Consolidated Statements of Convertible Preferred Stock and Stockholders' Deficit - USD ($) $ in Thousands	Total	Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2018	$ (110,927)	$ 532,120	$ 3	$ 3,247		$ (114,177)
Beginning balance, shares at Dec. 31, 2018		210,863,764	2,998,017
Issuance of Series C convertible preferred stock, net of issuance costs of $50		$ 5,661
Issuance of Series C convertible preferred stock, net of issuance costs of $50, shares		1,779,093
Issuance of common stock upon exercise of stock options	613			613
Issuance of common stock upon exercise of stock options, shares			178,969
Vesting of restricted common stock	400		$ 1	399
Vesting of restricted common stock ,shares			860,490
Stock-based compensation expense	4,456			4,456
Unrealized gain (loss) on investments	325				$ 325
Net loss	(75,305)					(75,305)
Ending balance at Dec. 31, 2019	(180,438)	$ 537,781	$ 4	8,715	325	(189,482)
Ending balance, shares at Dec. 31, 2019		212,642,857	4,037,476
Extinguishment upon modification of Series C preferred stock	(177,789)	$ 177,789		(15,455)		(162,334)
Conversion of convertible preferred stock into common stock upon initial public offering	715,570	$ (715,570)	$ 62	715,508
Conversion of convertible preferred stock into common stock upon initial public offering, shares		(212,642,857)	61,992,534
Issuance of common stock in public offering, net of discounts and issuance costs of $34,707	425,293		$ 23	425,270
Issuance of common stock in public offering, net of discounts and issuance costs of $34,707, shares			23,000,000
Issuance of common stock upon exercise of stock options	$ 1,216			1,216
Issuance of common stock upon exercise of stock options, shares	297,000		297,000
Vesting of restricted common stock	$ 154		$ 1	153
Vesting of restricted common stock ,shares			579,825
Stock-based compensation expense	31,960			31,960
Unrealized gain (loss) on investments	(261)				(261)
Net loss	(52,412)					(52,412)
Ending balance at Dec. 31, 2020	$ 763,293		$ 90	$ 1,167,367	$ 64	$ (404,228)
Ending balance, shares at Dec. 31, 2020			89,906,835