Johannes Jacob Pieter Kastelein, Chief Scientific Officer and Director of NewAmsterdam Pharma Co N.V. (NASDAQ:NAMS), filed a Form 4 on August 25, 2026, reporting the exercise of options and sale of 125,000 ordinary shares on August 24, 2026, pursuant to a pre-established Rule 10b5-1 trading plan.

Key Highlights

  • Option exercise: Kastelein exercised options covering 125,000 ordinary shares at an exercise price of EUR 1.16392 per share on August 24, 2026.
  • Share sale: 125,000 ordinary shares were disposed of at a weighted average price of $26.91, with individual transaction prices ranging from $26.72 to $27.70 per share.
  • Remaining indirect holdings: Following the reported transactions, Kastelein indirectly holds 69,302 ordinary shares through Futurum B.V. via NAP PoolCo B.V.
  • Direct holdings: The filing also reports 53,500 ordinary shares held directly, including 48,166 shares subject to restricted stock unit awards that remain subject to vesting.
  • Trading plan: The transactions were executed pursuant to a Rule 10b5-1 trading plan adopted by Futurum B.V. on March 31, 2026.
  • Derivative securities: After the option exercise, Kastelein beneficially owns 395,229 options (right to buy) held indirectly through Futurum B.V. via NAP PoolCo B.V., with an expiration date of July 6, 2031.

Details of Kastelein's Reported Transactions in NewAmsterdam Pharma Ordinary Shares

According to the filing, Kastelein serves as both a Director and Chief Scientific Officer of NewAmsterdam Pharma Co N.V., a company registered in the Netherlands with its address listed as Gooimeer 2-35, Naarden. The transactions reported involve ordinary shares of the company, which trades on NASDAQ under the symbol NAMS.

The filing discloses that on August 24, 2026, Kastelein exercised options on 125,000 ordinary shares under transaction code "M," bringing his indirect beneficial ownership to 194,302 shares immediately following that exercise. The same date, 125,000 shares were sold under transaction code "S" at a weighted average price of $26.91 per share, with individual sales prices ranging from $26.72 to $27.70 per share across multiple transactions. The filing notes that full details of each individual transaction price are available upon request to the issuer, any security holder, or SEC staff.

The options exercised were originally granted on November 22, 2022, replacing an option originally granted on July 6, 2021, which was cancelled in connection with NewAmsterdam Pharma Company N.V.'s business combination with Frazier Lifesciences Acquisition Corporation, according to the filing. The filing states that 292,214 of the shares underlying the option vested immediately on the grant date, with 25% of the remaining shares vesting on January 1, 2021, and the remainder vesting in equal monthly installments over three years, subject to continued service. All indirect holdings and the options are held by Futurum B.V. through NAP PoolCo B.V. for Kastelein's benefit, with the filing specifying that Kastelein "exercises sole voting and investment control" over those securities. The filing was signed by Michael Marino by Power of Attorney for Kastelein on August 25, 2026.

What Was Disclosed

The Form 4 filed August 25, 2026 reports that NewAmsterdam Pharma Co N.V.'s Chief Scientific Officer exercised options on and subsequently sold 125,000 ordinary shares on August 24, 2026, under a Rule 10b5-1 plan adopted March 31, 2026, leaving him with indirect holdings of 69,302 shares and direct holdings of 53,500 shares.