William K Heiden

Insider

First SEC filing: June 11, 2026 · Latest: June 11, 2026

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Insider at Companies where this person is a reporting insider.
Insider transactions Every share this person bought or sold, from Form 4 filings.
Derivatives Options and other derivative holdings reported by this person.

Insider at

Insider transactions

1 buys (P) 0 sells (S) Net: $73,755 + 36 non-open-market transactions below Avg return of open purchases vs now: 178.9% last 12 months, based on the transactions shown below

Price change vs current quote, split-adjusted for corporate actions since the filing — not benchmarked, not annualized, not size-weighted

36 other filings hidden

Date	Ticker	Code	Shares	Price	Value	Owned after	Δ own	A/D	vs now
June 9, 2026	ATRA	A	12,000	—	—	34,188 Direct	+54.08%	Acquired	(price as of 2026-08-20)
May 19, 2026	MGNX	A	22,000	—	—	22,000 Direct	—	Acquired	(price as of 2026-08-20)
May 19, 2026	MGNX	A	3,750	—	—	3,750 Direct	—	Acquired	(price as of 2026-08-20)
May 18, 2026	MGNX	M	3,750	—	—	0 Direct	-100.00%	Disposed	(price as of 2026-08-20)
May 18, 2026	MGNX	M	3,750	—	—	114,750 Direct	+3.38%	Acquired	(price as of 2026-08-20)
Aug. 20, 2025	MGNX	P	49,500	$1.49	$73,755	111,000 Direct	+80.49%	Acquired	178.9% (price as of 2026-08-20)
Aug. 19, 2025	MGNX	P	50,500	$1.52	$76,760	61,500 Direct	+459.09%	Acquired	173.4% (price as of 2026-08-20)
June 10, 2025	ATRA	A	7,828	—	—	22,188 Direct	+54.51%	Acquired	(price as of 2026-08-20)
May 21, 2025	MGNX	A	22,000	—	—	22,000 Direct	—	Acquired	(price as of 2026-08-20)
May 21, 2025	MGNX	A	3,750	—	—	3,750 Direct	—	Acquired	(price as of 2026-08-20)
May 20, 2025	MGNX	M	6,500	—	—	0 Direct	-100.00%	Disposed	(price as of 2026-08-20)
May 20, 2025	MGNX	M	6,500	—	—	11,000 Direct	+144.44%	Acquired	(price as of 2026-08-20)
May 21, 2024	MGNX	A	16,500	—	—	16,500 Direct	—	Acquired	(price as of 2026-08-20)
May 21, 2024	MGNX	A	6,500	—	—	6,500 Direct	—	Acquired	(price as of 2026-08-20)
May 20, 2024	MGNX	M	4,500	—	—	0 Direct	-100.00%	Disposed	(price as of 2026-08-20)
May 20, 2024	MGNX	M	4,500	—	—	4,500 Direct	—	Acquired	(price as of 2026-08-20)
March 31, 2024	ATRA	A	150,000	—	—	359,000 Direct	+71.77%	Acquired	(price as of 2026-08-20)
Nov. 10, 2023	ATRA	P	100,000	$0.25	$25,000	209,000 Direct	+91.74%	Acquired	52.6% (price as of 2026-08-20)
May 31, 2023	MGNX	A	4,500	—	—	4,500 Direct	—	Acquired	(price as of 2026-08-20)
May 31, 2023	MGNX	A	19,000	—	—	19,000 Direct	—	Acquired	(price as of 2026-08-20)
May 31, 2023	ATRA	A	79,500	—	—	79,500 Direct	—	Acquired	(price as of 2026-08-20)
May 31, 2023	ATRA	A	57,000	—	—	109,000 Direct	+109.62%	Acquired	(price as of 2026-08-20)
June 23, 2022	ATRA	A	31,500	—	—	31,500 Direct	—	Acquired	(price as of 2026-08-20)
June 23, 2022	ATRA	A	20,500	—	—	52,000 Direct	+65.08%	Acquired	(price as of 2026-08-20)
May 23, 2022	MGNX	A	36,000	—	—	36,000 Direct	—	Acquired	(price as of 2026-08-20)
June 8, 2021	ATRA	A	11,000	—	—	31,500 Direct	+53.66%	Acquired	(price as of 2026-08-20)
June 8, 2021	ATRA	A	17,500	—	—	17,500 Direct	—	Acquired	(price as of 2026-08-20)
June 16, 2020	ATRA	A	24,500	—	—	24,500 Direct	—	Acquired	(price as of 2026-08-20)
June 16, 2020	ATRA	A	8,000	—	—	20,500 Direct	+64.00%	Acquired	(price as of 2026-08-20)
June 27, 2019	ATRA	A	13,000	—	—	13,000 Direct	—	Acquired	(price as of 2026-08-20)
June 27, 2019	ATRA	A	4,000	—	—	12,500 Direct	+47.06%	Acquired	(price as of 2026-08-20)
June 14, 2018	ATRA	A	5,000	—	—	5,000 Direct	—	Acquired	(price as of 2026-08-20)
June 14, 2018	ATRA	A	1,500	—	—	8,500 Direct	+21.43%	Acquired	(price as of 2026-08-20)
June 8, 2017	ATRA	A	5,000	—	—	7,000 Direct	+250.00%	Acquired	(price as of 2026-08-20)
June 8, 2017	ATRA	A	21,500	—	—	21,500 Direct	—	Acquired	(price as of 2026-08-20)
Jan. 3, 2017	ATRA	A	5,500	—	—	5,500 Direct	—	Acquired	(price as of 2026-08-20)
Jan. 3, 2017	ATRA	A	2,000	—	—	2,000 Direct	—	Acquired	(price as of 2026-08-20)
Jan. 4, 2016	ATRA	A	10,500	—	—	10,500 Direct	—	Acquired	(price as of 2026-08-20)
Nov. 23, 2015	ATRA	A	15,500	—	—	15,500 Direct	—	Acquired	(price as of 2026-08-20)

