$MCRB

$1.80 -$0.18 (9.09%) Close

$MCRB Overview Financial Statements SEC Filings Executives News Red Flags Capital Raising Ownership Insider Transactions Congressional Trades

Ownership

13F as of Q2 2026 · 9.9M shares outstanding

Who owns MCRB?

By type of holder

Institutions 22.3% Insiders 0.9% Everyone else 76.9%

Concentration Top 10 holders own 20.9%

Flagship Pioneering, LLC 11.6% · Vanguard Capital Management LLC 2.9%

Institutional ownership

22.3%

-0.9 pts vs last qtr

Institutional holders

+1 vs last qtr

Net shares bought

−94.4K

by institutions in Q2 2026

New / sold out

7 / 6

positions opened vs closed

How is ownership changing?

Institutions, last 8 quarters

Biggest buyers in Q2 2026

Marshall Wace, LLP +32.7K
XTX Topco Ltd NEW +20.7K

Biggest sellers in Q2 2026

Susquehanna International Group, LLP SOLD OUT −105.3K
American Century Companies Inc −34.0K

Who is planning to sell?

Notices of proposed sale, last 12 months

$79.3K

2 notices from 1 person

Shares covered

8.7K

0.09% of the company

Arranged in advance

100%

of the value is under a 10b5-1 plan

Under a 10b5-1 plan No plan

Largest proposed sellers

Teresa L Young Officer 10b5-1 $79.3K

Every notice on Red Flags →

A Form 144 is notice of a planned sale, not the sale itself. What insiders actually sold is on Insider Transactions.

Is your stake being diluted?

Diluted share count, FY2023–FY2025

+38.6%

+17.72% a year

Each share's claim on the business

−27.8%

shrank without buying or selling a share

Spent on buybacks vs paid in stock

— vs $65.9M

over 3 fiscal years

Diluted shares, split-adjusted

Buybacks Stock-based comp

How patient are the owners?

Institutional shares by how long they've been held

5+ years80% 3–5 years1% 1–3 years14% Under 1 year5%

Quarterly turnover

6.9%

of institutional shares changed hands

Top 10 managers, median time held

5 years

Super Investors

Investment managers reporting MCRB on Form 13F

Holder	Shares	% of company	Change vs last qtr	Held since	% of their book
FP Flagship Pioneering, LLC	1.2M	11.63%	Unchanged	≤2021	0.6%
Shares held by quarter Peak holding23.1M (Q3'24) Change over 8 quarters−22.0M Share of the company11.630% Flagship Pioneering, LLC's full portfolio →
VC Vanguard Capital Management LLC	287.8K	2.89%	−6.4K (−2.2%)	≤2021	0.0%
Shares held by quarter Peak holding294.1K (Q1'26) Change over 8 quarters+287.8K Share of the company2.890% Vanguard Capital Management LLC's full portfolio →

Flagship Pioneering, LLC

1.2M

% of company

11.63%

Change vs last qtr

Unchanged

Held since

≤2021

Vanguard Capital Management LLC

287.8K

% of company

2.89%

Change vs last qtr

−6.4K (−2.2%)

Held since

≤2021

28 more super investors behind a free account

See every manager holding Seres Therapeutics, Inc., how their position has changed, and how long they've held it.

Institutional Funds

Mutual funds and ETFs reporting MCRB on Form N-PORT; together they hold 5.2% of the company

Fund	Position value	Shares	% of company	% of the fund	As of
VT Vanguard Total Stock Market Index Fund Vanguard Index Funds	$1.63M	206.2K	2.07%	0.00%	June 30, 2026
VE Vanguard Extended Market Index Fund Vanguard Index Funds	$598K	75.8K	0.76%	0.00%	June 30, 2026

Vanguard Total Stock Market Index Fund

Vanguard Index Funds

Position value

$1.63M

% of company

2.07%

% of the fund

0.00%

As of

June 30, 2026

Vanguard Extended Market Index Fund

Vanguard Index Funds

Position value

$598K

% of company

0.76%

% of the fund

0.00%

As of

June 30, 2026

23 more funds behind a free account

See every fund holding Seres Therapeutics, Inc. and how much of the fund the position is.

Insiders and 5%+ holders

From Forms 3/4/5 and Schedules 13D/G

Holder	Shares	% of company	Change vs last qtr	8 quarters	Held since	% of their book
VM von Moltke Lisa Insider	39.9K	0.40%	—	—	—	—
Insider holdings come from Form 3/4/5 filings, which are not quarterly. Share of the company0.400% von Moltke Lisa's insider activity →
SE Shaff Eric D. Insider	12.5K	0.13%	—	—	—	—
Insider holdings come from Form 3/4/5 filings, which are not quarterly. Share of the company0.130% Shaff Eric D.'s insider activity →

von Moltke Lisa

Insider

39.9K

% of company

0.40%

Change vs last qtr

—

Held since

—

Shaff Eric D.

Insider

12.5K

% of company

0.13%

Change vs last qtr

—

Held since

—

4 more holders behind a free account

See every insider and 5%+ holder of Seres Therapeutics, Inc..

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