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Stock-based Compensation (Tables)
9 Months Ended
Sep. 30, 2018
Stock-based Compensation  
Schedule of stock-based compensation expense

Total compensation cost recognized for all stock‑based compensation awards in the Company’s condensed consolidated statements of operations was as follows (in thousands):

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Three Months Ended

 

Nine Months Ended

 

 

September 30, 

 

September 30, 

 

 

2018

 

2017

    

2018

    

2017

Research and development

 

$

3,506

 

$

2,431

 

$

11,412

 

$

9,130

General and administrative

 

 

3,193

 

 

2,037

 

 

8,839

 

 

6,157

Total stock-compensation expense

 

$

6,699

 

$

4,468

 

$

20,251

 

$

15,287

 

Schedule of changes in unvested restricted stock

 

 

 

 

 

 

 

    

 

    

Weighted

 

 

 

 

Average

 

 

 

 

Grant Date

 

 

 

 

Fair Value

 

 

Shares

 

Per Share

Unvested Restricted Common Stock as of December 31, 2017

 

513,225

 

$

18.70

Issued

 

 —

 

 

 —

Vested

 

(225,225)

 

$

6.75

Forfeited

 

 —

 

 

 —

Unvested Restricted Common Stock as of September 30, 2018

 

288,000

 

$

28.05

 

Schedule of stock option activity

 

 

 

 

 

 

 

 

 

 

 

 

    

 

    

Weighted Average

    

Remaining

    

Aggregate Intrinsic

 

 

Shares

 

Exercise Price

 

Contractual Life (years)

 

Value (in thousands)

Outstanding at December 31, 2017

 

4,372,136

 

$

17.28

 

8.5

 

$

60,591

Granted

 

1,643,185

 

$

36.29

 

 —

 

 

 —

Exercised

 

(634,331)

 

$

13.73

 

 —

 

 

 —

Cancelled

 

(558,504)

 

$

24.88

 

 —

 

 

 —

Outstanding at September 30, 2018

 

4,822,486

 

$

23.38

 

8.2

 

$

48,750

Exercisable at September 30, 2018

 

1,881,620

 

$

17.65

 

7.5

 

$

28,201

 

Schedule of assumptions used to value stock options

 

 

 

 

 

 

 

 

 

 

 

 

 

 

    

Three Months Ended

 

Nine Months Ended

 

 

 

September 30, 

 

September 30, 

 

 

 

2018

 

2017

    

2018

    

 

2017

 

Risk free interest rate

 

2.9

%  

 

1.9

%  

 

2.6

%  

 

2.1

% 

Expected dividend yield

 

 —

 

 

 —

 

 

 —

 

 

 —

 

Expected term (in years)

 

6.25

 

 

6.25

 

 

6.25

 

 

6.25

 

Expected volatility

 

77.3

%  

 

78.0

%  

 

79.8

%  

 

77.9

%