Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 56,992	$ 81,146
Prepaid expenses and other current assets	1,038	562
Total current assets	58,030	81,708
Restricted cash	2,396	2,383
Property and equipment, net	32	798
Build-to-suit lease asset, net (Note 7)	8,651	8,888
Intangible asset, net	341
Other assets	20
Total assets	69,470	93,777
Current liabilities
Accounts payable	426	1,500
Accrued liabilities	1,365	4,093
Deferred revenue	146
Total current liabilities	1,937	5,593
Contingent payable	264
Build-to-suit lease obligation (Note 7)	7,324	5,428
Total liabilities	9,525	11,021
Commitments and contingencies (Note 8)
Stockholders' equity
Preferred stock, $0.0001 par value, 5,000,000 shares authorized at December 31, 2018 and December 31, 2017; zero shares issued and outstanding at December 31, 2018 and December 31, 2017
Common stock, $0.0001 par value, 100,000,000 shares authorized at December 31, 2018 and December 31, 2017; 11,266,151 and 5,989,688 shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively	1	1
Additional paid-in capital	510,509	456,987
Accumulated deficit	(450,565)	(374,232)
Total stockholders' equity	59,945	82,756
Total liabilities and stockholders’ equity	$ 69,470	$ 93,777