Consolidated Statements of Operations and Comprehensive Loss (USD $)
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Revenues $ 110,000 $ 407,708 $ 390,625
Operating expenses:      
Research and development costs 7,134,301 6,105,984 7,354,857
General and administrative expenses 5,254,915 4,247,037 5,839,188
Depreciation and amortization 244,725 211,143 187,050
Total operating expenses 12,633,941 10,564,164 13,381,095
Operating loss (12,523,941) (10,156,456) (12,990,470)
Other income (expense):      
Interest income 68,000 34,154 60,955
Interest expense (1,394,274) (2,699) (821)
Warrant modification expense (5,017,156) 0 0
Gain (loss) from change in fair value of derivative instruments (965,329) 0 161,809
Litigation settlement 838 3,484 250,000
Total other income (expense) (7,307,921) 34,939 471,943
Net loss (19,831,862) (10,121,517) (12,518,527)
Net loss per share - basic and diluted (in dollars per share) $ (0.27) $ (0.17) $ (0.26)
Weighted average common shares outstanding - basic and diluted (in shares) 72,279,210 58,153,929 48,340,557
Comprehensive loss:      
Net loss (19,831,862) (10,121,517) (12,518,527)
Foreign currency translation adjustment 7,241 0 0
Comprehensive loss $ (19,824,621) $ (10,121,517) $ (12,518,527)