Prepaid Expenses and Other (Detail) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Prepaid Expenses and Other
Clinical trial deposit	$ 348,000	$ 946,000
Insurance premiums	229,000	502,000
Biologics License Application ("BLA") consulting services deposit	182,000	182,000
Other	146,000	29,000
Annual service agreements	81,000	25,000
Lease deposit	34,000	34,000
Total prepaid expenses and other	$ 1,020,000	$ 1,718,000