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Stock award plan (Tables)
3 Months Ended
Mar. 31, 2015
Stock award plan  
Summary of stock option activity

 

 

Number of
options

 

Weighted-
average
exercise
price

 

Weighted-
average
remaining
contractual
term

 

Aggregate
intrinsic
value

 

 

 

 

 

 

 

 

 

(in 
thousands)

 

Outstanding at December 31, 2014

 

3,432,972

 

$

25.00

 

 

 

 

 

Granted

 

1,456,550

 

$

51.02

 

 

 

 

 

Exercised

 

(234,830

)

$

12.86

 

 

 

 

 

Forfeited

 

(26,265

)

$

47.52

 

 

 

 

 

Expired

 

(594

)

$

388.53

 

 

 

 

 

Outstanding at March 31, 2015

 

4,627,833

 

$

33.60

 

8.9 years

 

$

140,399

 

Vested or Expected to vest at March 31, 2015

 

4,332,726

 

$

32.74

 

8.9 years

 

$

133,232

 

Exercisable at March 31, 2015

 

1,037,262

 

$

30.98

 

8.2 years

 

$

45,137

 

 

Schedule of assumptions used to estimate fair value of grants made on the date of grant

 

 

 

Three months 
ended March 
31, 2015

 

Risk-free interest rate

 

1.54% — 1.77%

 

Expected volatility

 

67%-69%

 

Expected term

 

5.50 - 6.11 years

 

 

Summary of information on the Company's restricted stock

 

 

 

Restricted Stock

 

 

 

Number of
Shares

 

Weighted
Average 
Grant
Date Fair 
Value

 

January 1, 2015

 

718,400

 

$

10.72

 

Granted

 

 

 

Vested

 

(350,084

)

$

10.59

 

Forfeited

 

(3,346

)

$

10.82

 

Unvested at March 31, 2015

 

364,970

 

$

10.85

 

 

Schedule of share-based compensation expense recorded in the statement of operations

 

 

 

Three Months Ended March 
31,

 

 

 

2015

 

2014

 

 

 

 

 

 

 

Research and development

 

$

4,667 

 

$

1,944 

 

Selling, general and administrative

 

5,081 

 

1,761 

 

Total

 

$

9,748 

 

$

3,705