Kastelein Johannes Jacob Pieter

NewAmsterdam Pharma CSO Kastelein sells 300,000 shares for $9.1M over three days, reducing stake to 69.3K shares (81.2% reduction).

Kastelein Johannes Jacob Pieter, Chief Scientific Officer, executed 3 separate sales totaling 300,000 shares for $9,090,868.39 at a blended average price of $30.30 between March 5–9, 2026, reducing his holdings from 369.3K to 69.3K shares. This represents an 81.2% reduction in his position while the stock trades at $30.77 current price, down 25.8% from its 52-week high of $41.45 and down 10.3% over 30 days. The company context is material: revenue is $348.0K (latest quarter), net income stands at -$72.0M, annual revenue growth is -50.6%, and the company was unprofitable over its most recent full fiscal year. His prior trades at NAMS show no pattern of well-timed 90-day outcomes (0 of 3 prior sells had negative 90d returns after the sale), and his cross-ticker track record shows an average 90-day return of +37.2% following sells—indicating his past sales have typically preceded gains, not declines. The magnitude of this stake reduction, paired with severe revenue contraction and persistent losses, warrants close examination of whether fundamental deterioration is driving the exit or whether other factors are at play.

NewAmsterdam Pharma CSO sold 45,481 shares at blended $35.31 average (Feb 20) for $1.6M; holds 53.5K post-transaction.

Kastelein Johannes Jacob Pieter, Chief Scientific Officer, executed 2 separate sales totaling 45,481 shares for $1,605,997.94 on 2026-02-20, reducing holdings by -45.9% from 98,981 to 53,500 shares. This represents a material reduction in CSO equity stake at a company facing structural headwinds: quarterly revenue of $348,000.00 with negative net income of $-72,005,000.00, and annual revenue decline of -50.6% year-over-year. Regarding timing, his same-ticker history at NAMS shows 3 of 4 prior sells (August 2025 and March 2024) were followed by 30-day gains of 4.7% to 9.9%, indicating those prior dispositions were poorly timed against subsequent price appreciation. The current sale occurred at $35.31 against a 52-week high of $41.45 (-13.1% from peak), with the stock showing +8.1% 30-day momentum but -13.1% 90-day return. The combination of substantial share reduction by a senior scientific officer, alongside severe revenue contraction and operating losses, presents a noteworthy signal for investors to assess whether the CSO's divestiture reflects information asymmetry about the commercial trajectory or product viability.

Chief Scientific Officer sells 100,000 shares across 3 transactions for $2.5M; reduces stake by 59.1%; stock +45.2% in 90 days post-transaction period.

Kastelein Johannes Jacob Pieter executed 3 separate sales totaling 100,000 shares for $2,471,639.78 at an average price of $24.72, reducing his holdings from 169,302 shares to 69,302 shares. The magnitude of this disposition (59.1% reduction) represents a substantial reduction in his personal stake in NewAmsterdam Pharma. Notably, the stock has gained 45.2% over the 90-day period following the transaction dates, and his cross-ticker track record shows a 100% well-timed rate on prior sells (average 90d return -8.7% post-sale). However, this particular sale appears poorly-timed against recent price action: the stock has risen materially since the August 2025 transaction window. The company remains unprofitable (net income $-17,364,000.00 in the latest quarter) despite strong annual revenue growth of 223.4%, which underscores the speculative nature of the position.