Stock Incentive Plans (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Stock-Based Compensation Expense

Total stock-based compensation expense recorded as research and development and general and administrative expenses, respectively, for employees, directors and non-employees for the three months ended March 31, 2018 and 2017 is as follows:

	Three Months Ended March 31,
	2018		2017
Research and development	$	133,042	$	10,861
General and administrative		247,078		16,819
	$	380,120	$	27,680

Schedule of Stock Options Valuation Assumptions Using a Black-Scholes Option Pricing Model

The assumptions used in Black-Scholes option pricing model for the three months ended March 31, 2018 and 2017 are as follows:

	Three Months Ended March 31,
	2018	2017
Expected volatility	52.80% - 60.12%	53.01% - 59.40%
Weighted-average risk-free interest rate	2.33% - 2.69%	2.22% - 2.31%
Expected dividend yield	— %	— %
Expected term (in years)	5.5 - 7.6	6.3 - 8.6
Underlying common stock fair value	$6.63 - $16.00	$	0.63

Summary of Option Activity under Plans

A summary of option activity under the Plans for the three months ended March 31, 2018 is as follows:

	Number of Options			Weighted- Average Exercise Price per Share		Weighted Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
Outstanding at January 1, 2018		1,971,711		$	3.61		9.3	$	5,977,162
Granted		755,507		$	15.71
Exercised		(26,204	)	$	2.64
Cancelled/Forfeited		(16,609	)	$	1.28
Outstanding at March 31, 2018		2,684,405		$	7.03		9.3	$	31,329,115
Exercisable at March 31, 2018		216,985		$	0.41		8.0	$	3,969,527
Vested and expected to vest at March 31, 2018		2,684,405		$	7.03		9.3	$	31,329,115

Summary of Unvested Common Stock from Early Exercises Subject to Repurchase

A summary of the Company’s unvested common stock from early exercises that is subject to repurchase by the Company is as follows:

	Shares
Unvested shares - January 1, 2018		265,098
Vested		(34,137	)
Repurchased		—
Unvested shares - March 31, 2018		230,961