Accrued liabilities (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Schedule Of Accrued Liabilities Disclosure [Line Items]
Accrued compensation and related benefits	$ 56,428	$ 39,718
Accrued research and development expense	75,500	25,000
Total accrued liabilities	$ 131,928	$ 64,718