Kastelein Johannes Jacob Pieter, Chief Scientific Officer at NewAmsterdam Pharma ($NAMS), sold shares worth $13.4 million in nine open market transactions over the past year. His most recent sale occurred on March 9, 2026. These sales rank 914th among nearly 12,000 insiders by total value, above the average of $8.6 million across about six transactions per insider. He reported no open market purchases in this period.
| Transaction Date | Company | Ticker | Insider Name | Title | Transaction Type | Security | Shares | Price | Shares Owned Following | Total Shares Outstanding | % of Owned | % of Outstanding |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| March 9, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Option (right to buy) | 101409 | $0.00 | 520,229.0000 | 119,000,266 | 16.31% | 0.09% |
| March 6, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | S | Ordinary Shares | 94124 | $30.32 | 69,302.0000 | 119,000,266 | 57.59% | 0.08% |
| March 6, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Ordinary Shares | 94124 | $0.00 | 163,426.0000 | 119,000,266 | 135.82% | 0.08% |
| March 5, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | S | Ordinary Shares | 104467 | $30.30 | 69,302.0000 | 119,000,266 | 60.12% | 0.09% |
| March 5, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Ordinary Shares | 104467 | $0.00 | 173,769.0000 | 119,000,266 | 150.74% | 0.09% |
| March 6, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Option (right to buy) | 94124 | $0.00 | 621,638.0000 | 119,000,266 | 13.15% | 0.08% |
| March 5, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Option (right to buy) | 104467 | $0.00 | 715,762.0000 | 119,000,266 | 12.74% | 0.09% |
| March 9, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | S | Ordinary Shares | 101409 | $30.29 | 69,302.0000 | 119,000,266 | 59.40% | 0.09% |
| March 9, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Ordinary Shares | 101409 | $0.00 | 170,711.0000 | 119,000,266 | 146.33% | 0.09% |
| Feb. 20, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | S | Ordinary Shares | 30789 | $35.46 | 53,500.0000 | 119,000,266 | 36.53% | 0.03% |
| Feb. 20, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | S | Ordinary Shares | 14692 | $35.00 | 84,289.0000 | 119,000,266 | 14.84% | 0.01% |
| Jan. 7, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | A | Ordinary Shares | 25500 | $0.00 | 98,981.0000 | 119,000,266 | 34.70% | 0.02% |
| Jan. 5, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | S | Ordinary Shares | 6000 | $33.25 | 73,481.0000 | 119,000,266 | 7.55% | 0.01% |
| Jan. 7, 2026 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | A | Option (right to buy) | 115000 | $0.00 | 115,000.0000 | 119,000,266 | 9999.99% | 0.10% |
| Aug. 22, 2025 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | S | Ordinary Shares | 7658 | $25.49 | 69,302.0000 | 94,358,067 | 9.95% | 0.01% |
| Aug. 21, 2025 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | S | Ordinary Shares | 50000 | $24.29 | 119,302.0000 | 94,358,067 | 29.53% | 0.05% |
| Aug. 22, 2025 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | S | Ordinary Shares | 42342 | $25.08 | 76,960.0000 | 94,358,067 | 35.49% | 0.04% |
| March 26, 2025 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | A | Ordinary Shares | 19302 | $0.00 | 248,783.0000 | 94,358,067 | 8.41% | 0.02% |
| March 26, 2025 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Restricted Stock Unit | 45481 | $0.00 | 0.0000 | 94,358,067 | 100.00% | 0.05% |
| March 26, 2025 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | A | Restricted Stock Unit | 45481 | $0.00 | 45,481.0000 | 94,358,067 | 9999.99% | 0.05% |
| March 26, 2025 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Ordinary Shares | 45481 | $0.00 | 248,783.0000 | 94,358,067 | 22.37% | 0.05% |
| March 24, 2025 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Option (right to buy) | 150000 | $0.00 | 820,229.0000 | 94,358,067 | 15.46% | 0.16% |
| March 24, 2025 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Ordinary Shares | 150000 | $0.00 | 150,000.0000 | 94,358,067 | 9999.99% | 0.16% |
| Jan. 7, 2025 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | A | Ordinary Shares | 34000 | $0.00 | 34,000.0000 | 94,358,067 | 9999.99% | 0.04% |
| Jan. 2, 2025 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | A | Option (right to buy) | 200000 | $0.00 | 200,000.0000 | 94,358,067 | 9999.99% | 0.21% |
| March 26, 2024 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | S | Ordinary Shares | 190476 | $21.50 | 0.0000 | 82,161,956 | 100.00% | 0.23% |
| March 26, 2024 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Ordinary Shares | 201673 | $0.00 | 201,673.0000 | 82,161,956 | 9999.99% | 0.25% |
| March 26, 2024 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | F | Ordinary Shares | 11197 | $22.72 | 190,476.0000 | 82,161,956 | 5.55% | 0.01% |
| March 26, 2024 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | M | Option (right to buy) | 201673 | $0.00 | 970,229.0000 | 82,161,956 | 17.21% | 0.25% |
| Jan. 1, 2024 | NewAmsterdam Pharma Co N.V. | $NAMS | Kastelein Johannes Jacob Pieter | Chief Scientific Officer | A | Option (right to buy) | 500000 | $0.00 | 500,000.0000 | 82,161,956 | 9999.99% | 0.61% |