Annual report pursuant to Section 13 and 15(d)

Organization and Description of Business - Additional Information (Detail)

Organization and Description of Business - Additional Information (Detail)									12 Months Ended
	Mar. 22, 2021 USD ($) $ / shares shares	Aug. 14, 2020 USD ($)	May 27, 2020 USD ($) $ / shares shares	Dec. 18, 2019 USD ($) $ / shares shares	Dec. 12, 2019 USD ($) $ / shares shares	Aug. 03, 2018 USD ($) $ / shares shares	Jul. 25, 2017 USD ($) shares	Jul. 27, 2016 USD ($) shares	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Organization And Description Of Business [Line Items]
Accumulated deficit									$ (240,270,058)	$ (212,114,385)
Net cash used in operating activities									$ (33,186,315)	$ (27,427,893)	$ (26,258,849)
Number of shares issued \| shares			11,797,752	2,565,000	3,715,000
Public offering price, per unit \| $ / shares				$ 3.90	$ 2.70
Net proceeds received			$ 48,900,000
Gross Proceed			$ 3,000,000	$ 10,000,000	$ 13,000,000
Combined Net Proceeds					$ 21,300,000
Subsequent Event [Member]
Organization And Description Of Business [Line Items]
Number of shares issued \| shares	11,500,000
Public offering price, per unit \| $ / shares	$ 5.00
Gross Proceed	$ 53,700,000
Pfizer Warrants [Member]
Organization And Description Of Business [Line Items]
Warrants to purchase shares of common stock \| shares			505,617
Warrant exercise price per share \| $ / shares			$ 4.90
Follow-on Offering [Member]
Organization And Description Of Business [Line Items]
Number of shares issued \| shares			11,797,752			575,000	3,200,000	1,400,000
Warrants to purchase shares of common stock \| shares			8,848,314
Warrant exercise price per share \| $ / shares			$ 4.90
Public offering price, per unit \| $ / shares			$ 4.45			$ 20.00
Net proceeds received			$ 48,900,000			$ 10,400,000	$ 37,100,000	$ 32,000,000
Conversion ratio of common stock			0.75
Maximum amount of securities allowed to offer and time to time up		$ 150,000,000
Private Placement [Member]
Organization And Description Of Business [Line Items]
Public offering price, per unit \| $ / shares			$ 4.45		$ 2.70
Issuance of securities in private placement, Shares \| shares			674,156		1,111,111
IPO [Member]
Organization And Description Of Business [Line Items]
Conversion ratio of common stock			0.75