Acumen Pharmaceuticals, Inc. (ABOS) Ownership
ABOS ownership summary
as of October 18, 2026- Institutions
- 66.5% of shares outstanding
- Insiders
- 6.79% of shares outstanding
- Shares outstanding
- 72.3M
- Float
- 37.0M shares available to trade
- Short interest
- 6.11% 3.1M shares short
- Days to cover
- 6.26 short interest up 9.8% vs prior month
- Institutions 66.55%
- Insiders 6.79%
- Other investors 26.66%
ABOS top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | RA Capital Management, LLC | 29.03% | 21.0M | $35.5M | — | June 30, 2026 |
| 2 | Sands Capital Ventures, LLC | 5.14% | 3.7M | $6.3M | — | June 30, 2026 |
| 3 | BlackRock Inc | 3.44% | 2.5M | $4.2M | +2.3M (+1,296.4%) | June 30, 2026 |
| 4 | Alyeska Investment Group, L.P. | 3.39% | 2.5M | $4.1M | — | June 30, 2026 |
| 5 | Franklin Templeton Inc | 3.19% | 2.3M | $3.9M | — | June 30, 2026 |
| 6 | ADAR1 Capital Management LLC | 2.92% | 2.1M | $3.6M | −45,000 (−2.1%) | June 30, 2026 |
| 7 | Vanguard Capital Management, LLC | 2.31% | 1.7M | $2.8M | +165,795 (+11.0%) | June 30, 2026 |
| 8 | Knollwood Investment Advisory LLC | 2.25% | 1.6M | $2.8M | — | June 30, 2026 |
| 9 | Geode Capital Management, LLC | 1.58% | 1.1M | $1.9M | +725,620 (+174.3%) | June 30, 2026 |
| 10 | Ikarian Capital, LLC | 1.46% | 1.1M | $1.8M | — | June 30, 2026 |
| 11 | Hudson Bay Capital Management LP | 1.32% | 955K | $1.6M | −13,940 (−1.4%) | June 30, 2026 |
| 12 | Pathstone Holdings LLC | 1.19% | 859K | $1.5M | — | June 30, 2026 |
| 13 | Renaissance Technologies Corp | 0.93% | 675K | $1.1M | +201,079 (+42.4%) | June 30, 2026 |
| 14 | Two Sigma Investments LLC | 0.86% | 623K | $1.1M | +92,070 (+17.3%) | June 30, 2026 |
| 15 | State Street Corp | 0.83% | 601K | $1.0M | +448,800 (+295.8%) | June 30, 2026 |
| 16 | Northern Trust Corp | 0.50% | 361K | $609,657 | +285,532 (+379.6%) | June 30, 2026 |
| 17 | Vanguard Portfolio Management, LLC | 0.44% | 321K | $542,144 | +320,795 (0.0%) | June 30, 2026 |
| 18 | Dimensional Fund Advisors, Inc. | 0.40% | 292K | $492,735 | +171,803 (+143.5%) | June 30, 2026 |
| 19 | Vanguard Fiduciary Trust Co | 0.40% | 291K | $492,196 | +92,014 (+46.2%) | June 30, 2026 |
| 20 | Bank of America Corp | 0.38% | 275K | $464,380 | −45,435 (−14.2%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 10 holders added 4.8M shares and 3 cut 104K.
ABOS top mutual fund and ETF holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Franklin Biotechnology Discv A(acc)USD | 2.04% | 1.5M | $2.5M | — | August 31, 2026 |
| 2 | iShares Russell 2000 ETF | 1.62% | 1.2M | $2.0M | −13,504 (−1.1%) | September 30, 2026 |
| 3 | Vanguard MStar Total Stk Mkt Idx Invest | 1.55% | 1.1M | $1.9M | — | August 31, 2026 |
| 4 | Franklin Biotechnology Discovery A | 1.14% | 826K | $1.4M | — | August 31, 2026 |
| 5 | Fidelity Small Cap Index | 0.71% | 514K | $868,276 | −633 (−0.1%) | July 31, 2026 |
| 6 | iShares Russell 2000 Value ETF | 0.60% | 432K | $730,180 | +656 (+0.2%) | September 30, 2026 |
| 7 | Vanguard Russell 2000 ETF | 0.37% | 270K | $456,258 | +5,400 (+2.0%) | August 31, 2026 |
| 8 | Fidelity Extended Market Index | 0.32% | 228K | $386,089 | −1,228 (−0.5%) | August 31, 2026 |
| 9 | BSF Systematic US Eq Abs Ret A2 USD | 0.23% | 163K | $276,117 | — | December 31, 2025 |
| 10 | iShares Micro-Cap ETF | 0.21% | 151K | $255,732 | −1,044 (−0.7%) | September 30, 2026 |
| 11 | Schwab Small Cap Index | 0.16% | 115K | $194,499 | — | August 31, 2026 |
| 12 | A4Investments SICAV SIF ACCI IlanaA2EURH | 0.15% | 110K | $185,900 | — | September 30, 2026 |
| 13 | Dimensional US Small Cap ETF | 0.15% | 109K | $184,310 | — | September 30, 2026 |
| 14 | iShares Russell 2000 Small-Cap Idx Instl | 0.12% | 88K | $149,298 | — | August 31, 2026 |
| 15 | EA Bridgeway Ultra-Small Company Mkt ETF | 0.12% | 87K | $146,501 | — | September 30, 2026 |
| 16 | Bridgeway Ultra-Small Company | 0.10% | 75K | $126,750 | — | June 30, 2026 |
| 17 | Fidelity Total Market Index | 0.10% | 74K | $124,305 | +13,998 (+23.5%) | August 31, 2026 |
| 18 | Fidelity Series Total Market Index | 0.09% | 67K | $112,549 | — | August 31, 2026 |
| 19 | Fidelity Small Cap Value Index | 0.09% | 66K | $111,256 | — | July 31, 2026 |
| 20 | Nuveen Small Cap Blend Idx R6 | 0.09% | 63K | $107,070 | — | August 31, 2026 |
Funds report holdings monthly or quarterly; dates differ by fund.
