Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accrued Expenses and Other Current Liabilities.
Accrued compensation and benefits	$ 1,625	$ 1,526
Accrued contract manufacturing	1,395	1,003
Accrued tax	993
Accrued clinical costs	576	752
Accrued professional services	251	672
Accrued research costs	126	364
Current portion of operating lease liabilities	472
Other	547	529
Total accrued expenses and other current liabilities	$ 5,985	$ 4,846