Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 6,669	$ 9,125
Short-term investments	17,931	3,898
Accounts receivable	193	1,231
Unbilled revenue	168	4
Inventories — current	354	229
Prepaid expenses and other current assets	888	560
Total current assets	26,203	15,047
Property and equipment, net	265	299
Inventories — noncurrent	742	1,168
Other noncurrent assets	7	56
Total assets	27,217	16,570
Current liabilities:
Accounts payable and accrued expenses	2,303	2,496
Amounts due to related parties	18	29
Unearned revenue — current	316	1,000
Total current liabilities	2,637	3,525
Unearned revenue — noncurrent		2,038
Common stock warrant liabilities	8,658
Other noncurrent liabilities	3,000	3,000
Total liabilities	14,295	8,563
Stockholders’ equity:
Common stock, $0.001 par value—150,000,000 shares authorized as of September 30, 2018 and December 31, 2017; 4,774,919 and 2,134,154 shares issued and outstanding as of September 30, 2018 and December 31, 2017, respectively	45	42
Additional paid-in capital	190,599	175,223
Accumulated deficit	(177,720)	(167,257)
Accumulated other comprehensive loss	(2)	(1)
Total stockholders’ equity	12,922	8,007
Total liabilities and stockholders’ equity	$ 27,217	$ 16,570