Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2015

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

Summary of stock option activity

The following table summarizes stock option activity for employees and non-employees for the twelve months ended December 31, 2015:

	Shares		Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2014	926,832		$	3.40	9.67	$	6,846,054
Granted	994,748		13.07
Exercised	(47,280	)	8.63
Cancelled or forfeited	(49,327	)	10.69
Outstanding at December 31, 2015	1,824,973		$	8.34	8.90	$	9,073,673
Exercisable at December 31, 2015	372,508		$	5.17	8.75	$	2,883,387
Vested or expected to vest at December 31, 2015	1,617,617		$	8.05	8.82	$	8,625,871

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 and the assumptions regarding the fair value of the underlying Common Stock on each measurement date:

	Year Ended December 31, 2015		Period from February 26, 2014 (Inception) to December 31, 2014
Expected volatility	72.98% to 74.94%		75.8% to 76.4%
Risk-free interest rate	1.62% to 2.49%		1.59% to 2.71%
Expected term	5.3 - 10 years		6 - 10 years
Expected dividend yield	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, 2015		Period from February 26, 2014 (Inception) to December 31, 2014
Research and development	$	3,192,063	$	648,001
Selling, general and administrative	3,405,296		814,060
Total	$	6,597,359	$	1,462,061