300,000 W. R. Berkley (NYSE: WRB) shares bought by major holder

Rhea-AI Filing Summary

W. R. Berkley Corporation’s major shareholder Mitsui Sumitomo Insurance Co., Ltd. bought 300,000 shares of common stock in open-market purchases. The trades occurred on February 26–27, 2026 at weighted average prices around $71–$72 per share under a Rule 10b5-1 purchase plan adopted on October 3, 2025. Following these purchases, Mitsui Sumitomo directly holds 58,522,274 shares. MS&AD Insurance Group Holdings, Inc., Mitsui Sumitomo’s parent, may be deemed to beneficially own these securities but expressly disclaims beneficial ownership except to the extent of its pecuniary interest.

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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

X

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

MITSUI SUMITOMO INSURANCE CO LTD

(Last) (First) (Middle)

9, KANDA-SURUGADAI 3-CHOME, CHIYODA-KU

(Street)

TOKYO M0

(City) (State) (Zip)

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)

3. Date of Earliest Transaction (Month/Day/Year)
02/26/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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	02/26/2026		P(1)		145,491	A	$71.646(2)	58,367,765	D(3)
Common Stock	02/26/2026		P(1)		7,509	A	$72.114(4)	58,375,274	D(3)
Common Stock	02/27/2026		P(1)		147,000	A	$71.6256(5)	58,522,274	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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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

1. Name and Address of Reporting Person^*

MITSUI SUMITOMO INSURANCE CO LTD

(Last) (First) (Middle)

9, KANDA-SURUGADAI 3-CHOME, CHIYODA-KU

(Street)

TOKYO M0

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

MS&AD Insurance Group Holdings, Inc.

(Last) (First) (Middle)

TOKYO SUMITOMO TWIN BUILDING WEST TOWER,

27-2, SHINKAWA 2-CHOME, CHUO-KU,

(Street)

TOKYO M0

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

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 $71.3483 to $71.9977. 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 $72.00 to $72.39.

5. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $71.065 to $72.035.

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.

	MITSUI SUMITOMO INSURANCE CO., LTD., By: /s/ Hironori Morimoto, Name: Hironori Morimoto, Title: Authorized Signatory	02/27/2026
	MS&AD INSURANCE GROUP HOLDINGS, INC., By: /s/ Hironori Morimoto, Name: Hironori Morimoto, Title: Authorized Signatory	02/27/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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FAQ

What insider activity did WRB report in this Form 4 filing?

WRB reported that Mitsui Sumitomo Insurance Co., Ltd. purchased 300,000 shares of W. R. Berkley common stock. The open-market trades occurred on February 26–27, 2026 at weighted average prices in the low $70s per share under a pre-arranged Rule 10b5-1 plan.

Who bought W. R. Berkley (WRB) shares in this Form 4?

Mitsui Sumitomo Insurance Co., Ltd., a major shareholder of W. R. Berkley, bought the shares. It is a wholly owned subsidiary of MS&AD Insurance Group Holdings, Inc., which may be deemed a beneficial owner but disclaims beneficial ownership beyond its pecuniary interest.

How many WRB shares were purchased and at what prices?

A total of 300,000 W. R. Berkley common shares were purchased in three transactions. The weighted average prices were approximately $71.63 and $72.11 per share, with actual trade prices ranging from $71.065 to $72.39 according to the detailed footnotes.

On what dates did the WRB insider share purchases take place?

The W. R. Berkley share purchases took place on February 26 and February 27, 2026. Multiple trades were executed on those days, all reported as open-market purchases under a Rule 10b5-1 trading plan adopted several months earlier.

What is Mitsui Sumitomo’s WRB share ownership after these trades?

After these purchases, Mitsui Sumitomo Insurance Co., Ltd. directly holds 58,522,274 W. R. Berkley common shares. This total reflects the incremental addition of 300,000 shares from the reported open-market transactions executed in late February 2026.

Was the WRB insider buying done under a Rule 10b5-1 plan?

Yes, the purchases were made pursuant to a Rule 10b5-1 purchase plan adopted on October 3, 2025. Such pre-arranged plans allow trades to occur according to preset terms, helping separate trading decisions from day-to-day inside information.