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Stock-Based Compensation (Tables)
12 Months Ended
Dec. 31, 2017
Stock-Based Compensation  
Schedule of stock options outstanding

 

 

 

 

 

 

 

 

 

 

 

 

    

December 31, 

 

 

    

2017

    

2016

    

2015

 

Exercisable options

 

 

2,558,941

 

 

1,743,765

 

 

1,600,351

 

Weighted average exercise price per share of exercisable options

 

$

11.06

 

$

8.87

 

$

3.99

 

Weighted average grant date fair value per share of options granted during the year

 

$

16.92

 

$

10.30

 

$

10.66

 

Options available for future grants

 

 

3,394,651

 

 

2,943,216

 

 

2,917,182

 

Weighted average remaining contractual life

 

 

6.58

 

 

7.82

 

 

6.98

 

 

Summary of stock option activity

 

 

 

 

 

 

 

 

 

 

 

 

 

    

 

    

 

 

    

Weighted-

    

 

 

 

 

 

 

 

Weighted-

 

Average

 

 

 

 

 

 

 

 

Average

 

Remaining

 

 

 

 

 

 

 

 

Exercise

 

Contractual

 

Aggregate

 

 

 

Number of

 

Price

 

Term

 

Intrinsic Value

 

 

    

Shares

    

(Per Share)(1)

    

(in years)

    

(in thousands)(2)

 

Balances at December 31, 2015

 

3,370,901

 

$

8.50

 

6.98

 

 

 

 

Options granted

 

1,429,500

 

 

15.08

 

 

 

 

 

 

Options forfeited

 

(54,503)

 

 

12.21

 

 

 

 

 

 

Options expired

 

(1,031)

 

 

15.69

 

 

 

 

 

 

Options exercised(3)

 

(699,066)

 

 

1.66

 

 

 

 

 

 

Balances at December 31, 2016

 

4,045,801

 

 

11.95

 

7.82

 

$

58,131

 

Options granted

 

1,511,100

 

 

22.61

 

 

 

 

 

 

Options forfeited

 

(96,856)

 

 

 

 

 

 

 

 

 

Options expired

 

(3,000)

 

 

 

 

 

 

 

 

 

Options exercised(3)

 

(363,603)

 

 

 

 

 

 

 

 

 

Balances at December 31, 2017

 

5,093,442

 

$

15.32

 

 

 

$

 

 

As of December 31, 2017

 

 

 

 

 

 

 

 

 

 

 

Options vested and expected to vest

 

5,093,442

 

$

15.32

 

7.62

 

$

35,495

 

Exercisable

 

2,558,941

 

$

11.06

 

6.58

 

$

28,017

 

 

Schedule of stock options outstanding and exercisable by exercise price

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Stock Options Outstanding

 

Stock Options Exercisable

 

 

 

 

 

Weighted-

 

 

 

 

 

 

 

 

 

 

 

 

 

Average

 

 

 

 

 

 

 

 

 

 

    

 

    

Remaining

    

Weighted-

    

 

    

Weighted-

 

Range of

 

 

 

Contractual

 

Average

 

 

 

Average

 

Exercise

 

Number of

 

Term

 

Exercise Price

 

Number of

 

Exercise Price

 

Prices

 

Shares

 

(in years)

 

Per Share

 

Shares

 

Per Share

 

$0.59 – $4.25

 

622,046

 

4.82

 

$

3.17

 

622,046

 

$

3.17

 

$9.26 – $13.89

 

1,781,232

 

7.26

 

$

11.87

 

1,205,142

 

$

11.64

 

$14.10 – $21.15

 

968,314

 

7.40

 

$

15.8

 

634,199

 

$

15.68

 

$21.28 – $26.76

 

1,721,850

 

9.13

 

$

23.0

 

97,554

 

$

24.13

 

 

 

5,093,442

 

7.62

 

$

15.32

 

2,558,941

 

$

11.06

 

 

Schedule of total employee, director and non-employee stock-based compensation expense recognized

 

 

 

 

 

 

 

 

 

 

 

 

 

Year Ended

 

 

 

December 31, 

 

(In thousands)

    

2017

    

2016

    

2015

 

General and administrative

 

$

5,617

 

$

3,592

 

$

2,218

 

Research and development

 

 

8,034

 

 

4,256

 

 

2,650

 

 

 

$

13,651

 

$

7,848

 

$

4,869

 

 

Schedule of weighted average assumptions used for estimation of fair value of stock options

 

 

 

 

 

 

 

 

 

 

 

 

 

Options

 

 

    

2017

    

2016

    

2015

 

Common stock fair value per share

 

$

19.61 - 25.67

 

$

11.50 - 26.76

 

$

11.82 - 22.35

 

Expected volatility

 

 

77.42% - 96.73%

 

 

75.77% - 90.83%

 

 

69.17% - 86.46%

 

Risk-free interest rate

 

 

.96% - 2.37%

 

 

1.03% - 2.18% 

 

 

1.44% - 1.84%

 

Expected dividend yield

 

 

 

 

 

 

 

Expected term (in years)

 

 

5.23 - 6.08

 

 

5.23 - 6.08

 

 

5.23 - 6.08

 

 

Schedule of weighted average assumptions used for estimation of fair value of ESPP

 

 

 

 

 

 

 

 

 

ESPP

 

    

2017

    

2016

    

2015

Expected term (years)

 

0.5 - 2.0

 

0.5 - 2.0

 

0.5 - 2.0

Expected volatility

 

67.8% - 79.8%

 

67.8% - 79.8%

 

67.8% - 82.9%

Risk-free interest rate

 

.47% - 1.8%

 

.47% - .93%

 

.07% - .93%

Expected dividend yield

 

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