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Atlas Venture Life Science Advisors, LLC: SION position timeline

Available 13F reports, 13D and 13G stakes and each Form 3, 4 and 5 line of Atlas Venture Life Science Advisors, LLC on SION, newest first. How the timeline and the estimate are built.

Atlas Venture Life Science Advisors, LLC held 2,995,602 SION shares at 2026-06-30 per its 13F-HR filed 2026-08-13.

the latest 13F is the newest step

  1. period ended2026-06-30
    13F 2,995,602 shares
    Change vs previous 13F 0 shares

    14.95% of the 13F portfolio, value $131,776,532.

    13F-HR 0001104659-26-095933 filed by Atlas Venture Life Science Advisors, LLC
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).

  2. period ended2026-03-31
    13F 2,995,602 shares
    Change vs previous 13F 0 shares

    15.2% of the 13F portfolio, value $120,093,684.

    13F-HR 0001104659-26-061232 filed by Atlas Venture Life Science Advisors, LLC
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).

  3. period ended2025-12-31
    13F 2,995,602 shares
    Change vs previous 13F -619,925 shares

    14.24% of the 13F portfolio, value $123,239,066.

    13F-HR 0001104659-26-014463 filed by Atlas Venture Life Science Advisors, LLC
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).

  4. period ended2025-09-30
    13F 3,615,527 shares
    Change vs previous 13F -78,493 shares

    14.13% of the 13F portfolio, value $106,332,649.

    13F-HR 0001104659-25-111321 filed by Atlas Venture Life Science Advisors, LLC
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).

  5. period ended2025-06-30
    13F 3,694,020 shares
    Change vs previous 13F 0 shares

    9.68% of the 13F portfolio, value $64,091,247.

    13F-HR 0001104659-25-076898 filed by Atlas Venture Life Science Advisors, LLC
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).

  6. period ended2025-03-31
    13F 3,694,020 shares
    Change vs previous 13F not available

    7.41% of the 13F portfolio, value $38,639,449.

    13F-HR 0001104659-25-048527 filed by Atlas Venture Life Science Advisors, LLC
    Filed (acceptance time not in the bulk data set), ingested

    Acceptance time not in the bulk data set (spec §4.2).