Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 2,930	$ 2,013
Short-term investments	12,767	48,547
Accounts receivable	73	349
Unbilled revenue	61	184
Inventories — current	236	252
Prepaid expenses and other current assets	1,099	877
Total current assets	17,166	52,222
Property and equipment, net	369	508
Inventories — noncurrent	1,179	1,327
Long-term investments		2,498
Other noncurrent assets	264	19
Total assets	18,978	56,574
Current liabilities:
Accounts payable and accrued expenses	1,863	2,359
Amounts due to related parties	31	30
Unearned revenue — current	626	740
Total current liabilities	2,520	3,129
Notes payable — noncurrent		25,127
Unearned revenue — noncurrent	2,791	3,120
Other noncurrent liabilities	3,000	3,000
Total liabilities	8,311	34,376
Stockholders’ equity:
Common stock, $0.001 par value—150,000,000 and 400,000,000 shares authorized as of September 30, 2017 and December 31, 2016; 42,683,063 and 44,487,678 shares issued and outstanding as of September 30, 2017 and December 31, 2016	43	44
Additional paid-in capital	174,925	173,723
Accumulated deficit	(164,297)	(151,550)
Accumulated other comprehensive loss	(4)	(19)
Total stockholders’ equity	10,667	22,198
Total liabilities and stockholders’ equity	$ 18,978	$ 56,574