Stockholders' Equity - Schedule of Common Stock Reserved for Issuance (Detail) - shares	Mar. 31, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Total common stock reserved for future issuance	15,849,373	17,205,249
Series A Warrants [Member]
Class Of Stock [Line Items]
Total common stock reserved for future issuance	7,771,951	7,790,879
Series B Warrants [Member]
Class Of Stock [Line Items]
Total common stock reserved for future issuance	212,477	2,524,732
Equity Incentive Plans [Member]
Class Of Stock [Line Items]
Total common stock reserved for future issuance	1,452,859	1,207,827
Awards outstanding	5,466,822	4,937,189
2015 Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Total common stock reserved for future issuance	17,500	17,500
Warrants to Purchase Common Stock [Member]
Class Of Stock [Line Items]
Outstanding warrants	1,839	727,122
Underwritten Public Offering [Member] | Pre-funded Warrants to Purchase Common Stock [Member]
Class Of Stock [Line Items]
Total common stock reserved for future issuance	925,925