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Stock-Based Compensation (Tables)
12 Months Ended
Dec. 31, 2018
Stock-Based Compensation  
Schedule of total employee, director and non-employee stock-based compensation expense recognized

 

 

 

 

 

 

 

 

 

 

 

 

 

Year Ended

 

 

 

December 31, 

 

(In thousands)

 

2018

 

2017

 

2016

 

General and administrative

    

$

7,699

    

$

5,617

    

$

3,592

 

Research and development

 

 

12,849

 

 

8,034

 

 

4,256

 

 

 

$

20,548

 

$

13,651

 

$

7,848

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Year Ended

 

 

 

December 31, 

 

(In thousands)

 

2018

 

2017

 

2016

 

Stock options

    

$

19,537

    

$

13,153

    

$

7,470

 

ESPP

 

 

744

 

 

498

 

 

378

 

Restricted stock units

 

 

267

 

 

 —

 

 

 —

 

 

 

$

20,548

 

$

13,651

 

$

7,848

 

 

Schedule of stock options outstanding

 

 

 

 

 

 

 

 

 

 

 

 

    

December 31, 

 

 

 

2018

 

2017

 

2016

 

Exercisable options

 

 

3,058,659

 

 

2,558,941

 

 

1,743,765

 

Weighted average exercise price per share of exercisable options

 

$

15.12

 

$

11.06

 

$

8.87

 

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

 

$

18.06

 

$

16.92

 

$

10.30

 

Options available for future grants

 

 

3,576,574

 

 

3,394,691

 

 

2,943,216

 

Weighted average remaining contractual life

 

 

7.51

 

 

7.62

 

 

7.82

 

 

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, 2016

 

4,045,801

 

 

11.95

 

7.82

 

$

58,131

 

Options granted

 

1,511,100

 

 

22.61

 

 

 

 

 

 

Options forfeited

 

(96,856)

 

 

17.08

 

 

 

 

 

 

Options expired

 

(3,000)

 

 

21.99

 

 

 

 

 

 

Options exercised(3)

 

(363,603)

 

 

7.69

 

 

 

 

 

 

Balances at December 31, 2017

 

5,093,442

 

 

15.32

 

7.62

 

$

35,495

 

Options granted

 

1,805,937

 

 

27.43

 

 

 

 

 

 

Options forfeited

 

(107,720)

 

 

21.66

 

 

 

 

 

 

Options exercised(3)

 

(824,731)

 

 

9.24

 

 

 

 

 

 

Balances at December 31, 2018

 

5,966,928

 

$

19.71

 

7.51

 

$

99,273

 

As of December 31, 2018

 

 

 

 

 

 

 

 

 

 

 

Options vested and expected to vest

 

5,966,928

 

$

19.71

 

7.51

 

$

99,273

 

Exercisable

 

3,058,659

 

$

15.12

 

6.42

 

$

64,417

 

 

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

 

291,433

 

4.49

 

$

3.63

 

291,433

 

$

3.63

 

$9.78 – $14.75

 

1,560,249

 

6.39

 

$

12.10

 

1,281,242

 

$

11.97

 

$14.77 – $22.18

 

852,138

 

6.62

 

$

17.00

 

706,562

 

$

16.35

 

$22.20 – $33.78

 

2,929,571

 

8.42

 

$

23.92

 

760,672

 

$

23.08

 

$34.56 – $43.16

 

333,537

 

9.68

 

$

39.26

 

18,750

 

$

38.93

 

 

 

5,966,928

 

7.51

 

$

19.71

 

3,058,659

 

$

15.12

 

 

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

 

 

 

 

 

 

 

 

 

 

 

 

 

Options

 

 

    

2018

    

2017

    

2016

 

Common stock fair value per share

 

$

21.80 - 43.16

 

$

19.61 - 25.67

 

$

11.50 - 26.76

 

Expected volatility

 

 

70.97% - 73.10%

 

 

77.42% - 96.73%

 

 

75.77% - 90.83%

 

Risk-free interest rate

 

 

2.29% - 3.10%

 

 

0.96% - 2.37%

 

 

1.03% - 2.18% 

 

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

 

 

    

2018

    

2017

    

2016

 

Expected term (years)

 

0.5 - 2.0

 

0.5 - 2.0

 

0.5 - 2.0

 

Expected volatility

 

57.0% - 71.4%

 

67.8% - 79.8%

 

67.8% - 79.8%

 

Risk-free interest rate

 

1.47% - 2.70%

 

0.47% - 1.80%

 

0.47% - 0.93%

 

Expected dividend yield

 

 —

 

 —

 

 —

 

 

Summary of restricted stock unity activity

 

 

 

 

 

 

 

 

 

 

Weighted-

 

 

 

 

Average

 

 

 

 

Grant Date

 

 

Number of

 

Fair Value

 

 

Shares

 

(Per Unit)

Unvested at December 31, 2017

 

 —

 

 

 —

Granted

 

33,933

 

$

27.64

Vested

 

 —

 

 

 —

Forfeited

 

 —

 

 

 —

Unvested at December 31, 2018

 

33,933

 

$

27.64