Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 146,242	$ 33,006
Marketable securities	62,423	100,011
Restricted cash - current	10	10
Receivable from collaboration partner and contract asset - related party	2,997	6,755
Research and development tax incentive receivable	276
Prepaid expenses and other current assets	5,518	5,529
Total current assets	217,466	145,311
Property and equipment, net	1,553	1,681
Restricted cash - noncurrent	450	450
Operating lease right-of-use asset	5,511	6,042
Deferred tax asset		1,433
Total assets	224,980	154,917
Current liabilities:
Accounts payable	2,855	2,790
Payable to collaboration partner - related party	1,003	1,262
Accrued expenses and other payables	12,917	12,360
Deferred revenue - related party - current	17,230	17,738
Operating lease liability - current	1,355	1,256
Total current liabilities	35,360	35,406
Long-term debt, net		9,794
Deferred revenue - related party - noncurrent	16,784	23,792
Operating lease liability - noncurrent	5,259	5,961
Other liability - noncurrent	92
Total liabilities	57,495	74,953
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.00001 par value, 10,000,000 shares authorized; no shares issued and outstanding
Common stock, $0.00001 par value, 90,000,000 shares authorized; 36,802,139 and 27,217,649 shares issued and outstanding as of June 30, 2020 and December 31, 2019, respectively
Additional paid-in capital	424,855	297,846
Accumulated other comprehensive loss	(208)	(221)
Accumulated deficit	(257,162)	(217,661)
Total stockholders' equity	167,485	79,964
Total liabilities and stockholders' equity	$ 224,980	$ 154,917