Convertible Preferred Stock and Common Stock - Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2021	Dec. 31, 2020
Conversion of Preferred Stock
Class Of Stock [Line Items]
Common stock reserved for future issuance	17,031,887	17,031,887
Preferred Stock Warrants
Class Of Stock [Line Items]
Common stock reserved for future issuance	331,503	180,819
Forward Obligation
Class Of Stock [Line Items]
Common stock reserved for future issuance	224,842	224,842
Stock Options Issued and Outstanding under the 2007 and 2017 Plan
Class Of Stock [Line Items]
Common stock reserved for future issuance	2,532,210	2,247,136
Common Shares Available for Future Grant under the 2017 Plan
Class Of Stock [Line Items]
Common stock reserved for future issuance	353,255	696,660