Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 63,278	$ 20,250
Certificates of deposit	747	1,494
Prepaid expenses	657	907
State research and development credit receivable	627	542
Other receivables	457	196
Total current assets	65,766	23,389
Leasehold improvements and equipment:
Leasehold improvements	5,093	5,085
Computer equipment	656	636
Lab equipment	3,330	3,297
Total leasehold improvements and equipment	9,079	9,018
Less accumulated depreciation and amortization	(3,190)	(2,978)
Leasehold improvements and equipment, net	5,889	6,040
Total assets	71,655	29,429
Current liabilities:
Accounts payable	865	972
Accrued expenses	2,015	1,659
Deferred rent	84	84
Current portion of long term debt	177	204
Total current liabilities	3,141	2,919
Long term liabilities:
Royalty obligation payable to Iowa Economic Development Authority	6,000	6,000
Notes payable and obligations under capital leases	1,136	1,178
Deferred rent, excluding current portion	1,384	1,405
Total long-term liabilities	8,520	8,583
Total liabilities	11,661	11,502
Equity (deficit):
Blank check preferred stock, $0.01 par value: Authorized shares — 5,000,000 at March 31, 2013 and December 31, 2012; issued and outstanding shares — 0 at March 31, 2013 and December 31, 2012	0	0
Common stock, $0.01 par value: Authorized shares — 38,833,334 at March 31, 2013 and December 31, 2012; issued and outstanding shares — 20,985,192 at March 31, 2013, and 20,591,240 at December 31, 2012	256	210
Additional paid-in capital	172,469	122,514
Deficit accumulated during the development stage	(112,731)	(104,797)
Total equity	59,994	17,927
Total liabilities and equity	$ 71,655	$ 29,429