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Share-based Compensation - Additional Information (Details) - $ / shares | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2021 | Dec. 31, 2018 | Aug. 31, 2021 | Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Common Stock, Shares, Issued | 32,129,970 | 32,129,970 | 706,701 |  | 23,410,348
Vested Upon Initiation of Clinical Program |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Common Stock, Shares, Issued |  |  | 530,027 |  |
Vesting period |  |  | 4 years |  |
Fair value of underlying shares |  |  | $ 0.96 |  |
2021 Equity Incentive Plan |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Common shares reserved for issuance | 5,440,344 | 5,440,344 |  |  |
2021 Employee Stock Purchase Plan |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Common shares reserved for issuance | 291,324 | 291,324 |  |  |
Restricted Shares |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Vesting rights |  |  | Restricted common shares issued to the founders were to vest 25% upon the one-year anniversary of the initiation of a clinical program through one of its controlled subsidiaries, and monthly thereafter over the next 36 months. |  |
Restricted common shares granted | 0 |  |  |  |
Restricted Shares | Vested Upon Initiation of Clinical Program |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Restricted common shares granted |  |  | 530,027 |  |
Restricted Shares | Remaining Vesting Term |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Common Stock, Shares, Issued |  |  | 188,454 |  |
Restricted common shares granted |  |  | 188,454 |  |
Weighted average fair value of restricted common shares |  |  | $ 0.96 |  |
Restricted Shares | Employees |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Restricted common shares granted |  | 1,589,622 |  |  |
Weighted average fair value of restricted common shares |  | $ 3.65 |  |  |
Employee Stock Options | 2021 Equity Incentive Plan |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Vesting period | 4 years |  |  |  |
Fair value of underlying shares | $ 9.34 |  |  |  |
Employee Stock Options | Employees And Directors [Member] | 2021 Equity Incentive Plan |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Common shares granted | 1,232,759 |  |  |  |
Employee Stock Options | Non Employee Director [Member] | 2021 Equity Incentive Plan |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Common shares granted | 80,640 |  |  |  |
Fair value of underlying shares | $ 9.15 |  |  |  |
Employee Stock Options | Executive Officer And Chief Medical Officer [Member] | 2021 Equity Incentive Plan |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Common shares granted | 640,000 |  |  |  |
Fair value of underlying shares | $ 9.47 |  |  |  |
Vesting percentage | 25.00% |  |  |  |
IPO [Member] |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |
Shares Issued, Price Per Share |  |  |  | $ 13.00 |

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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details
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