Stock Plans and Stock Based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Share-based Payment Arrangement [Abstract]

Schedule of Key Assumptions for Options Awarded

The Black-Scholes option pricing model employs the following key assumptions for employee and director options awarded during the three months ended March 31, 2020 and 2019 based on the assumptions noted in the following table:

	Three Months Ended March 31,
	2020		2019
Expected term (years) – employees and officers	5.5		5.5
Expected term (years) – directors	5.5		5.5
Risk free interest rate	0.9-1.7%		2.5-2.6%
Expected Volatility	80	%	76	%
Expected Dividends	None		None

Schedule of Stock Option Activity

A summary of stock option activity under the 2010 Plan, the 2000 Stock Incentive Plan, the 2000 Director Stock Option Plan and nonstatutory inducement awards are summarized as follows:

	Number of Shares		Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life	Aggregate Intrinsic Value
Unvested, December 31, 2019	6,158,026		$	3.43	8.33
Granted	3,258,150		1.29
Exercised	—		—
Canceled	(55,749	)	7.52
Outstanding, March 31, 2020	9,360,427		$	2.66	8.64	$	—
Exercisable at March 31, 2020	2,966,332		$	5.04	7.40	$	—
Vested and unvested expected to vest at March 31, 2020	8,030,728		$	2.86	8.53	$	—

Schedule of Restricted Stock Award Activity

The following table presents a summary of unvested restricted stock awards (“RSAs”) under the 2010 Plan as of March 31, 2020:

	Number of Shares		Weighted Average Grant Date Fair Value
Unvested, December 31, 2019	30,937		$	3.45
Awarded	—		—
Vested	(10,313	)	3.45
Forfeited	—		—
Unvested, March 31, 2020	20,624		$	3.45

Schedule of Stock-Based Compensation Expense

For the three months ended March 31, 2020 and 2019, 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 March 31,
	2020		2019
Research and development expenses	$	170	$	176
General and administrative expenses	455		475
Total stock based compensation expense	$	625	$	651