Stock Award Plan and Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Stock Option Activity for Employees and Non-Employees

Stock option activity for employees and non-employees for the nine months ended September 30, 2020 is as follows:

	Shares Issuable Pursuant to Stock Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Terms (years)		Total Intrinsic Value (in thousands)
Outstanding January 1, 2020		9,040,328		$	6.98		7.3	$	7,420
Granted		2,148,344		$	6.80
Exercised		(198,762	)	$	5.75
Forfeited		(1,537,500	)	$	7.20
Expired		(105,356	)	$	9.63
Outstanding September 30, 2020		9,347,054		$	6.90		7.0	$	—
Exercisable September 30, 2020		5,543,155		$	6.75		5.9	$	—
Available for future grant		859,510

Summary of Assumptions Used in Black Scholes Model to Estimate Fair Value of Stock Options

The Company uses the Black-Scholes model to estimate the fair value of stock options granted. For stock options granted during the nine months ended September 30, 2020 and 2019, the Company utilized the following assumptions:

	Nine Months Ended September 30,
	2020		2019
Expected term (years)	5.5-6.25		5.5
Risk free interest rate	0.37-0.42%		1.91-1.96%
Volatility	68-71%		74-77%
Dividend yield	0%		0%
Weighted average grant date fair value per share of    common stock	$	1.62	$	3.26

Schedule of RSU Activity

RSU activity under the Plan for the nine months ended September 30, 2020 is as follows:

				Weighted- Average
				Grant Date
	RSUs			Fair Value
Unvested January 1, 2020		68,650		$	11.29
Granted		—		$	—
Vested		(10,000	)	$	6.05
Forfeited		(10,000	)	$	6.05
Unvested September 30, 2020		48,650		$	13.45

Schedule of Stock-Based Compensation Expense Included in the Company's Consolidated Statements of Operations

The following table presents stock-based compensation expense included in the Company’s consolidated statements of operations:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
Research and development	$	813,443	$	651,835	$	2,189,595	$	2,005,816
General and administrative		1,242,592		1,569,354		5,550,109		4,997,464
Total	$	2,056,035	$	2,221,189	$	7,739,704	$	7,003,280