Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Equity / (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive Income / (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ (32,626)			$ 3	$ 245	$ (49)	$ (32,825)
Beginning balance, shares at Dec. 31, 2018		9,008,919	9,152,108
Beginning balance at Dec. 31, 2018		$ 17,178	$ 86,868
Beginning balance, shares at Dec. 31, 2018				3,412,366
Exercise of stock options	64			$ 1	63
Exercise of stock options, shares				154,557
Stock based compensation	190				190
Vesting of Series B redeemable convertible preferred stock in lieu of rent			$ 92
Other comprehensive income (loss)	26					26
Net loss	(5,681)						(5,681)
Ending balance at Mar. 31, 2019	(38,027)			$ 4	498	(23)	(38,506)
Ending balance, shares at Mar. 31, 2019		9,008,919	9,152,108
Ending balance at Mar. 31, 2019		$ 17,178	$ 86,960
Ending balance, shares at Mar. 31, 2019				3,566,923
Beginning balance at Dec. 31, 2019	115,478			$ 27	185,196	60	(69,805)
Beginning balance, shares at Dec. 31, 2019				26,869,413
Issuance of common stock in connection with private placement, net of issuance costs of $7,310	117,690			$ 2	117,688
Issuance of common stock in connection with private placement, shares				2,500,000
Exercise of stock options	191				191
Exercise of stock options, shares				35,127
Stock based compensation	1,955				1,955
Other comprehensive income (loss)	(97)					(97)
Net loss	(17,176)						(17,176)
Ending balance at Mar. 31, 2020	$ 218,041			$ 29	$ 305,030	$ (37)	$ (86,981)
Ending balance, shares at Mar. 31, 2020				29,404,540