NewAmsterdam Pharma (NAMS) CSO executes 45,481-share stock sale

Rhea-AI Filing Summary

NewAmsterdam Pharma Co N.V. Chief Scientific Officer Johannes Jacob Pieter Kastelein reported open-market sales of company ordinary shares. On February 20, 2026, he sold 14,692 shares at a weighted average price of $35.00 per share and 30,789 shares at a weighted average price of $35.46 per share. The filing notes that these sales occurred through multiple trades, with prices ranging from $34.24 to $35.23 for the first block and from $35.24 to $35.86 for the second block. Following these transactions, he directly owned 53,500 ordinary shares of NewAmsterdam Pharma.

Insider Trade Summary

Net Seller: 45,481 shares ($1,605,998)

Net Sell 2 txns

Insider Kastelein Johannes Jacob Pieter

Role Chief Scientific Officer

Sold 45,481 shs ($1.61M)

Type	Security	Shares	Price	Value
Sale	Ordinary Shares	14,692	$35.00	$514K
Sale	Ordinary Shares	30,789	$35.46	$1.09M

Holdings After Transaction: Ordinary Shares — 84,289 shares (Direct)

Footnotes (1)

1. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $34.24 to $35.23 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. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $35.24 to $35.86 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.

Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a 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). See Instruction 10.

1. Name and Address of Reporting Person^*

Kastelein Johannes Jacob Pieter

(Last) (First) (Middle)

C/O NEWAMSTERDAM PHARMA COMPANY N.V.

GOOIMEER 2-35

(Street)

NAARDEN P7 1411 DC

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
NewAmsterdam Pharma Co N.V. [ NAMS ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Scientific Officer

3. Date of Earliest Transaction (Month/Day/Year)
02/20/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Ordinary Shares	02/20/2026		S		14,692	D	$35(1)	84,289	D
Ordinary Shares	02/20/2026		S		30,789	D	$35.46(2)	53,500	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $34.24 to $35.23 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.

2. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $35.24 to $35.86 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.

	/s/ Louise Kooij by Power of Attorney from Johannes Jacob Pieter Kastelein	02/24/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transaction did NewAmsterdam Pharma (NAMS) report on this Form 4?

NewAmsterdam Pharma reported that its Chief Scientific Officer, Johannes Jacob Pieter Kastelein, sold ordinary shares in two open-market transactions on February 20, 2026. These sales reduced his directly held stake but left him owning 53,500 ordinary shares afterward.

How many NewAmsterdam Pharma (NAMS) shares did the CSO sell?

The Chief Scientific Officer sold a total of 45,481 ordinary shares. This consisted of 14,692 shares in one transaction and 30,789 shares in a second transaction, both executed on February 20, 2026 in open-market sales.

At what prices were the NewAmsterdam Pharma (NAMS) shares sold?

The reported weighted average prices were $35.00 and $35.46 per share for the two transactions. Underlying trades occurred in ranges of $34.24–$35.23 and $35.24–$35.86, according to the footnotes describing the multiple individual sale prices.

How many NewAmsterdam Pharma (NAMS) shares does the CSO own after these sales?

After completing the reported open-market sales, the Chief Scientific Officer directly owned 53,500 ordinary shares of NewAmsterdam Pharma. This post-transaction holding reflects the remaining stake following the aggregate sale of 45,481 shares disclosed in the Form 4.

Were the NewAmsterdam Pharma (NAMS) insider sales executed in one trade or multiple trades?

The sales were executed in multiple trades. Footnotes explain that each reported weighted average price reflects numerous individual transactions within specified price ranges, and detailed trade information is available upon request from the issuer, security holders, or the SEC staff.

What is the role of the insider who sold NewAmsterdam Pharma (NAMS) shares?

The insider is Johannes Jacob Pieter Kastelein, who serves as a director and Chief Scientific Officer of NewAmsterdam Pharma. His officer title and director status are disclosed, along with the direct ownership of ordinary shares before and after the reported sales.