$MBX

$52.97 +$2.68 (5.33%) Close

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

Ownership

13F as of Q2 2026 · 48.2M shares outstanding

Who owns MBX?

By type of holder

Institutions 100.0% Insiders 0.0% Everyone else 0.0%

Concentration Top 10 holders own 106.0%

Frazier Life Sciences Management, L.P. 13.8% · FMR LLC 11.1%

Institutional ownership

100.0%

0 pts vs last qtr

Institutional holders

170

+13 vs last qtr

Net shares bought

+2.9M

by institutions in Q2 2026

New / sold out

37 / 24

positions opened vs closed

How is ownership changing?

Institutions, last 8 quarters

Biggest buyers in Q2 2026

Paradigm Biocapital Advisors LP NEW +2.5M
FMR LLC +2.4M

Biggest sellers in Q2 2026

Deep Track Capital, LP −1.0M
Citadel Advisors LLC SOLD OUT −932.8K

Who is planning to sell?

Notices of proposed sale, last 12 months

$7.84M

17 notices from 4 people

Shares covered

210.7K

0.44% of the company

Arranged in advance

34%

of the value is under a 10b5-1 plan

Under a 10b5-1 plan No plan

Largest proposed sellers

Bartram Richard Former officer $3.68M
Azoulay Salomon Officer $2.72M

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, FY2024–FY2025

+243.0%

+243.01% a year

Each share's claim on the business

−70.8%

shrank without buying or selling a share

Spent on buybacks vs paid in stock

— vs $13.9M

over 2 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+ years0% 3–5 years0% 1–3 years80% Under 1 year20%

Quarterly turnover

16.1%

of institutional shares changed hands

Top 10 managers, median time held

1.8 years

Super Investors

Investment managers reporting MBX on Form 13F

Holder	Shares	% of company	Change vs last qtr	Held since	% of their book
FL Frazier Life Sciences Management, L.P.	6.7M	13.81%	Unchanged	2024	8.0%
Shares held by quarter Peak holding6.7M (Q3'25) Change over 8 quarters+666.7K Share of the company13.810% Frazier Life Sciences Management, L.P.'s full portfolio →
F FMR LLC	5.3M	11.05%	+2.4M (+81.3%)	2024	0.0%
Shares held by quarter Peak holding5.3M (Q2'26) Change over 8 quarters+5.3M Share of the company11.050% FMR LLC's full portfolio →

Frazier Life Sciences Management, L.P.

6.7M

% of company

13.81%

Change vs last qtr

Unchanged

Held since

2024

FMR LLC

5.3M

% of company

11.05%

Change vs last qtr

+2.4M (+81.3%)

Held since

2024

28 more super investors behind a free account

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

Institutional Funds

Mutual funds and ETFs reporting MBX on Form N-PORT; together they hold 29.6% of the company

Fund	Position value	Shares	% of company	% of the fund	As of
VT Vanguard Total Stock Market Index Fund Vanguard Index Funds	$62.7M	1.1M	2.36%	0.00%	June 30, 2026
FA Fidelity Advisor Biotechnology Fund Fidelity Advisor Series VII	$53.9M	817.6K	1.70%	2.45%	July 31, 2026

Vanguard Total Stock Market Index Fund

Vanguard Index Funds

Position value

$62.7M

% of company

2.36%

% of the fund

0.00%

As of

June 30, 2026

Fidelity Advisor Biotechnology Fund

Fidelity Advisor Series VII

Position value

$53.9M

% of company

1.70%

% of the fund

2.45%

As of

July 31, 2026

23 more funds behind a free account

See every fund holding MBX Biosciences, 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
PJ Patrick J. Heron 5%+ holder 13D · 11.7%	5.2M	10.89%	—	—	—	—
This holder reports through Schedule 13D/G, not a quarterly 13F. Share of the company10.890% Disclosed stake13D · 11.7% View the 13D/G filing →
JN James N. Topper 5%+ holder 13D · 11.7%	5.2M	10.84%	—	—	—	—
This holder reports through Schedule 13D/G, not a quarterly 13F. Share of the company10.840% Disclosed stake13D · 11.7% View the 13D/G filing →

Patrick J. Heron

5%+ holder13D · 11.7%

5.2M

% of company

10.89%

Change vs last qtr

—

Held since

—

James N. Topper

5%+ holder13D · 11.7%

5.2M

% of company

10.84%

Change vs last qtr

—

Held since

—

34 more holders behind a free account

See every insider and 5%+ holder of MBX Biosciences, Inc..

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