SCHEDULE: Polaris Venture Partners Amends Alector Stake

Polaris Venture Partners and its affiliates have filed an Amendment No. 6 to their Schedule 13G, disclosing their updated passive beneficial ownership in Alector, Inc. common stock.

Summary

• Polaris Venture Management Co VI, L.L.C. and its affiliated funds (Polaris Venture Partners VI, L.P., Polaris Venture Partners Founders' Fund VI, L.P., Polaris Venture Partners VI (AIV), L.P., and Polaris Venture Partners VI (AIV-B), L.P.) collectively beneficially own 6,853,817 shares of Alector, Inc. common stock, representing 6.3% of the class.
• The individual managing members of Polaris Venture Management Co VI, L.L.C. (David Barrett, Brian Chee, Jonathan A. Flint, Terrance G. McGuire, Amir Nashat, and Bryce Youngren) are deemed to share voting and dispositive power over these 6,853,817 shares.
• Terrance G. McGuire, a former director, holds the largest individual beneficial ownership among the reporting persons, with an aggregate of 7,095,251 shares, representing 6.5% of the class, which includes shares held directly, through a family trust, and restricted stock units.
• The percentages of ownership are primarily based on 109,151,472 shares of Alector, Inc. common stock outstanding as of October 31, 2025, as reported in the Issuer's Form 10-Q.
• This filing is an Amendment No. 6 to the original Schedule 13G filed on February 12, 2020, updating the beneficial ownership information.

Sentiment

Score: 5

Explanation: The filing is a routine disclosure of beneficial ownership by a passive investor group and does not contain information that would significantly alter sentiment towards the company's operational or financial performance.

Positives

• The continued significant beneficial ownership by Polaris Venture Partners, a venture capital firm, may indicate ongoing confidence in Alector, Inc.'s long-term prospects.

Future Outlook

This Schedule 13G filing is a disclosure of beneficial ownership and does not contain any forward-looking statements or guidance regarding Alector, Inc.'s future outlook.

Industry Context

This filing reflects the ongoing investment activity of venture capital firms in publicly traded biotechnology companies like Alector, Inc. Such disclosures are standard for passive investors crossing certain ownership thresholds, providing transparency on significant institutional holdings.

Related Party Transactions

• Terrance G. McGuire, a managing member of Polaris Venture Management Co VI, L.L.C., holds 26,250 restricted stock units granted in his capacity as a former director of Alector, Inc.

Stakeholder Impact

• Shareholders: Provides transparency regarding significant institutional ownership, which can influence market perception and trading activity.

Key Dates

Keywords

Alector Inc., Polaris Venture Partners, Schedule 13G, Beneficial Ownership, Common Stock, Institutional Investor, Passive Investment