Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 60,215	$ 33,006
Marketable securities	57,298	100,011
Restricted cash - current	10	10
Receivable from collaboration partner and contract asset - related party	3,594	6,755
Research and development tax incentive receivable	153
Prepaid expenses and other current assets	4,716	5,529
Total current assets	125,986	145,311
Property and equipment, net	1,603	1,681
Restricted cash - noncurrent	450	450
Operating lease right-of-use asset	5,780	6,042
Deferred tax asset	1,082	1,433
Total assets	134,901	154,917
Current liabilities:
Accounts payable	3,704	2,790
Payable to collaboration partner - related party	1,116	1,262
Accrued expenses and other payables	11,616	12,360
Deferred revenue - related party - current	18,630	17,738
Operating lease liability - current	1,306	1,256
Total current liabilities	36,372	35,406
Long-term debt, net	9,832	9,794
Deferred revenue - related party - noncurrent	20,415	23,792
Operating lease liability - noncurrent	5,616	5,961
Total liabilities	72,235	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; 27,434,705 and 27,217,649 shares issued and outstanding as of March 31, 2020 and December 31, 2019, respectively
Additional paid-in capital	300,300	297,846
Accumulated other comprehensive gain (loss)	107	(221)
Accumulated deficit	(237,741)	(217,661)
Total stockholders’ equity	62,666	79,964
Total liabilities and stockholders’ equity	$ 134,901	$ 154,917