Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 60,541	$ 65,134
Prepaid expenses and other current assets	1,148	3,079
Total current assets	61,689	68,213
Restricted cash	2,430	2,423
Property and equipment, net	526	1,808
Operating lease right-of-use assets	2,958	8,697
Intangible asset, net	97	219
Other assets	10	761
Total assets	67,710	82,121
Current liabilities
Accounts payable	2,500	1,078
Accrued liabilities	2,323	1,497
Operating lease obligation, current portion	2,086	2,393
Current portion of deferred revenue	2,552
Total current liabilities	9,461	4,968
Deferred revenue, net of current portion	3,763
Contingent payable		264
Operating lease obligation, net of current portion	6,431	7,840
Total liabilities	19,655	13,072
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.0001 par value, 5,000,000 shares authorized at December 31, 2020 and December 31, 2019; zero shares issued and outstanding at December 31, 2020 and December 31, 2019
Common stock, $0.0001 par value, 100,000,000 shares authorized at December 31, 2020 and December 31, 2019; 16,481,099 and 15,001,795 shares issued and outstanding at December 31, 2020 and December 31, 2019, respectively	2	2
Additional paid-in capital	548,707	539,158
Accumulated deficit	(500,654)	(470,111)
Total stockholders' equity	48,055	69,049
Total liabilities and stockholders’ equity	$ 67,710	$ 82,121