Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 50,195	$ 82,233
Restricted cash - current	10	10
Available-for-sale securities	87,497	46,620
Receivable from collaboration partner and contract asset - related party	1,945	4,587
Research and development tax incentive receivable, net	173	1,429
Prepaid expenses and other current assets	4,203	2,624
Total current assets	144,023	137,503
Property and equipment, net	1,734	861
Restricted cash - noncurrent	450	450
Operating lease right-of-use asset	6,295
Deferred tax asset	2,125	658
Total assets	154,627	139,472
Current liabilities:
Accounts payable	1,583	5,711
Payable to collaboration partner - related party	1,020	1,061
Accrued expenses and other payables	10,486	11,163
Operating lease liability - current	1,209
Deferred revenue - related party	16,478	8,223
Total current liabilities	30,776	26,158
Deferred revenue - related party - noncurrent	22,200
Operating lease liability - noncurrent	6,293
Deferred rent		799
Total liabilities	59,269	26,957
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; 27,206,447 and 23,187,219 shares issued and outstanding as of September 30, 2019 and December 31, 2018, respectively
Additional paid-in capital	295,672	253,222
Accumulated other comprehensive loss	(154)	(233)
Accumulated deficit	(200,160)	(140,474)
Total stockholders’ equity	95,358	112,515
Total liabilities and stockholders’ equity	$ 154,627	$ 139,472