Johannes Jacob Pieter Kastelein - 05 Mar 2026 Form 4 Insider Report for NewAmsterdam Pharma Co N.V. (NAMS)

Role
Chief Scientific Officer, Director
Signature
/s/ Louise Kooij by Power of Attorney for Johannes Jacob Pieter Kastelein
Issuer symbol
NAMS
Transactions as of
05 Mar 2026
Net transactions value
-$9,090,868
Form type
4
Filing time
09 Mar 2026, 20:18:01 UTC
Previous filing
24 Feb 2026
SEC
View on sec.gov

Reporting Owners (1)

Name Relationship Address Signature Signature date CIK
Kastelein Johannes Jacob Pieter Chief Scientific Officer, Director C/O NEWAMSTERDAM PHARMA COMPANY N.V., GOOIMEER 2-35, NAARDEN, NETHERLANDS /s/ Louise Kooij by Power of Attorney for Johannes Jacob Pieter Kastelein 09 Mar 2026 0002000389

Transactions Table

Type Sym Class Transaction Value $ Shares Change % * Price $ Shares After Date Ownership Footnotes
transaction NAMS Ordinary Shares Options Exercise +104,467 +151% 173,769 05 Mar 2026 See footnote F1, F2
transaction NAMS Ordinary Shares Sale $3,165,350 -104,467 -60% $30.30 69,302 05 Mar 2026 See footnote F2, F3
transaction NAMS Ordinary Shares Options Exercise +94,124 +136% 163,426 06 Mar 2026 See footnote F1, F2
transaction NAMS Ordinary Shares Sale $2,853,840 -94,124 -58% $30.32 69,302 06 Mar 2026 See footnote F2, F4
transaction NAMS Ordinary Shares Options Exercise +101,409 +146% 170,711 09 Mar 2026 See footnote F1, F2
transaction NAMS Ordinary Shares Sale $3,071,679 -101,409 -59% $30.29 69,302 09 Mar 2026 See footnote F2, F5

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type Sym Class Transaction Value $ Shares Change % * Price $ Shares After Date Underlying Class Amount Exercise Price Ownership Footnotes
transaction NAMS Option (right to buy) Options Exercise -104,467 -13% $0.000000* 715,762 05 Mar 2026 Ordinary Shares 104,467 See footnote F1, F6, F7
transaction NAMS Option (right to buy) Options Exercise -94,124 -13% $0.000000* 621,638 06 Mar 2026 Ordinary Shares 94,124 See footnote F1, F6, F7
transaction NAMS Option (right to buy) Options Exercise -101,409 -16% $0.000000* 520,229 09 Mar 2026 Ordinary Shares 101,409 See footnote F1, F6, F7
* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Buy Plan / Sale Plan: These are also open market purchases/sales of shares, but in this case the transaction is part of a trading plan. Rule 10b5-1 allows insiders to setup a trading plan to buy/sell stocks over a certain period of time. Since the purchases/sales are predetermined, this protects the insiders from violating insider trading law.

Transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c).

Explanation of Responses:

Id Content
F1 The exercise price of the option is EUR 1.16392.
F2 The Ordinary Shares are held by Futurum B.V. ("Futurum") for the benefit of the Reporting Person. The Reporting Person exercises sole voting and investment control over the Ordinary Shares held by Futurum.
F3 The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $30.00 per share to $30.55 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold in each transaction.
F4 The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $30.00 per share to $30.42 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold in each transaction.
F5 The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $30.00 per share to $30.80 per share. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold in each transaction.
F6 The option was granted on November 22, 2022 to replace an option originally granted on July 6, 2021 which was cancelled in connection with the consummation of NewAmsterdam Pharma Company N.V.'s business combination with Frazier Lifesciences Acquisition Corporation. 292,214 of the shares underlying the option immediately vested on the grant date. 25% of the remaining shares underlying the option vested on January 1, 2021, the one-year anniversary of vesting start date, with the remaining shares vesting in equal monthly installments thereafter for three years, subject to the Reporting Person's continued service through each such date.
F7 The option was granted to and is held by Futurum through NAP PoolCo B.V. ("PoolCo") for the benefit of the Reporting Person. The Reporting Person exercises sole voting and investment control over the securities held by Futurum through PoolCo. PoolCo has no voting or investment control or pecuniary interest in the securities held on behalf of Futurum. Upon exercise of the option, the Ordinary Shares were issued to Futurum directly, pursuant to a written agreement among Futurum, PoolCo and the Issuer.