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Related Party Agreements (Narrative) (Details) - USD ($) $ in Thousands |  |  |  | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | ---
Jan. 06, 2023 | Jan. 01, 2022 | Jul. 22, 2016 | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022 | Dec. 31, 2022
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |
Common stock, shares issuable |  |  |  | 6,987 |  | 6,987 |  | 187,134
General and administrative |  |  |  | $ 2,131 | $ 3,389 | $ 7,507 | $ 9,815 |
Research and development |  |  |  | 9,477 | 15,419 | 34,313 | 46,872 |
Proceeds from debt issuance |  |  |  |  |  | 0 | 30,000 |
Research and development for licenses acquired |  |  |  | $ 50 | 40 | $ 50 | 40 |
Restricted Stock Awards [Member] |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |
Number of shares issued |  |  |  |  |  | 36,230 |  |
At the Market Offering [Member] |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |
Proceeds from issuance of common shares |  |  |  |  |  | $ 200 | 6,600 |
Fortress Biotech, Inc [Member] |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |
Shares issued for services (in shares) | 187,134 |  |  |  |  |  |  |
Common stock, shares issuable |  |  |  | 1,297 |  | 1,297 |  |
Sponsored Research and Clinical Trial Agreements [Member] |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |
Research and development |  |  |  | $ 364 | 1,836 | $ 3,739 | $ 4,884 |
Parent Company | Management Services Agreement (MSA) | Fortress Biotech, Inc [Member] |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |
Percentage of annual fees expense related to Management Services Agreement recorded in research and development expenses |  |  |  |  |  | 50.00% | 50.00% |
Percentage of annual fees expense related to Management Services Agreement recorded in general and administrative expenses |  |  |  |  |  | 50.00% | 50.00% |
Expenses from related party transaction |  |  |  | 100 | 200 | $ 400 | $ 800 |
Parent Company | Founders Agreement | Fortress Biotech, Inc [Member] |  |  |  |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |  |  |  |
Common shares issuable recorded - Founders Agreement |  |  |  |  |  | 4,000,000 |  |
Percentage of fully diluted equity |  | 2.50% | 2.50% |  |  |  |  |
General and administrative |  |  |  | $ 4,000 | $ 18,000 | $ 4,000 | $ 900 |
Research and development for licenses acquired |  |  |  |  |  |  |  | $ 1,100

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