Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Summary of Financial Instruments Measured at Fair Value on Recurring Basis

The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands):

	Fair Value Measurements at December 31, 2015
	Total		Level 1		Level 2		Level 3
Assets
Money market fund	$	3,803,929	$	3,803,929	—		—
Liabilities
Series A warrant liability	1,212,803		1,212,803		—		—
Series B warrant liability	865,000		—		—		865,000
Series C warrant liability	462,437		—		—		462,437
Total common stock warrant liability	$	2,540,240	$	1,212,803	—		$	1,327,437
	Fair Value Measurements at December 31, 2014
	Total		Level 1		Level 2		Level 3
Assets
Money market fund	$	7,891,888	$	7,891,888	$	—	$	—
Liabilities
Series A warrant liability	857,362		857,362		—		—
Series B warrant liability	17,438,731		—		—		17,438,731
Total common stock warrant liability	$	18,296,093	$	857,362	—		$	17,438,731

Summary of Changes in Fair Value of Level1 and Level 3 Financial Instruments

The following table sets forth a summary of the changes in the fair value of the Company’s Level 1 and Level 3 financial instruments, which are treated as liabilities, as follows:

	Series A Warrant					Series B Warrant					Series C Warrant
	Number of Warrants		Liability			Number of Warrants		Liability			Number of Warrants	Liability
Balance at December 31, 2014	2,449,605		$	857,362		2,449,605		$	17,438,731		—	$	—
Change in value of Series A Warrants	—		397,441			—		—			—	—
De-recognition of Series A Warrant liability upon exercise	(24,000	)	(42,000		)	—		—			—	—
De-recognition of Series B Warrant liability upon cash exercise of 619,512 warrants in Private Transaction (619,512 shares issued)	—		—			(619,512	)	(6,747,765		)	—	—
De-recognition of Series B Warrant liability upon cashless exercise of 1,713,045 warrants (5,879,560 shares issued)	—		—			(1,713,045	)	(12,527,991		)	—	—
De-recognition of Series B Warrant liability upon contribution of 468 warrants back to the Company	—		—			(468	)	(3,332		)	—	—
Change in value of Series B Warrants	—		—			—		2,705,357			—	—
Record Series C Warrant Liability as inducement charge (589,510 warrants in Private Transaction, 905 warrants in tender offer )	—		—			—		—			590,415	3,049,375
Change in value of Series C Warrants	—		—			—		—			—	(2,586,938		)
Balance at December 31, 2015	2,425,605		$	1,212,803		116,580		$	865,000		590,415	$	462,437