Who owns Arcellx (ACLX)
Which tracked institutional funds hold ACLX, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See ACLX company fundamentals →
Ownership as of the 2026-Q1 13F filings (latest filed 2026-05-21). 13F is disclosed up to 45 days after quarter-end, so the most recent quarter fills in over the following weeks.
How the tape is positioned
124 tracked funds added or opened ACLX while 73 trimmed or exited it between 2025-Q4 and 2026-Q1 — the tape is split. When large holders disagree on a name, the funds moving first are sometimes ahead of the story.
A prompt to read the filings, not a verdict. 13F is a quarter-end snapshot disclosed up to 45 days late; a fund adds or exits for mandate, benchmark, and timing reasons that have nothing to do with a view on the stock. This is a starting question, not a signal to trade.
Conviction spread
ACLX’s largest tracked holder by dollar value, GILEAD SCIENCES, INC., sizes it at 36.4% of its own reported 13F book, while the median holder sizes it at 0.2% of theirs — a 36.2pp conviction gap — its largest holder concentrates the name more heavily than the typical one.
Book-share is each fund’s reported value in ACLX divided by its whole reported 13F book, so it is comparable across funds of different sizes and is unaffected by stock splits. A higher share means a fund has committed more of its book to the name — a starting question about conviction, not a verdict or a signal to trade.
Institutional & insider positioning
Between 2025-Q4 and 2026-Q1, across 238 tracked filers holding ACLX, 157 increased or opened the position and 132 reduced or closed it; over the same quarter, open-market insider Form 4 buying and selling roughly offset.
This fuses two public signals for the same quarter — how tracked institutions changed their positions and whether insiders bought or sold in the open market. It describes what was filed; it is a starting question, not a verdict or a signal to trade.
New buyers & exits
Funds opening or closing a position in ACLX between the 2025-Q4 and 2026-Q1 13F filings, and the largest changes among funds holding it in both. New buyers and exits are counted on fund presence (split-invariant); adds and trims are measured on reported value.
New buyers 63
- Pentwater Capital Management LP$330M
- VANGUARD CAPITAL MANAGEMENT LLC$278M
- VANGUARD PORTFOLIO MANAGEMENT LLC$278M
- FIL Ltd$269M
- HBK INVESTMENTS L P$262M
- GLAZER CAPITAL, LLC$173M
Full exits 50
- VANGUARD GROUP INC$266M
- Vestal Point Capital, LP$191M
- PERCEPTIVE ADVISORS LLC$96M
- RA CAPITAL MANAGEMENT, L.P.$83M
- BAMCO INC /NY/$40M
- LORD, ABBETT & CO. LLC$29M
Largest adds
- GILEAD SCIENCES, INC.$333M
- Paradigm Biocapital Advisors LP$290M
- NEA Management Company, LLC$151M
- SR One Capital Management, LP$116M
- BlackRock, Inc.$113M
- GOLDMAN SACHS GROUP INC$107M
Largest trims
- FMR LLC$219M
- T. Rowe Price Investment Management, Inc.$110M
- PRICE T ROWE ASSOCIATES INC /MD/$100M
- CITADEL ADVISORS LLC$95M
- JANUS HENDERSON GROUP PLC$50M
- Woodline Partners LP$34M
Institutional holders
One row per tracked fund, largest reported value first. “% of value” is the fund’s share of this security’s tracked institutional value — not of shares outstanding. Rows marked stale are from an earlier filing than the security’s latest quarter — that fund is absent from the newest snapshot (position exited, or reported under a different name).
