Stock-based Activity (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

Stock-based Activity Tables

Stock-based Compensation

	Three Months Ended		Three Months Ended		Nine Months Ended		Nine Months Ended
	September 30,		September 30,		September 30,		September 30,
	2015		2014		2015		2014
Research and development	$	307,892	$	32,082	$	633,593	$	109,509
General and administrative		1,186,931		111,650		2,333,010		401,090
Total share-based compensation expense	$	1,494,823	$	143,732	$	2,966,603	$	510,599

	Years Ended December 31,
	2014		2013
Research and development	$	163,019	$	166,796
General and administrative		441,957		159,848
Total share-based compensation expense	$	604,976	$	326,644

Stock-based Award Activity

	Options Outstanding			Weighted-Average Exercise Price
Outstanding at December 31, 2014		242,893		$	3.92
Granted		3,015,850			2.23
Exercised		(2,779	)		0.29
Forfeited/cancelled/expired		(12,923	)		7.42
Outstanding and expected to vest at September 30, 2015		3,243,041		$	2.36
Vested and exercisable at September 30, 2015		170,063		$	3.60

The following table summarizes the Company’s stock option activity for the years ended December 31, 2014 and 2013:

	Options Outstanding		Weighted- Average Exercise Price
Outstanding at December 31, 2012		58,639	$	0.83
Granted		93,378		1.44
Exercised		—		—
Forfeited/cancelled/expired		—		—
Outstanding at December 31, 2013		152,017	$	1.19
Granted		90,876		8.47
Exercised		—		—
Forfeited/cancelled/expired		—		—
Outstanding and expected to vest at December 31, 2014		242,893	$	3.92
Vested and exercisable at December 31, 2014		154,877	$	3.77

Restricted stock grants

	Shares		Weighted-Average Grant-Date Fair Value
Nonvested at December 31, 2014		—	$	—
Granted		2,300,850		2.28
Vested		—		—
Forfeited		—		—
Nonvested at September 30, 2015		2,300,850	$	2.28

Valuation Assumptions Used to Determine Stock-based Expense

Treasury yield for a period consistent with the expected term of the stock award in effect at the time of the grant.

	Years Ended December 31,
	2014			2013
Risk-free interest rate		0.1 to 2	%		0.6	%
Dividend yield		—	%		—	%
Expected volatility		84 to 100	%		86	%
Expected life of options, in years		5 and 6.25			5
Weighted-average grant date fair value	$	4.73		$	11.84

Common stock reserved for future issuance

Common stock reserved for conversion of preferred stock	22,482,400
Common stock reserved for exercise of warrants	5,959,668
Common stock options outstanding	3,243,041
Unvested restricted stock awards	2,300,850
Authorized for future grant or issuance under the Stock Plan	2,970,012
Total	36,955,971

Common stock reserved for future issuance consists of the following at December 31, 2014:

Common stock reserved for conversion of preferred stock and warrants	2,591,256
Common stock options outstanding	242,893
Authorized for future grant or issuance under the Stock Plan	326,431
Total	3,160,580