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Composition of Certain Financial Statement Captions - Other Current Assets (Details) - USD ($) $ in Thousands | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Other Current Assets [Abstract] |  |
Prepaid services | $ 622 | $ 131
Prepaid insurance | 695 | 639
Other | 7 | 59
Total other current assets | $ 1,324 | $ 829

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