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Flagship Pioneering Special Opportunities Fund II, L.P.

CIK 1761283 · last filed 2023-02-27

Flagship Pioneering Special Opportunities Fund II, L.P. is a corporate insider who has filed 2 SEC Form 4 insider transactions across 2 companies since 2020. The most recent filing shows the insider bought $76.8M of OMGA on Feb 27, 2023. Across all open-market trades the lifetime net is +$76.8M, making them a net buyer over the disclosed history. The firm reports its address in Cambridge, MA. 12 SEC filings were submitted jointly with NOUBAR AFEYAN.

"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

$0

Companies

2

Total Filings

2

Lifetime Open-Market Net

$76.83M

Filer Profile

Reported Address
55 CAMBRIDGE PARKWAY
CAMBRIDGE, MA 02142
Phone
(617) 868-1888
State of Incorporation
DE
Related Filers
NOUBAR AFEYAN — 12 joint filings, latest 2026-03-02
Flagship Pioneering Inc. — 10 joint filings, latest 2026-01-15
Flagship Pioneering Special Opportunities Fund II General Partner LLC — 10 joint filings, latest 2026-01-15
Flagship Ventures Fund V General Partner LLC — 6 joint filings, latest 2026-01-15
Flagship Ventures Fund V, L.P. — 6 joint filings, latest 2026-01-15
Flagship Pioneering Fund VI, L.P. — 4 joint filings, latest 2026-03-02
Nutritional Health LTP Fund, L.P. — 4 joint filings, latest 2026-03-02
Flagship Ventures Opportunities Fund I General Partner LLC — 3 joint filings, latest 2026-01-15
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
Omega Therapeutics, Inc. (OMGA) Delisted 10%+ Owner 970,588 $0.14 $138.4K $76.83M 1 2023-02-27
Sigilon Therapeutics, Inc. (SGTX) Delisted 10%+ Owner 683,761 $22.47 $15.36M $0 1 2020-12-10

Recent Filings

2 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
2023-02-27 Omega Therapeutics, Inc. (OMGA) Delisted Buy (P) +13,293,240 $76.83M EDGAR
2020-12-10 Sigilon Therapeutics, Inc. (SGTX) Delisted Conv (C) +62,222,214 $0 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.