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

Mitsui Sumitomo Insurance Co. Ltd. and MS&AD Insurance Group Holdings, Inc. increased their beneficial ownership in W.R. Berkley Corp. through a series of common stock purchases under a Rule 10b5-1 plan.

Summary

• Mitsui Sumitomo Insurance Co. Ltd. (MSI) and its parent, MS&AD Insurance Group Holdings, Inc. (MS&AD), acquired additional common stock in W.R. Berkley Corp. (WRB).
• The purchases were executed under a Rule 10b5-1 purchase plan adopted on October 3, 2025.
• On December 30, 2025, 205,000 shares were acquired at a weighted average price of $70.8284, increasing MSI's beneficial ownership to 50,296,511 shares.
• On December 31, 2025, an additional 230,000 shares were acquired at a weighted average price of $70.2652, bringing the total beneficial ownership to 50,526,511 shares.
• On January 2, 2026, 237,734 shares were acquired at a weighted average price of $69.3477, resulting in a total beneficial ownership of 50,764,245 shares.
• MS&AD disclaims beneficial ownership of the reported securities except to the extent of its pecuniary interest, as MSI is a wholly-owned subsidiary.
• The reporting persons also disclaim beneficial ownership of securities owned by WR Berkley & Others LLC (WRBO) and deny forming a 'group' with WRBO, as detailed in a Schedule 13D filing from December 11, 2025.

Sentiment

Score: 7

Explanation: The filing indicates strong insider confidence through systematic buying by a major institutional shareholder, which is generally a positive signal. The transactions are part of a pre-arranged plan, suggesting a deliberate long-term strategy. No negative information is disclosed.

Positives

• Significant insider buying by a major institutional shareholder (10% owner) indicates confidence in W.R. Berkley Corp.'s future prospects.
• The purchases were made under a pre-arranged Rule 10b5-1 plan, suggesting a systematic investment strategy rather than opportunistic trading.
• The increasing stake by Mitsui Sumitomo and MS&AD reinforces their long-term commitment to W.R. Berkley.

Future Outlook

The filing does not contain explicit forward-looking statements or guidance from W.R. Berkley Corp. It reports past insider transactions executed under a pre-arranged plan.

Management Comments

• The purchases reported on this Form 4 were effected pursuant to a Rule 10b5-1 purchase plan, adopted October 3, 2025.
• 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.
• MS&AD 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

This filing reflects a significant institutional investor's continued accumulation of shares in an insurance company. In the broader financial services and insurance industry, such sustained insider buying by a major shareholder can be interpreted as a positive signal regarding the company's stability and growth prospects, especially given the current economic climate and evolving regulatory landscape for insurers.

Comparison to Industry Standards

• The consistent buying activity by a 10% owner, Mitsui Sumitomo, aligns with strategies seen in other long-term institutional investors who build strategic stakes in companies within their core investment sectors.
• The use of a Rule 10b5-1 plan for these purchases is a standard practice for insiders to execute trades systematically and avoid accusations of trading on material non-public information, a common governance practice across industries.
• While specific comparable companies or projects are not mentioned in the filing, the accumulation of shares by a major insurance group (MS&AD) in another established insurer (W.R. Berkley) suggests a strategic alignment or belief in the target company's market position, similar to how Berkshire Hathaway invests in other financial institutions.

Corporate Governance

Related Party Transactions

• The filing mentions that MSI, W.R. Berkley Corp., and WR Berkley & Others LLC (WRBO) are party to certain agreements described in a Schedule 13D filed on December 11, 2025. While details are not in this Form 4, the reference implies existing relationships and agreements.

Stakeholder Impact

• Shareholders: Increased confidence due to significant insider buying by a major institutional investor, potentially signaling positive long-term prospects for W.R. Berkley Corp.
• Management: The continued investment by a 10% owner could be seen as an endorsement of current management and strategic direction.
• Regulatory Authorities: The filing adheres to SEC disclosure requirements for insider transactions, demonstrating compliance.

Next Steps

• The reporting persons undertake to provide full information regarding the number of shares purchased at each separate price within the reported ranges upon request to W.R. Berkley Corporation, any security holder, or the SEC staff.
• Continued monitoring of future Form 4 filings by Mitsui Sumitomo and MS&AD for further changes in beneficial ownership.

Key Dates

Recommendation

The consistent and significant accumulation of W.R. Berkley Corp. common stock by a major institutional shareholder, Mitsui Sumitomo Insurance Co. Ltd. (a 10% owner), and its parent MS&AD Insurance Group Holdings, Inc., signals strong insider confidence. These purchases, executed under a pre-arranged Rule 10b5-1 plan, suggest a deliberate, long-term investment strategy rather than speculative trading. Such sustained buying by a well-informed entity typically indicates a belief in the company's fundamental value and future growth prospects, making it an attractive signal for investors to consider a 'buy' position.

Keywords

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