Seres Therapeutics, Inc. (MCRB) Ownership
MCRB ownership summary
as of October 18, 2026- Institutions
- 22.8% of shares outstanding
- Insiders
- 11.49% of shares outstanding
- Shares outstanding
- 10.0M
- Float
- 8.7M shares available to trade
- Short interest
- 4.05% 314K shares short
- Days to cover
- 5.53 short interest up 4.3% vs prior month
- Institutions 22.84%
- Insiders 11.49%
- Other investors 65.67%
MCRB top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Flagship Ventures Management, Inc. | 11.51% | 1.2M | $2.8M | — | June 30, 2026 |
| 2 | Vanguard Capital Management, LLC | 2.86% | 288K | $707,929 | −6,367 (−2.2%) | June 30, 2026 |
| 3 | Marshall Wace Asset Management Ltd | 1.71% | 172K | $423,723 | +32,706 (+23.4%) | June 30, 2026 |
| 4 | Vontobel Holding Ltd. | 1.22% | 123K | $302,518 | −15,493 (−11.2%) | June 30, 2026 |
| 5 | BlackRock Inc | 1.11% | 111K | $273,060 | +8,974 (+8.8%) | June 30, 2026 |
| 6 | Geode Capital Management, LLC | 0.80% | 80K | $196,736 | +5,139 (+6.9%) | June 30, 2026 |
| 7 | Susquehanna International Group, LLP | 0.58% | 58K | $143,487 | −47,011 (−44.6%) | June 30, 2026 |
| 8 | Vanguard Fiduciary Trust Co | 0.48% | 49K | $119,765 | +9,042 (+22.8%) | June 30, 2026 |
| 9 | State Street Corp | 0.34% | 34K | $83,396 | — | June 30, 2026 |
| 10 | Lion Point Capital, LP | 0.31% | 32K | $77,662 | — | June 30, 2026 |
| 11 | Charles Schwab Investment Management Inc | 0.31% | 31K | $76,381 | −581 (−1.8%) | June 30, 2026 |
| 12 | American Century Companies Inc | 0.28% | 28K | $69,650 | −34,003 (−54.6%) | June 30, 2026 |
| 13 | XTX Topco Ltd | 0.21% | 21K | $51,001 | +20,732 (0.0%) | June 30, 2026 |
| 14 | The Goldman Sachs Group Inc | 0.15% | 15K | $37,463 | +15,229 (0.0%) | June 30, 2026 |
| 15 | Northern Trust Corp | 0.15% | 15K | $36,322 | — | June 30, 2026 |
| 16 | Amvescap Plc. | 0.13% | 13K | $31,916 | −1,573 (−10.8%) | June 30, 2026 |
| 17 | Morgan Stanley - Brokerage Accounts | 0.12% | 12K | $29,859 | −9,562 (−44.1%) | June 30, 2026 |
| 18 | Citadel Advisors Llc | 0.10% | 11K | $25,840 | +10,504 (0.0%) | June 30, 2026 |
| 19 | SIMPLEX TRADING, LLC | 0.05% | 4,598 | $11,311 | +1,528 (+49.8%) | June 30, 2026 |
| 20 | SBI Securities Co Ltd | 0.04% | 4,182 | $10,288 | +700 (+20.1%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 9 holders added 105K shares and 7 cut 115K.
