Form 4: Mirum Director Sells 50,000 Shares After Option Exercise

Mirum Pharmaceuticals director Michael G. Grey exercised options for 50,000 shares and immediately sold them for $78 per share.

Summary

• Michael G. Grey, a Director of Mirum Pharmaceuticals, Inc. (MIRM), engaged in an equity transaction on December 19, 2025.
• Grey exercised a stock option to acquire 50,000 shares of common stock at an exercise price of $2.936 per share.
• Immediately following the option exercise, Grey disposed of these 50,000 shares of common stock at a price of $78 per share.
• This transaction was conducted pursuant to a Rule 10b5-1 Plan adopted on August 22, 2025.
• After these transactions, Michael G. Grey directly holds 0 shares of common stock.
• Grey indirectly holds 186,410 shares of common stock through The Grey Family Trust dated November 12, 1999.
• Grey also indirectly holds 93,750 shares of common stock through The Grey 2018 Irrevocable Children's Trust.
• Additionally, Grey directly holds 181,176 stock options following the reported transaction.

Sentiment

Score: 5

Explanation: The transaction is a pre-arranged exercise and sale by a director, which is a personal financial event. While insider selling can sometimes be viewed negatively, the existence of a 10b5-1 plan suggests a planned, rather than reactive, disposition, making the sentiment neutral regarding company performance.

Positives

• The director realized a significant profit by selling shares at $78, substantially higher than the exercise price of $2.936 per share.

Negatives

• A director selling a substantial number of shares, even under a pre-arranged plan, could be perceived negatively by some investors.

Risks

• No specific risks are mentioned in this Form 4 filing, which primarily reports an insider transaction.

Future Outlook

This Form 4 filing reports a past insider transaction and does not contain any forward-looking statements or guidance regarding the company's future outlook.

Industry Context

This filing reports a routine insider transaction (exercise and sell) by a director, which is a common occurrence in publicly traded companies. It does not provide broader industry trends or competitive insights.

Related Party Transactions

• Michael G. Grey indirectly holds common stock through The Grey Family Trust dated November 12, 1999, and The Grey 2018 Irrevocable Children's Trust, which are considered related parties.

Stakeholder Impact

• Shareholders may note the director's sale of shares, although the transaction was pre-planned under a Rule 10b5-1 plan, which typically mitigates concerns about opportunistic selling.

Key Dates

Keywords

Mirum Pharmaceuticals, MIRM, Form 4, Insider Trading, Stock Option Exercise, Share Sale, Director Transaction, Michael G. Grey, Equity Transaction, 10b5-1 Plan