Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Assumptions Used To Estimate Fair Value of Options

The assumptions used to estimate fair value and the resulting grant date fair values are as follows:

	Employees						Non-employee
	Years Ended December 31,						Years Ended December 31,
	2021			2020			2021			2020
Weighted average expected volatility		62.10	%		64.67	%		69.56	%		66.55	%
Weighted average risk-free interest rate		0.64	%		1.18	%		0.74	%		0.36	%
Weighted average expected term (in years)		5.15			5.97			5.79			5.50

Schedule of Share-based Compensation, Stock Options, Activity

The activity for the 2009 Plan, 2014 Plan and 2015 Plan for the years ended December 31, 2021 is summarized as follows:

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value ($000)
Outstanding — December 31, 2020		830,343		$	21.52		7.71	$	96
Granted		874,050		$	7.30
Forfeited/expired		(162,267	)	$	7.95
Outstanding — December 31, 2021		1,542,126		$	14.89		7.45	$	42
Exercisable — December 31, 2021		739,332		$	22.73		5.91	$	11
Vested or expected to vest —December 31, 2021		1,542,126		$	14.89		7.45	$	42

Schedule of Restricted Stock Units ("RSU") Activity

Restricted stock unit ("RSU") activity under the 2014 Plan and 2015 Plan for the years ended December 31, 2021, is summarized as follows:

	Number of Shares			Weighted Average Grant Date Fair Value Per Share
Non-vested at December 31, 2020		29,087		$	9.52
Granted		130,175		$	7.83
Vested		(10,335	)	$	10.60
Forfeited		(15,093	)	$	7.85
Non-vested at December 31, 2021		133,834		$	7.98

Stock-Based Compensation Expense Related to Stock Options

Stock-based compensation expense related to stock options is included in the following line items in the accompanying statements of operations (in thousands):

	Years Ended December 31,
	2021		2020
Research and development	$	631	$	806
Selling, general and administrative		1,457		1,414
Total stock-based compensation expense	$	2,088	$	2,220