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Commitments and Contingencies - Additional Information (Detail) |  |  |  | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | ---
Sep. 04, 2024 ft² | Apr. 19, 2024 USD ($) ft² | Aug. 12, 2022 | Sep. 30, 2024 USD ($) | Sep. 30, 2023 USD ($) | Sep. 30, 2024 USD ($) Milestone | Sep. 30, 2023 USD ($) Milestone | Dec. 31, 2023 USD ($) | Dec. 31, 2022 USD ($) ft² | Dec. 31, 2021 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Other Commitments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Rental expense |  |  |  | $ 100,000 | $ 100,000 | $ 300,000 | $ 300,000 |  |  |  |  |
ROU assets and lease liabilities |  |  |  | 471,000 |  | $ 471,000 |  | $ 365,000 |  |  |  |
Remaining term of office lease |  |  |  |  |  | 3 years |  |  |  |  |  |
Debt outstanding |  |  |  | 0 |  | $ 0 |  |  |  |  |  |
Indemnification obligations amount |  |  |  | 0 |  | $ 0 |  |  |  |  |  |
ALS Therapy Development Foundation, Inc. License Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |
Other Commitments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Fee due for milestones achieved |  |  |  |  |  |  |  |  |  |  | $ 1,000,000.0 | $ 1,000,000.0
Common stock issued in lieu of making a cash payment |  |  |  |  |  |  |  |  |  |  | $ 1,000,000.0 | $ 1,000,000.0
Number of Milestones Achieved | Milestone |  |  |  |  |  | 0 | 0 |  |  |  |  |
Remaining milestone payments for first licensed product |  |  |  | 6,000,000.0 |  | $ 6,000,000.0 |  |  |  |  |  |
Annual License Maintenance Fee |  |  |  |  |  |  |  | $ 100,000 | $ 100,000 | $ 100,000 |  |
ALS Therapy Development Foundation, Inc. License Agreement [Member] | Achievement of 500 Million Aggregate Sales [Member] |  |  |  |  |  |  |  |  |  |  |  |
Other Commitments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Reaching of aggregate net sales |  |  |  |  |  | 500,000,000.0 |  |  |  |  |  |
Amount of one-time milestone payment |  |  |  | 15,000,000.0 |  | 15,000,000.0 |  |  |  |  |  |
ALS Therapy Development Foundation, Inc. License Agreement [Member] | Achievement of 1 Billion Aggregate Sales [Member] |  |  |  |  |  |  |  |  |  |  |  |
Other Commitments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Reaching of aggregate net sales |  |  |  |  |  | 1,000,000,000.0 |  |  |  |  |  |
Amount of one-time milestone payment |  |  |  | 30,000,000.0 |  | $ 30,000,000.0 |  |  |  |  |  |
Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |
Other Commitments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Remaining term of office lease |  |  |  |  |  | 1 year |  |  |  |  |  |
Maximum [Member] | ALS Therapy Development Foundation, Inc. License Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |
Other Commitments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Development and regulatory milestone payments |  |  |  | $ 2,500,000 |  | $ 2,500,000 |  |  |  |  |  |
Irvine, California [Member] |  |  |  |  |  |  |  |  |  |  |  |
Other Commitments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Area of office space | ft² |  | 5,817 |  |  |  |  |  |  | 5,197 |  |  |
Operating lease, term of contract |  | 38 months |  |  |  |  |  |  |  |  |  |
Lease expiration date |  | Jun. 30, 2027 | Dec. 31, 2024 |  |  |  |  |  |  |  |  |
ROU assets and lease liabilities |  | $ 500,000 |  |  |  |  |  |  |  |  |  |
Burlington, Massachusetts [Member] |  |  |  |  |  |  |  |  |  |  |  |
Other Commitments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Area of office space | ft² | 6,138 |  |  |  |  |  |  |  |  |  |  |
Operating lease, term of contract | 36 months |  |  |  |  |  |  |  |  |  |  |
Lease expiration date | Nov. 21, 2027 |  |  |  |  |  |  |  |  |  |  |

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