Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 244,990	$ 234,854
Accounts receivable, net	3,671	0
Grants and other receivables	211	46
Inventory	4,950	2,013
Prepaid expenses and other current assets	2,232	1,254
Total current assets	256,054	238,167
Property and equipment, net	3,596	2,564
Other assets	300	405
Total assets	259,950	241,136
Current liabilities:
Accounts payable	6,951	5,893
Accrued expenses	16,254	8,698
Deferred other income	8	186
Total current liabilities	23,213	14,777
Long-term debt, net	72,138	71,863
Other liabilities	267	0
Total liabilities	95,618	86,640
Stockholders' equity:
Common stock, $0.001 par value; 200,000,000 shares authorized at June 30, 2018 and December 31, 2017; 41,121,557 and 37,802,556 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively	41	38
Additional paid-in capital	430,803	365,838
Accumulated deficit	(266,423)	(211,269)
Accumulated other comprehensive loss	(89)	(111)
Total stockholders' equity	164,332	154,496
Total liabilities and stockholders' equity	$ 259,950	$ 241,136