Note 7 - Accrued Expenses - Summary of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accrued clinical trial costs	$ 3,254	$ 2,570
Accrued consulting and service fee expenses	2,097	1,860
Accrued payroll and related costs	1,785	2,400
Accrued legal and professional fees	790	1,022
Accrued contract manufacturing costs	674	666
Other	837	1,037
Accrued expenses	$ 9,437	$ 9,555