NewAmsterdam Pharma Co. N.V. Insider Trading

NAMS

Last 12 months

Insiders bought 227K and sold $63.3M on the open market.

71% of the selling was scheduled in advance under 10b5-1 plans. Chief Executive Officer Michael H. Davidson sold $14.8M on Mar 2, 72% of their stake, outside a plan.

Net open-market

−$63M

1 buy · 20 sales

Under a 10b5-1 plan

71%

of the value sold

Insiders who bought / sold

1 / 6

executives and directors

Last open-market buy

Sep 2026

Sep 14, 2026

Get an email when NAMS's executives or directors buy, or make a large sale outside a plan.

Trades · last 2 years

Date	Insider	Trade	Shares	Price	Value	Of their stake	Filing
Sep 30	Johannes Jacob Pieter Kastelein Chief Scientific Officer	Sold10b5-1 plan	50,246	$25.03	$1.26M	29%	Form 4
Sep 14	Michael H. Davidson Chief Executive Officer	Bought	10,000	$22.65	227K	0.9%	Form 4
Sep 4	John W Smither Director	SoldNo plan	1,600	$25.32	41K	15%	Form 4
Aug 24	Johannes Jacob Pieter Kastelein Chief Scientific Officer	Sold10b5-1 plan	125,000	$26.91	$3.36M	50%	Form 4
Jul 20	Louise Frederika Kooij Chief Accounting Officer	Sold10b5-1 plan 3 parts	105,000	$30.34 average	$3.19M	81%	Form 4
Jun 22	Louise Frederika Kooij Chief Accounting Officer	Sold10b5-1 plan 2 parts	40,000	$30.20 average	$1.21M	62%	Form 4
May 26	Louise Frederika Kooij Chief Accounting Officer	Sold10b5-1 plan	65,000	$35.69	$2.32M	73%	Form 4
Mar 11	Louis G Lange Director	SoldNo plan 2 parts	44,619	$30.42 average	$1.36M	81%	Form 4
Mar 5 – 9	Johannes Jacob Pieter Kastelein Chief Scientific Officer	Sold10b5-1 plan 3 parts	300,000	$30.30 average	$9.09M	81%	Form 4
Mar 6	Louis G Lange Director	SoldNo plan	28,186	$29.41	829K	34%	Form 4
Mar 2	Michael H. Davidson Chief Executive Officer	SoldNo plan	443,707	$33.25	$14.8M	72%	Form 4
Feb 24 – 26	Michael H. Davidson Chief Executive Officer	Sold10b5-1 plan 7 parts	306,293	$34.53 average	$10.6M	40%	Form 4
Feb 20	Johannes Jacob Pieter Kastelein Chief Scientific Officer	SoldNo plan 2 parts	45,481	$35.31 average	$1.61M	46%	Form 4
Jan 27 – 28	Louise Frederika Kooij Chief Accounting Officer	Sold10b5-1 plan 2 parts	72,428	$32.25 average	$2.34M	75%	Form 4
Jan 23 – 26	Louise Frederika Kooij Chief Accounting Officer	Sold10b5-1 plan 4 parts	72,572	$33.29 average	$2.42M	75%	Form 4
Jan 20 – 21	Mayur Ian Somaiya Chief Financial Officer	Sold10b5-1 plan 5 parts	100,000	$32.61 average	$3.26M	63%	Form 4
