Atlas Venture Fund X, L.P.
CIK 1628098 · last filed 2024-01-25
"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.
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Disclosed Exposure
$836.70M
Companies
6
Total Filings
65
Lifetime Open-Market Net
-$46.33M
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 |
|---|---|---|---|---|---|---|---|
| IRON | 10%+ Owner | 2,105,846 | $81.21 | $171.02M | -$91.33M | 1 | 2024-01-25 |
| Generation Bio Co. (GBIO) Delisted | 10%+ Owner | 827,888 | $5.34 | $4.42M | $0 | 4 | 2021-09-21 |
| KYMR | 10%+ Owner | 5,763,012 | $109.62 | $631.74M | $0 | 2 | 2021-05-18 |
| Dianthus Therapeutics, Inc. /DE/ (MGTA) Delisted | 10%+ Owner | 196,775 | $11.19 | $2.20M | $0 | 2 | 2021-02-16 |
| REPL | 10%+ Owner | 2,486,296 | $13.65 | $33.94M | $0 | 4 | 2020-09-17 |
| Tectonic Therapeutic, Inc. (AVRO) Delisted | 10%+ Owner | 396,373 | $16.80 | $6.66M | $45.00M | 2 | 2019-07-29 |
Recent Filings · Page 2 of 7
65 filingsInsider 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 |
|---|---|---|---|---|---|
| 2026-03-02 | KYMR | Notice (144) | −200,000 | -$18.27M | EDGAR |
| 2025-12-17 | IRON | Notice (144) | −818 | -$74.8K | EDGAR |
| 2025-12-16 | IRON | Notice (144) | −22,666 | -$2.09M | EDGAR |
| 2025-12-16 | IRON | Notice (144) | −52,000 | -$4.76M | EDGAR |
| 2025-12-15 | IRON | Notice (144) | −32,035 | -$2.94M | EDGAR |
| 2025-12-15 | IRON | Notice (144) | −36,877 | -$3.39M | EDGAR |
| 2025-12-12 | IRON | Notice (144) | −49,299 | -$4.61M | EDGAR |
| 2025-12-12 | KYMR | Notice (144) | −570 | -$51.1K | EDGAR |
| 2025-12-11 | KYMR | Notice (144) | −5,125 | -$450.0K | EDGAR |
| 2025-12-10 | KYMR | Notice (144) | −193,040 | -$17.35M | EDGAR |
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.
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.