Selected Balance Sheet Information - Schedule of accrued expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Selected Balance Sheet Information
Accrued clinical consulting services	$ 672	$ 684
Accrued vendor payments	285	456
Accrued manufacturing costs	105	635
Other accrued expenses	0	1
Total	$ 1,062	$ 1,776