MSI boosts W. R. Berkley (WRB) stake with 698K-share 10b5-1 purchases

Rhea-AI Filing Summary

Mitsui Sumitomo Insurance Co., Ltd. (MSI), a 10% owner of W. R. Berkley Corporation, reported sizable open‑market share purchases under a pre-set trading plan. On January 22, 2026, MSI bought 330,000 shares of W. R. Berkley common stock at a weighted average price of $67.4505. On January 23, 2026, MSI made two additional purchases of 201,081 shares at a weighted average price of $66.7699 and 166,919 shares at a weighted average price of $67.1803. These transactions were effected pursuant to a Rule 10b5-1 purchase plan adopted on October 3, 2025. Following the reported trades, MSI directly held 54,589,504 W. R. Berkley common shares. Because MSI is a wholly owned subsidiary of MS&AD Insurance Group Holdings, Inc., MS&AD 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
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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)
01/22/2026

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	01/22/2026		P(1)		330,000	A	$67.4505(2)	54,221,504	D(3)
Common Stock	01/23/2026		P(1)		201,081	A	$66.7699(4)	54,422,585	D(3)
Common Stock	01/23/2026		P(1)		166,919	A	$67.1803(5)	54,589,504	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 $67.09 to $67.66. 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 $66.5195 to $66.9993.

5. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $67.00 to $67.9353.

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	01/23/2026
	MS&AD INSURANCE GROUP HOLDINGS, INC., By: /s/ Hironori Morimoto, Name: Hironori Morimoto, Title: Authorized Signatory	01/23/2026
	** Signature of Reporting Person	Date
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FAQ

What insider activity did WRB report in this Form 4?

The filing shows that Mitsui Sumitomo Insurance Co., Ltd. (MSI), a 10% owner of W. R. Berkley Corporation (WRB), purchased several blocks of WRB common stock in the open market on January 22 and 23, 2026, increasing its directly held position to 54,589,504 shares.

How many W. R. Berkley (WRB) shares did MSI buy and at what prices?

MSI bought 330,000 WRB common shares on January 22, 2026 at a weighted average price of $67.4505. On January 23, 2026, it purchased 201,081 shares at $66.7699 and 166,919 shares at $67.1803, all in open-market transactions.

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

Yes. The filing states that the purchases reported on this Form 4 were effected pursuant to a Rule 10b5-1 purchase plan that was adopted on October 3, 2025, indicating the trades followed a pre-arranged schedule.

Who is considered to own the WRB shares in this Form 4?

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 may be deemed to beneficially own the reported securities, but it expressly disclaims beneficial ownership except to the extent of its pecuniary interest.

How many W. R. Berkley (WRB) shares did MSI own after these transactions?

After the reported purchases, MSI directly owned 54,589,504 shares of W. R. Berkley common stock, as shown in the share balances following the final transaction on January 23, 2026.

What does it mean that MSI and MS&AD are 10% owners of WRB?

The reporting persons are indicated as 10% owners of W. R. Berkley, meaning their holdings represent at least 10% of the company’s outstanding common stock, which triggers ongoing reporting obligations for their transactions.

Are the WRB insider purchase prices in this Form 4 single trades or averages?

The prices reported in the Form 4 are weighted average prices. The filing notes that each block of shares was bought in multiple transactions within specified price ranges, and the reporting persons undertake to provide detailed trade-by-trade information upon request.