3-CHOME, CHIYODA-KU TOKYO, M0 X MS&AD Insurance Group Holdings, Inc. TOKYO SUMITOMO TWIN BUILDING WEST TOWER, 27-2, SHINKAWA 2-CHOME, CHUO-KU, TOKYO, M0 X Signatures MITSUI SUMITOMO INSURANCE CO., LTD., By: /s/ Hironori Morimoto, Name: Hironori Morimoto, Title: Authorized Signatory 01/30/2026 Signature of Reporting Person Date MS&AD INSURANCE GROUP HOLDINGS, INC., By: /s/ Hironori Morimoto, Name: Hironori Morimoto, Title: Authorized Signatory 01/30/2026 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The purchases reported on this Form 4 were effected pursuant to a Rule 10b5-1 purchase plan, adopted October 3, 2025. ( 2 )The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $67.43 to $68.40. The Reporting Persons undertake to provide to W.R. Berkley Corporation (the "Issuer"), any security holder of the Issuer, or the staff of the U.S. Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the ranges set forth in this footnote and in footnotes 4 and 5. ( 3 )The shares are held directly by Mitsui Sumitomo Insurance Co., Ltd. ("MSI"). Because MSI is a wholly-owned subsidiary of MS&AD Insurance Group Holdings, Inc. ("MS&AD"), MS&AD may be deemed to beneficially own the reported securities. MS&AD expressly disclaims beneficial ownership of the reported securities, except to the extent of its pecuniary interest therein. ( 4 )The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $68.4004 to $69.015. ( 5 )The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $67.83 to $68.645.

Remarks: MSI, the Issuer and WR Berkley & Others LLC ("WRBO") are party to certain agreements described in, and filed as exhibits to, the Reporting Persons' Schedule 13D filed with the U.S. Securities and Exchange Commission on December 11, 2025. The Reporting Persons disclaim beneficial ownership of the securities of the Issuer owned by WRBO and disclaim that the Reporting Persons and WRBO constitute a "group" within the meaning of Rule 13d-5(b)(1) under the Securities Exchange Act of 1934, as amended.

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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