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Preferred Stock, Common Stock and Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Detail) - shares
Dec. 31, 2019
Dec. 31, 2018
Apr. 26, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]      
Stock options issued and outstanding 3,114,371 3,017,624  
Authorized for future option grants 1,587,155 986,801  
Warrants to purchase common stock 2,713,561 2,713,561  
Authorized for employee stock purchase plan 263,065 163,065  
Total common stock reserved for future issuance 7,678,152 6,881,051 6,286,425