SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

3 Months Ended

Mar. 31, 2022

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Summary of allocation of stock-based compensation expense included in operating expenses on condensed consolidated statements of operations related to share-based payment awards

The following table summarizes the stock-based compensation expense included in operating expenses on our condensed consolidated statements of operations related to stock options and employee stock purchases for the three months ended March 31, 2022 and 2021, which was allocated as follows:

	Three Months Ended March 31,
(In thousands)	2022		2021
Research and development	$	855	$	825
General and administrative		837		969
Stock-based compensation expense included in operating expenses	$	1,692	$	1,794

Schedule of assumptions used to estimate the fair value of service-based stock options granted

The fair value of service-based stock options granted during the three months ended March 31, 2022 and 2021 has been estimated at the date of grant using the Black Scholes option-pricing model with the following assumptions:

	Three Months Ended March 31,
	2022	2021
Dividend yield	0%	0%
Expected volatility range	77.7% to 78.2%	77.9% to 78.3%
Risk-free interest rate range	1.69% to 2.23%	0.51% to 0.94%
Expected term	5.5 years	5.5 years

Schedule of assumptions used to estimate the fair value of employee stock purchases under the purchase plan

The fair value of employees’ stock purchase rights during the three months ended March 31, 2022 and 2021 has been estimated using the Black Scholes option-pricing model with the following assumptions:

	Three Months Ended March 31,
	2022	2021
Dividend yield	0%	0%
Expected volatility range	50.9% to 61.4%	50.7% to 68.0%
Risk-free interest rate range	0.09% to 0.40%	0.09% to 0.16%
Expected term range	6 months to 12 months	6 months to 12 months