Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue
Collaborations, licenses, milestones, and royalties	$ 13,089	$ 19,485	$ 45,474	$ 131,424
Operating expenses
Research and development	43,458	33,299	77,401	61,481
General and administrative	7,231	5,758	14,449	11,270
Total operating expenses	50,689	39,057	91,850	72,751
Income (loss) from operations	(37,600)	(19,572)	(46,376)	58,673
Other income (expenses)
Interest income, net	2,090	3,615	5,129	6,501
Other income (expense), net	492	(27)	(1,845)	(212)
Total other income, net	2,582	3,588	3,284	6,289
Net income (loss) before income tax expense	(35,018)	(15,984)	(43,092)	64,962
Income tax expense		50		950
Net income (loss)	(35,018)	(16,034)	(43,092)	64,012
Other comprehensive income
Net unrealized gain on marketable securities	427	1,284	322	2,600
Comprehensive income (loss)	$ (34,591)	$ (14,750)	$ (42,770)	$ 66,612
Net income (loss) per share attributable to common stockholders:
Basic net income (loss) (in dollars per share)	$ (0.61)	$ (0.28)	$ (0.76)	$ 1.14
Diluted net income (loss) (in dollars per share)	$ (0.61)	$ (0.28)	$ (0.76)	$ 1.10
Weighted average shares used to compute net income (loss) per share attributable to common stockholders:
Basic (in shares)	57,059,610	56,399,255	57,003,162	56,351,377
Diluted (in shares)	57,059,610	56,399,255	57,003,162	58,042,819