Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 9,887	$ 5,759
Short-term investments	14,852	20,035
Accounts receivable	3,476	5,063
Prepaid expenses and other current assets	1,017	1,397
Total current assets	29,232	32,254
Long-term investments	2,409	1,995
Materials inventory	2,995	3,357
Property and equipment, net	7,096	10,964
Intangible assets, net	3,081	4,001
Other assets	577	597
Total assets	45,390	53,168
Current liabilities:
Accounts payable	1,014	309
Accrued liabilities	1,046	1,451
Accrued compensation and employee benefits	2,564	1,663
Deferred revenue	2,018	1,533
Total current liabilities	6,642	4,956
Deferred rent	2,994	3,149
Other long-term liabilities	28	67
Total liabilities	9,664	8,172
Commitments and contingencies (note 5)
Stockholders’ equity:
Common stock, par value $0.001 per share—200,000,000 shares authorized; 49,559,701 and 49,513,528 shares issued and outstanding as of September 30, 2017 and December 31, 2016, respectively	50	50
Additional paid-in capital	214,538	213,313
Accumulated other comprehensive loss	(9)	(32)
Accumulated deficit	(178,853)	(168,335)
Total stockholders’ equity	35,726	44,996
Total liabilities and stockholders’ equity	$ 45,390	$ 53,168