Accounts Payable, Accrued Expenses and Other - Schedule of Accounts Payable, Accrued Expenses and Other (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accounts payable	$ 50	$ 271
Accrued goods and services	348	372
Accrued clinical trial costs	128	320
Accrued drug purchase costs	371	371
Accrued restructuring expenses	7	66	$ 122	$ 921
Deferred tax incentives	1,314	1,314
Total accounts payable, accrued expenses and other	$ 2,218	$ 2,714