Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 65,134	$ 56,992
Prepaid expenses and other current assets	3,079	1,038
Total current assets	68,213	58,030
Restricted cash	2,423	2,396
Property and equipment, net	1,808	32
Operating lease right-of-use assets	8,697
Build-to-suit lease asset, net		8,651
Intangible asset, net	219	341
Other assets	761	20
Total assets	82,121	69,470
Current liabilities
Accounts payable	1,078	426
Accrued liabilities	1,497	1,365
Operating lease obligation, current portion	2,393
Deferred revenue		146
Total current liabilities	4,968	1,937
Contingent payable	264	264
Operating lease obligation	7,840
Build-to-suit lease obligation		7,324
Total liabilities	13,072	9,525
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.0001 par value, 5,000,000 shares authorized at December 31, 2019 and December 31, 2018; zero shares issued and outstanding at December 31, 2019 and December 31, 2018
Common stock, $0.0001 par value, 100,000,000 shares authorized at December 31, 2019 and December 31, 2018; 15,001,795 and 11,266,151 shares issued and outstanding at December 31, 2019 and December 31, 2018, respectively	2	1
Additional paid-in capital	539,158	510,509
Accumulated deficit	(470,111)	(450,565)
Total stockholders' equity	69,049	59,945
Total liabilities and stockholders’ equity	$ 82,121	$ 69,470