Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2022

Equity [Abstract]

Summary of Estimated Fair Value of Stock Option Award

The estimated fair value of each stock option award granted was determined on the date of grant using the Black-Scholes option-pricing valuation model with the following assumptions for option grants during the three and six months ended June 30, 2022 and 2021:

	Three Months Ended June 30,		Six Months Ended June 30,
	2022	2021	2022	2021
Common Stock Options
Risk free interest rate	2.82% - 3.55%	0.91% - 1.08%	1.67% - 3.55%	0.57% - 1.08%
Expected option term	5.5 - 6.0 years	5.5 - 6.0 years	5.5 - 6.0 years	5.5 - 6.0 years
Expected volatility of common stock	97.04% - 113.23%	105.93%-107.53%	97.04% - 113.23%	103.45%-107.53%
Expected dividend yield	0.0%	0.0%	0.0%	0.0%

Summary of Estimated Fair Value of Shares to be Acquired under Employee Stock Purchase Plan

The estimated fair value of the shares to be acquired under the ESPP was determined on the initiation date of each six-month purchase period using the Black-Scholes option-pricing valuation model with the following assumptions for ESPP shares to be purchased during the three and six months ended June 30, 2022 and 2021:

	Three and Six Months Ended June 30, 2022		Three and Six Months Ended June 30, 2021
Employee Stock Purchase Plan
Risk free interest rate		—	0.13%
Expected term		—	0.5 years
Expected volatility of common stock		—	111.98%
Expected dividend yield		—	0.0%

Summary of Recognized Stock-Based Compensation Expense

There were no employee withholdings to purchase shares during the six-month purchase period beginning September 1, 2021 and March 1, 2022.

The Company recognized stock-based compensation expense to employees and directors in its research and development and its selling, general and administrative functions during the three and six months ended June 30, 2022 and 2021 as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	3,752	$	23,820	$	5,608	$	92,200
Selling, general and administrative		363,172		375,591		742,377		868,559
Total stock-based compensation expense	$	366,924	$	399,411	$	747,985	$	960,759