Quarterly report pursuant to Section 13 or 15(d)

Stock Plans (Tables)

v3.7.0.1
Stock Plans (Tables)
 6 Months Ended
Jun. 30, 2017
Stock Plans [Abstract]  
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]
The following table summarizes the stock-based compensation expense recorded for awards under the stock option plans for the three and six-month periods ended June 30, 2017 and 2016:
 
 
 
Three Months Ended
 
Six Months Ended
 
 
 
June 30,
 
June 30,
 
(in thousands, except per share amounts)
 
2017
 
2016
 
2017
 
2016
 
Research and development
 
$
128
 
$
85
 
$
245
 
$
217
 
General and administrative
 
 
254
 
 
164
 
 
558
 
 
364
 
Total stock-based compensation expenses
 
$
382
 
$
249
 
$
803
 
$
581
 
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 stock-based compensation expense for the three and six-month periods ended June 30, 2017 and 2016:
 
 
 
Three Months Ended
 
Six Months Ended
 
 
 
June 30,
 
June 30,
 
 
 
2017
 
2016
 
2017
 
2016
 
Weighted-average risk-free interest rate
 
 
2.0
%
 
1.5
%
 
2.1
%
 
1.5
%
Expected dividend payments
 
 
—
 
 
—
 
 
—
 
 
—
 
Expected holding period (years) 1
 
 
6.5
 
 
6.5
 
 
6.5
 
 
6.5
 
Weighted-average volatility factor 2
 
 
0.88
 
 
0.92
 
 
0.88
 
 
0.92
 
Estimated forfeiture rates 3
 
 
27
%
 
29
%
 
28
%
 
29
%
 
(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 Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]
The following table summarizes option activity for the six-month period ended June 30, 2017:
 
 
 
 
 
 
 
Weighted
 
 
 
 
 
 
 
Weighted
 
Average
 
 
 
 
 
 
 
Average
 
Remaining
 
Aggregate
 
 
 
 
 
Exercise
 
Option
 
Intrinsic
 
(in thousands, except per share amounts)
 
Options
 
Price
 
Term
 
Value
 
Outstanding at January 1, 2017
 
 
2,002
 
$
5.67
 
 
5.68
 
$
203
 
Granted
 
 
496
 
 
3.70
 
 
 
 
 
 
 
Exercised
 
 
—
 
 
—
 
 
 
 
 
 
 
Expired or cancelled
 
 
(19)
 
 
13.43
 
 
 
 
 
 
 
Forfeited
 
 
—
 
 
—
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Outstanding at June 30, 2017
 
 
2,479
 
$
5.22
 
 
6.13
 
$
—
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Exercisable at June 30, 2017
 
 
1,938
 
$
5.54
 
 
5.23
 
$
—