Home

Atlas Venture Fund XII, L.P.

CIK 1812049 · last filed 2025-08-07

Atlas Venture Fund XII, L.P. is a corporate insider who has filed 12 SEC Form 4 insider transactions across 2 companies since 2022. The most recent filing, for IRON, was dated Sep 3, 2026. Across all open-market trades the lifetime net is +$44.9M, making them a net buyer over the disclosed history. The firm reports its address in Cambridge, MA. 4 SEC filings were submitted jointly with Atlas Venture Associates Opportunity I, L.P.

"Disclosed insider exposure" sums this person's most-recently-reported share counts across each company they're an insider in, multiplied by the current underlying price. It is not net worth — it misses retail holdings, private investments, real estate, index funds, and any company where the person isn't an SEC-reporting insider. For informational purposes only.

Loading insider history…
Disclosed Exposure

$0

Companies

2

Total Filings

12

Lifetime Open-Market Net

$44.94M

Filer Profile

Reported Address
400 TECHNOLOGY SQUARE
10TH FLOOR
CAMBRIDGE, MA 02139
Phone
(857) 201-2700
State of Incorporation
DE
Related Filers
Atlas Venture Associates Opportunity I, L.P. — 4 joint filings, latest 2025-08-07
Atlas Venture Associates Opportunity I, LLC — 4 joint filings, latest 2025-08-07
Atlas Venture Opportunity Fund I, L.P. — 4 joint filings, latest 2025-08-07
ATLAS VENTURE ASSOCIATES X, L.P. — 1 joint filings, latest 2021-02-11
Atlas Venture Associates X, LLC — 1 joint filings, latest 2021-02-11
Atlas Venture Fund X, L.P. — 1 joint filings, latest 2021-02-11
Atlas Venture Associates XI, L.P. — same reported address
Atlas Venture Associates XI, LLC — same reported address
Profile details as reported on the filer's SEC submissions — for individual insiders the address is often in care of the issuer. Related filers are identified from jointly filed SEC submissions and shared reported addresses. View filings on SEC EDGAR.

Holdings By Company

Latest on-record share count from this person's most recent non-derivative Form 4 transaction in each company. Disclosed exposure = shares × current underlying price.
Symbol Role Shares Price Disclosed Exposure Lifetime OM Net Filings Latest Filed
Jade Biosciences, Inc. (AVTE) Delisted 10%+ Owner 66,512 $93.80 $6.24M $0 2 2022-07-19
Vigil Neuroscience, Inc. (VIGL) Delisted 10%+ Owner 4,808,896 $8.05 $38.71M $44.94M 1 2022-01-11

Recent Filings

12 filings
Insider activity across all companies, newest first. Form 4 rows are post-trade confirmations (buys, sells, grants, exercises). Notice (144) rows are pre-trade notices of intent to sell restricted or control stock under Rule 144 — they may not all execute. Compare adjacent dates to see which notices became actual sales.
Filed Symbol Action Net Shares Net $ Link
2026-09-03 IRON Notice (144) −54 -$4.3K EDGAR
2025-12-17 IRON Notice (144) −148 -$13.5K EDGAR
2025-12-16 IRON Notice (144) −4,359 -$401.0K EDGAR
2025-12-15 IRON Notice (144) −6,160 -$565.8K EDGAR
2025-12-12 IRON Notice (144) −9,481 -$887.4K EDGAR
2025-08-07 — Disp (D) −35,021,244 $0
2025-06-25 JBIO Notice (144) −28,977 -$303.7K EDGAR
2025-06-24 JBIO Notice (144) −16,132 -$159.2K EDGAR
2025-05-06 JBIO Notice (144) −5,883 -$67.7K EDGAR
2022-07-19 Jade Biosciences, Inc. (AVTE) Delisted Other (J) −310,388 $0 EDGAR
Showing 1–10 of 12
Page 1 of 2
Form 4 codes: P = open-market purchase · S = open-market sale · A = grant/award · M = option exercise · F = tax withholding at vest · G = bona-fide gift · D = disposition to issuer · J = other (see filing footnote). Only P / S codes carry directional signal.
Notice (144 / 144/A): Form 144 is a notice of intent to sell restricted/control stock under Rule 144, filed before the sale; 144/A is an amendment. Many notices are pre-scheduled under Rule 10b5-1 plans. A Form 4 with code S typically follows within a few days when the planned sale executes; missing follow-up Form 4s suggest the notice was cancelled or modified.