Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Condensed Consolidated Statements of Operations and Comprehensive Loss        
Collaboration and other research and development revenues $ 962 $ 670 $ 5,155 $ 837
Operating expenses:        
Research and development 10,832 3,850 30,144 13,020
General and administrative 11,295 4,202 33,215 10,756
Total operating expenses 22,127 8,052 63,359 23,776
Operating loss (21,165) (7,382) (58,204) (22,939)
Other income (expense), net        
Other income (expense), net 3 21 (22) (37,219)
Interest income (expense), net 142 (44) 419 (109)
Total other income (expense), net 145 (23) 397 (37,328)
Net loss and comprehensive loss (21,020) (7,405) (57,807) (60,267)
Reconciliation of net loss to net loss attributable to common stockholders:        
Net loss (21,020) (7,405) (57,807) (60,267)
Accretion of redeemable convertible preferred stock to redemption value   (104) (47) (295)
Net loss attributable to common stockholders $ (21,020) $ (7,509) $ (57,854) $ (60,562)
Net loss per share attributable to common stockholders, basic and diluted $ (0.59) $ (2.57) $ (1.86) $ (25.53)
Weighted-average common shares outstanding, basic and diluted 35,505,429 2,925,843 31,040,670 2,371,976