Seres Therapeutics Inc
Ownership
Ownership Structure
Who owns Seres Therapeutics Inc (MCRB)? This page shows the largest institutions and funds, the ownership structure and the latest insider transactions. 87.0% of the shares are freely tradable; institutional investors hold 24.4%.
Largest Shareholders
Institutions
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| Flagship Ventures Management, Inc. | 11.51 | 1,155,850 | +0.0 | 06/30/2026 |
| Vanguard Capital Management, LLC | 2.86 | 287,776 | -2.2 | 06/30/2026 |
| Marshall Wace Asset Management Ltd | 1.71 | 172,245 | +23.4 | 06/30/2026 |
| Vontobel Holding Ltd. | 1.22 | 122,975 | -11.2 | 06/30/2026 |
| BlackRock Inc | 1.11 | 111,000 | +8.8 | 06/30/2026 |
| Geode Capital Management, LLC | 0.80 | 79,974 | +6.9 | 06/30/2026 |
| Susquehanna International Group, LLP | 0.58 | 58,328 | -44.6 | 06/30/2026 |
| Vanguard Fiduciary Trust Co | 0.48 | 48,685 | +22.8 | 06/30/2026 |
Funds
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| Vanguard MStar Total Stk Mkt Idx Invest | 2.05 | 206,170 | +0.0 | 09/30/2026 |
| Fidelity Extended Market Index | 0.39 | 39,507 | +7.9 | 08/31/2026 |
Largest reported positions according to regulatory filings; stake as a percentage of shares outstanding, change versus the previous filing. Source: fundamentals data.
Insider holdings
| Person | Role | Shares | Value | As of | Type |
|---|---|---|---|---|---|
| Shaff Eric D. | Director | 12,499 | 24,998 $ | Aug 17, 2026 | direct |
| Brady Kelly | See Remarks | 8,679 | 17,358 $ | Aug 17, 2026 | direct |
| DesRosier Thomas | See Remarks | 8,117 | 16,234 $ | Aug 17, 2026 | direct |
| Henn Matthew R | See Remarks | 7,995 | 15,990 $ | Aug 17, 2026 | direct |
Holdings as of each person's most recent SEC Form 4 filing — excluding options and RSUs, which are not shares yet. Holdings may have changed between two filings.
Insiders
Insider Transactions
| Date | Person | Role | Type | Shares | Price | Value |
|---|---|---|---|---|---|---|
| Aug 17, 2026 | Brady Kelly | See Remarks | Sell | 64 | 4.55 | 291 |
| Aug 17, 2026 | Shaff Eric D. | Director | Sell | 263 | 4.55 | 1,197 |
| Aug 17, 2026 | Henn Matthew R | See Remarks | Sell | 81 | 4.55 | 369 |
| Aug 17, 2026 | DesRosier Thomas | See Remarks | Sell | 82 | 4.55 | 373 |
| Aug 15, 2026 | Brady Kelly | See Remarks | Other | 181 | – | – |
| Aug 15, 2026 | Shaff Eric D. | Director | Other | 722 | – | – |
| Aug 15, 2026 | Henn Matthew R | See Remarks | Other | 238 | – | – |
| Aug 15, 2026 | DesRosier Thomas | See Remarks | Other | 245 | – | – |
Reportable transactions by officers and major shareholders from SEC Form 4 filings. "Other" includes things like stock grants and option exercises without a buy/sell character. View all insider transactions →
Data as of: November 3, 2026 · Source: fundamental data & SEC filings (annual and quarterly reports, 10-K/10-Q)
Note: pure fact-based analysis, not investment advice and not a solicitation to buy or sell. All figures without guarantee.