Quarterly report pursuant to Section 13 or 15(d)

Stock Plans (Tables)

Stock Plans (Tables)

3 Months Ended

Mar. 31, 2019

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

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

	Three Months Ended March 31,
(in thousands)	2019		2018
Research and development	$	77	$	163
Selling, general and administrative		59		269
Total stock-based compensation expense	$	136	$	432

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]

We use the Black-Scholes-Merton option-pricing model with the following assumptions to estimate the fair value of our stock options:

	Three Months Ended March 31,
	2019			2018
Weighted-average risk-free interest rate		2.58	%		2.75	%
Expected dividend payments		—			—
Expected holding period (years) 1		6.3			6.4
Weighted-average volatility factor 2		0.91			0.89
Estimated forfeiture rates for options granted 3		25	%		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.

Share-based Payment Arrangement, Option, Activity [Table Text Block]

The following table summarizes option activity:

	Options (in thousands)			Weighted Average Exercise Price per share		Weighted Average Remaining Option Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2019		665		$	17.94		6.44	$	4
Granted		5			1.60
Forfeited		(8	)		31.17
Outstanding at March 31, 2019		662		$	11.92		6.24	$	67
Exercisable at March 31, 2019		576		$	13.48		5.75	$	31