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Equity Plans (Tables)
 12 Months Ended
Dec. 31, 2019
Schedule of activity under equity incentive plans

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Weighted-

 

Weighted-

 

 

 

 

 

 

Average

 

Average

 

 

 

 

 

 

Exercise

 

Remaining

 

Aggregate

 

 

Options

 

Price Per

 

Contractual

 

Intrinsic

 

    

Outstanding

    

Share

    

Life (years)

    

Value (1)

 

 

 

 

 

 

 

 

 

(in millions)

Balances at December 31, 2018

 

3,178,441

  

$

12.23

 

7.52

 

 

 

Options granted

 

1,328,800

  

 

9.36

 

  

 

 

  

Options exercised

 

(307,055)

 

 

3.81

  

 

  

 

 

Options forfeited

 

(518,665)

 

 

14.08

 

 

 

 

 

Balances at December 31, 2019

 

3,681,521

  

$

11.64

 

7.78

 

$

2.4

Options exercisable – December 31, 2019

 

1,973,866

  

$

11.82

 

6.93

 

$

2.3

Options vested and expected to vest – December 31, 2019

 

3,681,521

 

$

11.64

 

7.78

 

$

2.4

____________________

(1) The aggregate intrinsic values were calculated as the difference between the exercise price of the options and the closing price of the Company’s common stock on December 31, 2019. The calculation excludes options with an exercise price higher than the closing price of the Company’s common stock on December 31, 2019.

 

Schedule of stock-based compensation expense

Total stock-based compensation expense was as follows (in thousands):

 

 

 

 

 

 

 

 

 

 

 

 

Year Ended December 31, 

 

    

2019

    

2018

    

2017

Research and development

 

$

4,350

 

$

3,424

 

$

2,008

General and administrative

 

 

4,003

 

 

3,495

 

 

2,233

Total stock-based compensation expense

 

$

8,353

 

$

6,919

 

$

4,241

 

Employee stock options  
Black-Scholes option-pricing model assumptions

 

 

 

 

 

 

 

 

Year Ended December 31, 

 

 

2019

    

2018

 

2017

 

Expected term (in years)

5.00 - 6.08

 

5.49 - 6.08

 

5.50 - 6.08

 

Expected volatility

61.0% - 64.8%

 

62.0% - 66.5%

 

61.6% - 65.4%

 

Risk-free interest rate

1.42% - 2.58%

 

2.42% - 3.03%

 

1.88% - 2.24%

 

Dividend yield

—

 

—

 

—

 

 

Restricted stock units  
Schedule of activity under equity incentive plans

 

 

 

 

 

 

 

 

 

 

Weighted

 

 

 

 

Average

 

 

Number of

 

Grant Date

 

    

Shares

    

Fair Value

Unvested at December 31, 2018

 

418,450

  

$

10.45

Restricted grant units granted

 
160,650

 

 

8.02

Restricted grant units vested

 

(197,703)

 

 

9.29

Restricted grant units forfeited

 

(102,915)

 

 

9.88

Unvested at December 31, 2019

 

278,482

 

$

10.08

 

ESPP rights  
Black-Scholes option-pricing model assumptions

 

 

 

 

 

 

 

 

 

 

 

 

Year Ended December 31, 

 

 

 

2019

    

 

2018

 

 

2017

 

Expected term (in years)

 

0.50

 

 

0.50

 

 

0.50

 

Expected volatility

 

58.9%  -65.3%

 

 

49.0%  -63.4%

 

 
52.4%

 

Risk-free interest rate

 

1.89%  -2.32%

 

 

1.89%  -2.32%

 

 

0.89% - 1.16%

 

Dividend yield

 

 —

 

 

 —

 

 

 —