As of September 29, 2026, the three largest insider holders of ATNM are Sandesh Seth (Chief Executive Officer, 1.97Mn shares), C. David Nicholson, (Director, 63.30K shares), Richard I Steinhart (Director, 63.12K shares).
| # | Insider | Position | Direct | Indirect | Total | Share of Insiders | Last Filed |
|---|---|---|---|---|---|---|---|
| 1 | Sandesh Seth | Chief Executive Officer | 1,965,355 | 0 | 1,965,355 | 88.0% | 04 Sep, 2026 |
| 2 | C. David Nicholson, | Director | 63,300 | 0 | 63,300 | 2.8% | 04 Sep, 2026 |
| 3 | Richard I Steinhart | Director | 63,116 | 0 | 63,116 | 2.8% | 04 Sep, 2026 |
| 4 | Ajit Shetty | Director | 62,357 | 0 | 62,357 | 2.8% | 04 Sep, 2026 |
| 5 | Jeffrey W. Chell | Director | 61,600 | 0 | 61,600 | 2.8% | 04 Sep, 2026 |
| 6 | June Sherie Almenoff | Director | 18,000 | 0 | 18,000 | 0.8% | 04 Sep, 2026 |
Each row is that insider’s most recently reported position, from Form 4 filings over the last 60 months — which is why this total does not tie to the quarterly series above, where a quarter counts only the insiders who filed in it. Shares held through a fund or institutional portfolio are counted on the institutional ownership page instead.
| Date | Insider | Position | Transaction | Shares | Price | Value | Shares Held After | Ownership |
|---|---|---|---|---|---|---|---|---|
| 02 Sep, 2026 | Ajit Shetty | Director | Acquired A | 61,600 | $0.00 | $0 | 62,357 | Direct |
| 02 Sep, 2026 | June Sherie Almenoff | Director | Acquired A | 18,000 | $0.00 | $0 | 18,000 | Direct |
| 02 Sep, 2026 | Jeffrey W. Chell | Director | Acquired A | 61,600 | $0.00 | $0 | 61,600 | Direct |
| 02 Sep, 2026 | C. David Nicholson, | Director | Acquired A | 62,800 | $0.00 | $0 | 63,300 | Direct |
| 02 Sep, 2026 | Richard I Steinhart | Director | Acquired A | 62,800 | $0.00 | $0 | 63,116 | Direct |
| 02 Sep, 2026 | Sandesh Seth | Chief Executive Officer | Acquired A | 753,600 | $0.00 | $0 | 938,081 | Direct |
| 02 Sep, 2026 | C. David Nicholson, | Director | Acquired A | 94,200 | $0.00 | $0 | 94,200 | Direct |
| 02 Sep, 2026 | Jeffrey W. Chell | Director | Acquired A | 92,400 | $0.00 | $0 | 92,400 | Direct |
| 02 Sep, 2026 | June Sherie Almenoff | Director | Acquired A | 27,000 | $0.00 | $0 | 27,000 | Direct |
| 02 Sep, 2026 | Sandesh Seth | Chief Executive Officer | Acquired A | 1,027,274 | $0.00 | $0 | 1,965,355 | Direct |
| 02 Sep, 2026 | Ajit Shetty | Director | Acquired A | 92,400 | $0.00 | $0 | 92,400 | Direct |
| 02 Sep, 2026 | Richard I Steinhart | Director | Acquired A | 94,200 | $0.00 | $0 | 94,200 | Direct |
| 02 Sep, 2026 | Sandesh Seth | Chief Executive Officer | Acquired A | 1,130,400 | $0.00 | $0 | 1,130,400 | Direct |
| 18 Aug, 2025 | Sandesh Seth | Chief Executive Officer | Disposed F | 120,900 | $1.71 | $206.74K | 184,481 | Direct |
| 31 Mar, 2025 | Ajit Shetty | Director | Disposed D | 2,500 | $0.00 | $0 | 0 | Direct |
| 31 Mar, 2025 | Steve O'Loughlin | Chief Financial Officer | Disposed D | 3,333 | $0.00 | $0 | 0 | Direct |
| 31 Mar, 2025 | June Sherie Almenoff | Director | Disposed D | 50,000 | $0.00 | $0 | 0 | Direct |
| 31 Mar, 2025 | Sandesh Seth | Chief Executive Officer | Disposed D | 16,666 | $0.00 | $0 | 0 | Direct |
| 31 Mar, 2025 | C. David Nicholson, | Director | Disposed D | 2,500 | $0.00 | $0 | 0 | Direct |
| 31 Mar, 2025 | Jeffrey W. Chell | Director | Disposed D | 2,500 | $0.00 | $0 | 0 | Direct |