Mitsui Sumitomo boosts W.R. Berkley (WRB) stake via Rule 10b5-1 buys

Rhea-AI Filing Summary

Mitsui Sumitomo Insurance Co., Ltd., a 10% owner of W. R. Berkley Corporation, reported a series of share purchases executed under a Rule 10b5-1 purchase plan adopted on October 3, 2025. On February 5 and 6, 2026, MSI bought blocks of common stock at weighted average prices between about $70.46 and $71.39 per share, in transactions of 6,528, 13,472, 15,694 and 4,306 shares.

Following these purchases, MSI was reported as directly holding 56,458,656 W. R. Berkley common shares. MS&AD Insurance Group Holdings, Inc., MSI’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)
02/05/2026

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	02/05/2026		P(1)		6,528	A	$70.7889(2)	56,425,184	D(3)
Common Stock	02/05/2026		P(1)		13,472	A	$71.2528(4)	56,438,656	D(3)
Common Stock	02/06/2026		P(1)		15,694	A	$70.4608(5)	56,454,350	D(3)
Common Stock	02/06/2026		P(1)		4,306	A	$71.3915(6)	56,458,656	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 $70.4471 to $70.9964. 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, 5 and 6.

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 $71.0009 to $71.60.

5. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $70.1381 to $70.9994.

6. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $71.0012 to $71.8345.

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	02/06/2026
	MS&AD INSURANCE GROUP HOLDINGS, INC., By: /s/ Hironori Morimoto, Name: Hironori Morimoto, Title: Authorized Signatory	02/06/2026
	** Signature of Reporting Person	Date
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FAQ

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

The filing shows Mitsui Sumitomo Insurance Co., Ltd. purchased additional W. R. Berkley common stock in several small transactions on February 5 and 6, 2026 under a pre-set Rule 10b5-1 plan, modestly increasing its already large share position.

How many WRB shares does Mitsui Sumitomo Insurance hold after these trades?

After the reported purchases, Mitsui Sumitomo Insurance Co., Ltd. held 56,458,656 shares of W. R. Berkley common stock. This reflects incremental buying by an existing 10% owner rather than a new position, according to the Form 4 disclosure language.

At what prices did Mitsui Sumitomo Insurance buy WRB shares?

The reported purchases used weighted average prices per share. Individual transactions were priced at $70.7889, $71.2528, $70.4608, and $71.3915, with each figure representing averages across multiple trades within specified price ranges on February 5 and 6, 2026.

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

Yes. The purchases were made under a Rule 10b5-1 purchase plan adopted on October 3, 2025. Such plans pre-schedule trades, aiming to separate trading decisions from day-to-day information, as described in the Form 4’s explanation of responses.

How is MS&AD Insurance Group related to these WRB shares?

The shares are held directly by Mitsui Sumitomo Insurance Co., Ltd., a wholly owned subsidiary of MS&AD Insurance Group Holdings, Inc. MS&AD may be deemed to beneficially own the securities but expressly disclaims beneficial ownership except for its pecuniary interest.

Does this Form 4 indicate a sale or a purchase of WRB stock?

The Form 4 reports purchases of W. R. Berkley common stock, coded as transaction type “P” for buy. All listed transactions increased Mitsui Sumitomo Insurance Co., Ltd.’s directly held share count, rather than reducing its position in the company.