Receivables from collaborations were as follows (in thousands): | | | | | | | | | | | | | | | | | | | December 31, 2023 | | Billed | | Unbilled | | Total | Royalty receivables from partners | $ | — | | | $ | 2,296 | | | $ | 2,296 | | Total receivables from collaborators | $ | — | | | $ | 2,296 | | | $ | 2,296 | |
| | | | | | | | | | | | | | | | | | | December 31, 2022 | | Billed | | Unbilled | | Total | U.S. Department of Health and Human Services, net | $ | 7,218 | | | $ | 284 | | | $ | 7,502 | | Royalty receivables from partners | 741 | | | — | | | 741 | | Other collaborations | — | | | 25 | | | 25 | | Total receivables from collaborators | $ | 7,959 | | | $ | 309 | | | $ | 8,268 | |
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