| Fund | Shares | Reported value | % of value | Quarter |
|---|---|---|---|---|
| GILEAD SCIENCES, INC. | 6,720,803 | $772M | 10.6% | 2026-Q1 |
| Paradigm Biocapital Advisors LP added | 5,774,016 | $663M | 9.1% | 2026-Q1 |
| NEA Management Company, LLC | 3,045,262 | $350M | 4.8% | 2026-Q1 |
| BlackRock, Inc. trimmed | 2,998,176 | $344M | 4.7% | 2026-Q1 |
| Pentwater Capital Management LP new | 2,870,000 | $330M | 4.5% | 2026-Q1 |
| VANGUARD CAPITAL MANAGEMENT LLC new | 2,425,218 | $278M | 3.8% | 2026-Q1 |
| VANGUARD PORTFOLIO MANAGEMENT LLC new | 2,424,818 | $278M | 3.8% | 2026-Q1 |
| SR One Capital Management, LP | 2,346,630 | $269M | 3.7% | 2026-Q1 |
| FIL Ltd new | 2,339,192 | $269M | 3.7% | 2026-Q1 |
| HBK INVESTMENTS L P new | 2,278,517 | $262M | 3.6% | 2026-Q1 |
| T. Rowe Price Investment Management, Inc. trimmed | 2,255,878 | $259M | 3.6% | 2026-Q1 |
| STATE STREET CORP trimmed | 1,675,895 | $192M | 2.6% | 2026-Q1 |
| GLAZER CAPITAL, LLC new | 1,507,128 | $173M | 2.4% | 2026-Q1 |
| GOLDMAN SACHS GROUP INC added | 1,312,155 | $151M | 2.1% | 2026-Q1 |
| GEODE CAPITAL MANAGEMENT, LLC added | 1,028,666 | $118M | 1.6% | 2026-Q1 |
| MORGAN STANLEY added | 925,813 | $106M | 1.5% | 2026-Q1 |
| JPMORGAN CHASE & CO trimmed | 593,573 | $68M | 0.9% | 2026-Q1 |
| Davidson Kempner Capital Management LP new | 559,644 | $64M | 0.9% | 2026-Q1 |
| TIG Advisors, LLC new | 541,378 | $62M | 0.9% | 2026-Q1 |
| MILLENNIUM MANAGEMENT LLC added | 502,846 | $58M | 0.8% | 2026-Q1 |
| BALYASNY ASSET MANAGEMENT L.P. added | 479,763 | $55M | 0.8% | 2026-Q1 |
| TUDOR INVESTMENT CORP ET AL added | 462,588 | $53M | 0.7% | 2026-Q1 |
| BANK OF AMERICA CORP /DE/ added | 452,333 | $52M | 0.7% | 2026-Q1 |
| Magnetar Financial LLC new | 394,931 | $45M | 0.6% | 2026-Q1 |
| ALPINE ASSOCIATES MANAGEMENT INC. new | 378,000 | $43M | 0.6% | 2026-Q1 |
| NEXPOINT ASSET MANAGEMENT, L.P. new | 373,150 | $43M | 0.6% | 2026-Q1 |
| Affinity Asset Advisors, LLC trimmed | 362,764 | $42M | 0.6% | 2026-Q1 |
| NORTHERN TRUST CORP added | 350,065 | $40M | 0.6% | 2026-Q1 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC added | 346,092 | $40M | 0.5% | 2026-Q1 |
| ALLIANCEBERNSTEIN L.P. added | 544,227 | $35M | 0.5% | 2026-Q1 |
| VANGUARD FIDUCIARY TRUST CO new | 308,546 | $35M | 0.5% | 2026-Q1 |
| Qube Research & Technologies Ltd added | 303,847 | $35M | 0.5% | 2026-Q1 |
| First Trust Capital Management L.P. new | 238,235 | $27M | 0.4% | 2026-Q1 |
| AQR Arbitrage LLC new | 231,730 | $27M | 0.4% | 2026-Q1 |
| AJU IB Investment Co., Ltd. | 223,486 | $26M | 0.4% | 2026-Q1 |
| LMR Partners LLP new | 212,495 | $24M | 0.3% | 2026-Q1 |
| BARCLAYS PLC added | 207,642 | $24M | 0.3% | 2026-Q1 |
| SOROS FUND MANAGEMENT LLC new | 200,000 | $23M | 0.3% | 2026-Q1 |
| GABELLI FUNDS LLC new | 195,900 | $22M | 0.3% | 2026-Q1 |
| UBS Group AG trimmed | 194,709 | $22M | 0.3% | 2026-Q1 |
