Quarterly report pursuant to Section 13 or 15(d)

Stock Plans (Tables)

Stock Plans (Tables)

6 Months Ended

Jun. 30, 2019

Schedule of stock-based compensation expense recorded for awards under our stock option plans

The following table summarizes the stock-based compensation expense recorded for awards under our stock option plans (in thousands):


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2019		2018		2019		2018
Research and development	$	14	$	156	$	91	$	318
Selling, general and administrative		336		246		395		516
Total stock-based compensation	$	350	$	402	$	486	$	834

Schedule of estimate the fair value of stock options


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2019		2018		2019		2018
Weighted-average risk-free interest rate	2.1	%	2.9	%	2.2	%	2.7	%
Expected dividend payments	—		—		—		—
Expected holding period (years) 1	5.9		6.4		5.4		6.4
Weighted-average volatility factor 2	0.93		0.91		0.94		0.89
Estimated forfeiture rates for options granted 3	21	%	25	%	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 option activity

The following table summarizes option activity:


				Weighted
		Weighted		Average
		Average		Remaining	Aggregate
		Exercise		Option	Intrinsic
	Options (in	Price per		Term (in	Value (in
	thousands)	share		years)	thousands)
Outstanding at January 1, 2019	665	$	17.94	6.44	$	4.0
Granted	854		1.64
Cancelled	(217)		26.49
Outstanding at June 30, 2019	1,302		5.82	8.47		0.8
Exercisable at June 30, 2019	669		9.83	7.23		0.1