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Stock Plans and Stock Based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

A summary of stock option activity under the 2010 Plan and inducement awards are summarized as follows:


	Number of Shares	Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life	Aggregate Intrinsic Value
Outstanding, December 31, 2021	10,363,769	$	3.80	7.41
Granted	4,694,350	3.14
Exercised	—	—
Canceled/Forfeited	(472,820)	7.29
Outstanding, June 30, 2022	14,585,299	$	3.47	7.73	$	19
Exercisable at June 30, 2022	7,398,636	$	3.32	6.55	$	11
Vested and unvested expected to vest at June 30, 2022	13,783,730	$	3.46	7.64	$	18

The weighted average grant date fair values of the stock options granted during the six months ended June 30, 2022 and 2021 were $2.57 and $9.42, respectively, and were calculated using the following estimated assumptions:


	Six Months Ended June 30,
	2022	2021
Expected term (years)	5.5	5.5


Risk free interest rate	1.4-2.5%	0.4-1.4%
Expected Volatility	110%-112%	107	%
Expected Dividends	None	None

Nonvested Restricted Stock Shares Activity

The following table presents a summary of unvested restricted stock awards (“RSAs”) under the 2010 Plan as of June 30, 2022:


	Number of Shares	Weighted Average Grant Date Fair Value
Unvested, December 31, 2021	10,312	$	3.45
Awarded	—	—
Vested	(10,312)	3.45
Forfeited	—	—
Unvested, June 30, 2022	—	$	—

Schedule of Share Based Compensation Allocation of Recognized Period Costs

For the three and six months ended June 30, 2022 and 2021, the Company recorded stock-based compensation expense to the following line items in its costs and expenses section of the Condensed Consolidated Statements of Operations and Comprehensive Loss, including expense related to its ESPP:


	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands)	2022		2021		2022		2021
Research and development expenses	$	854	$	440	$	1,579	$	778
General and administrative expenses	1,112		835		2,105		1,596
Total stock-based compensation expense	$	1,966	$	1,275	$	3,684	$	2,374