Brian S Posner

ACGL

Brian S Posner serves as director at Arch Capital Group Ltd. (ACGL). This page tracks their complete SEC Form 4 insider trading history including stock purchases and sales.

Total Buys

6 trades

$209.0K

Total Sells

3 trades

$249.7K

Net Position

Net Seller

$40.6K

Companies Traded

DYN, ACGL, BIIB

Active Period

Jun 2021 – Apr 2026

9 total trades

Most Recent

Buy DYN

Apr 1, 2026 · $34.2K

Brian S Posner's Insider Trading at Arch Capital Group Ltd. (ACGL)

Buys

3 · $91.0K

Sells

2 · $151.0K

Total Shares Bought

5,000

Total Shares Sold

6,000

ACGL Price Chart

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Date	Type	Shares	Avg Price	Value
Aug 1, 2025	Buy	1,000	$17.34	$17.3K
Oct 28, 2022	Buy	2,000	$17.60	$35.2K
Apr 29, 2022	Buy	2,000	$19.23	$38.5K
Sep 30, 2021	Sell	2,000	$25.00	$50.0K
Jun 14, 2021	Sell	4,000	$25.24	$101.0K

Brian S Posner's Insider Trading at Dyne Therapeutics, Inc. (DYN)

Buys

3 · $118.0K

Sells

0 · $0.00

Total Shares Bought

7,000

Total Shares Sold

DYN Price Chart

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Date	Type	Shares	Avg Price	Value	Shares After
Apr 1, 2026	Buy	2,000	$17.08	$34.2K	15,500
Mar 13, 2026	Buy	2,000	$19.35	$38.7K	13,500
Mar 10, 2026	Buy	3,000	$15.06	$45.2K	11,500

Brian S Posner's Insider Trading at Biogen Inc. (BIIB)

Buys

0 · $0.00

Sells

1 · $98.7K

Total Shares Bought

Total Shares Sold

360

BIIB Price Chart

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Date	Type	Shares	Avg Price	Value	Shares After
Jun 4, 2021	Sell	360	$274.17	$98.7K	0

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Douglas Kerr

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Nicole Murphy

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BIIBBuy · Feb 17, 2026

Maamoun Rajeh

PRESIDENT, ARCH CAPITAL GROUP

ACGLSell · Feb 11, 2026

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