Jan 7	Michael H. Davidson Chief Executive Officer	Sold10b5-1 plan	11,582	—	—	2.5%	Form 4
Jan 5	Johannes Jacob Pieter Kastelein Chief Scientific Officer	Sold10b5-1 plan	6,000	$33.25	200K	5.7%	Form 4
Jan 5	Louise Frederika Kooij Chief Accounting Officer	Sold10b5-1 plan	2,647	$33.25	88K	9.8%	Form 4
Jan 5	Mayur Ian Somaiya Chief Financial Officer	Sold10b5-1 plan	5,118	$33.25	170K	8.1%	Form 4
Dec 23, 2025 – Dec 26, 2025	Louise Frederika Kooij Chief Accounting Officer	Sold10b5-1 plan 3 parts	145,000	$35.84 average	$5.2M	91%	Form 4
Sep 15, 2025	James N Topper Director	Bought	660	$23.70	16K	<0.1%	Form 4
Sep 9, 2025	Louise Frederika Kooij Chief Accounting Officer	SoldNo plan 2 parts	150,000	$25.83 average	$3.87M	91%	Form 4
Sep 8, 2025	James N Topper Director	Bought	1,260	$24.99	31K	<0.1%	Form 4
Sep 3, 2025	Louise Frederika Kooij Chief Accounting Officer	SoldNo plan	18,073	$25.09	453K	55%	Form 4
Aug 25, 2025	Louise Frederika Kooij Chief Accounting Officer	SoldNo plan	8,269	$24.86	206K	36%	Form 4
Aug 21, 2025 – Aug 22, 2025	Johannes Jacob Pieter Kastelein Chief Scientific Officer	SoldNo plan 3 parts	100,000	$24.72 average	$2.47M	59%	Form 4
Aug 11, 2025	James N Topper Director	Bought	471	$23.98	11K	<0.1%	Form 4
Jul 15, 2025 – Jul 16, 2025	Douglas F Kling Chief Operating Officer	Sold10b5-1 plan 3 parts	98,612	$21.26 average	$2.1M	69%	Form 4
Jun 24, 2025 – Jun 25, 2025	James N Topper Director	Bought 2 parts	3,780	$18.37 average	69K	<0.1%	Form 4
Jun 16, 2025	James N Topper Director	Bought	8,584	$19.50	167K	0.1%	Form 4
Jun 16, 2025	Douglas F Kling Chief Operating Officer	Sold10b5-1 plan 2 parts	100,000	$19.29 average	$1.93M	69%	Form 4
May 15, 2025	Douglas F Kling Chief Operating Officer	Sold10b5-1 plan	100,000	—	—	69%	Form 4
Apr 15, 2025	Douglas F Kling Chief Operating Officer	Sold10b5-1 plan 2 parts	100,000	—	—	69%	Form 4
Mar 26, 2025	James N Topper Director	Bought	1,135	$22.49	26K	<0.1%	Form 4
Mar 26, 2025	Douglas F Kling Chief Operating Officer	SoldNo plan	16,539	—	—	27%	Form 4
Mar 26, 2025	Michael H. Davidson Chief Executive Officer	SoldNo plan	12,258	—	—	3.0%	Form 4
Mar 17, 2025	Douglas F Kling Chief Operating Officer	Sold10b5-1 plan	100,000	—	—	69%	Form 4
Mar 4, 2025	James N Topper Director	Bought	4,005	$21.02	84K	<0.1%	Form 4
Mar 4, 2025	Louise Frederika Kooij Chief Accounting Officer	SoldNo plan	150,000	$20.37	$3.06M	91%	Form 4

