RA Capital Nexus Fund III, L.P.
CIK 1883840 · last filed 2026-08-14
RA Capital Nexus Fund III, L.P. is a corporate insider who has filed 14 SEC Form 4 insider transactions across 4 companies since 2023. The most recent filing shows the insider sold $63.5M of SEPN on Aug 14, 2026. Across all open-market trades the lifetime net is −$58.2M, making them a net seller over the disclosed history. Current disclosed insider exposure totals $328.9M across reported positions. The firm reports its address in Boston, MA. 57 SEC filings were submitted jointly with Peter Kolchinsky.
"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.
Charts
Trading activity, where the exposure sits, and each trade against the stock price.
SEPN price and trades
Daily close with each Form 4 filing on this company marked: green = open-market buy, red = open-market sale, purple = grants, exercises, gifts and other non-market transactions. Marker size scales with the dollar value.
Shares held
Shares owned after each reported transaction on this company (direct holdings as reported).
Open-market buying and selling
by monthDollar value of open-market purchases (code P, up) and sales (code S, down) across all companies, by filing month. Grants, exercises and gifts are excluded.
Exposure by company
latestMost recently reported shares × current price. Faded bars (*) have had no filing in 3 years, so the person may no longer hold them. Click a bar to chart that company.
Filer Profile
BOSTON, MA 02116
Holdings By Company
| Symbol | Role | Shares | Price | Disclosed Exposure | Lifetime OM Net | Filings | Latest Filed |
|---|---|---|---|---|---|---|---|
| SEPN | Director | 4,777,415 | $47.88 | $228.74M | -$63.45M | 1 | 2026-08-14 |
| MLYS | Director | 5,456,521 | $17.00 | $92.76M | $20.00M | 3 | 2026-02-20 |
| EVMN | Director | 784,345 | $6.04 | $4.74M | $0 | 1 | 2026-02-17 |
| SION | Director | 715,988 | $3.73 | $2.67M | -$14.76M | 1 | 2025-10-28 |
Recent Filings
14 filings| Filed | Symbol | Action | Net Shares | Net $ | Link |
|---|---|---|---|---|---|
| 2026-08-14 | SEPN | Sell (S) | −1,493,000 | -$63.45M | EDGAR |
| 2026-08-12 | SEPN | Notice (144) | −746,500 | -$35.97M | EDGAR |
| 2026-02-20 | MLYS | Grant (A) | +6,200 | $0 | EDGAR |
| 2026-02-17 | EVMN | Grant (A) | +35,868 | $1000.0K | EDGAR |
| 2025-11-21 | SION | Notice (144) | −6,440 | -$281.2K | EDGAR |
| 2025-11-20 | SION | Notice (144) | −1,313 | -$51.1K | EDGAR |
| 2025-11-19 | SION | Notice (144) | −12,134 | -$466.1K | EDGAR |
| 2025-11-18 | SION | Notice (144) | −1,770 | -$69.1K | EDGAR |
| 2025-11-17 | SION | Notice (144) | −20,969 | -$837.3K | EDGAR |
| 2025-10-28 | SION | Sell (S) | −373,610 | -$14.76M | EDGAR |
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.