Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 104,440	$ 86,042
Marketable securities, current	76,698	195,491
Related party collaboration receivable	8,012	18,496
Prepaid expenses and other current assets	8,619	4,630
Total current assets	197,769	304,659
Property and equipment, net	25,435	17,986
Deposits and other non-current assets	2,316	1,723
Marketable securities, non-current		1,920
Operating lease, right-of-use assets	36,064	28,472
Total assets	261,584	354,760
Current liabilities:
Accounts payable	634	4,070
Accrued expenses	14,205	21,516
Other current liabilities	4,198	3,193
Deferred revenue, current	7,729	47,233
Total current liabilities	26,766	76,012
Deferred revenue, non-current	36,088	147,260
Other non-current liabilities	44,410	31,976
Total liabilities	107,264	255,248
Commitments and contingencies (see note 9)
Stockholders' equity:
Preferred stock, $0.001 par value: 5,000,000 shares authorized; no shares issued and outstanding at December 31, 2020 and 2019
Common stock, $0.001 par value: 120,000,000 shares authorized; 37,368,027 and 36,865,116 shares issued and outstanding at December 31, 2020 and 2019, respectively	37	37
Additional paid-in capital	430,324	412,227
Accumulated other comprehensive loss	(134)	(104)
Accumulated deficit	(275,907)	(312,648)
Total stockholders' equity	154,320	99,512
Total liabilities and stockholders' equity	$ 261,584	$ 354,760