CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (USD $)
In Thousands, except Per Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Operating expenses:      
Research and development $ 35,448 $ 25,930 $ 21,712
General and administrative 18,159 15,472 10,518
Total operating expenses 53,607 41,402 32,230
Loss from operations (53,607) (41,402) (32,230)
Interest income 242 200 246
Net loss (53,365) (41,202) (31,984)
Accretion of preferred stock     (6)
Net loss applicable to common stockholders (53,365) (41,202) (31,990)
Net loss per share applicable to common stockholders-basic and diluted $ (2.07) $ (1.82) $ (1.70)
Weighted-average number of common shares used in net loss per share applicable to common stockholders-basic and diluted 25,804 22,680 18,765
Net loss (53,365) (41,202) (31,984)
Unrealized gains (losses) on available-for-sale securities (17) 6 24
Comprehensive loss $ (53,382) $ (41,196) $ (31,960)