Stock Incentive Plans (Tables)

6 Months Ended

Jun. 30, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Stock-Based Compensation Expense

Total stock-based compensation expense for employees, directors and non-employees for the three and six months ended June 30, 2018 and 2017 is as follows:

	Three months ended June 30,				Six months ended June 30,
	2018		2017		2018		2017
Research and development	$	167,306	$	11,262	$	300,347	$	22,123
General and administrative		401,766		19,316		648,845		36,135
	$	569,072	$	30,578	$	949,192	$	58,258

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 and six months ended June 30, 2018 and 2017 are as follows:

	Three months ended June 30,		Six months ended June 30,
	2018	2017	2018	2017
Expected volatility	56.36%	53.52%	52.80% - 60.12%	53.52% - 53.53%
Weighted-average risk-free interest rate	2.84%	2.00%	2.33% - 2.84%	2.00% - 2.28%
Expected dividend yield	— %	— %	— %	— %
Expected term (in years)	6.25	6.25	5.5 - 7.6	6.25
Underlying common stock fair value	$20.98	$0.63	$6.63 - $20.98	$0.63

Summary of Option Activity under Plans

A summary of option activity under the Plans for the six months ended June 30, 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		793,287		$	15.96
Exercised		(53,884	)	$	1.58
Cancelled/Forfeited		(69,314	)	$	2.82
Outstanding at June 30, 2018		2,641,800		$	7.37		9.1	$	34,438,555
Exercisable at June 30, 2018		454,799		$	2.45		8.4	$	8,163,075
Expected to vest at June 30, 2018		2,187,001		$	8.97		9.3	$	26,008,045

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		(61,501	)
Exercised		16,150
Repurchased		—
Unvested shares - June 30, 2018		219,747