| Verition Fund Management LLC added | 187,354 | $22M | 0.3% | 2026-Q1 |
| WATER ISLAND CAPITAL LLC new | 183,409 | $21M | 0.3% | 2026-Q1 |
| Man Group plc added | 180,000 | $21M | 0.3% | 2026-Q1 |
| Rock Springs Capital Management LP | 169,859 | $20M | 0.3% | 2026-Q1 |
| GABELLI & Co INVESTMENT ADVISERS, INC. new | 152,400 | $17M | 0.2% | 2026-Q1 |
| BNP PARIBAS FINANCIAL MARKETS added | 151,558 | $17M | 0.2% | 2026-Q1 |
| Groupe la Francaise new | 151,046 | $17M | 0.2% | 2026-Q1 |
| Bank of New York Mellon Corp added | 143,099 | $16M | 0.2% | 2026-Q1 |
| CREDIT INDUSTRIEL ET COMMERCIAL new | 134,648 | $15M | 0.2% | 2026-Q1 |
| Woodline Partners LP trimmed | 123,750 | $14M | 0.2% | 2026-Q1 |
| GARDNER LEWIS ASSET MANAGEMENT L P new | 123,197 | $14M | 0.2% | 2026-Q1 |
| Hudson Bay Capital Management LP trimmed | 122,900 | $14M | 0.2% | 2026-Q1 |
| PICTON MAHONEY ASSET MANAGEMENT new | 120,000 | $14M | 0.2% | 2026-Q1 |
| FMR LLC trimmed | 119,309 | $14M | 0.2% | 2026-Q1 |
| Slotnik Capital, LLC new | 118,000 | $14M | 0.2% | 2026-Q1 |
| ODDO BHF ASSET MANAGEMENT SAS new | 115,000 | $13M | 0.2% | 2026-Q1 |
| PRELUDE CAPITAL MANAGEMENT, LLC new | 98,849 | $11M | 0.2% | 2026-Q1 |
| RENAISSANCE TECHNOLOGIES LLC added | 96,400 | $11M | 0.2% | 2026-Q1 |
| JANUS HENDERSON GROUP PLC trimmed | 90,280 | $10M | 0.1% | 2026-Q1 |
| CIBRA Capital Ltd new | 88,623 | $10M | 0.1% | 2026-Q1 |
| Nuveen, LLC added | 85,294 | $10M | 0.1% | 2026-Q1 |
| DEUTSCHE BANK AG\ trimmed | 80,664 | $9M | 0.1% | 2026-Q1 |
| Cinctive Capital Management LP added | 80,000 | $9M | 0.1% | 2026-Q1 |
| Chicago Capital Management, LLC new | 92,951 | $8M | 0.1% | 2026-Q1 |
| Sagefield Capital LP new | 65,097 | $7M | 0.1% | 2026-Q1 |
| Athos Capital Ltd new | 64,900 | $7M | 0.1% | 2026-Q1 |
| Russell Investments Group, Ltd. trimmed | 61,905 | $7M | 0.1% | 2026-Q1 |
| SAMSARA BIOCAPITAL, LLC | 60,873 | $7M | 0.1% | 2026-Q1 |
| UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC trimmed | 57,289 | $7M | 0.1% | 2026-Q1 |
| Voleon Capital Management LP new | 56,720 | $7M | 0.1% | 2026-Q1 |
| PSquared Asset Management AG new | 55,251 | $6M | 0.1% | 2026-Q1 |
| Swiss National Bank | 54,700 | $6M | 0.1% | 2026-Q1 |
| VANGUARD GROUP INC added | 4,081,519 | $266M | 3.7% | 2025-Q4 stale |
| Vestal Point Capital, LP added | 2,925,000 | $191M | 2.6% | 2025-Q4 stale |
| PERCEPTIVE ADVISORS LLC trimmed | 1,466,071 | $96M | 1.3% | 2025-Q4 stale |
| RA CAPITAL MANAGEMENT, L.P. trimmed | 1,267,156 | $83M | 1.1% | 2025-Q4 stale |
| Capital World Investors | 783,011 | $64M | 0.9% | 2025-Q3 stale |
| Cormorant Asset Management, LP trimmed | 775,000 | $64M | 0.9% | 2025-Q3 stale |
| BAMCO INC /NY/ added | 609,697 | $40M | 0.5% | 2025-Q4 stale |
| LORD, ABBETT & CO. LLC added | 449,634 | $29M | 0.4% | 2025-Q4 stale |
