Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
License revenue	$ 10,385	$ 4,303	$ 5,025
License revenue from related party			2,000
Reagent sales		213	257
Grant revenue	8	73	306
Total revenues	10,393	4,589	7,588
Costs of revenues
Licensing costs	1,703	861	1,405
Costs of reagent sales	6	98	98
Research and development	57,224	45,482	17,279
General and administrative	27,229	23,590	11,912
Other operating expenses (income)	116	(102)	31
Total operating expenses	86,278	69,929	30,725
Loss from operations	(75,885)	(65,340)	(23,137)
Other Income (Expense)
Investment income	2,716	1,938	346
Interest expense			(20)
Total other income (expense)	2,716	1,938	326
Loss before income taxes	(73,169)	(63,402)	(22,811)
Income Tax Benefit	0	435	0
Net loss	(73,169)	(62,967)	(22,811)
Other Comprehensive Income (Loss)
Unrealized gain (loss) on available-for-sale securities, net of reclassifications and income tax expense	(682)	686	(719)
Total other comprehensive income (loss)	(682)	686	(719)
Comprehensive loss	(73,851)	(62,281)	(23,530)
Reconciliation of net loss to net loss applicable to common stockholders
Net loss	(73,169)	(62,967)	(22,811)
Net accretion and dividends on convertible preferred stock			(1,747)
Net gain on extinguishment of convertible preferred stock			759
Net loss applicable to common stockholders	$ (73,169)	$ (62,967)	$ (23,799)
Basic and diluted net loss per common share	$ (2.45)	$ (2.38)	$ (2.59)
Weighted-average basic and diluted common shares	29,878	26,409	9,173