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Stock Based Compensation
 12 Months Ended
Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]  
Stock Based Compensation

16.

STOCK-Based Compensation

Stock options granted have a contractual term of 10 years and generally vest over a 2-4 year period. A limited number of stock options vest immediately in certain circumstances. The following table summarizes the status of the Company’s stock option activity granted under the Plans to employees, directors, and consultants (in thousands, except stock option amounts):

 

 

 

Stock Options

 

 

Weighted-

Average

Exercise Price

 

 

Weighted-

Average

Remaining

Contractual

Term

 

 

Aggregate

Intrinsic Value

 

Outstanding at December 31, 2016

 

 

9,280,689

 

 

$

6.26

 

 

 

7.26

 

 

$

43,994

 

Granted

 

 

1,741,732

 

 

 

11.46

 

 

 

—

 

 

 

 

 

Exercised

 

 

(404,698

)

 

 

5.63

 

 

 

—

 

 

 

 

 

Forfeited

 

 

(430,882

)

 

 

5.89

 

 

 

—

 

 

 

 

 

Expired

 

 

(10,198

)

 

 

           4.04

 

 

 

—

 

 

 

 

 

Outstanding at December 31, 2017

 

 

10,176,643

 

 

$

7.19

 

 

 

6.83

 

 

$

88,615

 

Vested an exercisable at December 31, 2017

 

 

7,824,015

 

 

$

6.25

 

 

 

6.22

 

 

$

75,527

 

 

The total fair-value of stock options vested and recorded as compensation expense during the years ended December 31, 2017, 2016, and 2015 was $8.0 million, $11.0 million, and $8.9 million, respectively. As of December 31, 2017 and 2016 $14.6 million and $11.0 million of unrecognized compensation expense related to non-vested stock options is expected to be recognized over a weighted-average period of approximately 1.9 years and 1.6 years, respectively. The total intrinsic value of stock options exercised was approximately $4.2 million and $0.1 million for the years ended December 31, 2017 and 2016, respectively.

The Company determines the fair value of stock option awards on the grant date using the Black-Scholes option pricing model, which is impacted by assumptions regarding a number of highly subjective variables. The following table summarizes the weighted-average assumptions used as inputs to the Black-Scholes option pricing model during the periods indicated:

 

 

 

Year Ended December 31,

 

 

 

2017

 

 

2016

 

 

2015

 

Weighted average grant date fair value

 

$

7.01

 

 

$

5.53

 

 

$

4.25

 

Expected dividend yield

 

 

—

%

 

 

—

%

 

 

—

%

Expected stock price volatility

 

 

66

%

 

 

65

%

 

 

62

%

Risk-free interest rate

 

 

1.74

%

 

 

1.29

%

 

 

1.56

%

Expected life of options (in years)

 

 

6.2

 

 

 

6.0

 

 

 

5.9

 

 

Employee Stock Grants

The Company grants common stock to key officers and directors as additional compensation in certain circumstances. The fair value of these grants is recorded as compensation expense throughout the requisite service period (See Note 13—Related Party Transactions for further detail on these grants). Compensation expense recorded for these restricted stock grants and stock granted upon the IPO amounted to $6.6 million, $8.5 million, and $4.0 million for the years ended December 31, 2017, 2016, and 2015, respectively.

Restricted Stock

The following table summarizes restricted stock activity:

 

 

 

Shares of

Restricted

Stock

 

 

Weighted

Average Fair

Value

 

Nonvested at December 31, 2016

 

 

661,982

 

 

$

9.00

 

Granted

 

 

—

 

 

 

9.00

 

Vested

 

 

(421,982

)

 

 

9.00

 

Nonvested at December 31, 2017

 

 

240,000

 

 

$

9.00

 

 

Warrants

The Company has granted warrants to purchase common stock. The Company determined the fair value of the warrants on the grant date using the Black-Scholes option pricing model, consistent with the valuations of stock options described above. As of December 31, 2016, 344,000 fully vested warrants were outstanding. During June 2017, the holder exercised their warrants and as of December 31, 2017, there were no outstanding warrants.

Stock-Based Compensation Expense

The components of stock-based compensation and the amounts recorded within research and development expenses and selling, general, and administrative expenses in the Company’s consolidated statements of operations and comprehensive loss consisted of the following for the years ended December 31, 2017, 2016, and 2015 (in thousands):

 

 

 

Year Ended December 31,

 

 

 

2017

 

 

2016

 

 

2015

 

Stock options

 

$

8,031

 

 

$

10,977

 

 

$

8,932

 

Restricted stock expense

 

 

2,160

 

 

 

8,534

 

 

 

4,035

 

Stock awarded to directors and officers

 

 

4,400

 

 

 

—

 

 

 

2,560

 

Total stock-based compensation expense

 

$

14,591

 

 

$

19,511

 

 

$

15,527

 

Cost of sales

 

$

137

 

 

$

—

 

 

$

—

 

Research and development expenses

 

 

2,030

 

 

 

8,573

 

 

 

5,600

 

Selling, general, and administrative expenses

 

 

12,424

 

 

 

10,938

 

 

 

9,927

 

Total stock-based compensation expense

 

$

14,591

 

 

$

19,511

 

 

$

15,527