Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

The following table summarizes stock option activity for employees and non-employees for the twelve months ended December 31, 2016:



	Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2015	1,824,973		$	8.34	8.90	$	9,073,673
Granted	763,320		10.03
Exercised	(8,516	)	2.59
Cancelled or forfeited	(423,527	)	9.86
Outstanding at December 31, 2016	2,156,250		$	8.66	7.94	$	1,605,684
Exercisable at December 31, 2016	875,868		$	7.49	6.87	$	1,082,490
Vested or expected to vest at December 31, 2016	2,117,832		$	8.64	7.92	$	1,594,651

Schedule of fair value assumptions

The Company estimates the fair value of each stock option award on the grant date using the Black-Scholes option-pricing model based on the following assumptions regarding the fair value of the underlying Common Stock on each measurement date:



	Year Ended December 31, 2016		Year Ended December 31, 2015		Period from February 26, 2014 (Inception) to December 31, 2014
Expected volatility	71.01% to 74.20%		72.98% to 74.94%		75.8% to 76.4%
Risk-free interest rate	1.23% to 2.40%		1.62% to 2.49%		1.59% to 2.71%
Expected term	5.3 - 10 years		5.3 - 10 years		6 - 10 years
Expected dividend yield	0	%	0	%	0	%

Summary of stock-based compensation expense

Total stock-based compensation expense recognized for employee and non-employee restricted common stock, and stock options granted to employees and non-employees is included in the Company's consolidated statements of operations and comprehensive loss as follows:



	Year Ended December 31, 2016		Year Ended December 31, 2015		Period from February 26, 2014 (Inception) to December 31, 2014
Research and development	$	2,435,565	$	3,192,063	$	648,001
Selling, general and administrative	4,137,398		3,405,296		814,060
Total	$	6,572,963	$	6,597,359	$	1,462,061