Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current Assets
Cash and cash equivalents	$ 48,384	$ 56,992
Prepaid expenses and other current assets	3,667	1,038
Total current assets	52,051	58,030
Restricted cash	2,409	2,396
Property and equipment, net	1,996	32
Operating lease right-of-use assets	9,501
Build-to-suit lease asset		8,651
Intangible asset, net	280	341
Other assets	509	20
Total assets	66,746	69,470
Current liabilities
Accounts payable	711	426
Accrued liabilities	1,400	1,365
Operating lease obligation, current portion	2,505
Deferred revenue		146
Total current liabilities	4,616	1,937
Contingent payable	264	264
Operating lease obligation	8,995
Build-to-suit lease obligation		7,324
Total liabilities	13,875	9,525
Commitments and contingencies (Note 6)
Stockholders' equity
Common stock, $0.0001 par value, 100,000,000 shares authorized at June 30, 2019 and December 31, 2018; 11,284,580 and 11,266,151 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	1	1
Additional paid-in capital	512,511	510,509
Accumulated deficit	(459,641)	(450,565)
Total stockholders' equity	52,871	59,945
Total liabilities and stockholders’ equity	$ 66,746	$ 69,470