CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED SHARES AND STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Series C Preferred Stock [Member]	Series D Preferred Stock [Member]	Pfizer Purchase Agreement [Member]	Series A, B, C and D Convertible Preferred Stock [Member]	Series A, B, C and D Convertible Preferred Stock [Member] Series C Preferred Stock [Member]	Series A, B, C and D Convertible Preferred Stock [Member] Series D Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Pfizer Purchase Agreement [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Series C Preferred Stock [Member]	Additional Paid-in Capital [Member] Series D Preferred Stock [Member]	Additional Paid-in Capital [Member] Pfizer Purchase Agreement [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balances at Dec. 31, 2019	$ 74,574							$ 19		$ 273,966				$ (199,427)	$ 16
Balance, Shares at Dec. 31, 2019					2,720			19,190,695
Issuance of common stock upon the exercise of stock options	2,189									2,189
Issuance of common stock upon the exercise of stock options, shares								324,433
Issuance of common stock and preferred stock net of offering costs and issuance costs	77,929	$ 20,542	$ 30,221				$ 3	$ 8		77,921	$ 20,542	$ 30,218
Issuance of common stock and preferred stock net of offering costs, shares						2,287	3,215,000	8,025,119
Beneficial conversion feature of Series C preferred stock						$ (549)					549
Deemed dividends related to immediate accretion of beneficial conversion feature of Series C preferred stock						$ 549					$ (549)
Conversion of convertible preferred stock to common stock								$ 2		(2)
Conversion of convertible preferred stock to common stock, shares					(1,720)			1,720,000
Share-based compensation expense	4,888									4,888
Unrealized gain (loss) on available-for-sale securities	(23)														(23)
Net loss	(78,280)													(78,280)
Balances at Dec. 31, 2020	132,040				$ 3			$ 29		409,722				(277,707)	(7)
Balance, shares at Dec. 31, 2020					3,218,287			29,260,247
Issuance of common stock upon the exercise of stock options	$ 1,450									1,450
Issuance of common stock upon the exercise of stock options, shares	160,674							160,674
Issuance of common stock and preferred stock net of offering costs and issuance costs	$ 7,831			$ 27,289				$ 1	$ 2	7,830			$ 27,287
Issuance of common stock and preferred stock net of offering costs, shares			3,215,000					475,469	2,362,348
Conversion of convertible preferred stock to common stock, shares					(135)			135,000
Share-based compensation expense	9,430									9,430
Unrealized gain (loss) on available-for-sale securities	5														5
Net loss	(89,756)													(89,756)
Balances at Dec. 31, 2021	$ 88,289				$ 3			$ 32		$ 455,719				$ (367,463)	$ (2)
Balance, shares at Dec. 31, 2021					3,218,152			32,393,738