The following table summarizes option activity under the Company's equity-based compensation plans for the six months ended June 30, 2024:


	Number of Shares	Weighted Average Exercise Price per Share
Options outstanding January 1, 2024	369,839	$	148.40
Granted	—	—
Forfeited	(11,200)	36.67
Exercised	—	—
Expired	(26,046)	160.05
Options outstanding June 30, 2024	332,593	$	151.25

The following table shows summary information for outstanding options and options that are exercisable (vested) as of June 30, 2024:


	Options Outstanding		Options Exercisable
Number of options	332,593		308,815
Weighted average remaining contractual term (in years)	4.48		4.27
Weighted average exercise price	$	151.25	$	158.49
Weighted average fair value	$	—	$	—
Aggregate intrinsic value (in thousands)	$	—	$	—

The following table summarizes RSU activity for the six months ended June 30, 2024:


	Number of Shares	Weighted Average Grant Date Fair Value per Share
Outstanding January 1, 2024	1,239,436	$	9.15
Granted	3,157,438	1.30
Forfeited	(212,417)	5.70
Released	(583,351)	4.02
Outstanding June 30, 2024	3,601,106	$	3.30

The table below summarizes equity-based compensation expense for the three and six months ended June 30, 2024 and 2023 (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Cost of sales	$	34	$	98	$	92	$	188
Research and development	164		256		543		861
Sales, general and administrative	768		1,299		1,628		1,159
	$	966	$	1,653	$	2,263	$	2,208

The table below summarizes share-based compensation cost capitalized to inventory for the three and six months ended June 30, 2024 and 2023 (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Cost capitalized to inventory	$	19	$	35	$	109	$	109

As of June 30, 2024, unrecognized equity-based compensation expense related to unvested stock options and unvested RSUs was $0.1 million and $5.6 million, respectively. This is expected to be recognized over the years 2024 through 2028.