Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 174,565	$ 127,789
Marketable securities	165,832	264,589
Accounts receivable, net	5,060	410
Inventories	3,374	1,799
Prepaid expenses and other current assets	3,007	3,403
Total current assets	351,838	397,990
Property and equipment, net	10,690	11,189
Long-term investments		31,538
Restricted cash		600
Total assets	362,528	441,317
Current liabilities
Accounts payable	5,672	6,222
Accrued expenses and other current liabilities	11,640	14,383
Current portion of long-term debt	9,967	9,967
Total current liabilities	27,279	30,572
Long-term debt, net	8,288	12,936
2024 convertible notes, net	140,902	137,107
Other long-term liabilities	552	428
Total liabilities	177,021	181,043
Commitments and contingencies
Preferred stock, $0.001 par value; 10,000,000 shares authorized at June 30, 2018 and December 31, 2017 and 0 shares issued and outstanding at June 30, 2018 and December 31, 2017	0	0
Stockholders' equity
Common stock, $0.001 par value; 100,000,000 shares authorized; 37,807,523 and 37,610,897 shares issued and outstanding, at June 30, 2018 and December 31, 2017, respectively	38	38
Additional paid-in capital	620,390	609,810
Accumulated other comprehensive loss	(310)	(407)
Accumulated deficit	(434,611)	(349,167)
Total stockholders' equity	185,507	260,274
Total liabilities and stockholders' equity	$ 362,528	$ 441,317