Accounts Payable and Accrued Expenses - Summary of Accounts Payable and Accrued Expenses (Detail) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Accounts Payable And Accrued Liabilities Current [Line Items]
Accounts payable and accrued expenses	$ 1,726,506	$ 2,278,398
Research and Development Expense [Member]
Accounts Payable And Accrued Liabilities Current [Line Items]
Accounts payable and accrued expenses	656,354	1,339,851
Professional Fees [Member]
Accounts Payable And Accrued Liabilities Current [Line Items]
Accounts payable and accrued expenses	615,219	735,990
General and Administrative Expense [Member]
Accounts Payable And Accrued Liabilities Current [Line Items]
Accounts payable and accrued expenses	380,659	121,554
Compensation Related Expenses [Member]
Accounts Payable And Accrued Liabilities Current [Line Items]
Accounts payable and accrued expenses	$ 74,274	$ 81,003