CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue:
Research and development revenue under collaborative agreements	$ 14,128	$ 0	$ 23,725	$ 0
Total revenue	14,128	0	23,725	0
Expenses:
Research and development	18,487	10,944	83,282	22,734
General and administrative	6,915	2,762	11,590	7,014
Total operating expenses	25,402	13,706	94,872	29,748
Loss from operations	(11,274)	(13,706)	(71,147)	(29,748)
Other income (expense):
Investment income	295	91	358	177
Interest expense	(965)	0	(1,507)	0
Net loss	$ (11,944)	$ (13,615)	$ (72,296)	$ (29,571)
Net loss per share of preferred stock, basic and diluted (in dollars per share)	$ (0.41)	$ (0.47)	$ (2.50)	$ (1.02)
Weighted-average shares of preferred stock outstanding, basic and diluted (in shares)	28,884,540	28,884,540	28,884,540	28,884,540