Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 200,990	$ 234,854
Accounts receivable, net	2,310	0
Grants and other receivables	242	46
Inventory	7,132	2,013
Prepaid expenses and other current assets	2,183	1,254
Total current assets	212,857	238,167
Property and equipment, net	3,884	2,564
Other assets	248	405
Total assets	216,989	241,136
Current liabilities:
Accounts payable	7,116	5,893
Accrued expenses	18,421	8,698
Deferred other income	160	186
Total current liabilities	25,697	14,777
Long-term debt, net	72,500	71,863
Other liabilities	181	0
Total liabilities	98,378	86,640
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock, $0.001 par value; 200,000,000 December 31, 2018 and 2017; 41,227,530 and 37,802,556 shares issued and outstanding at December 31, 2018 and December 31, 2017, respectively	41	38
Additional paid-in capital	436,554	365,838
Accumulated deficit	(317,927)	(211,269)
Accumulated other comprehensive loss	(57)	(111)
Total stockholders' equity	118,611	154,496
Total liabilities and stockholders' equity	$ 216,989	$ 241,136