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Business Acquisition - Additional Information (Detail) - USD ($) |  |  |  | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | ---
Dec. 23, 2020 | Dec. 18, 2020 | Sep. 14, 2020 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020
Business Acquisition [Line Items] |  |  |  |  |  |  |
Common stock, par value |  |  |  |  | $ 0.001 |  | $ 0.001
Goodwill |  |  |  |  | $ 48,648,000 |  | $ 48,648,000
Business acquisition costs |  |  |  | $ 2,700,000 | $ 0 | $ 2,700,000 |
General and Administrative [Member] |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Business acquisition costs |  |  |  |  |  |  | $ 2,900,000
Series X1 Non-voting Convertible Preferred Stock [Member] |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Preferred stock, par value |  | $ 0.001 |  |  | $ 0.001 |  | $ 0.001
Issuance of common stock in connection with conversion of Series X preferred stock, Shares |  | 231,068 |  |  |  |  |
Preferred stock, shares outstanding |  |  |  |  | 108,070 |  | 108,070
Common Stock [Member] |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Shares of common stock issued upon conversion of each share of preferred stock |  | 12,837,056 |  |  |  |  |
Common Stock [Member] |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Issuance of common stock in connection with conversion of Series X preferred stock, Shares |  |  |  |  |  | 182,500 |
Shares of common stock sold | 1,004,111 |  |  |  |  |  |
Proceeds from issuance of common stock | $ 9,000,000.0 |  |  |  |  |  |
Anelixis [Member] |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Business acquisition, date of acquisition |  |  | Sep. 14, 2020 |  |  |  |
Common stock, par value |  |  | $ 0.001 |  |  |  |
Goodwill |  |  | $ 48,648,000 |  |  |  |
Estimated fair value related to clinical development program |  |  | 32,386,000 |  |  |  |
Anelixis [Member] | In-Process Research and Development [Member] |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Estimated fair value related to clinical development program |  |  | $ 32,400,000 |  |  |  |
Anelixis [Member] | Series X1 Preferred Stock [Member] |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Shares Issued to stockholders of acquiree |  |  | 140,026 |  |  |  |
Anelixis [Member] | Series X1 Preferred Stock [Member] | Stock Purchase Agreement [Member] |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Preferred stock shares agreed to sell |  |  | 199,112 |  |  |  |
Preferred stock shares aggregate purchase price |  |  | $ 99,100,000 |  |  |  |
Business combination additional commitments in equity financing |  |  | $ 9,000,000.0 |  |  |  |
Anelixis [Member] | Common Stock [Member] |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Shares Issued to stockholders of acquiree |  |  | 175,488 |  |  |  |
Shares of common stock issued upon conversion of each share of preferred stock |  |  | 55.5556 |  |  |  |

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- Definition Date when the acquirer obtains control of the acquiree, in YYYY-MM-DD format. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=123586518&loc=d3e848-128460 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=123586518&loc=d3e845-128460 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
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- Definition This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 23 -URI http://asc.fasb.org/extlink&oid=123586518&loc=d3e1043-128460 + Details
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