Sep 3010b5-1 plan
Johannes Jacob Pieter Kastelein
Chief Scientific Officer · sold 50,246 at $25.03
$1.26M
29% of stake
Sep 14
Michael H. Davidson
Chief Executive Officer · bought 10,000 at $22.65
227K
0.9% of stake
Sep 4No plan
John W Smither
Director · sold 1,600 at $25.32
41K
15% of stake
Aug 2410b5-1 plan
Johannes Jacob Pieter Kastelein
Chief Scientific Officer · sold 125,000 at $26.91
$3.36M
50% of stake
Jul 2010b5-1 plan
Louise Frederika Kooij
Chief Accounting Officer · sold 105,000 at avg $30.34
$3.19M
81% of stake
Jun 2210b5-1 plan
Louise Frederika Kooij
Chief Accounting Officer · sold 40,000 at avg $30.20
$1.21M
62% of stake
May 2610b5-1 plan
Louise Frederika Kooij
Chief Accounting Officer · sold 65,000 at $35.69
$2.32M
73% of stake
Mar 11No plan
Louis G Lange
Director · sold 44,619 at avg $30.42
$1.36M
81% of stake
Mar 5 – 910b5-1 plan
Johannes Jacob Pieter Kastelein
Chief Scientific Officer · sold 300,000 at avg $30.30
$9.09M
81% of stake
Mar 6No plan
Louis G Lange
Director · sold 28,186 at $29.41
829K
34% of stake
Mar 2No plan
Michael H. Davidson
Chief Executive Officer · sold 443,707 at $33.25
$14.8M
72% of stake
Feb 24 – 2610b5-1 plan
Michael H. Davidson
Chief Executive Officer · sold 306,293 at avg $34.53
$10.6M
40% of stake
Feb 20No plan
Johannes Jacob Pieter Kastelein
Chief Scientific Officer · sold 45,481 at avg $35.31
$1.61M
46% of stake
Jan 27 – 2810b5-1 plan
Louise Frederika Kooij
Chief Accounting Officer · sold 72,428 at avg $32.25
$2.34M
75% of stake
Jan 23 – 2610b5-1 plan
Louise Frederika Kooij
Chief Accounting Officer · sold 72,572 at avg $33.29
$2.42M
75% of stake
Jan 20 – 2110b5-1 plan
Mayur Ian Somaiya
Chief Financial Officer · sold 100,000 at avg $32.61
$3.26M
63% of stake
Jan 710b5-1 plan
Michael H. Davidson
Chief Executive Officer · sold 11,582
—
2.5% of stake
Jan 510b5-1 plan
Johannes Jacob Pieter Kastelein
Chief Scientific Officer · sold 6,000 at $33.25
200K
5.7% of stake
Jan 510b5-1 plan
Louise Frederika Kooij
Chief Accounting Officer · sold 2,647 at $33.25
88K
9.8% of stake
Jan 510b5-1 plan
Mayur Ian Somaiya
Chief Financial Officer · sold 5,118 at $33.25
170K
8.1% of stake
Dec 23, 2025 – Dec 26, 202510b5-1 plan
Louise Frederika Kooij
Chief Accounting Officer · sold 145,000 at avg $35.84
$5.2M
91% of stake
Sep 15, 2025
James N Topper
Director · bought 660 at $23.70
16K
<0.1% of stake
Sep 9, 2025No plan
Louise Frederika Kooij
Chief Accounting Officer · sold 150,000 at avg $25.83
$3.87M
91% of stake
Sep 8, 2025
James N Topper
Director · bought 1,260 at $24.99
31K
<0.1% of stake
Sep 3, 2025No plan
Louise Frederika Kooij
Chief Accounting Officer · sold 18,073 at $25.09
453K
55% of stake
Aug 25, 2025No plan
Louise Frederika Kooij
Chief Accounting Officer · sold 8,269 at $24.86
206K
36% of stake
Aug 21, 2025 – Aug 22, 2025No plan
Johannes Jacob Pieter Kastelein
Chief Scientific Officer · sold 100,000 at avg $24.72
$2.47M
59% of stake
Aug 11, 2025
James N Topper
Director · bought 471 at $23.98
11K
<0.1% of stake
Jul 15, 2025 – Jul 16, 202510b5-1 plan
Douglas F Kling
Chief Operating Officer · sold 98,612 at avg $21.26
$2.1M
69% of stake
Jun 24, 2025 – Jun 25, 2025
James N Topper
Director · bought 3,780 at avg $18.37
69K
<0.1% of stake
Jun 16, 2025
James N Topper
Director · bought 8,584 at $19.50
167K
0.1% of stake
Jun 16, 202510b5-1 plan
Douglas F Kling
Chief Operating Officer · sold 100,000 at avg $19.29
$1.93M
69% of stake
May 15, 202510b5-1 plan
Douglas F Kling
Chief Operating Officer · sold 100,000
—
69% of stake
Apr 15, 202510b5-1 plan
Douglas F Kling
Chief Operating Officer · sold 100,000
—
69% of stake
Mar 26, 2025
James N Topper
Director · bought 1,135 at $22.49
26K
<0.1% of stake
Mar 26, 2025No plan
Douglas F Kling
Chief Operating Officer · sold 16,539
—
27% of stake
Mar 26, 2025No plan
Michael H. Davidson
Chief Executive Officer · sold 12,258
—
3.0% of stake
Mar 17, 202510b5-1 plan
Douglas F Kling
Chief Operating Officer · sold 100,000
—
69% of stake
Mar 4, 2025
James N Topper
Director · bought 4,005 at $21.02
84K
<0.1% of stake
Mar 4, 2025No plan
Louise Frederika Kooij
Chief Accounting Officer · sold 150,000 at $20.37
$3.06M
91% of stake

How to read this. Insiders sell for many reasons: taxes, diversifying, a house. Open-market buys are rarer and say more. A 10b5-1 plan is a trading schedule set up months in advance, so those sales were not timed on news. Large holders (funds and 10% owners) are listed under Everything but not counted as insiders. If you own or watch NAMS, we send a push when an executive buys or makes a large sale outside a plan.

Source: SEC Form 4 filings, filed within two business days of each trade and checked for new ones every hour.

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Held by ETFs

NAMS is in 16 US ETFs. The largest of them, with NAMS's weight in each:

Spot a number that looks wrong? Check it in NAMS's SEC filings or

Download this analysis as a PDF (Pro)

Data sourced from SEC EDGAR filings and third-party price providers. Scores, valuations, and metrics are algorithmic estimates. This is not investment advice. See our Terms and Methodology.

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