Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current Assets
Cash and cash equivalents	$ 60,700	$ 65,134
Prepaid expenses and other current assets	580	3,079
Total current assets	61,280	68,213
Restricted cash	2,428	2,423
Property and equipment, net	1,216	1,808
Operating lease right-of-use assets	5,741	8,697
Intangible asset, net	188	219
Other assets	689	761
Total assets	71,542	82,121
Current liabilities
Accounts payable	1,188	1,078
Accrued liabilities	1,447	1,497
Operating lease obligation, current portion	2,324	2,393
Total current liabilities	4,959	4,968
Contingent payable	295	264
Operating lease obligation	7,285	7,840
Total liabilities	12,539	13,072
Commitments and contingencies
Stockholders' equity
Common stock, $0.0001 par value, 100,000,000 shares authorized at March 31, 2020 and December 31, 2019; 15,015,932 and 15,001,795 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively	2	2
Additional paid-in capital	539,908	539,158
Accumulated deficit	(480,907)	(470,111)
Total stockholders' equity	59,003	69,049
Total liabilities and stockholders’ equity	$ 71,542	$ 82,121