Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current Assets:
Cash and cash equivalents	$ 38,001	$ 80,304
Short-term investments	91,155	112,187
Accounts receivable	3,990	3,977
Restricted investment	10,695	10,695
Other current assets	16,885	17,380
Total current assets	160,726	224,543
Restricted cash and investments	783	783
Property and equipment, net of accumulated depreciation of $25,826 and $24,594 as of March 31, 2016 and December 31, 2015, respectively	36,982	37,344
Patent costs, net of accumulated amortization of $2,774 and $2,620 as of March 31, 2016 and December 31, 2015, respectively	6,728	6,642
Other non-current assets	8,145	4,470
Total assets	213,364	273,782
Current Liabilities:
Accounts payable	18,673	20,234
Accrued expenses	24,277	29,053
Current portion of long-term debt	7,604	5,936
Current portion of notes payable		2,493
Deferred revenue	3,303	3,303
Other current liabilities	1,303	1,275
Total current liabilities	55,160	62,294
Long-term debt	13,373	14,969
Deferred rent and other	5,869	6,172
Total liabilities	$ 74,402	$ 83,435
Commitments and contingencies (Note 10)
Stockholders’ Equity:
Preferred stock, $.0001 par value, 3,333,333 shares authorized; none issued and outstanding
Common stock, $.0001 par value, 99,000,000 shares authorized; 45,767,497 and 45,629,529 issued and outstanding at March 31, 2016 and December 31, 2015, respectively	$ 5	$ 5
Additional paid-in capital	1,097,787	1,089,508
Accumulated other comprehensive loss	(5)	(111)
Accumulated deficit	(958,825)	(899,055)
Total stockholders’ equity	138,962	190,347
Total liabilities and stockholders’ equity	$ 213,364	$ 273,782