Annual report pursuant to Section 13 and 15(d)

Stock Plans (Tables)

Stock Plans (Tables)

12 Months Ended

Dec. 31, 2019

The following table summarizes option activity for the year ended December 31, 2019:


		Weighted		Weighted
		Average		Average	Aggregate
		Exercise		Remaining	Intrinsic
	Shares	Price per		Contractual	Value
	(in thousands)	Share		Term (years)	(in thousands)
Outstanding at January 1, 2019	665	$	17.94	6.44	$	4
Granted	854		1.64
Cancelled/expired	(327)		18.06
Outstanding at December 31, 2019	1,192	$	6.23	7.85	$	—
Exercisable at December 31, 2019	738	$	9.05	6.98	$	—

Schedule of assumptions to estimate the stock-based compensation expense:

We use the Black-Scholes-Merton option-pricing model with the following assumptions to estimate the stock-based compensation expense:


	Years Ended December 31,
	2019		2018
Weighted-average risk-free interest rate	2.21	%	2.84	%
Expected dividend payments	—		—
Expected holding period (years)(1)	5.41		6.39
Weighted-average volatility factor(2)	0.94		0.88
Estimated forfeiture rates for options granted	21	%	26	%

(1)

Expected holding period is based on historical experience of similar awards, giving consideration to the contractual terms of the stock-based awards, vesting schedules and the expectations of future employee behavior.

(2)

Weighted average volatility is based on the historical volatility of our common stock.

(3)Estimated forfeiture rates are based on historical data.

Schedule of the stock-based compensation expense

The following table summarizes the stock-based compensation expense (in thousands):


	Years Ended December 31,
	2019		2018
Research and development	$	91	$	575
General and administrative		481		982
Total stock-based compensation expenses	$	572	$	1,557