ARCELLX (ACLX) Institutional Ownership & Top Holders
The most recent SEC Form 13F filings (Q1 2026) show 6 hedge funds and institutional investors holding a combined 10.3M shares of ARCELLX (ACLX), valued at $1.2B. The median portfolio weight is 3.4%.
The latest institutional ownership changes for ACLX show net buying, with the combined position up by 1.6M shares (18.7%) from the previous quarter.
Among 13F filers, the funds with the highest portfolio allocation to ACLX are Paradigm Biocapital Advisors (13.5% of its 13F portfolio), Slotnik Capital (4.0%), and Glazer Capital (3.7%). In Q1 2026, Slotnik Capital made the largest position increase (+4.0%), while Vestal Point Capital made the largest reduction (-7.0%).
Top 6 Institutional Holders in ARCELLX (ACLX), Ranked by Portfolio Weight
Based on the latest SEC Form 13F filings (Q1 2026).
| # | Fund | Shares | Market Value | Portfolio Weight |
|---|---|---|---|---|
| 1 | Paradigm Biocapital Advisors | 5,774,016 | $663.0M | 13.5% |
| 2 | Slotnik Capital | 118,000 | $13.5M | 4.0% |
| 3 | Glazer Capital | 1,507,128 | $173.0M | 3.7% |
| 4 | RK Capital Management | 11,858 | $1.4M | 3.1% |
| 5 | Pentwater Capital Management | 2,870,000 | $329.5M | 2.3% |
| 6 | SAMSARA BIOCAPITAL | 60,873 | $7.0M | 0.7% |
- 6Institutional investors
- 10,341,875Shares held (disclosed)
- $1.2B13F market value
- 3.4%Median portfolio weight
Ownership History
Quarter-by-quarter share count, market value, and portfolio conviction weight (up to 5 of the heaviest weight-by-portfolio funds) of ACLX. Sourced from 13F filings; reflects long equity positions only.
Quarter-over-Quarter ActivityQ1 2026
The biggest weight-increase and weight-decrease changes among funds that hold ACLX. Deltas compare the selected filing to the previous reporting quarter.
Top buyers
- Slotnik Capital+4.0% · +118,000 shares
- Glazer Capital+3.7% · +1,507,128 shares
- Paradigm Biocapital Advisors+3.6% · +50,000 shares
Top sellers
- Vestal Point Capital-7.0% · -2,925,000 shares
Options Activity
- Total puts4,442 (+4,442)
Ownership Statistics
- Funds holding
- 6
- Median weight
- 3.4%
- Largest holder
- Paradigm Biocapital Advisors · 13.5%
- Smallest holder
- SAMSARA BIOCAPITAL · 0.7%
- Shares held
- 10,341,875 (+1,631,986)
All Institutional HoldersSortable · searchable
All institutional investors (Max 50) holding ACLX in the selected quarter. Click a fund name to drill into its full 13F portfolio.
| 1 | Paradigm Biocapital Advisors | 5,774,016 | $663.0M | 13.5% |
| 2 | Slotnik Capital | 118,000 | $13.5M | 4.0% |
| 3 | Glazer Capital | 1,507,128 | $173.0M | 3.7% |
| 4 | RK Capital Management | 11,858 | $1.4M | 3.1% |
| 5 | Pentwater Capital Management | 2,870,000 | $329.5M | 2.3% |
| 6 | SAMSARA BIOCAPITAL | 60,873 | $7.0M | 0.7% |
Institutional Investor Count Over Time
Number of institutional investors disclosing a long position in ARCELLX INC (ACLX) each reporting quarter. Sourced from SEC Form 13F-HR filings.
Methodology & FAQ
Methodology: How We Track ACLX Institutional Holdings
Our data is systematically aggregated directly from quarterly Form 13F-HR disclosures submitted to the U.S. Securities and Exchange Commission (SEC).
- Who Must File (Reporting Threshold): This dataset includes filings from U.S. institutional investment managers, hedge funds, mutual funds, university endowments, and family offices managing at least $100 million in Section 13(f) securities (including equities, options, convertibles, ETFs, and warrants).
- What is Included (Data Scope): We capture long positions in Section 13(f) securities for ARCELLX INC (ACLX). By SEC regulation, 13F filings do not require the disclosure of short positions, non-U.S. holdings, or OTC derivatives. Listed options are excluded from portfolio weight calculations to ensure comparability across filers.
- Portfolio Weight Explained (Metric Definition): “Portfolio Weight” shows how much of a fund's total reported 13F portfolio value (excluding listed options) is allocated to ACLX on the specific reporting date.
- How to Use This Data (Interpretation): Quarter-over-quarter changes in shares and portfolio weight reflect a combination of active trading and market price movements. These are descriptive metrics of fund allocation, not explicit buy or sell signals.
How do you measure hedge fund conviction and institutional concentration in ACLX?
We evaluate fund conviction by looking at portfolio weight rather than just absolute share count. By tracking how the largest holders —such as Paradigm Biocapital Advisors , Slotnik Capital , and Glazer Capital as of Q1 2026— change their position sizing quarter-over-quarter, we help investors distinguish between deliberate position sizing changes and passive mark-to-market drift.
Does the ACLX ownership data include short interest or options?
SEC Form 13F mandates the disclosure of long positions in Section 13(f) securities, which includes equities and listed options (put and call contracts), but excludes short interest, swaps, and OTC derivatives by regulatory design. On this platform, listed options are excluded from portfolio weight calculations to ensure comparability across filers.
Are family offices and university endowments included in this ACLX data?
Yes. In addition to traditional hedge funds and large asset managers, any institutional entity exercising investment discretion over at least $100 million in Section 13(f) securities must file a Form 13F. This explicitly includes single-family offices and university endowments. If a qualifying family office or endowment holds ACLX stock, their allocation is systematically aggregated alongside traditional fund data.
When is the institutional ownership data updated, and is there a reporting lag?
Institutional investment managers are required to file their Form 13F within 45 days after the end of a calendar quarter (the standard “T+45” window). Our platform re-ingests new filings from the SEC EDGAR database on a nightly cycle, typically within 24–48 hours of publication, providing a point-in-time snapshot of reported consensus positioning for ACLX as of each filing date.