Form 4: Mitsui Sumitomo Boosts WRB Stake via 10b5-1 Plan

Mitsui Sumitomo Insurance Co. Ltd., a 10% owner of W.R. Berkley Corp., acquired additional common stock through a Rule 10b5-1 plan in December 2025.

Summary

• Mitsui Sumitomo Insurance Co. Ltd. (MSI), a 10% owner of W.R. Berkley Corp. (WRB), acquired a total of 610,350 shares of WRB common stock across four separate transactions in December 2025.
• The acquisitions occurred on December 18, 2025 (204,350 shares at a weighted average price of $69.3815), December 19, 2025 (204,000 shares at a weighted average price of $69.503), and December 22, 2025 (39,940 shares at a weighted average price of $69.9716 and 162,060 shares at a weighted average price of $70.3257).
• These purchases were executed under a pre-arranged Rule 10b5-1 purchase plan adopted on October 3, 2025.
• Following these transactions, MSI's direct beneficial ownership of WRB common stock increased to 49,211,938 shares.
• MS&AD Insurance Group Holdings, Inc., the parent company of MSI, may be deemed to beneficially own these securities but expressly disclaims beneficial ownership except for its pecuniary interest.

Sentiment

Score: 7

Explanation: The acquisition of additional shares by a significant 10% owner, Mitsui Sumitomo Insurance Co. Ltd., through a pre-planned Rule 10b5-1 program, indicates continued confidence in W.R. Berkley Corp. This insider buying activity is generally viewed positively by the market.

Positives

• A significant 10% owner, Mitsui Sumitomo Insurance Co. Ltd., increased its stake in W.R. Berkley Corp. by acquiring 610,350 additional common shares.
• The acquisitions were conducted through a Rule 10b5-1 purchase plan, indicating a pre-meditated and structured investment strategy rather than opportunistic trading.
• The increased beneficial ownership by a major institutional investor signals continued confidence in W.R. Berkley Corp.'s future prospects.

Future Outlook

This Form 4 filing reports past transactions and does not contain explicit forward-looking statements or guidance from W.R. Berkley Corp. or the reporting persons regarding future performance or strategy.

Management Comments

• MS&AD Insurance Group Holdings, Inc. expressly disclaims beneficial ownership of the reported securities, except to the extent of its pecuniary interest therein.
• 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.

Industry Context

A 10% owner in the insurance sector increasing its stake in another insurance company (W.R. Berkley) through a pre-planned program could signal confidence in the sector's stability or the specific company's strategic direction and financial health. This type of insider buying by a significant institutional investor is a common activity for strategic partners or large institutional holders within the financial services industry.

Related Party Transactions

• Reference to certain agreements between Mitsui Sumitomo Insurance Co. Ltd., W.R. Berkley Corp., and WR Berkley & Others LLC (WRBO) described in the Reporting Persons' Schedule 13D filed with the U.S. Securities and Exchange Commission on December 11, 2025.

Stakeholder Impact

• Shareholders: May view the increased stake by a significant institutional investor as a positive signal, potentially boosting confidence in the company's stock.
• Company: Indicates strong alignment and continued support from a major strategic investor.

Key Dates

Recommendation

The significant acquisition of shares by a 10% owner, Mitsui Sumitomo Insurance Co. Ltd., through a Rule 10b5-1 plan signals confidence in W.R. Berkley Corp. This insider buying activity is generally a positive indicator. However, a Form 4 filing primarily reports transactions and does not provide comprehensive financial or operational details to warrant a 'buy' or 'sell' recommendation without further fundamental analysis. Investors should 'hold' and consider this information alongside broader market conditions and the company's financial performance.

Keywords

W.R. Berkley Corp, WRB, Mitsui Sumitomo Insurance, MS&AD Insurance Group Holdings, Insider Trading, Form 4, Stock Acquisition, 10b5-1 Plan, Insurance, Financial Services