ABOS insider transactions
latest 20| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2026-01-22 | Eric Siemers | Sell | $1.82 | 895 | $1,629 |
| 2026-01-22 | Matt Zuga | Sell | $1.86 | 1,687 | $3,138 |
| 2026-01-22 | Russell Barton | Sell | $1.84 | 462 | $850 |
| 2026-01-22 | Daniel Joseph Oconnell | Sell | $1.88 | 2,689 | $5,055 |
| 2026-01-21 | Daniel Joseph Oconnell | Sell | $1.81 | 9,346 | $16,916 |
| 2026-01-21 | Eric Siemers | Sell | $1.80 | 2,331 | $4,196 |
| 2026-01-21 | Matt Zuga | Sell | $1.81 | 2,473 | $4,476 |
| 2026-01-21 | Russell Barton | Sell | $1.81 | 2,315 | $4,190 |
| 2026-01-12 | Daniel Joseph Oconnell | Sell | $1.73 | 5,388 | $9,321 |
| 2026-01-09 | Daniel Joseph Oconnell | Sell | $1.76 | 12,941 | $22,776 |
| 2026-01-08 | Russell Barton | Sell | $1.86 | 3,530 | $6,566 |
| 2026-01-08 | Matt Zuga | Sell | $1.82 | 6,888 | $12,536 |
| 2026-01-08 | James J Doherty | Sell | $1.82 | 6,467 | $11,770 |
| 2026-01-08 | Daniel Joseph Oconnell | Sell | $1.82 | 8,143 | $14,820 |
| 2026-01-07 | Daniel Joseph Oconnell | Sell | $1.99 | 37,755 | $75,132 |
| 2026-01-07 | James J Doherty | Sell | $1.99 | 1,700 | $3,383 |
| 2026-01-07 | Matt Zuga | Sell | $1.99 | 5,805 | $11,552 |
| 2026-01-07 | Russell Barton | Sell | $1.99 | 1,700 | $3,383 |
| 2026-01-06 | Daniel Joseph Oconnell | Sell | $1.97 | 5,102 | $10,051 |
| 2026-01-06 | Eric Siemers | Sell | $1.97 | 6,834 | $13,463 |
Reported trades by company officers, directors and other filers (including disclosures by members of Congress where EODHD lists them). "—" where the filing gives no share count.
ABOS shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns ABOS
Institutional investors own 66.5% of Acumen Pharmaceuticals's shares and insiders 6.79%. The largest holder is RA Capital Management, LLC with 29.03% of the shares (21.0M), as of June 30, 2026. Among the top 20 institutions, 10 added shares and 3 reduced their stake in the latest filings. Short interest is 6.11% of the float, or 6.26 days of average trading volume. The share count rose 111.4% since 2020.
Related: ABOS analyst forecast, ABOS key metrics. See the ABOS stock overview for the latest quote and news.
ABOS ownership FAQ
Who owns the most Acumen Pharmaceuticals stock?
The largest shareholders of Acumen Pharmaceuticals are RA Capital Management, LLC (29.03%), Sands Capital Ventures, LLC (5.14%), BlackRock Inc (3.44%), Alyeska Investment Group, L.P. (3.39%), Franklin Templeton Inc (3.19%).
What percentage of Acumen Pharmaceuticals is owned by institutions?
Institutions hold 66.5% of Acumen Pharmaceuticals's shares outstanding; insiders hold 6.79%.
Which funds own Acumen Pharmaceuticals?
The largest fund holders of Acumen Pharmaceuticals are Franklin Biotechnology Discv A(acc)USD (2.04%), iShares Russell 2000 ETF (1.62%), Vanguard MStar Total Stk Mkt Idx Invest (1.55%), Franklin Biotechnology Discovery A (1.14%), Fidelity Small Cap Index (0.71%).
What is Acumen Pharmaceuticals's short interest?
3.1M shares of Acumen Pharmaceuticals were sold short, 6.11% of the float; at the average daily volume it would take 6.26 days to cover.
Are insiders buying or selling Acumen Pharmaceuticals?
Of the latest 20 reported insider transactions in Acumen Pharmaceuticals (since January 6, 2026), 0 were purchases and 20 were sales.
How many shares of Acumen Pharmaceuticals are outstanding?
Acumen Pharmaceuticals has 72.3M shares outstanding, of which 37.0M are in the public float.