Quarterly report pursuant to Section 13 or 15(d)

Stock Plans (Tables)

v3.10.0.1
Stock Plans (Tables)
 6 Months Ended
Jun. 30, 2018
Share-based Compensation [Abstract]  
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, 2018 and 2017:
 
 
 
Three Months Ended

‎
June 30,
 
 
Six Months Ended

‎
June 30,
 
(in thousands, except per share amounts)
 
2018
 
 
2017
 
 
2018
 
 
2017
 
Research and development
 
$
156
 
 
$
128
 
 
$
318
 
 
$
245
 
General and administrative
 
 
246
 
 
 
254
 
 
 
516
 
 
 
558
 
Total stock-based compensation expenses
 
$
402
 
 
$
382
 
 
$
834
 
 
$
803
 
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, 2018 and 2017:
 
 
 
Three Months Ended

‎
June 30,
 
 
Six Months Ended

‎
June 30,
 
 
 
2018
 
 
2017
 
 
2018
 
 
2017
 
Weighted-average risk-free interest rate
 
 
2.9
%
 
 
2.0
%
 
 
2.7
%
 
 
2.1
%
Expected dividend payments
 
 
—
 
 
 
—
 
 
 
—
 
 
 
—
 
Expected holding period (years)
1
 
 
6.4
 
 
 
6.5
 
 
 
6.4
 
 
 
6.5
 
Weighted-average volatility factor
2
 
 
0.91
 
 
 
0.88
 
 
 
0.89
 
 
 
0.88
 
Estimated forfeiture rates
3
 
 
25
%
 
 
27
%
 
 
26
%
 
 
28
%
 
(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, 2018:
 
 
(in thousands, except per share amounts)
 
Options
 
 
Weighted
Average
Exercise
Price
 
 
Weighted
Average
Remaining
Option
Term
 
 
Aggregate
Intrinsic
Value
 
Outstanding at January 1, 2018
 
 
2,728
 
 
$
4.32
 
 
 
5.75
 
 
$
30
 
Granted
 
 
950
 
 
 
0.97
 
 
 
 
 
 
 
 
 
Exercised
 
 
—
 
 
 
—
 
 
 
 
 
 
 
 
 
Expired
 
 
(18
)
 
 
8.36
 
 
 
 
 
 
 
 
 
Cancelled or forfeited
 
 
(12
)
 
 
5.46
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Outstanding at June 30, 2018
 
 
3,648
 
 
$
3.42
 
 
 
6.44
 
 
$
115
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Exercisable at June 30, 2018
 
 
2,796
 
 
$
4.00
 
 
 
5.88
 
 
$
57