MCRB top mutual fund and ETF holders
16 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Vanguard MStar Total Stk Mkt Idx Invest | 2.05% | 206K | $507,178 | — | August 31, 2026 |
| 2 | Fidelity Extended Market Index | 0.39% | 40K | $97,187 | +2,877 (+7.9%) | August 31, 2026 |
| 3 | Abante Quant Value FI | 0.25% | 25K | $60,607 | +11,505 (+87.6%) | August 31, 2026 |
| 4 | iShares Micro-Cap ETF | 0.24% | 24K | $59,581 | −167 (−0.7%) | September 30, 2026 |
| 5 | Fidelity Total Market Index | 0.14% | 14K | $34,120 | — | August 31, 2026 |
| 6 | Invesco RAFI US 1500 Small-Mid ETF | 0.13% | 13K | $31,778 | — | September 30, 2026 |
| 7 | Fidelity Series Total Market Index | 0.10% | 10K | $24,952 | — | August 31, 2026 |
| 8 | Goldman Sachs Absolute Ret Trckr Instl | 0.10% | 10K | $24,760 | +7,533 (+297.5%) | June 30, 2026 |
| 9 | EA Bridgeway Ultra-Small Company Mkt ETF | 0.07% | 7,398 | $18,199 | — | September 30, 2026 |
| 10 | Vanguard Balanced Index Inv | 0.04% | 4,386 | $10,790 | — | August 31, 2026 |
| 11 | Vanguard U.S. Eq Idx £ Acc | 0.02% | 1,975 | $4,858 | — | August 31, 2026 |
| 12 | 1290 VT Micro Cap K | 0.02% | 1,689 | $4,155 | — | August 31, 2026 |
| 13 | Pacific Select Large-Cap Growth I | 0.01% | 1,430 | $3,518 | — | September 30, 2026 |
| 14 | WisdomTree US SmallCap Earnings ETF | 0.01% | 1,274 | $3,134 | — | September 30, 2026 |
| 15 | Avantis® U.S. Small Cap Value Instl | 0.01% | 1,176 | $2,893 | — | August 31, 2026 |
| 16 | Avantis US Small Cap Equity ETF | 0.01% | 1,003 | $2,467 | — | September 30, 2026 |
Funds report holdings monthly or quarterly; dates differ by fund.
MCRB insider transactions
latest 3| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2025-11-15 | Eric D Shaff | Sell | $17.30 | 217 | $3,754 |
| 2025-11-15 | Matthew R Henn | Sell | $17.30 | 1,257 | $21,746 |
| 2025-11-15 | Thomas Desrosier | Sell | $17.30 | 76 | $1,315 |
Reported trades by company officers, directors and other filers (including disclosures by members of Congress where EODHD lists them). "—" where the filing gives no share count.
MCRB shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns MCRB
Institutional investors own 22.8% of Seres Therapeutics's shares and insiders 11.49%. The largest holder is Flagship Ventures Management, Inc. with 11.51% of the shares (1.2M), as of June 30, 2026. Among the top 20 institutions, 9 added shares and 7 reduced their stake in the latest filings. Short interest is 4.05% of the float, or 5.53 days of average trading volume. The share count rose 422.0% since 2014.
Related: MCRB analyst forecast, MCRB key metrics. See the MCRB stock overview for the latest quote and news.
MCRB ownership FAQ
Who owns the most Seres Therapeutics stock?
The largest shareholders of Seres Therapeutics are Flagship Ventures Management, Inc. (11.51%), Vanguard Capital Management, LLC (2.86%), Marshall Wace Asset Management Ltd (1.71%), Vontobel Holding Ltd. (1.22%), BlackRock Inc (1.11%).
What percentage of Seres Therapeutics is owned by institutions?
Institutions hold 22.8% of Seres Therapeutics's shares outstanding; insiders hold 11.49%.
Which funds own Seres Therapeutics?
The largest fund holders of Seres Therapeutics are Vanguard MStar Total Stk Mkt Idx Invest (2.05%), Fidelity Extended Market Index (0.39%), Abante Quant Value FI (0.25%), iShares Micro-Cap ETF (0.24%), Fidelity Total Market Index (0.14%).
What is Seres Therapeutics's short interest?
314K shares of Seres Therapeutics were sold short, 4.05% of the float; at the average daily volume it would take 5.53 days to cover.
Are insiders buying or selling Seres Therapeutics?
Of the latest 3 reported insider transactions in Seres Therapeutics (since November 15, 2025), 0 were purchases and 3 were sales.
How many shares of Seres Therapeutics are outstanding?
Seres Therapeutics has 10.0M shares outstanding, of which 8.7M are in the public float.