Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 120,702	$ 131,490
Prepaid expenses and other current assets	2,701	5,921
Income tax receivable	114	5,975
Other receivables	10,670	24,526
Total current assets	134,187	167,912
Property and equipment, net	5,527	6,835
Total assets	139,714	174,747
Current liabilities:
Accounts payable	11,860	22,883
Accrued expenses	13,832	14,309
Current portion of unearned revenue	112	391
Current portion of deferred rent	93	90
Current portion of notes payable and obligations under capital leases	194	232
Total current liabilities	26,091	37,905
Long-term liabilities:
Royalty obligation payable to Iowa Economic Development Authority	6,000	6,000
Notes payable and obligations under capital leases	138	285
Deferred rent	1,021	1,091
Total long-term liabilities	7,159	7,376
Total liabilities	33,250	45,281
Stockholders' equity:
Blank check preferred stock, $0.01 par value: Authorized shares — 5,000,000 at September 30, 2017 and December 31, 2016; issued and outstanding shares — 0 at September 30, 2017 and December 31, 2016	0	0
Common stock, $0.01 par value: Authorized shares — 75,000,000 at September 30, 2017 and December 31, 2016; issued 31,375,528 and 29,193,718 at September 30, 2017 and December 31, 2016, respectively, and outstanding 31,319,751 and 29,163,673 at September 30, 2017 and December 31, 2016, respectively	314	292
Additional paid-in capital	331,036	295,535
Treasury stock, at cost: 55,777 and 30,045 shares at September 30, 2017 and December 31, 2016, respectively	(1,113)	(853)
Accumulated deficit	(223,773)	(165,508)
Total stockholders' equity	106,464	129,466
Total liabilities and stockholders' equity	$ 139,714	$ 174,747