Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 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 months ended March 31, 2022 and 2021:

	Three Months Ended March 31,
	2022	2021
Common Stock Options
Risk free interest rate	1.67%	0.57%
Expected option term	6.0 years	6.0 years
Expected volatility of common stock	105.86%	103.45%
Expected dividend yield	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 months ended March 31, 2022 and 2021:

	Three Months Ended March 31,
	2022	2021
Employee Stock Purchase Plan
Risk free interest rate	—	0.13%
Expected term	—	0.50 years
Expected volatility of common stock	—	111.98
Expected dividend yield	—	0.0%

Summary of Recognized Stock-Based Compensation Expense

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 months ended March 31, 2022 and 2021 as follows:

	Three Months Ended March 31,
	2022		2021
Research and development	$	1,856	$	68,380
Selling, general and administrative		379,205		492,968
Total stock-based compensation expense	$	381,061	$	561,348