Mitsui Sumitomo adds 258K W.R. Berkley (WRB) shares via 10b5-1 plan

Rhea-AI Filing Summary

Mitsui Sumitomo Insurance Co., Ltd., a major shareholder of W. R. Berkley, reported four open-market purchases of the company’s common stock under a Rule 10b5-1 purchase plan adopted on October 3, 2025.

The trades on March 2–3, 2026 totaled 258,176 shares at weighted average prices of about $71–$73 per share, increasing its direct holdings to as many as 58,780,450 shares after the last transaction. The shares are held directly by Mitsui Sumitomo, a wholly owned subsidiary of MS&AD Insurance Group Holdings, Inc., which may be deemed a beneficial owner but expressly disclaims beneficial ownership except to the extent of its pecuniary interest.

Insider Trade Summary

Net Buyer: 258,176 shares ($18,745,005)

Net Buy 4 txns

Insider MITSUI SUMITOMO INSURANCE CO LTD, MS&AD Insurance Group Holdings, Inc.

Role 10% Owner | 10% Owner

Bought 258,176 shs ($18.75M)

Type	Security	Shares	Price	Value
Purchase	Common Stock	38,991	$71.5961	$2.79M
Purchase	Common Stock	73,185	$72.5238	$5.31M
Purchase	Common Stock	45,103	$72.2854	$3.26M
Purchase	Common Stock	100,897	$73.198	$7.39M

Holdings After Transaction: Common Stock — 58,707,265 shares (Direct)

Footnotes (1)

1. The purchases reported on this Form 4 were effected pursuant to a Rule 10b5-1 purchase plan, adopted October 3, 2025. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $71.72 to $72.69. 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. 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. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $72.71 to $73.415. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $71.1095 to $71.9984. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $72.00 to $72.725.

Form 4 Insider Transactions: What Each Field Means →

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)
03/02/2026

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	03/02/2026		P(1)		45,103	A	$72.2854(2)	58,567,377	D(3)
Common Stock	03/02/2026		P(1)		100,897	A	$73.198(4)	58,668,274	D(3)
Common Stock	03/03/2026		P(1)		38,991	A	$71.5961(5)	58,707,265	D(3)
Common Stock	03/03/2026		P(1)		73,185	A	$72.5238(6)	58,780,450	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 $71.72 to $72.69. 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 $72.71 to $73.415.

5. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $71.1095 to $71.9984.

6. The price reported is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $72.00 to $72.725.

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	03/03/2026
	MS&AD INSURANCE GROUP HOLDINGS, INC., By: /s/ Hironori Morimoto, Name: Hironori Morimoto, Title: Authorized Signatory	03/03/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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FAQ

What insider transactions did Mitsui Sumitomo report for W. R. Berkley (WRB)?

Mitsui Sumitomo Insurance Co., Ltd. reported four open-market purchases of W. R. Berkley common stock, totaling 258,176 shares. These trades occurred on March 2–3, 2026 at weighted average prices of roughly $71–$73 per share, increasing its direct shareholdings.

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

After the reported purchases, Mitsui Sumitomo Insurance Co., Ltd. held up to 58,780,450 W. R. Berkley common shares. This figure reflects the total shares following the final transaction recorded on March 3, 2026, as disclosed in the insider ownership table.

Were the W. R. Berkley (WRB) insider purchases made under a trading plan?

Yes. The purchases were effected under a Rule 10b5-1 purchase plan adopted on October 3, 2025. Such pre-arranged trading plans allow large shareholders to systematically buy or sell shares according to preset instructions, helping separate transactions from day-to-day market decisions.

What prices were paid for the W. R. Berkley (WRB) shares in these insider trades?

The filing reports weighted average prices for each trade block, with underlying transactions executed in ranges such as $71.1095–$71.9984, $71.72–$72.69, $72.00–$72.725, and $72.71–$73.415. Full breakdowns by exact price are available on request from the parties listed.

Who is considered the beneficial owner of these W. R. Berkley (WRB) shares?

The shares are held directly by Mitsui Sumitomo Insurance Co., Ltd.. Its parent, MS&AD Insurance Group Holdings, Inc., may be deemed to beneficially own the reported securities but expressly disclaims beneficial ownership except to the extent of its pecuniary interest, according to the disclosure.

Are these W. R. Berkley (WRB) insider purchases part of routine trading activity?

The transactions were executed pursuant to a pre-established Rule 10b5-1 plan, suggesting a systematic, pre-planned buying program. Such plans are commonly used by significant shareholders to conduct trading on a scheduled basis rather than through ad hoc, discretionary purchases.