Quarterly report pursuant to Section 13 or 15(d)

Stock Warrants - Schedule of Warrants Outstanding (Detail)

v3.20.2
Stock Warrants - Schedule of Warrants Outstanding (Detail) - $ / shares
6 Months Ended
Jun. 30, 2020
May 27, 2020
Dec. 31, 2019
Class of Warrant or Right [Line Items]      
Shares Underlying Outstanding Warrants 12,360,430   3,033,910
Weighted-average exercise price per share $ 9.16   $ 22.61
Placement Agent Warrants [Member]      
Class of Warrant or Right [Line Items]      
Shares Underlying Outstanding Warrants     18,915
Other Warrants [Member]      
Class of Warrant or Right [Line Items]      
Shares Underlying Outstanding Warrants [1] 6,854   15,350
Exercise Price Less Than or Equal to $10.00 [Member]      
Class of Warrant or Right [Line Items]      
Shares Underlying Outstanding Warrants 9,354,502    
Expiration Start Date Sep. 01, 2021    
Expiration End Date May 27, 2023    
Exercise Price $10.01 - $19.99 [Member]      
Class of Warrant or Right [Line Items]      
Shares Underlying Outstanding Warrants 1,599,645    
Expiration End Date Jul. 25, 2022    
Exercise Price Greater Than or Equal to $ 20.00 [Member]      
Class of Warrant or Right [Line Items]      
Shares Underlying Outstanding Warrants 1,406,283    
Expiration Start Date Oct. 26, 2020    
Expiration End Date Jan. 05, 2022    
Pfizer Warrants [Member]      
Class of Warrant or Right [Line Items]      
Shares Underlying Outstanding Warrants 505,617    
Exercise Prices   $ 4.90  
2020 Warrants [Member]      
Class of Warrant or Right [Line Items]      
Shares Underlying Outstanding Warrants 8,848,314    
Minimum [Member] | Exercise Price Less Than or Equal to $10.00 [Member]      
Class of Warrant or Right [Line Items]      
Exercise Prices $ 10.00    
Minimum [Member] | Exercise Price $10.01 - $19.99 [Member]      
Class of Warrant or Right [Line Items]      
Exercise Prices 10.01    
Maximum [Member] | Exercise Price $10.01 - $19.99 [Member]      
Class of Warrant or Right [Line Items]      
Exercise Prices 19.99    
Maximum [Member] | Exercise Price Greater Than or Equal to $ 20.00 [Member]      
Class of Warrant or Right [Line Items]      
Exercise Prices $ 20.00    
2016 Warrants [Member]      
Class of Warrant or Right [Line Items]      
Shares Underlying Outstanding Warrants 1,400,000   1,400,000
2017 Warrants [Member]      
Class of Warrant or Right [Line Items]      
Shares Underlying Outstanding Warrants 1,599,645   1,599,645
[1] Other warrants are comprised of warrants issued prior to the Company’s IPO, generally in exchange for services rendered to the Company.