CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Revenues	$ 8	$ 137	$ 40	$ 975
Operating expenses:
Research and development	15,993	13,272	31,097	25,150
General and administrative	4,410	3,659	8,837	7,480
Impairment loss on construction-in-progress		8,070		8,070
Total operating expenses	20,403	25,001	39,934	40,700
Loss from operations	(20,395)	(24,864)	(39,894)	(39,725)
Other income (expense):
Interest expense	(65)	(22)	(127)	(34)
Interest income	328	33	349	75
Other income (expense), net	25	26	135	(7)
Total other income (expense), net	288	37	357	34
Income tax benefit			0	0
Net loss	(20,107)	(24,827)	(39,537)	(39,691)
Other comprehensive income - unrealized (loss) gain on short-term investments	(120)	1	(120)	6
Comprehensive loss	$ (20,227)	$ (24,826)	$ (39,657)	$ (39,685)
Net loss per share, basic	$ (0.42)	$ (0.60)	$ (0.90)	$ (0.99)
Net loss per share, diluted	$ (0.42)	$ (0.60)	$ (0.90)	$ (0.99)
Weighted-average common shares outstanding, basic	47,502,599	41,356,643	44,150,835	40,142,561
Weighted-average common shares outstanding, diluted	47,502,599	41,356,643	44,150,835	40,142,561