Accounts Payable and Accrued Expenses - Summary of Accounts Payable and Accrued Expenses (Detail) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Accounts Payable And Accrued Liabilities Current [Line Items]
Accounts payable and accrued expenses	$ 1,682,693	$ 2,278,398
Research and Development Expenses [Member]
Accounts Payable And Accrued Liabilities Current [Line Items]
Accounts payable and accrued expenses	695,724	1,339,851
Professional Fees [Member]
Accounts Payable And Accrued Liabilities Current [Line Items]
Accounts payable and accrued expenses	664,326	735,990
General and Administrative Expenses [Member]
Accounts Payable And Accrued Liabilities Current [Line Items]
Accounts payable and accrued expenses	247,800	121,554
Compensation Related Expenses [Member]
Accounts Payable And Accrued Liabilities Current [Line Items]
Accounts payable and accrued expenses	$ 74,843	$ 81,003