Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 176,986	$ 195,620
Certificates of deposit	997	2,180
Prepaid expenses and other current assets	2,832	4,954
Income tax receivable	1,796	0
State research and development credit receivable	130	0
Other receivables	6,684	5,388
Total current assets	189,425	208,142
Leasehold improvements and equipment:
Leasehold improvements	7,592	7,427
Computer equipment	2,847	2,582
Lab equipment	6,095	5,832
Contract manufacturing organization equipment	1,075	1,075
Total leasehold improvements and equipment	17,609	16,916
Less accumulated depreciation and amortization	(7,111)	(6,516)
Leasehold improvements and equipment, net	10,498	10,400
Total assets	199,923	218,542
Current liabilities:
Accounts payable	3,039	3,661
Accrued expenses	11,065	8,761
Income taxes payable	0	859
Current portion of unearned revenue	864	892
Current portion of deferred rent	89	96
Current portion of obligations under capital leases	84	13
Current portion of notes payable	164	558
Total current liabilities	15,305	14,840
Long-term liabilities:
Royalty obligation payable to Iowa Economic Development Authority	6,000	6,000
Notes payable and obligations under capital leases	453	368
Unearned revenue	223	407
Deferred rent	1,129	1,153
Total long-term liabilities	7,805	7,928
Total liabilities	23,110	22,768
Stockholders' Equity:
Blank check preferred stock, $0.01 par value: Authorized shares — 5,000,000 at March 31, 2016 and December 31, 2015; issued and outstanding shares — 0 at March 31, 2016 and December 31, 2015	0	0
Common stock, $0.01 par value: Authorized shares — 75,000,000 at March 31, 2016 and December 31, 2015; issued 28,884,959 and 28,838,176 at March 31, 2016 and December 31, 2015, respectively, and outstanding 28,860,925 and 28,814,142 at March 31, 2016 and December 31, 2015, respectively	289	288
Additional paid-in capital	281,368	276,610
Treasury stock, at cost: 24,034 and 24,034 shares at March 31, 2016 and December 31, 2015, respectively	(771)	(771)
Accumulated deficit	(104,073)	(80,353)
Total stockholders' equity	176,813	195,774
Total liabilities and stockholders' equity	$ 199,923	$ 218,542