Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Detail) - shares	Sep. 30, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	19,471,497	13,808,059
Employee Stock Option [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	8,083,363	7,423,777
Restricted Stock Units [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	870,536	599,850
2018 Stock Option and Incentive Plan [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	6,661,524	2,583,736
2018 Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	1,467,026	1,151,010
2019 Inducement Plan [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	752,048	412,686
2020 Inducement Plan [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	1,637,000	1,637,000