CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' (DEFICIT) EQUITY - USD ($) $ in Thousands	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Series B‑1 Tranche A Redeemable Convertible Preferred Stock	Series B‑1 Tranche B Redeemable Convertible Preferred Stock	Common Stock	Additional Paid-in Capital ASU 2018-07	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit ASU 2018-07	Accumulated Deficit	Total
Decrease in Temporary Equity and increase (decrease) in Stockholders' Equity
ASU 2018‑07 modified retrospective adjustment						$ (13)			$ 13
Balance at Dec. 31, 2017	$ 23,866	$ 24,550	$ 24,423	$ 31,874
Balance (in shares) at Dec. 31, 2017	33,499,900	25,000,000	42,372,882	54,067,796
Balance at Dec. 31, 2017					$ 3		$ 1,377			$ (57,170)	$ (55,790)
Balance (in shares) at Dec. 31, 2017					12,639
Decrease in Temporary Equity and increase (decrease) in Stockholders' Equity
Stock-based compensation expense							1,201				1,201
Reorganization adjustment					$ (3)		3
Conversion of preferred stock into common stock upon initial public offering	$ (23,866)	$ (24,550)	$ (24,423)	$ (31,874)	$ 8		104,705				104,713
Conversion of preferred stock into common stock upon initial public offering (in shares)	(33,499,900)	(25,000,000)	(42,372,882)	(54,067,796)	8,084,414
Issuance of common stock upon initial public offering and sale of common stock, net of issuance costs of $9,378 and $284					$ 5		65,619				65,624
Issuance of common stock upon initial public offering and sale of common stock, net of issuance costs of $9,378 and $284 (in shares)					5,000,000
Exercise of stock options							96				96
Exercise of stock options (in shares)					27,789
Unrealized (loss) gain on investments held								$ (9)			(9)
Net loss										(32,952)	(32,952)
Balance at Dec. 31, 2018					$ 13		172,988	(9)		(90,109)	82,883
Balance (in shares) at Dec. 31, 2018					13,124,842
Balance at Dec. 31, 2019	$ 0	$ 0	$ 0	$ 0
Balance (in shares) at Dec. 31, 2019	0	0	0	0
Decrease in Temporary Equity and increase (decrease) in Stockholders' Equity
Stock-based compensation expense							2,421				2,421
Issuance of common stock upon initial public offering and sale of common stock, net of issuance costs of $9,378 and $284 (in shares)					50,000
Exercise of stock options							52				52
Exercise of stock options (in shares)					12,554
Issuance of commitment shares in connection with Aspire Common Stock Purchase Agreement							642				642
Issuance of commitment shares in connection with Aspire Common Stock Purchase Agreement (in shares)					104,167
Unrealized (loss) gain on investments held								$ 9			9
Net loss										(43,850)	(43,850)
Balance at Dec. 31, 2019					$ 13		$ 176,103			$ (133,959)	$ 42,157
Balance (in shares) at Dec. 31, 2019					13,291,563