Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 13,519	$ 14,941
Short-term investments	46,555	61,170
Contract and other receivables	373	1,657
Prepaid materials, net	4,783	5,552
Prepaid expenses and other current assets	1,506	4,154
Total current assets	66,736	87,474
Property and equipment, net	9,708	11,830
Intangibles, net	775	1,015
Other assets	590	342
Total assets	77,809	100,661
Current liabilities:
Accounts payable	5,743	5,840
Accrued liabilities	4,941	5,577
Accrued compensation	1,985	2,318
Current portion of term loan, less debt issuance costs	19,859	0
Current portion of deferred revenue	72	72
Total current liabilities	32,600	13,807
Term loan, less current portion and debt issuance costs	0	19,802
Deferred revenue, less current portion	1,921	1,993
Deferred rent, less current portion	8,072	8,840
Other long-term liabilities	0	144
Total liabilities	42,593	44,586
Commitments and Contingencies (Note 8)
Stockholders’ equity:
Common stock, $0.001 par value; 200,000,000 shares authorized, 103,955,147 and 52,924,805 shares issued and outstanding at December 31, 2017 and 2016, respectively	104	53
Additional paid-in capital	381,104	329,496
Accumulated other comprehensive loss	(134)	(123)
Accumulated deficit	(345,858)	(273,351)
Total stockholders’ equity	35,216	56,075
Total liabilities and stockholders’ equity	$ 77,809	$ 100,661