Form 4: Mitsui Sumitomo Boosts W.R. Berkley Stake via 10b5-1 Plan

Mitsui Sumitomo Insurance Co. Ltd., a 10% owner, acquired 535,000 shares of W.R. Berkley Corporation common stock through a Rule 10b5-1 plan.

Summary

• Mitsui Sumitomo Insurance Co. Ltd. (MSI), a 10% owner of W.R. Berkley Corporation (WRB), purchased a total of 535,000 shares of common stock over two days.
• These purchases were executed pursuant to a Rule 10b5-1 purchase plan, which was adopted on October 3, 2025.
• On January 15, 2026, MSI acquired 166,907 shares at a weighted average price of $68.675 and an additional 68,093 shares at a weighted average price of $69.4472.
• On January 16, 2026, MSI acquired 241,309 shares at a weighted average price of $68.031 and another 58,691 shares at a weighted average price of $68.7857.
• Following these transactions, MSI directly holds 53,261,504 shares of W.R. Berkley Corporation common stock.
• MS&AD Insurance Group Holdings, Inc., as the wholly-owned parent of MSI, may be deemed to beneficially own these securities but expressly disclaims beneficial ownership except to the extent of its pecuniary interest.

Sentiment

Score: 8

Explanation: The significant increase in ownership by a major institutional investor (10% owner) through a pre-planned acquisition strategy indicates strong confidence in the company's value and future performance, which is a positive signal for the market.

Positives

• A significant 10% owner, Mitsui Sumitomo Insurance Co. Ltd., is increasing its stake in W.R. Berkley Corporation, signaling confidence in the company's future prospects.
• The purchases were made through a pre-arranged Rule 10b5-1 plan, indicating a systematic investment strategy rather than a reactive trade.

Future Outlook

The execution of transactions under a Rule 10b5-1 plan suggests a pre-determined strategy for acquiring shares, indicating a long-term investment perspective from the reporting persons.

Management Comments

• Hironori Morimoto, Authorized Signatory for Mitsui Sumitomo Insurance Co., LTD. and MS&AD Insurance Group Holdings, Inc., signed the filing.

Industry Context

The continued investment by major Japanese insurance groups, Mitsui Sumitomo and MS&AD, into W.R. Berkley, a prominent U.S. property and casualty insurer, highlights potential strategic alignment or confidence in the global insurance sector's stability and growth prospects.

Related Party Transactions

• Mitsui Sumitomo Insurance Co., Ltd., W.R. Berkley Corporation, and WR Berkley & Others LLC (WRBO) are party to certain agreements described in the Reporting Persons' Schedule 13D filed on December 11, 2025. The reporting persons disclaim beneficial ownership of securities owned by WRBO and disclaim that they and WRBO constitute a 'group' under Rule 13d-5(b)(1).

Stakeholder Impact

• Shareholders may view the increased stake by a major institutional investor as a positive indicator of the company's long-term value and stability.
• The systematic nature of the purchases via a 10b5-1 plan suggests a considered investment strategy, potentially reassuring to other investors.

Key Dates

Recommendation

A major 10% institutional owner, Mitsui Sumitomo Insurance, has significantly increased its stake in W.R. Berkley Corporation by acquiring 535,000 shares through a pre-arranged 10b5-1 plan. This substantial investment signals strong confidence in the company's valuation and future prospects from a sophisticated investor, making it a compelling 'buy' signal for other investors.

Keywords

W.R. Berkley Corporation, WRB, Mitsui Sumitomo Insurance, MS&AD Insurance Group Holdings, SEC Form 4, Insider Trading, Stock Purchase, 10b5-1 Plan, Beneficial Ownership, Insurance