CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 42,326	$ 46,732
Marketable securities	206,803	227,311
Accounts receivable from collaboration	3,055	3,374
Prepaid expenses and other current assets	4,568	5,363
Total current assets	256,752	282,780
Property and equipment, net	1,780	1,830
Operating lease right-of-use (ROU) assets	11,479	11,975
Other assets	1,661	1,684
Indefinite-lived intangible asset	29,000	29,000
Goodwill	12,638	12,638
Total assets	313,310	339,907
Current liabilities
Accounts payable	2,104	1,731
Accrued clinical expenses	4,633	4,826
Other accrued expenses	4,430	8,286
Deferred revenue - short-term	6,715	6,411
Operating lease liabilities - short-term	3,264	3,186
Total current liabilities	21,146	24,440
Deferred tax liabilities	2,531	2,531
Deferred revenue - long-term	29,326	30,637
Operating lease liabilities - long-term	8,539	9,082
Total liabilities	61,542	66,690
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued or outstanding
Common stock, $0.001 par value; 100,000,000 shares authorized as of March 31, 2020 and December 31, 2019; 32,624,725 and 32,558,307 shares issued and outstanding as of March 31, 2020 and December 31, 2019, respectively	32	32
Additional paid-in capital	717,898	712,807
Accumulated other comprehensive loss	(86)	(201)
Accumulated deficit	(466,076)	(439,421)
Total stockholders' equity	251,768	273,217
Total liabilities and stockholders' equity	$ 313,310	$ 339,907