W.R. Berkley (NYSE: WRB) major holder reports Rule 10b5-1 buys in Form 4

Rhea-AI Filing Summary

Mitsui Sumitomo Insurance Co., Ltd., a 10% owner of W.R. Berkley Corporation, reported a series of open-market purchases of the company’s common stock. On January 15, 2026, it bought blocks of 166,907 shares at $68.675 and 68,093 shares at $69.4472. On January 16, 2026, it purchased 241,309 shares at $68.031 and 58,691 shares at $68.7857.

The filing states these purchases were made under a Rule 10b5-1 purchase plan adopted on October 3, 2025, indicating they were pre-arranged. After these transactions, Mitsui Sumitomo Insurance directly held 53,261,504 shares of W.R. Berkley common stock. Because Mitsui Sumitomo Insurance is a wholly owned subsidiary of MS&AD Insurance Group Holdings, Inc., MS&AD may be deemed to beneficially own these securities, though it 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

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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)
01/15/2026

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	01/15/2026		P(1)		166,907	A	$68.675(2)	52,893,411	D(3)
Common Stock	01/15/2026		P(1)		68,093	A	$69.4472(4)	52,961,504	D(3)
Common Stock	01/16/2026		P(1)		241,309	A	$68.031(5)	53,202,813	D(3)
Common Stock	01/16/2026		P(1)		58,691	A	$68.7857(6)	53,261,504	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 $68.31 to $68.9978. 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 $69.00 to $69.775.

5. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $67.68 to $68.67.

6. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $68.6711 to $69.055.

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	01/16/2026
	MS&AD INSURANCE GROUP HOLDINGS, INC., By: /s/ Hironori Morimoto, Name: Hironori Morimoto, Title: Authorized Signatory	01/16/2026
	** Signature of Reporting Person	Date
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FAQ

Who reported insider transactions in W.R. Berkley (WRB)?

The filing reports transactions by Mitsui Sumitomo Insurance Co., Ltd., a 10% owner of W.R. Berkley Corporation. MS&AD Insurance Group Holdings, Inc. is also listed as a reporting person and may be deemed to beneficially own the securities through its wholly owned subsidiary, while expressly disclaiming beneficial ownership except for its pecuniary interest.

What type of W.R. Berkley (WRB) security was purchased and on which dates?

The reporting persons disclosed purchases of W.R. Berkley common stock on January 15, 2026 and January 16, 2026, with all transactions classified as open-market purchases coded "P" in the filing.

How many W.R. Berkley (WRB) shares were bought in each reported transaction?

The filing lists four purchases: 166,907 shares and 68,093 shares on January 15, 2026, and 241,309 shares and 58,691 shares on January 16, 2026.

At what prices were the W.R. Berkley (WRB) shares purchased?

The reported weighted average prices were $68.675, $69.4472, $68.031 and $68.7857 per share, with footnotes explaining that each figure reflects multiple trades within specified price ranges.

How many W.R. Berkley (WRB) shares does Mitsui Sumitomo Insurance hold after these trades?

After the reported purchases, Mitsui Sumitomo Insurance Co., Ltd. is shown as directly holding 53,261,504 shares of W.R. Berkley common stock.

Were the W.R. Berkley (WRB) insider purchases made under a Rule 10b5-1 plan?

Yes. A footnote states that the purchases reported in this Form 4 were effected pursuant to a Rule 10b5-1 purchase plan adopted on October 3, 2025, indicating they followed a pre-established trading plan.

What does MS&AD disclose about its beneficial ownership of W.R. Berkley (WRB) shares?

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