Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 144,321	$ 86,042
Marketable securities, current	85,349	195,491
Related party collaboration receivable	12,686	18,496
Prepaid expenses and other current assets	4,301	4,630
Total current assets	246,657	304,659
Property and equipment, net	20,205	17,986
Deposits and other non-current assets	2,183	1,723
Marketable securities, non-current	1,422	1,920
Operating lease, right-of-use asset	26,988	28,472
Total assets	297,455	354,760
Current liabilities:
Accounts payable	2,045	4,070
Accrued expenses	18,154	21,516
Other current liabilities	3,421	3,193
Deferred revenue, current	43,911	47,233
Total current liabilities	67,531	76,012
Deferred revenue, non-current	122,856	147,260
Other non-current liabilities	30,184	31,976
Total liabilities	220,571	255,248
Commitments and contingencies (see note 6 & 8)
Stockholders' equity:
Preferred stock $0.001 par value: 5,000,000 shares authorized at June 30, 2020 and December 31, 2019; no shares issued and outstanding at June 30, 2020 and December 31, 2019
Common stock, $0.001 par value: 120,000,000 shares authorized at June 30, 2020 and December 31, 2019; 37,203,627 and 36,865,116 shares issued and outstanding at June 30, 2020 and December 31, 2019, respectively	37	37
Additional paid-in capital	422,294	412,227
Accumulated other comprehensive income (loss)	145	(104)
Accumulated deficit	(345,592)	(312,648)
Total stockholders' equity	76,884	99,512
Total liabilities and stockholders' equity	$ 297,455	$ 354,760