Flagship Pioneering, LLC
Long book
$1.16B
Q1 2026
Positions
5
Top-10 weight
100%
concentration
Last quarter
+40.9%
SPY +14.8%
Turnover
20%
of book per quarter
Strategy in plain words
auto-generated from filingsFlagship Pioneering, LLC is a diversified fundamental manager, specialised in healthcare (100% of the long book), running a $1.16B US long book across 5 positions.
The portfolio is extremely concentrated — the top 10 positions are almost the whole book. Turnover is modest: positions are typically held for years. Current anchor positions: GENERATE BIOMEDICINES INC, MODERNA INC, SANA BIOTECHNOLOGY INC, FOGHORN THERAPEUTICS INC, SERES THERAPEUTICS INC.
Over the last 9 quarters its long book ran on average 5.2pp per quarter behind the S&P 500, beating the index in 5 of 9 quarters. We rate its filings as signal-bearing: position changes reflect genuine views.
Implied long-book return vs S&P 500
methodology: positions priced quarterly, no shorts/options Fund long book S&P 500
Q1 2024
-0.4%
Q2 2024
-29.0%
Q3 2024
-43.8%
Q4 2024
-24.5%
Q1 2025
+13.9%
Q2 2025
+9.0%
Q3 2025
+10.7%
Q4 2025
+16.7%
Q1 2026
+40.9%
Sector allocation
Healthcare 100%
Long book by quarter
What does Flagship Pioneering, own?
Q1 2026 13F| Company | Sector | Shares | Value | % of book | Change |
|---|---|---|---|---|---|
| GENB GENERATE BIOMEDICINES INC | Healthcare | 62.7M | $783.4M | 67.4% | New |
| MRNA MODERNA INC | Healthcare | 4.6M | $235.3M | 20.3% | Held |
| SANA SANA BIOTECHNOLOGY INC | Healthcare | 25.0M | $72.0M | 6.2% | Held |
| FHTX FOGHORN THERAPEUTICS INC | Healthcare | 12.7M | $60.6M | 5.2% | Held |
| MCRB SERES THERAPEUTICS INC | Healthcare | 1.2M | $10.3M | 0.9% | Held |
13F filing history
| Period | Form | Filed | Entries | Reported value | Flags | Source |
|---|---|---|---|---|---|---|
| Q1 2026 | 13F-HR | May 15, 2026 | 7 | $1.16B | canonical | SEC ↗ |
| Q4 2025 | 13F-HR | Feb 17, 2026 | 5 | $324.0M | canonical | SEC ↗ |
| Q3 2025 | 13F-HR | Nov 14, 2025 | 8 | $292.6M | canonical | SEC ↗ |
| Q2 2025 | 13F-HR | Aug 14, 2025 | 8 | $268.5M | canonical | SEC ↗ |
| Q1 2025 | 13F-HR | May 15, 2025 | 8 | $235.8M | canonical | SEC ↗ |
| Q4 2024 | 13F-HR | Feb 14, 2025 | 10 | $334.2M | canonical | SEC ↗ |
| Q3 2024 | 13F-HR | Nov 14, 2024 | 12 | $591.9M | canonical | SEC ↗ |
| Q2 2024 | 13F-HR | Aug 14, 2024 | 12 | $843.4M | canonical | SEC ↗ |
| Q1 2024 | 13F-HR | May 15, 2024 | 13 | $1.52B | canonical | SEC ↗ |