Form 4: Foresite Labs Boosts ALUMIS Stake with $3M Stock Purchases

Foresite Labs, a 10% owner and director of ALUMIS INC., significantly increased its indirect beneficial ownership through multiple common stock purchases in mid-November 2025.

Summary

• Foresite Labs, LLC and Foresite Labs Affiliates 2021, LLC, both 10% owners and directors of ALUMIS INC. (ALMS), reported multiple purchases of common stock.
• Between November 17, 2025, and November 19, 2025, a total of 507,874 shares of common stock were acquired indirectly.
• The purchases occurred at prices ranging from $5.59 to $6.56 per share.
• Specific transactions include: 50,000 shares at $5.60, 150,000 shares at $5.59, 117,374 shares at $6.19, and 190,500 shares at $6.56.
• Following these transactions, Foresite Capital Opportunity Fund V, L.P. (Opportunity Fund V) indirectly beneficially owns 2,542,003 shares.
• The total indirect beneficial ownership across all associated Foresite entities (Opportunity Fund V, Fund VI, Fund V, Labs Co-Invest V, Labs Fund I, and Labs Affiliates 2021, LLC) amounts to 15,703,828 shares of ALUMIS INC. common stock.
• James B. Tananbaum, managing member of several Foresite entities, may be deemed to have sole voting and dispositive power over a significant portion of these shares.

Sentiment

Score: 8

Explanation: The sentiment is highly positive due to significant insider buying by a 10% owner and director. This indicates strong confidence in the company's valuation and future prospects from those with deep knowledge of the business.

Positives

• Significant insider buying by a 10% owner and director signals strong confidence in ALUMIS INC.'s future prospects.
• The purchases occurred over several days, indicating a sustained belief in the company's value.
• The increasing share price during the transaction period (from $5.59 to $6.56) suggests growing market demand or positive sentiment around ALUMIS INC.

Risks

• The reporting persons disclaim the existence of a 'group' as defined in Rule 13d-5 of the Securities Exchange Act of 1934, as amended (the 'Exchange Act').
• Other than the specific funds/LLCs holding the shares, the reporting persons disclaim beneficial ownership of the shares, except to the extent of their pecuniary interest in such securities.

Future Outlook

This filing does not contain forward-looking statements or guidance regarding ALUMIS INC.'s future performance.

Management Comments

• James B. Tananbaum, Manager of Foresite Labs, LLC, signed the filing, indicating his involvement in the transactions and oversight of the reporting entities.

Industry Context

Insider buying, especially by significant shareholders and directors, is often interpreted as a positive signal within the investment community, suggesting that those with intimate knowledge of the company believe its stock is undervalued or poised for growth. This can be particularly impactful in sectors like biotechnology or pharmaceuticals (common for 'Labs' associated companies) where future prospects are heavily tied to R&D success and clinical milestones.

Related Party Transactions

• The reported transactions represent purchases of common stock by Foresite Labs, LLC and Foresite Labs Affiliates 2021, LLC, which are 10% owners and directors of ALUMIS INC., making these related-party transactions.

Stakeholder Impact

• Shareholders may view this insider buying as a strong vote of confidence from a major investor and director, potentially leading to increased investor interest and positive sentiment towards ALUMIS INC. stock.

Key Dates

Recommendation

The substantial insider buying by a 10% owner and director, Foresite Labs, signals a high degree of confidence in ALUMIS INC.'s intrinsic value and future growth trajectory. Such actions by well-informed parties often precede positive developments or reflect a belief that the stock is currently undervalued. This strong signal warrants a 'strong buy' recommendation for investors seeking to align with significant insider conviction.

Keywords

ALUMIS INC., ALMS, Foresite Labs, Insider Buying, Form 4, Beneficial Ownership, Common Stock, Director Purchases, 10% Owner