43 institutions reported holding $22.8M of SERES THERAPEUTICS INC (MCRB) in SEC 13F filings for 2026-03-31. Largest institutional holders: Flagship Pioneering Inc. ($10.3M), VANGUARD CAPITAL MANAGEMENT LLC ($2.6M), SUSQUEHANNA INTERNATIONAL GROUP, LLP ($2.0M), MARSHALL WACE, LLP ($1.2M), Vontobel Holding Ltd. ($1.2M). Source: SEC Form 13F.
| Rank | Institution | Value | Shares | Change |
|---|---|---|---|---|
| 1 | Flagship Pioneering Inc. | $10.3M | 1.2M | Hold |
| 2 | VANGUARD CAPITAL MANAGEMENT LLC | $2.6M | 294,143 | New |
| 3 | SUSQUEHANNA INTERNATIONAL GROUP, LLP | $2.0M | 226,939 | Trimmed |
| 4 | MARSHALL WACE, LLP | $1.2M | 139,539 | Added |
| 5 | Vontobel Holding Ltd. | $1.2M | 138,468 | Added |
| 6 | BlackRock, Inc. | $904,970 | 102,026 | Trimmed |
| 7 | GEODE CAPITAL MANAGEMENT, LLC | $664,108 | 74,835 | Trimmed |
| 8 | AMERICAN CENTURY COMPANIES INC | $552,743 | 62,316 | Added |
| 9 | CITADEL ADVISORS LLC | $527,765 | 59,500 | Trimmed |
| 10 | GROUP ONE TRADING LLC | $501,368 | 56,524 | Trimmed |
| 11 | VANGUARD FIDUCIARY TRUST CO | $351,633 | 39,643 | New |
| 12 | STATE STREET CORP | $300,702 | 33,901 | Hold |
| 13 | CHARLES SCHWAB INVESTMENT MANAGEMENT INC | $280,558 | 31,630 | Added |
| 14 | Lion Point Capital, LP | $280,026 | 31,570 | Hold |
| 15 | SIMPLEX TRADING, LLC | $232,127 | 26,170 | Trimmed |
| 16 | MORGAN STANLEY | $192,478 | 21,700 | Trimmed |
| 17 | TWO SIGMA INVESTMENTS, LP | $166,703 | 18,794 | Trimmed |
| 18 | NORTHERN TRUST CORP | $130,966 | 14,765 | Hold |
| 19 | Invesco Ltd. | $129,032 | 14,547 | Added |
| 20 | UBS Group AG | $62,357 | 7,030 | Added |
| 21 | BARCLAYS PLC | $57,717 | 6,507 | Trimmed |
| 22 | SBI Securities Co., Ltd. | $30,885 | 3,482 | Hold |
| 23 | Vanguard Global Advisers, LLC | $17,518 | 1,975 | New |
| 24 | FMR LLC | $15,540 | 1,752 | Added |
| 25 | Rachor Investment Advisory Services, LLC | $13,101 | 1,477 | Hold |
Source: SEC Form 13F filings · as of 2026-03-31