Summary of Significant Accounting Policies - Summary of Outstanding Potentially Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	6,119,660	5,835,226	6,119,660	5,835,226
Warrants to purchase common stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	1,841,879	2,713,561	1,841,879	2,713,561
Common stock options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	4,273,065	3,114,371	4,273,065	3,114,371
Employee stock purchase plan [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	4,716	7,294	4,716	7,294