Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accrued Liabilities, Current [Abstract]
Accrued contract research costs	$ 32,202	$ 13,775
Compensation and benefits	1,917	2,779
Professional fees	862	1,177
Other	4,967	5,906
Total	$ 39,948	$ 23,637

Amount of expenses incurred but not yet paid classified as other, due within one year or the normal operating cycle, if longer.

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