Nature of Business - Additional Information (Detail) - USD ($)		1 Months Ended	3 Months Ended						9 Months Ended
	Jan. 07, 2020	Apr. 30, 2019	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Oct. 18, 2019
Nature Of Business [Line Items]
Proceeds from issuance of common stock and warrants									$ 5,806,133	$ 11,621,325
Net cash used in operating activities									(18,500,737)	(13,860,701)
Net loss			$ (6,120,711)	$ (6,850,534)	$ (8,825,815)	$ (6,957,530)	$ (6,126,080)	$ (3,191,986)	(21,797,060)	$ (16,275,596)
Working capital			10,600,000						10,600,000
Non-cash gain on warrant exchange									2,228,697
Non-cash expense									2,700,000
Non-cash expenses related to change in fair value of warrant liability									3,000,000
Underwriters Public Offering [Member]
Nature Of Business [Line Items]
Proceeds from issuance of common stock and warrants		$ 11,300,000
Underwriters Public Offering [Member] | Common Stock [Member]
Nature Of Business [Line Items]
Number of shares issued upon new issue						582,968		8,000,000
Share price (in dollars per share)		$ 1.50
Sale Agreement [Member] | Jefferies [Member]
Nature Of Business [Line Items]
Cash proceeds from private placement									6,100,000
Offering expense									300,000
Available for offering			$ 22,200,000						$ 22,200,000
Number of shares issued upon new issue									4,453,939
Sale Agreement [Member] | Jefferies [Member] | Maximum [Member]
Nature Of Business [Line Items]
Aggregate offering											$ 30,000,000
Securities Purchase Agreement [Member] | Eagle Pharmaceuticals, Inc [Member]
Nature Of Business [Line Items]
Share price (in dollars per share)	$ 2.00
Milestone payments upon occurrence of milestone event payable	$ 20,000,000
Milestone payments upon occurrence of milestone event payable in cash	10,000,000
Milestone payments upon occurrence of milestone event payable in shares	$ 10,000,000
Milestone payments upon occurrence of milestone event payable in shares, Percentage of premium over share price	15.00%
Restricted period for Sale of shares description	shares will be restricted from sale until the earlier of three months following the milestone event or the three-year anniversary of the agreement
Securities Purchase Agreement [Member] | Eagle Pharmaceuticals, Inc [Member] | Common Stock [Member]
Nature Of Business [Line Items]
Cash proceeds from private placement	$ 20,000,000
Number of shares issued upon new issue	10,000,000
Share price (in dollars per share)	$ 2.00