P = Open-market purchase · S = Sale · A = Grant/award · M = Option exercise · G = Gift · F = Tax withholding

Insider transactions are not a recommendation; sales are often driven by liquidity or tax reasons.

Derivative holdings (Form 4 Table II)

Options, RSUs and convertible securities reported on Form 4 Table II.

Date	Ticker	Security	Underlying	Exercise price	Expiration	Shares	A/D
May 19, 2026	MGNX	Stock Option (right to buy)	Common Stock (22,000)	$4.52	May 19, 2036	22,000	Acquired
May 19, 2026	MGNX	Restricted Stock Unit	Common Stock (3,750)	—	—	3,750	Acquired
May 18, 2026	MGNX	Restricted Stock Unit	Common Stock (3,750)	—	—	3,750	Disposed
May 21, 2025	MGNX	Stock Option (right to buy)	Common Stock (22,000)	$1.49	May 21, 2035	22,000	Acquired
May 21, 2025	MGNX	Restricted Stock Unit	Common Stock (3,750)	—	—	3,750	Acquired
May 20, 2025	MGNX	Restricted Stock Unit	Common Stock (6,500)	—	—	6,500	Disposed
May 21, 2024	MGNX	Stock Option (right to buy)	Common Stock (16,500)	$4.26	May 21, 2034	16,500	Acquired
May 21, 2024	MGNX	Restricted Stock Unit	Common Stock (6,500)	—	—	6,500	Acquired
May 20, 2024	MGNX	Restricted Stock Unit	Common Stock (4,500)	—	—	4,500	Disposed
May 31, 2023	MGNX	Restricted Stock Unit	Common Stock (4,500)	—	—	4,500	Acquired
May 31, 2023	MGNX	Stock Option (right to buy)	Common Stock (19,000)	$4.67	May 31, 2033	19,000	Acquired
May 31, 2023	ATRA	Non-Qualified Stock Option (Right to Buy)	Common Stock (79,500)	$1.53	May 30, 2033	79,500	Acquired
June 23, 2022	ATRA	Non-Qualified Stock Option (Right to Buy)	Common Stock (31,500)	$7.35	June 22, 2032	31,500	Acquired
May 23, 2022	MGNX	Stock Option (right to buy)	Common Stock (36,000)	$3.96	May 23, 2032	36,000	Acquired
June 8, 2021	ATRA	Non-Qualified Stock Option (Right to Buy)	Common Stock (17,500)	$13.80	June 7, 2031	17,500	Acquired
June 16, 2020	ATRA	Non-Qualified Stock Option (Right to Buy)	Common Stock (24,500)	$10.54	June 15, 2030	24,500	Acquired
June 27, 2019	ATRA	Non-Qualified Stock Option (Right to Buy)	Common Stock (13,000)	$20.25	June 26, 2029	13,000	Acquired
June 14, 2018	ATRA	Non-Qualified Stock Option (Right to Buy)	Common Stock (5,000)	$45.65	June 13, 2025	5,000	Acquired
June 8, 2017	ATRA	Non-Qualified Stock Option (Right to Buy)	Common Stock (21,500)	$13.20	June 8, 2024	21,500	Acquired
Jan. 3, 2017	ATRA	Non-Qualified Stock Option (Right to Buy)	Common Stock (5,500)	$15.08	Jan. 3, 2024	5,500	Acquired
Jan. 4, 2016	ATRA	Non-Qualified Stock Option (Right to Buy)	Common Stock (10,500)	$24.05	Jan. 4, 2023	10,500	Acquired
Nov. 23, 2015	ATRA	Non-Qualified Stock Option (Right to Buy)	Common Stock (15,500)	$34.98	Nov. 22, 2022	15,500	Acquired

Exercise/conversion price is blank when not applicable (e.g. RSUs).