Mitsui Sumitomo adds W.R. Berkley (WRB) shares under Rule 10b5-1 plan

Rhea-AI Filing Summary

W.R. Berkley Corporation insider Mitsui Sumitomo Insurance Co., Ltd., together with MS&AD Insurance Group Holdings, reported sizable open-market purchases of common stock under a pre-arranged Rule 10b5-1 trading plan adopted on October 3, 2025. On December 30, 2025, the reporting persons bought 205,000 shares at a weighted average price of $70.8284, bringing their beneficial holdings to 50,296,511 shares. On December 31, 2025, they purchased another 230,000 shares at a weighted average price of $70.2652, increasing holdings to 50,526,511 shares. On January 2, 2026, they bought a further 237,734 shares at a weighted average price of $69.3477, resulting in beneficial ownership of 50,764,245 shares held directly by Mitsui Sumitomo Insurance. The reporting persons state these prices reflect multiple trades within disclosed price ranges and clarify that MS&AD’s interest is through its wholly owned subsidiary.

Insights

Equity ownership and governance analyst

Large existing holder increases W.R. Berkley stake via 10b5-1 plan purchases.

The filing shows Mitsui Sumitomo Insurance Co., Ltd., already a significant holder and director-related party, buying additional W.R. Berkley common shares on three trading days. Purchases total 205,000, 230,000 and 237,734 shares at weighted average prices of $70.8284, $70.2652 and $69.3477, respectively. After these trades, Mitsui Sumitomo directly holds 50,764,245 shares.

The transactions were executed under a Rule 10b5-1 purchase plan adopted on October 3, 2025, indicating a pre-set trading schedule rather than discretionary market timing. The filing also notes that MS&AD Insurance Group Holdings may be deemed a beneficial owner through its subsidiary but expressly disclaims beneficial ownership beyond its pecuniary interest, which is typical legal positioning.

Because these are open-market purchases rather than sales, they do not introduce new dilution. The main implication is incremental consolidation of a large shareholder’s position and ongoing alignment with the issuer’s equity, while governance dynamics and any future changes in ownership structure would be understood through subsequent ownership and Schedule 13D updates.

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)
12/30/2025

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	12/30/2025		P(1)		205,000	A	$70.8284(2)	50,296,511	D(3)
Common Stock	12/31/2025		P(1)		230,000	A	$70.2652(4)	50,526,511	D(3)
Common Stock	01/02/2026		P(1)		237,734	A	$69.3477(5)	50,764,245	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 $70.6 to $71.145. 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 $70.08 to $70.785.

5. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $68.92 to $69.77.

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	01/02/2026
	MS&AD INSURANCE GROUP HOLDINGS, INC., By: /s/ Hironori Morimoto, Name: Hironori Morimoto, Title: Authorized Signatory	01/02/2026
	** Signature of Reporting Person	Date
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FAQ

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

The filing reports that Mitsui Sumitomo Insurance Co., Ltd., related to W.R. Berkley Corporation (WRB) as a director-affiliated holder, bought common stock in three open-market transactions on December 30, 2025, December 31, 2025 and January 2, 2026.

How many W.R. Berkley (WRB) shares were purchased and at what prices?

The reporting persons purchased 205,000 shares at a weighted average price of $70.8284 on December 30, 2025, 230,000 shares at $70.2652 on December 31, 2025, and 237,734 shares at $69.3477 on January 2, 2026.

What is the new beneficial ownership reported for WRB shares?

After the reported transactions, Mitsui Sumitomo Insurance Co., Ltd. is shown as directly beneficially owning 50,764,245 shares of W.R. Berkley common stock.

Were the WRB share purchases made under a Rule 10b5-1 trading plan?

Yes. The filing states that the purchases were effected under a Rule 10b5-1 purchase plan adopted on October 3, 2025, indicating a pre-arranged trading program.

Why are the WRB share prices reported as weighted averages?

The filing explains that each day’s price is a weighted average because the shares were purchased in multiple transactions within price ranges, and the reporting persons undertake to provide detailed trade data upon request.

How are MS&AD Insurance Group Holdings and Mitsui Sumitomo related in this WRB filing?

The filing notes that Mitsui Sumitomo Insurance Co., Ltd. is a wholly owned subsidiary of MS&AD Insurance Group Holdings, Inc., which may be deemed to beneficially own the securities through that subsidiary, while expressly disclaiming beneficial ownership beyond its pecuniary interest.

Do the reporting persons claim to be a group with WR Berkley & Others LLC in WRB?

No. The remarks state that the reporting persons disclaim beneficial ownership of securities owned by WR Berkley & Others LLC and disclaim that they and WRBO constitute a "group" under Rule 13d-5(b)(1).