Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 165,227	$ 86,042
Marketable securities, current	85,704	195,491
Related party collaboration receivable	16,283	18,496
Prepaid expenses and other current assets	5,262	4,630
Total current assets	272,476	304,659
Property and equipment, net	18,586	17,986
Deposits and other non-current assets	2,378	1,723
Marketable securities, non-current	1,432	1,920
Operating lease, right-of-use asset	27,738	28,472
Total assets	322,610	354,760
Current liabilities:
Accounts payable	4,815	4,070
Accrued expenses	17,493	21,516
Other current liabilities	3,306	3,193
Deferred revenue, current	46,923	47,233
Total current liabilities	72,537	76,012
Deferred revenue, non-current	139,227	147,260
Other non-current liabilities	31,089	31,976
Total liabilities	242,853	255,248
Commitments and contingencies (see note 8)
Stockholders' equity:
Preferred stock $0.001 par value: 5,000,000 shares authorized at March 31, 2020 and December 31, 2019; no shares issued and outstanding at March 31, 2020 and December 31, 2019
Common stock, $0.001 par value: 120,000,000 shares authorized at March 31, 2020 and December 31, 2019; 36,976,751 and 36,575,983 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively	37	37
Additional paid-in capital	416,210	412,227
Accumulated other comprehensive income (loss)	421	(104)
Accumulated deficit	(336,911)	(312,648)
Total stockholders' equity	79,757	99,512
Total liabilities and stockholders' equity	$ 322,610	$ 354,760