Stock-Based Compensation (Tables)
 9 Months Ended
Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Summary of stock option activity
The Company’s stock option awards activity and related information for the nine months ended September 30, 2016 were as follows (in thousands, except share and per share data):
 
 
 
 
 
 
 
Weighted-avg.
 
 
 
 Shares
 
 
 
 Weighted-avg.
 
Remaining
 
Aggregate
 
 Available
 
 Stock Options
 
 Exercise Price
 
Contractual
 
Intrinsic
 
 for Grant
 
 Outstanding
 
 Per Share
 
Life (in Years)
 
Value
 
 
 
 
 
 
 
 
 
 
 Balance at December 31, 2015
1,299,301

 
2,429,511

 
$
7.00

 
8.01
 
$
287

 Additional shares authorized
1,400,000

 
—

 
 
 
 
 
 
 Stock options granted
(1,537,000
)
 
1,537,000

 
$
2.94

 
 
 
 
 Stock options canceled
354,951

 
(354,951
)
 
$
7.00

 
 
 
 
 Stock options exercised
—

 
(23,938
)
 
$
1.09

 
 
 
 
 Balance at September 30, 2016
1,517,252

 
3,587,622

 
$
5.30

 
7.88
 
$
230

 
 
 
 
 
 
 
 
 
 
At September 30, 2016:
 
 
 
 
 
 
 
 
 
    Vested and expected to vest
 
 
3,474,777

 
$
5.36

 
7.84
 
$
228

    Exercisable
 
 
1,532,114

 
$
7.16

 
6.48
 
$
187
Stock-based compensation expense
The Company recognized stock-based compensation expense within the condensed consolidated statements of operations and comprehensive loss as follows (in thousands):
 
Three Months Ended
September 30,
 
Nine Months Ended
September 30,
 
2016
 
2015
 
2016
 
2015
Research and development
$
139

 
$
192

 
$
516

 
$
456

General and administrative
864

 
766

 
2,652

 
2,404

Total
$
1,003

 
$
958

 
$
3,168

 
$
2,860
Stock option valuation assumptions
The fair values of these options were determined using a Monte Carlo simulation model incorporating the following ranges of weighted-average assumptions:
 
 
Nine Months Ended
September 30, 2016
Expected dividend yield

—
Risk-free interest rates

1.82% - 2.05%
Expected term in years

6.02 - 8.00
Expected volatility

77% - 89%
Weighted-average fair value per share

1.33 - 1.42
The fair value of all stock options granted was estimated using the following ranges of weighted-average assumptions:


Three Months Ended
September 30,

Nine Months Ended
September 30,


2016

2015

2016

2015
Expected dividend yield

—

—

—

—
Risk-free interest rates

0.59% - 1.39%

1.59% - 1.64%

0.59% - 1.97%

1.52% - 2.08%
Expected term in years

0.95 - 4.43

5.52 - 6.08

0.95 - 8.14

5.49 - 8.06
Expected volatility

73% - 87%

78% - 80%

73% - 94%

78% - 92%