Net Loss Per Share (Tables)

6 Months Ended

Jun. 30, 2016

Earnings Per Share [Abstract]

Reconciliation of Numerator and Denominator Used in Computing Basic and Diluted Net Loss per Share

The following table provides a reconciliation of the numerator and denominator used in computing basic and diluted net loss per share for the periods presented:

	Three Months Ended June 30,						Six Months Ended June 30,
	2016			2015			2016			2015
Numerator:
Net loss	$	(6,851,603	)	$	(6,452,342	)	$	(13,878,027	)	$	(10,540,477	)
Accretion of stock issuance costs		—			(10,969	)		—			(35,046	)
Accretion of discount on Series E warrants		—			(40,146	)		—			(127,616	)
Series E and D, Convertible Preferred Stock dividends		—			(367,350	)		—			(1,165,932	)
Net loss attributable to common stockholders	$	(6,851,603	)	$	(6,870,807	)	$	(13,878,027	)	$	(11,869,071	)
Denominator:
Weighted-average common shares outstanding-basic and    diluted		7,018,502			3,973,055			6,952,012			2,163,295
Net loss per share attributable to common stockholders,    basic and diluted	$	(0.98	)	$	(1.73	)	$	(2.00	)	$	(5.49	)

Outstanding Options and Warrants Excluded from Computation of Diluted Net Loss per Share

The following outstanding options and warrants were excluded from the computation of diluted net loss per share for the periods presented because their effect would have been anti-dilutive:

	Six Months Ended June 30,
	2016		2015
Options to purchase common stock		1,055,831		610,090
Common stock warrant		219,723		170,587
Restricted stock units		24,999		—