Insider · CIK 0001628098
Atlas Venture Fund X, L.P.
Files at GBIO (Generation Bio Co.). First filing -, latest -.
Atlas Venture Fund X, L.P. files SEC Form 4 as 10% owner at GBIO (Generation Bio Co.). No open-market trade is on file; the transactions below are grants, exercises and other rows that carry no view on the price.
A track record needs three past buys with six months of prices behind them; Atlas Venture Fund X, L.P. has 0, so none is measured yet.
Signals
This insider’s open-market buys and sells, scored.
Planned sales
Form 144 notices this insider filed before selling restricted or control stock, newest first.
| Filed | Company | Shares | Value | Sale date | Past 3 months |
|---|---|---|---|---|---|
| Mar 2, 2026 | KYMR KYMERA THERAPEUTICS, INC. | 200,000 0.24% of outstanding | $18M | Mar 2, 2026 | none |
| Dec 17, 2025 | IRON Disc Medicine, Inc. | 818 0.00% of outstanding | $75k | Dec 17, 2025 | none |
| Dec 16, 2025 | IRON Disc Medicine, Inc. | 52,000 0.14% of outstanding | $4.8M | Dec 16, 2025 | $41M |
| Dec 16, 2025 | IRON Disc Medicine, Inc. | 22,666 0.06% of outstanding | $2.1M | Dec 16, 2025 | none |
| Dec 15, 2025 | IRON Disc Medicine, Inc. | 36,877 0.10% of outstanding | $3.4M | Dec 15, 2025 | $29M |
| Dec 15, 2025 | IRON Disc Medicine, Inc. | 32,035 0.08% of outstanding | $2.9M | Dec 15, 2025 | none |
| Dec 12, 2025 | KYMR Kymera Therapeutics, Inc. | 570 0.00% of outstanding | $51k | Dec 12, 2025 | $18M |
| Dec 12, 2025 | IRON Disc Medicine, Inc. | 49,299 0.13% of outstanding | $4.6M | Dec 12, 2025 | none |
| Dec 11, 2025 | KYMR Kymera Therapeutics, Inc. | 5,125 0.01% of outstanding | $450k | Dec 11, 2025 | $18M |
| Dec 10, 2025 | KYMR Kymera Therapeutics, Inc. | 193,040 0.24% of outstanding | $17M | Dec 10, 2025 | none |
| Oct 17, 2025 | IRON Disc Medicine, Inc. | 50,000 0.14% of outstanding | $3.7M | Oct 17, 2025 | $25M |
| Oct 16, 2025 | IRON Disc Medicine, Inc. | 1,425 0.00% of outstanding | $110k | Oct 16, 2025 | $25M |
| Oct 15, 2025 | IRON Disc Medicine, Inc. | 22,160 0.06% of outstanding | $1.6M | Oct 15, 2025 | $21M |
| Aug 22, 2025 | IRON Disc Medicine, Inc. | 4,080 0.01% of outstanding | $244k | Aug 22, 2025 | none |
| Aug 14, 2025 | IRON Disc Medicine, Inc. | 12,862 0.04% of outstanding | $786k | Aug 14, 2025 | none |
| Aug 13, 2025 | IRON Disc Medicine, Inc. | 44,520 0.13% of outstanding | $2.6M | Aug 13, 2025 | $8.9M |
| Aug 5, 2025 | IRON Disc Medicine, Inc. | 705 0.00% of outstanding | $42k | Aug 5, 2025 | $8.8M |
| Jul 30, 2025 | IRON Disc Medicine, Inc. | 15,146 0.04% of outstanding | $906k | Jul 30, 2025 | $7.4M |
| Jul 24, 2025 | IRON Disc Medicine, Inc. | 23,245 0.07% of outstanding | $1.4M | Jul 24, 2025 | $5.2M |
| Jul 23, 2025 | IRON Disc Medicine, Inc. | 53,215 0.15% of outstanding | $3.2M | Jul 23, 2025 | $113k |
| Jul 18, 2025 | IRON Disc Medicine, Inc. | 1,184 0.00% of outstanding | $68k | Jul 18, 2025 | none |
| Feb 5, 2025 | IRON Disc Medicine, Inc. | 112,211 0.38% of outstanding | $6.1M | Feb 5, 2025 | $705k |
| Feb 4, 2025 | IRON Disc Medicine, Inc. | 6,350 0.02% of outstanding | $349k | Feb 4, 2025 | $355k |
| Feb 3, 2025 | IRON Disc Medicine, Inc. | 6,439 0.02% of outstanding | $359k | Feb 3, 2025 | none |
Transactions
Every row this insider has filed, 3 in all, newest first.
| Date | Company | Transaction | Shares | Price | Value | Holdings after | Filed |
|---|---|---|---|---|---|---|---|
| Feb 9, 2026 | GBIO Generation Bio Co. | UTender of shares Common Stock | -711,193 | - | - | 0 | Feb 9, 2026 |
| Feb 9, 2026 | GBIO Generation Bio Co. | UTender of shares Common Stockindirect: See footnote | -116,693 | - | - | 0 | Feb 9, 2026 |
| Feb 9, 2026 | GBIO Generation Bio Co. | UTender of shares Common Stockindirect: See footnote | -60 | - | - | 0 | Feb 9, 2026 |
Questions about Atlas Venture Fund X, L.P.
Answered from the filings on this page, as of the latest one.
Is Atlas Venture Fund X, L.P. buying or selling?
Atlas Venture Fund X, L.P. has no open-market buy or sell on SEC Form 4; the filings on record are grants, exercises and other transactions.
How did Atlas Venture Fund X, L.P.'s past buys perform?
Not measured yet. InsiderTell needs three past buys with six months of prices to publish a track record, and Atlas Venture Fund X, L.P. has 0.
Where does Atlas Venture Fund X, L.P. file Form 4?
Atlas Venture Fund X, L.P. has filed Form 4 at GBIO (Generation Bio Co.). A Form 4 is required of officers, directors and holders of more than 10% of a share class within two business days of a trade.
Not investment advice. Scores and forward returns are decision support built from public SEC filings and past prices; they describe what happened after comparable filings, not what will happen after this one. Do your own research and size your risk.