Ranked by reported Q1 2026 13F market value
Share of total reported institutional value in ATNM held by the largest 10 / 25 filers.
| # | Institution | Shares Held | Market Value | QoQ Change | Ownership % | % of Fund |
|---|---|---|---|---|---|---|
| 1 | VANGUARD CAPITAL MANAGEMENT LLC | 1.3M | $1.2M | — | 4.002% | 0.00% |
| 2 | MILLENNIUM MANAGEMENT LLC | 565K | $562K | -6.2% | 1.800% | 0.00% |
| 3 | RENAISSANCE TECHNOLOGIES LLC | 472K | $469K | +20.7% | 1.503% | 0.00% |
| 4 | BlackRock, Inc. | 371K | $369K | +1.2% | 1.183% | 0.00% |
| 5 | TWO SIGMA INVESTMENTS, LP | 337K | $336K | +60.8% | 1.075% | 0.00% |
| 6 | GEODE CAPITAL MANAGEMENT, LLC | 336K | $335K | +2.1% | 1.071% | 0.00% |
| 7 | GAGNON SECURITIES LLC | 201K | $200K | -0.3% | 0.642% | 0.05% |
| 8 | VANGUARD FIDUCIARY TRUST CO | 160K | $159K | — | 0.511% | 0.00% |
| 9 | STATE STREET CORP | 126K | $126K | 0.0% | 0.402% | 0.00% |
| 10 | SUSQUEHANNA INTERNATIONAL GROUP, LLP | 124K | $123K | +29.7% | 0.395% | 0.00% |
| 11 | Gen-Wealth Partners Inc | 107K | $107K | -0.0% | 0.341% | 0.03% |
| 12 | NORTHERN TRUST CORP | 76K | $75K | +78.0% | 0.242% | 0.00% |
| 13 | GOLDMAN SACHS GROUP INC | 70K | $70K | -0.2% | 0.224% | 0.00% |
| 14 | BRIDGEWAY CAPITAL MANAGEMENT, LLC | 40K | $40K | 0.0% | 0.128% | 0.00% |
| 15 | TWO SIGMA SECURITIES, LLC | 36K | $36K | +176.8% | 0.114% | 0.00% |
| 16 | NINE MASTS CAPITAL Ltd | 35K | $35K | +172.2% | 0.112% | 0.01% |
| 17 | DIMENSIONAL FUND ADVISORS LP | 35K | $35K | 0.0% | 0.111% | 0.00% |
| 18 | XTX Topco Ltd | 30K | $30K | +16.3% | 0.096% | 0.00% |
| 19 | Vontobel Holding Ltd. | 30K | $30K | 0.0% | 0.096% | 0.00% |
| 20 | Gerald Baker Financial Group LLC | 23K | $29K | — | 0.072% | 0.01% |
| 21 | MAYPORT, LLC | 22K | $22K | 0.0% | 0.070% | 0.00% |
| 22 | NORTH STAR ASSET MANAGEMENT INC | 20K | $20K | 0.0% | 0.064% | 0.00% |
| 23 | ADVISOR GROUP HOLDINGS, INC. | 20K | $20K | -2.0% | 0.063% | 0.00% |
| 24 | WELLS FARGO & COMPANY/MN | 20K | $20K | 0.0% | 0.063% | 0.00% |
| 25 | Qube Research & Technologies Ltd | 18K | $18K | -4.1% | 0.057% | 0.00% |
denotes a marquee investor (Buffett, Burry, ARK, Tiger Global, Pershing Square, Baupost and other widely-followed managers). “% of Fund” shows how much of that investor’s total 13F portfolio is invested in ATNM — a direct measure of their conviction.
Filings activity in ATNM during Q1 2026, grouped by how each filer changed its position.
8 quarters of 13F filings · Δ columns show change vs prior quarter
| Quarter | Inst. Holders | Δ Holders | Ownership % | Δ Ownership | Total 13F Value | Δ Value |
|---|---|---|---|---|---|---|
| Q1 2026 | 52 | 12% | 14.54% | 6.08 pp | $5M | 29% |
| Q4 2025 | 59 | +0.0% | 20.62% | 2.34 pp | $7M | 10% |
| Q3 2025 | 59 | 6.3% | 22.96% | +1.42 pp | $7M | +6.6% |
| Q2 2025 | 63 | 11% | 21.54% | 16.98 pp | $7M | 44% |
| Q1 2025 | 71 | +1.4% | 38.52% | +6.36 pp | $12M | +20% |
| Q4 2024 | 70 | 2.8% | 32.16% | 14.85 pp | $10M | 32% |
| Q3 2024 | 72 | 2.7% | 47.01% | 141.09 pp | $15M | 75% |
| Q2 2024 | 74 | — | 188.10% | — | $60M | — |
Source: SEC 13F institutional filings. Ownership % requires market cap data and will show once linked. Δ columns compare to the immediately prior filed quarter.
Quick answers to the most common questions about buying ATNM stock.
Based on Q1 2026 13F filings, institutional ownership of Actinium Pharmaceuticals, Inc. stands at 14.5%, held across 52 reporting institutions.
VANGUARD CAPITAL MANAGEMENT LLC is the largest reported institutional holder of ATNM, with approximately 1,255,516 shares worth $0.00B as of Q1 2026.
Yes — 5 widely-followed marquee investors appear among the top 25 institutional holders of ATNM, including MILLENNIUM MANAGEMENT LLC, RENAISSANCE TECHNOLOGIES LLC, TWO SIGMA INVESTMENTS, LP, SUSQUEHANNA INTERNATIONAL GROUP, LLP, TWO SIGMA SECURITIES, LLC.
Our composite Smart Money Score for ATNM is 48 out of 100 (Neutral). It combines net institutional buying activity, ownership shift, marquee investor presence, and holder-count growth.
7 institutions opened new positions in ATNM during Q1 2026, while 14 fully exited. 7 added to existing positions and 37 trimmed.
ATNM institutional ownership fell by 6.08 percentage points quarter-over-quarter, with a net change of -7 holders.
The top 10 institutions account for 85.3% of all reported 13F value in ATNM, and the top 25 account for 98.0%.
All data is sourced from SEC Form 13F filings, which institutional investment managers with at least $100M in assets are required to file each quarter. We process every 13F filing from EDGAR and recompute the aggregates after each cycle. Insider transactions are sourced from Form 4 filings.
Actinium Pharmaceuticals, Inc. (ATNM) Institutional Ownership