Flagship Pioneering, LLC holds a concentrated book of 5 reported positions worth $1.5B as of Q2 2026 (disclosed Aug 14, 2026, a ~45-day 13F lag). Their largest long position is Generate Biomedicines Inc at 69% of the reported non-option book. Cloning the disclosed picks since 2025 would be +53% (+47.8%/yr). That is a simulation of the disclosed long book, not audited returns.
The reported book (valued from quarter-end) returned +104.2%, a 51.6-point gap that is the cost of the ~45-day 13F disclosure lag a real follower can't avoid.
Growth of $10,000 cloning Flagship Pioneering, LLC's disclosed long 13F book, rebalanced on each filing date (so it reflects each quarter's actual reporting lag, ~45 days for the latest filing, with no look-ahead), total-return basis (dividends reinvested), derived from end-of-day prices. “Their reported book” values the same picks from quarter-end, before they were public. S&P 500 is SPY total return over the same window. Excludes shorts, cash, options and non-13F holdings. Not investment advice.
Top-heavy: concentrated book
Excluding Generate Biomedicines Inc (69% of the book), the rest is a concentrated book:
Share of the disclosed book in its largest positions. A higher top-5 share means a more concentrated, higher-conviction portfolio.
100% mapped to company sectors
Direct operating-company sectors from our SIC-based security master. ETF/fund and unclassified holdings stay visible separately; this is not ETF look-through exposure.
Other tracked managers holding the same core names as Flagship Pioneering, LLC
| Manager / fund | Shared names | Their $ in those |
|---|---|---|
| Baillie Gifford & Co | 2 / 5 | $1.0B |
| Virtus Investment Advisers, LLC | 3 / 5 | $2.5M |
| Leonteq Securities AG | 2 / 5 | $15.4M |
| Two Sigma Investments, LP | 3 / 5 | $465.2M |
| Susquehanna Portfolio Strategies, LLC | 2 / 5 | $24.4M |
| Siren, L.L.C. | 2 / 5 | $15.9M |
| China Universal Asset Management Co., Ltd. | 3 / 5 | $4.6M |
| Algert Global LLC | 2 / 5 | $19.8M |
Ranked by the share of each fund's own book sitting in the names it shares with Flagship Pioneering, LLC: only funds sharing at least a tenth of the book qualify. Index giants, bank custody books and market makers are excluded. They hold everything, so their overlap says nothing.
Bars show each position's share of the portfolio. Click a row for its position history.
| # | Security | Value | Shares | % Port | Last move | History |
|---|---|---|---|---|---|---|
| 1 | Generate Biomedicines Inc COM SHS | $1.1B | 62.67M | 68.7% | —Held | |
| 2 | Moderna Inc COM | $324.4M | 4.63M | 21.1% | —Held | |
| 3 | Sana Biotechnology Inc COM | $87.3M | 25.00M | 5.7% | —Held | |
| 4 | Foghorn Therapeutics Inc COM | $61.8M | 12.67M | 4.0% | —Held | |
| 5 | Seres Therapeutics Inc COM NEW | $9.1M | 1.16M | 0.6% | —Held |
This fund page is the Follow view. The Build view lets your agent pull holdings, quarter changes, overlap, and source filings through API or MCP.
curl -H "Authorization: Bearer YOUR_API_KEY" \ "https://arkolith.com/api/v1/funds/1400240/holdings"
Use Arkolith to show Flagship Pioneering, LLC's latest holdings, largest changes, and filing provenance.
As-of date vs the date the SEC received each filing
Reported 13F total per quarter. Raw filing totals can include option notional.
Holdings from SEC EDGAR 13F-HR filings, updated quarterly, filed up to 45 days after quarter-end. Public domain. Book totals and portfolio weights cover reported non-option positions, which can include notes and warrants. Disclosed put/call options are listed separately and excluded from those totals. The performance line is a simulation of the disclosed long book, not an audited return.