Condensed Statements of Redeemable Convertible Preferred Stock and Stockholders' Deficit (Unaudited) - USD ($) $ in Thousands	Total	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Common Stock	Additional Paid in Capital	Other Comprehensive Income / (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ (20,280)			$ 3	$ 66		$ (20,349)
Beginning balance, shares at Dec. 31, 2017		9,008,919
Beginning balance at Dec. 31, 2017		$ 17,178
Beginning balance, shares at Dec. 31, 2017				3,361,016
Stock based compensation	13				13
Net Loss	(3,377)						(3,377)
Ending balance at Mar. 31, 2018	(23,644)			$ 3	79		(23,726)
Ending balance, shares at Mar. 31, 2018		9,008,919
Ending balance at Mar. 31, 2018		$ 17,178
Ending balance, shares at Mar. 31, 2018				3,361,016
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	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