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Principal Activities and Organization - Schedule of Principal Subsidiaries (Detail) | 9 Months Ended
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Sep. 30, 2020
I-Mab Biopharma Hong Kong Limited [Member] |
Place of incorporation | Hong Kong
Date of incorporation | Jul. 08, 2016
Percentage of direct or indirect ownership by the company | 100.00%
Principal activities | Investment holding
I-Mab Shanghai [Member] |
Place of incorporation | PRC
Date of incorporation | Aug. 24, 2016
Percentage of direct or indirect ownership by the company | 100.00%
Principal activities | Research and development of innovative medicines
I-MabTianjin [Member] |
Place of incorporation | PRC
Date of incorporation | Jul. 15, 2017
Percentage of direct or indirect ownership by the company | 100.00%
Principal activities | Research and development of innovative medicines
I-MabBiopharma US Ltd. [Member] |
Place of incorporation | U.S.
Date of incorporation | Feb. 28, 2018
Percentage of direct or indirect ownership by the company | 100.00%
Principal activities | Research and development of innovative medicines

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