Ranked by reported Q2 2026 13F market value
Share of total reported institutional value in MCRB held by the largest 10 / 25 filers.
| # | Institution | Shares Held | Market Value | QoQ Change | Ownership % | % of Fund |
|---|---|---|---|---|---|---|
| 1 | Flagship Pioneering, LLC | 1.2M | $9.1M | 0.0% | 11.936% | 0.59% |
| 2 | VANGUARD CAPITAL MANAGEMENT LLC | 288K | $2.3M | -2.2% | 2.972% | 0.00% |
| 3 | MARSHALL WACE, LLP | 172K | $1.4M | +23.4% | 1.779% | 0.00% |
| 4 | SUSQUEHANNA INTERNATIONAL GROUP, LLP | 133K | $1.1M | -41.3% | 1.376% | 0.00% |
| 5 | Vontobel Holding Ltd. | 123K | $970K | -11.2% | 1.270% | 0.00% |
| 6 | BlackRock, Inc. | 111K | $876K | +8.8% | 1.146% | 0.00% |
| 7 | GEODE CAPITAL MANAGEMENT, LLC | 80K | $631K | +6.9% | 0.826% | 0.00% |
| 8 | CITADEL ADVISORS LLC | 54K | $426K | -9.2% | 0.558% | 0.00% |
| 9 | VANGUARD FIDUCIARY TRUST CO | 49K | $384K | +22.8% | 0.503% | 0.00% |
| 10 | STATE STREET CORP | 34K | $267K | 0.0% | 0.350% | 0.00% |
| 11 | Lion Point Capital, LP | 32K | $249K | 0.0% | 0.326% | 1.19% |
| 12 | CHARLES SCHWAB INVESTMENT MANAGEMENT INC | 31K | $245K | -1.8% | 0.321% | 0.00% |
| 13 | AMERICAN CENTURY COMPANIES INC | 28K | $223K | -54.6% | 0.292% | 0.00% |
| 14 | XTX Topco Ltd | 21K | $164K | — | 0.214% | 0.00% |
| 15 | GOLDMAN SACHS GROUP INC | 15K | $120K | — | 0.157% | 0.00% |
| 16 | NORTHERN TRUST CORP | 15K | $116K | 0.0% | 0.152% | 0.00% |
| 17 | Invesco Ltd. | 13K | $102K | -10.8% | 0.134% | 0.00% |
| 18 | MORGAN STANLEY | 12K | $96K | -44.1% | 0.125% | 0.00% |
| 19 | RAFFA WEALTH MANAGEMENT, LLC | 2 | $49K | — | 0.000% | 0.00% |
| 20 | SIMPLEX TRADING, LLC | 5K | $36K | +49.8% | 0.048% | 0.00% |
| 21 | SBI Securities Co., Ltd. | 4K | $33K | +20.1% | 0.043% | 0.00% |
| 22 | GROUP ONE TRADING LLC | 4K | $29K | +350.7% | 0.038% | 0.00% |
| 23 | JPMORGAN CHASE & CO | 4K | $28K | — | 0.037% | 0.00% |
| 24 | Vanguard Global Advisers, LLC | 2K | $16K | 0.0% | 0.020% | 0.00% |
| 25 | FMR LLC | 2K | $12K | -12.8% | 0.016% | 0.00% |
denotes a marquee investor (Buffett, Burry, ARK, Tiger Global, Pershing Square, Baupost and other widely-followed managers). “% of Fund” shows how much of that investor’s total 13F portfolio is invested in MCRB — a direct measure of their conviction.
Filings activity in MCRB during Q2 2026, grouped by how each filer changed its position.
8 quarters of 13F filings · Δ columns show change vs prior quarter
| Quarter | Inst. Holders | Δ Holders | Ownership % | Δ Ownership | Total 13F Value | Δ Value |
|---|---|---|---|---|---|---|
| Q2 2026 | 36 | +2.9% | 24.67% | 2.71 pp | $19M | 15% |
| Q1 2026 | 35 | 7.9% | 27.38% | 1.74 pp | $22M | 46% |
| Q4 2025 | 38 | 2.6% | 29.12% | 6.37 pp | $41M | 28% |
| Q3 2025 | 39 | +18% | 35.49% | +7.84 pp | $57M | +115% |
| Q2 2025 | 33 | 48% | 27.65% | 8.11 pp | $27M | 38% |
| Q1 2025 | 64 | 7.2% | 35.76% | 2.83 pp | $43M | 21% |
| Q4 2024 | 69 | 10% | 38.59% | 161.40 pp | $55M | 82% |
| Q3 2024 | 77 | — | 199.99% | — | $296M | — |
Source: SEC 13F institutional filings. Ownership % requires market cap data and will show once linked. Δ columns compare to the immediately prior filed quarter.
Quick answers to the most common questions about buying MCRB stock.
Based on Q2 2026 13F filings, institutional ownership of Seres Therapeutics, Inc. stands at 24.7%, held across 36 reporting institutions.
Flagship Pioneering, LLC is the largest reported institutional holder of MCRB, with approximately 1,155,850 shares worth $0.01B as of Q2 2026.
Yes — 2 widely-followed marquee investors appear among the top 25 institutional holders of MCRB, including SUSQUEHANNA INTERNATIONAL GROUP, LLP, CITADEL ADVISORS LLC.
Our composite Smart Money Score for MCRB is 45 out of 100 (Neutral). It combines net institutional buying activity, ownership shift, marquee investor presence, and holder-count growth.
6 institutions opened new positions in MCRB during Q2 2026, while 6 fully exited. 5 added to existing positions and 23 trimmed.
MCRB institutional ownership fell by 2.71 percentage points quarter-over-quarter, with a net change of +1 holders.
The top 10 institutions account for 91.8% of all reported 13F value in MCRB, and the top 25 account for 99.9%.
All data is sourced from SEC Form 13F filings, which institutional investment managers with at least $100M in assets are required to file each quarter. We process every 13F filing from EDGAR and recompute the aggregates after each cycle. Insider transactions are sourced from Form 4 filings.
Seres Therapeutics, Inc. (MCRB) Institutional Ownership