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v3.19.1

FORMER COLLABORATION AGREEMENT (Details) | Sep. 28, 2018 | Sep. 27, 2018 | Dec. 15, 2014 item | Mar. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
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Former Collaborative Arrangement [Line Items] |  |  |  |  |
Amount due to Janssen Biotech, Inc. |  |  |  | $ 2,071,000 | $ 2,610,000
Former Collaboration Agreement |  |  |  |  |
Former Collaborative Arrangement [Line Items] |  |  |  |  |
Number of agreed upon studies | item |  |  | 2 |  |
Percentage of costs to be paid by Geron |  |  | 50.00% |  |
Percentage of costs to be paid by Janssen |  |  | 50.00% |  |
Percentage of costs to be paid by Geron before termination of Collaboration Agreement |  | 50.00% |  |  |
Percentage of costs to be paid by Geron after termination of Collaboration Agreement | 100.00% |  |  |  |
Amount due to Janssen Biotech, Inc. |  |  |  | $ 2,071,000 |
Former Collaborative Arrangement IP Exclusively Licensed |  |  |  |  |
Former Collaborative Arrangement [Line Items] |  |  |  |  |
Percentage of costs to be paid by Geron |  |  | 50.00% |  |
Percentage of costs to be paid by Janssen |  |  | 50.00% |  |

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