Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Consolidated Statements of Operations and Comprehensive Income (Loss)
Collaboration revenue	$ 171,128	$ 104,391	$ 7,619
Operating expenses:
Research and development	108,753	119,735	64,905
General and administrative	34,991	36,335	33,809
Total operating expenses	143,744	156,070	98,714
Operating income (loss)	27,384	(51,679)	(91,095)
Other income (expense), net:
Interest income	1,659	6,457	3,310
Other income (expense), net	7,698	1,625	(683)
Total other income	9,357	8,082	2,627
Income (loss) before income taxes	36,741	(43,597)	(88,468)
Income tax benefit			180
Net income (loss)	36,741	(43,597)	(88,288)
Other comprehensive (loss) income
Net unrealized (loss) gain on available-for-sale-securities	(30)	29	34
Total other comprehensive (loss) income	(30)	29	34
Comprehensive income (loss)	$ 36,711	$ (43,568)	$ (88,254)
Net income (loss) per share, basic	$ 0.99	$ (1.21)	$ (2.75)
Net income (loss) per share, diluted	$ 0.98	$ (1.21)	$ (2.75)
Weighted-average common shares outstanding, basic	37,132,447	35,898,266	32,065,781
Weighted-average common shares outstanding, diluted	37,348,514	35,898,266	32,065,781