SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - STOCK OPTIONS AND EMPLOYEE STOCK PURCHASE PLAN (Details)	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Stock Options
Stock-Based Compensation
Vesting period of awards	4 years
Assumptions used to estimate fair value of awards
Dividend yield (as a percent)	0.00%	0.00%
Expected volatility range, minimum (as a percent)	77.70%	77.80%
Expected volatility range, maximum (as a percent)	79.90%	78.30%
Risk-free interest rate range, minimum (as a percent)	1.69%	0.51%
Risk-free interest rate range, maximum (as a percent)	3.41%	0.94%
Expected term	5 years 6 months	5 years 6 months
Employee Stock Purchase Plan
Assumptions used to estimate fair value of awards
Dividend yield (as a percent)	0.00%	0.00%
Expected volatility range, minimum (as a percent)	50.90%	50.70%
Expected volatility range, maximum (as a percent)	61.40%	68.00%
Risk-free interest rate range, minimum (as a percent)	0.09%	0.09%
Risk-free interest rate range, maximum (as a percent)	0.40%	0.16%
Employee Stock Purchase Plan | Minimum
Assumptions used to estimate fair value of awards
Expected term	6 months	6 months
Employee Stock Purchase Plan | Maximum
Assumptions used to estimate fair value of awards
Expected term	12 months	12 months