Form 4: Mirum Director Exercises Options, Sells Shares

Mirum Pharmaceuticals Director Michael G. Grey exercised stock options and sold 50,000 shares of common stock for $70 per share.

Summary

• Director Michael G. Grey exercised 50,000 stock options at an exercise price of $2.936 per share on November 21, 2025.
• Concurrently, he sold 50,000 shares of Mirum Pharmaceuticals, Inc. common stock at a price of $70 per share on November 21, 2025.
• The sale was executed pursuant to a Rule 10b5-1 trading plan adopted on August 22, 2025.
• Following these transactions, Mr. Grey directly owns 0 shares of common stock.
• He indirectly owns 186,410 shares through The Grey Family Trust dated November 12, 1999, and 93,750 shares through The Grey 2018 Irrevocable Children's Trust.
• He also directly holds 281,176 stock options, separate from the exercised options, with an expiration date of March 11, 2029.

Sentiment

Score: 7

Explanation: The transaction shows a director realizing significant value from stock options, indicating strong past stock performance. While an insider sale, it was pre-planned, mitigating negative sentiment. The substantial gain is a positive signal regarding the company's value creation.

Positives

• Director Michael G. Grey realized a significant gain by exercising options at $2.936 and selling shares at $70, indicating a substantial increase in the company's stock value since the options were granted.
• The transaction was conducted under a pre-arranged Rule 10b5-1 plan, which suggests a planned financial move rather than a reaction to immediate company news.

Negatives

• An insider sale, even if pre-planned, reduces the director's direct equity stake, which can sometimes be perceived negatively by the market.

Future Outlook

This filing, a Form 4, is purely transactional and does not contain any forward-looking statements or guidance regarding the company's future performance or outlook.

Industry Context

This insider transaction reflects an individual director's financial planning and the monetization of previously granted equity. It does not directly provide insights into broader industry trends but underscores the value appreciation of Mirum Pharmaceuticals' stock, which can be a positive indicator within the biotechnology or pharmaceutical sector.

Comparison to Industry Standards

• The significant difference between the option exercise price ($2.936) and the sale price ($70) indicates substantial stock appreciation, which is a strong performance metric for Mirum Pharmaceuticals compared to many peers in the biotech industry that may not have achieved similar stock growth.
• The use of a Rule 10b5-1 plan for the sale is a standard practice for insiders to manage their equity holdings while adhering to insider trading regulations, aligning with corporate governance best practices across industries.

Related Party Transactions

• The reporting person, Michael G. Grey, indirectly holds shares through The Grey Family Trust and The Grey 2018 Irrevocable Children's Trust, which are considered related parties.

Stakeholder Impact

• Shareholders: The transaction demonstrates a director monetizing a significant gain, which could be seen as a positive reflection of the stock's performance. However, a sale by an insider, even if pre-planned, might sometimes raise questions about future confidence, though the context of option exercise often mitigates this.

Key Dates

Keywords

Mirum Pharmaceuticals, MIRM, Form 4, Insider Trading, Stock Option Exercise, Share Sale, Director Transaction, Rule 10b5-1