Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 113,184	$ 120,738
Prepaid expenses and other current assets	4,447	5,536
Income tax receivable	341	339
Other receivables	305	459
Total current assets	118,277	127,072
Property and equipment, net	3,520	3,727
Right-of-use asset	7,334	0
Income tax receivable	140	140
Total non-current assets	10,994	3,867
Total assets	129,271	130,939
Current liabilities:
Accounts payable	896	555
Accrued expenses	6,950	8,139
Current portion of deferred rent	0	92
Current portion of lease liability	963	0
Current portion of notes payable	63	61
Total current liabilities	8,872	8,847
Long-term liabilities:
Royalty obligation payable to Iowa Economic Development Authority	6,000	6,000
Notes payable	27	43
Lease liability	7,353	0
Deferred rent	0	906
Total long-term liabilities	13,380	6,949
Total liabilities	22,252	15,796
Stockholders' equity:
Blank check preferred stock, $0.01 par value: Authorized shares — 5,000,000 at March 31, 2019 and December 31, 2018; issued and outstanding shares — 0 at March 31, 2019 and December 31, 2018	0	0
Common stock, $0.01 par value: Authorized shares — 75,000,000 at March 31, 2019 and December 31, 2018; issued 37,387,876 and 37,343,547 at March 31, 2019 and December 31, 2018, respectively, and outstanding 37,276,102 and 37,251,220 at March 31, 2019 and December 31, 2018, respectively	373	373
Additional paid-in capital	409,143	407,199
Treasury stock, at cost: 111,774 and 92,327 shares at March 31, 2019 and December 31, 2018, respectively	(1,449)	(1,417)
Accumulated deficit	(301,048)	(291,012)
Total stockholders' equity	107,019	115,143
Total liabilities and stockholders' equity	$ 129,271	$ 130,939