| AMERICAN CENTURY COMPANIES INC added | 419,080 | $27M | 0.4% | 2025-Q4 stale |
| First Turn Management, LLC added | 313,733 | $26M | 0.4% | 2025-Q3 stale |
| Hood River Capital Management LLC new | 335,500 | $22M | 0.3% | 2025-Q4 stale |
| STEMPOINT CAPITAL LP added | 332,860 | $22M | 0.3% | 2025-Q4 stale |
| Fisher Asset Management, LLC new | 322,855 | $21M | 0.3% | 2025-Q4 stale |
| TD Asset Management Inc added | 300,856 | $20M | 0.3% | 2025-Q4 stale |
| Artia Global Partners LP trimmed | 229,085 | $15M | 0.2% | 2025-Q1 stale |
| WELLINGTON MANAGEMENT GROUP LLP trimmed | 214,776 | $14M | 0.2% | 2025-Q4 stale |
| BAKER BROS. ADVISORS LP | 166,825 | $14M | 0.2% | 2025-Q3 stale |
| Integral Health Asset Management, LLC added | 200,000 | $13M | 0.2% | 2025-Q4 stale |
| Catalio Capital Management, LP new | 156,109 | $10M | 0.1% | 2025-Q4 stale |
| Rhenman & Partners Asset Management AB added | 133,500 | $9M | 0.1% | 2025-Q4 stale |
| CLOUGH CAPITAL PARTNERS L P new | 129,780 | $8M | 0.1% | 2025-Q4 stale |
| Parkman Healthcare Partners LLC trimmed | 128,111 | $8M | 0.1% | 2025-Q4 stale |
| RAYMOND JAMES FINANCIAL INC trimmed | 122,346 | $8M | 0.1% | 2025-Q4 stale |
| Logos Global Management LP trimmed | 115,000 | $7M | 0.1% | 2025-Q4 stale |
| GREAT POINT PARTNERS LLC added | 100,000 | $7M | 0.1% | 2025-Q2 stale |
| Schonfeld Strategic Advisors LLC trimmed | 99,131 | $6M | 0.1% | 2025-Q4 stale |
| Monaco Asset Management SAM new | 78,589 | $6M | 0.1% | 2025-Q3 stale |
| Candriam S.C.A. added | 96,420 | $6M | 0.1% | 2025-Q4 stale |
Ownership over time
Tracked institutional holder count and total shares held by filing quarter (independent scales). The curated-era tail and any mid-ingest latest quarter are handled honestly — a partial quarter is not drawn as a collapse.
Reading this table
Funds hold the same stock for different reasons — an index fund “holds” almost everything, an active manager sizes a name to a mandate and a benchmark, and each fund entered at its own price and time. Because 13F is filed up to 45 days after quarter-end, every row is a backward-looking snapshot; a manager may have traded since. Share-class siblings (a company’s A and C shares) are rolled up to one line so a dual-class name is never double-counted. Compare like-for-like. A large holder is not an endorsement, and a fund exiting is not a warning — this is a starting question, not a verdict.
About 13F filings
A Form 13F is a quarterly disclosure that institutional investment managers with over $100 million in US-listed equities must file with the SEC. In plain English: it is a snapshot of the long stock positions a fund held at the end of a quarter. It covers long US-listed equities only — not short positions, options, cash, or private holdings — and the funds shown are the large sample we track, not the complete 13F universe.