Fair Value Measurement (Tables)

6 Months Ended

Jun. 30, 2014

Fair Value Disclosures [Abstract]

Financial Assets and Liabilities Measured at Fair Value

The following table presents financial assets and liabilities measured at fair value as of June 30, 2014:

	Fair Value Measurement at Report Date Using
	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Unobservable Inputs (Level 3)		As of June 30, 2014
Financial assets:
Cash equivalents:
Money market funds	$	421,373	$	—	$	—	$	421,373
U.S. Treasury debt obligations		16,912,645		—		—		16,912,645
Total financial assets	$	17,334,018	$	—	$	—	$	17,334,018
Financial liabilities:
Bonds payable	$	—	$	17,917	$	—	$	17,917
Loan payable net of discounts		—		—		11,106,905		11,106,905
Warrant liabilities		—		—		8,525,666		8,525,666
Total financial liabilities	$	—	$	17,917	$	19,632,571	$	19,650,488

Roll Forward for Financial Assets and Liabilities Measured at Fair Value Using Significant Other Observable Inputs (Level 2)

Level 2 Reconciliation

The following table presents a roll forward for financial assets and liabilities measured at fair value using significant other observable inputs (Level 2) for 2014:

	Level 2 Beginning Balance 12/31/13 $		Settled $			Level 2 Ending Balance 06/30/14 $
Bonds payable		125,000		(107,083	)		17,917

Roll Forward for Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Level 3)

Level 3 Reconciliation

The following table presents a roll forward for liabilities measured at fair value using significant unobservable inputs (Level 3) for 2014.

	Warrant Liabilities
Balance at December 31, 2013	$	5,541,809
Less fair value of warrants exercised		(997,237	)
Add change in fair value of warrants		3,981,094
Balance at June 30, 2014	$	8,525,666

	Loan payable net of discounts
Balance at December 31, 2013	$	12,909,244
Add loan proceeds		3,820,264
Add amortization of discount		110,401
Less repayments of principal		(1,900,374	)
Balance at June 30, 2014	$	14,939,535
Current portion	$	3,832,630
Non-current portion		11,106,905
Balance at June 30, 2014	$	14,939,535