[Form 4] BERKLEY W R CORP Insider Trading Activity

Rhea-AI Filing Summary

Mitsui Sumitomo Insurance Co., Ltd. (MSI), a 10% owner of W. R. Berkley Corporation, reported a series of open‑market common stock purchases under a pre‑arranged Rule 10b5‑1 plan adopted on October 3, 2025.

On January 26, 2026, MSI bought 293,611 shares at a weighted average price of $66.8554 and 76,389 shares at $67.877. On January 27, 2026, it executed several additional purchases, including 325,960 shares at $67.4036 and 8,582 shares at $68.561. On January 28, 2026, MSI purchased 280,354 shares at $67.5756 and 28,577 shares at $67.8935.

Following these transactions, MSI directly held up to 55,618,435 W. R. Berkley 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.

Insights

Equity ownership and governance analyst

Large institutional holder increased its W. R. Berkley stake through planned open‑market purchases.

Mitsui Sumitomo Insurance Co., Ltd. (MSI) reported multiple open‑market purchases of W. R. Berkley common stock from January 26–28, 2026, with trade sizes up to 325,960 shares at prices around $66–$69. These were executed under a Rule 10b5‑1 plan adopted on October 3, 2025, indicating the buying program was pre‑scheduled rather than reactive.

After the reported trades, MSI directly held as many as 55,618,435 shares, and both MSI and MS&AD Insurance Group Holdings, Inc. are listed as 10% owners. A footnote clarifies that MS&AD may be deemed a beneficial owner through its wholly owned subsidiary but disclaims beneficial ownership beyond its pecuniary interest.

Because these are purchases, not sales, and stem from a pre‑existing plan, they mainly update the ownership record rather than signal a new strategic event. Future company filings may provide additional context on how this ownership position relates to broader commercial or strategic relationships between MSI, MS&AD, and W. R. Berkley.

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)
01/26/2026

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	01/26/2026		P(1)		293,611	A	$66.8554(2)	54,883,115	D(3)
Common Stock	01/26/2026		P(1)		76,389	A	$67.877(4)	54,959,504	D(3)
Common Stock	01/27/2026		P(1)		800	A	$65.8618(5)	54,960,304	D(3)
Common Stock	01/27/2026		P(1)		11,987	A	$66.8658(6)	54,972,291	D(3)
Common Stock	01/27/2026		P(1)		325,960	A	$67.4036(7)	55,298,251	D(3)
Common Stock	01/27/2026		P(1)		8,582	A	$68.561(8)	55,306,833	D(3)
Common Stock	01/27/2026		P(1)		2,671	A	$69.0351(9)	55,309,504	D(3)
Common Stock	01/28/2026		P(1)		280,354	A	$67.5756(10)	55,589,858	D(3)
Common Stock	01/28/2026		P(1)		28,577	A	$67.8935(11)	55,618,435	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 $66.45 to $67.40. 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, 6, 7, 8, 9, 10 and 11.

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 $67.4004 to $68.19.

5. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $65.77 to $65.975.

6. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $66.03 to $66.9994.

7. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $67.00 to $67.82.

8. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $68.25 to $68.99.

9. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $69.00 to $69.37.

10. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $66.87 to $67.80.

11. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $67.8011 to $68.015.

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	01/28/2026
	MS&AD INSURANCE GROUP HOLDINGS, INC., By: /s/ Hironori Morimoto, Name: Hironori Morimoto, Title: Authorized Signatory	01/28/2026
	** Signature of Reporting Person	Date
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