$ABOS

$2.14 -$0.13 (5.73%) Live

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

Ownership

13F as of Q2 2026 · 72.3M shares outstanding

Who owns ABOS?

By type of holder

Institutions 66.0% Insiders 5.4% Everyone else 28.6%

Concentration Top 10 holders own 134.2%

Rajeev Shah 29.2% · Peter Kolchinsky 29.2%

Institutional ownership

66.0%

+2.4 pts vs last qtr

Institutional holders

+11 vs last qtr

Net shares bought

+1.7M

by institutions in Q2 2026

New / sold out

30 / 19

positions opened vs closed

How is ownership changing?

Institutions, last 8 quarters

Biggest buyers in Q2 2026

BlackRock, Inc. +2.3M
Geode Capital Management, LLC +725.6K

Biggest sellers in Q2 2026

FMR LLC −1.1M
SG Americas Securities, LLC SOLD OUT −719.3K

Who is planning to sell?

Notices of proposed sale, last 12 months

$625K

44 notices from 9 people

Shares covered

305.1K

0.42% of the company

Arranged in advance

86%

of the value is under a 10b5-1 plan

Under a 10b5-1 plan No plan

Largest proposed sellers

Meisner Derek M Officer 10b5-1 $249K
OConnell Daniel Joseph Officer 10b5-1 $163K

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, FY2021–FY2025

+201.9%

+31.82% a year

Each share's claim on the business

−66.9%

shrank without buying or selling a share

Spent on buybacks vs paid in stock

— vs $29.6M

over 5 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 years78% 1–3 years18% Under 1 year4%

Quarterly turnover

11.2%

of institutional shares changed hands

Top 10 managers, median time held

4.8 years

Super Investors

Investment managers reporting ABOS on Form 13F

Holder	Shares	% of company	Change vs last qtr	Held since	% of their book
RC Ra Capital Management, L.P. 13D · 29.5%	21.0M	29.02%	Unchanged	2021	0.5%
Shares held by quarter Peak holding21.0M (Q1'26) Change over 8 quarters+6.1M Share of the company29.020% Disclosed stake13D · 29.5% Ra Capital Management, L.P.'s full portfolio →
SC Sands Capital Alternatives, LLC	3.7M	5.14%	Unchanged	2021	1.6%
Shares held by quarter Peak holding3.7M (Q1'26) Change over 8 quarters+303.0K Share of the company5.140% Sands Capital Alternatives, LLC's full portfolio →

Ra Capital Management, L.P.

13D · 29.5%

21.0M

% of company

29.02%

Change vs last qtr

Unchanged

Held since

2021

Sands Capital Alternatives, LLC

3.7M

% of company

5.14%

Change vs last qtr

Unchanged

Held since

2021

28 more super investors behind a free account

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

Institutional Funds

Mutual funds and ETFs reporting ABOS on Form N-PORT; together they hold 10.2% of the company

Fund	Position value	Shares	% of company	% of the fund	As of
SH Select Health Care Portfolio Fidelity Select Portfolios	$3.58M	1.1M	1.58%	0.06%	February 28, 2026
VT Vanguard Total Stock Market Index Fund Vanguard Index Funds	$2.99M	1.1M	1.55%	0.00%	June 30, 2026

Select Health Care Portfolio

Fidelity Select Portfolios

Position value

$3.58M

% of company

1.58%

% of the fund

0.06%

As of

February 28, 2026

Vanguard Total Stock Market Index Fund

Vanguard Index Funds

Position value

$2.99M

% of company

1.55%

% of the fund

0.00%

As of

June 30, 2026

23 more funds behind a free account

See every fund holding Acumen Pharmaceuticals 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
RS Rajeev Shah 5%+ holder 13D · 29.5%	21.1M	29.18%	—	—	—	—
This holder reports through Schedule 13D/G, not a quarterly 13F. Share of the company29.180% Disclosed stake13D · 29.5% View the 13D/G filing →
PK Peter Kolchinsky 5%+ holder 13D · 29.5%	21.1M	29.18%	—	—	—	—
This holder reports through Schedule 13D/G, not a quarterly 13F. Share of the company29.180% Disclosed stake13D · 29.5% View the 13D/G filing →

Rajeev Shah

5%+ holder13D · 29.5%

21.1M

% of company

29.18%

Change vs last qtr

—

Held since

—

Peter Kolchinsky

5%+ holder13D · 29.5%

21.1M

% of company

29.18%

Change vs last qtr

—

Held since

—

15 more holders behind a free account

See every insider and 5%+ holder of Acumen Pharmaceuticals Inc.

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