Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 51,964	$ 20,250
Certificates of deposit	0	1,494
Prepaid expenses	405	907
State research and development credit receivable	557	542
Other receivables	1,223	196
Total current assets	54,149	23,389
Leasehold improvements and equipment:
Leasehold improvements	5,655	5,085
Computer equipment	982	636
Lab equipment	3,704	3,297
Total leasehold improvements and equipment	10,341	9,018
Less accumulated depreciation and amortization	(3,603)	(2,978)
Leasehold improvements and equipment, net	6,738	6,040
Total assets	60,887	29,429
Current liabilities:
Accounts payable	973	972
Accrued expenses	3,869	1,659
Deferred rent	84	84
Current portion of long term debt	188	204
Total current liabilities	5,114	2,919
Long term liabilities:
Royalty obligation payable to Iowa Economic Development Authority	6,000	6,000
Notes payable and obligations under capital leases	1,081	1,178
Deferred rent, excluding current portion	1,342	1,405
Total long-term liabilities	8,423	8,583
Total liabilities	13,537	11,502
Equity (deficit):
Blank check preferred stock, $0.01 par value: Authorized shares — 5,000,000 at September 30, 2013 and December 31, 2012; issued and outstanding shares — 0 at September 30, 2013 and December 31, 2012	0	0
Common stock, $0.01 par value: Authorized shares — 75,000,000 at September 30, 2013 and 38,833,334 at December 31, 2012; issued and outstanding shares — 25,703,634 at September 30, 2013, and 20,985,192 at December 31, 2012	257	210
Additional paid-in capital	175,024	122,514
Deficit accumulated during the development stage	(127,931)	(104,797)
Total equity	47,350	17,927
Total liabilities and equity	$ 60,887	$ 29,429