Basis of Presentation and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Schedule of Antidilutive Securities Excluded from the Calculation of Basic and Diluted Loss Per Share

Shares used in calculating diluted net loss per common share exclude as anti-dilutive the following share equivalents:

	December 31,
	2016	2015	2014
Options to purchase Common Stock	5,528,628	6,948,630	4,913,472
Warrants to purchase Common stock	4,538,606	4,565,947	5,251,660
Restricted Stock Units	272,000	—	—
Series A Convertible Preferred Stock	63,125	63,125	63,125
	10,402,359	11,577,702	10,228,257

Summary of the Company’s Diluted Net Loss Per Share

The following table summarizes the Company’s diluted net loss per share:

	December 31,
	2016			2015			2014
Numerator:
Net loss attributable to common stockholders	$	(39,227,959	)	$	(27,495,334	)	$	(14,348,499	)
Adjustment for gain from change in fair value of derivative financial instruments—warrants	(2,321,053		)	(4,396,061		)	(2,422,337		)
Net loss used for diluted loss per share	$	(41,549,012	)	$	(31,891,395	)	$	(16,770,836	)
Denominator:
Weighted-average shares used to compute basic net loss per share	30,174,838			26,201,713			18,904,280
Adjustments to reflect assumed exercise of warrants	106,425			250,452			166,832
Weighted-average shares used to compute diluted net loss per share	30,281,263			26,452,165			19,071,112
Net loss per share diluted	$	(1.37	)	$	(1.21	)	$	(0.88	)