Share-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

Schedule of assumptions that the Company used to determine the grant-date fair value of stock options granted

	Three Months Ended September 30, 2017			Nine Months Ended September 30, 2017
Risk-free interest rate	2.12		%	2.01		%
Expected term (in years)	6.30			5.82
Expected volatility	72.65		%	71.74		%
Expected dividend yield	0		%	0		%
Exercise price	$	30.72		$	15.21
Fair value of common share	$	30.54		$	14.97

Summary of stock option activity

					Weighted
			Weighted		Average
			Average		Remaining	Aggregate
	Number of		Exercise		Contractual	Intrinsic
	Shares		Price		Term	Value
					(in years)
Outstanding as of December 31, 2016	3,864,425		$	3.61	9.21	$	15,991
Granted	1,362,987		15.15		9.55
Exercised	(182,615	)	1.39
Forfeited	(11,760	)	4.44
Outstanding as of September 30, 2017	5,033,037		$	6.81	9.19	$	153,889
Options exercisable as of September 30, 2017	2,454,181		$	3.73	7.84	$	82,579
Options unvested as of September 30, 2017	2,578,856		$	9.74	8.69	$	71,310

Summary of classification of share-based compensation expense

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Research and development expenses	$	4,195	$	352	$	6,421	$	1,039
General and administrative expenses	2,061		392		4,384		1,128
	$	6,256	$	744	$	10,805	$	2,167

Non-employees

Schedule of assumptions that the Company used to determine the grant-date fair value of stock options granted

	Three Months Ended September 30, 2017			Nine Months Ended September 30, 2017
Risk-free interest rate	2.07		%	2.33		%
Expected term (in years)	10.00			10.00
Expected volatility	72.55		%	70.82		%
Expected dividend yield	0		%	0		%
Exercise price	$	37.54		$	15.41
Fair value of common share	$	37.54		$	15.15