STOCK BASED COMPENSATION - Stock-based compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Stock-based compensation
Total stock-based compensation expense	$ 2,856	$ 2,645	$ 7,164	$ 8,328
Research and development
Stock-based compensation
Total stock-based compensation expense	1,178	642	2,822	1,974
General and administrative
Stock-based compensation
Total stock-based compensation expense	$ 1,678	$ 2,003	$ 4,342	$ 6,354