Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 147,144	$ 200,990
Accounts receivable, net	13,643	2,310
Grants and other receivables	175	242
Inventory	3,484	7,132
Prepaid expenses and other current assets	3,614	2,183
Total current assets	168,060	212,857
Property and equipment, net	3,052	3,884
Other assets	1,538	248
Total assets	172,650	216,989
Current liabilities:
Accounts payable	3,625	7,116
Accrued expenses	32,514	18,421
Deferred other income	0	160
Total current liabilities	36,139	25,697
Long-term debt, net	74,531	72,500
Other liabilities	397	181
Total liabilities	111,067	98,378
Commitments and contingencies (Note 11)
Stockholders' equity:
Common stock, $0.001 par value; 200,000,000 shares authorized at December 31, 2019 and 2018; 45,906,162 and 41,227,530 shares issued and outstanding at December 31, 2019 and December 31, 2018, respectively	46	41
Additional paid-in capital	489,565	436,554
Accumulated deficit	(427,980)	(317,927)
Accumulated other comprehensive loss	(48)	(57)
Total stockholders' equity	61,583	118,611
Total liabilities and stockholders' equity	$ 172,650	$ 216,989