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
$846.13M
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 | $81.30 | $171.19M | -$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 | $110.81 | $638.60M | $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 | $14.62 | $36.34M | $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 3 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 |
|---|---|---|---|---|---|
| 2025-10-17 | IRON | Notice (144) | −50,000 | -$3.72M | EDGAR |
| 2025-10-16 | IRON | Notice (144) | −1,425 | -$109.7K | EDGAR |
| 2025-10-15 | IRON | Notice (144) | −22,160 | -$1.62M | EDGAR |
| 2025-08-22 | IRON | Notice (144) | −4,080 | -$243.8K | EDGAR |
| 2025-08-14 | IRON | Notice (144) | −12,862 | -$785.9K | EDGAR |
| 2025-08-13 | IRON | Notice (144) | −44,520 | -$2.63M | EDGAR |
| 2025-08-05 | IRON | Notice (144) | −705 | -$42.2K | EDGAR |
| 2025-07-30 | IRON | Notice (144) | −15,146 | -$905.7K | EDGAR |
| 2025-07-24 | IRON | Notice (144) | −23,245 | -$1.42M | EDGAR |
| 2025-07-23 | IRON | Notice (144) | −53,215 | -$3.23M | 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.