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Commitments and Contingencies - Schedule of Expense under JHU Agreement (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Loss Contingencies [Line Items] |  |
Total JHU Agreement expense | $ 29,832 | $ 37,502
JHU |  |
Loss Contingencies [Line Items] |  |
Total JHU Agreement expense | 203 | 395
Research and Development | JHU |  |
Loss Contingencies [Line Items] |  |
Total JHU Agreement expense | 38 | 194
General and Administrative | JHU |  |
Loss Contingencies [Line Items] |  |
Total JHU Agreement expense | $ 165 | $ 201

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