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v3.26.1

Financial Instruments (Tables) | 6 Months Ended
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Jun. 30, 2026
Financial Instruments Pledged as Collateral [Abstract] |
Schedule of Short-term and Long-term Investment Marketable Securities by Security Type | The following table summarizes Cullinan’s investments by security type at June 30, 2026 (in thousands):
|  | Amortized Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized Losses |  |  | Estimated Fair Value |
Short-term investments: |  |  |  |  |  |  |  |  |  |  |  |
U.S. government notes |  | $ | 129,965 |  |  | $ | 142 |  |  | $ | — |  |  | $ | 130,107 |
Corporate notes |  |  | 116,050 |  |  |  | 11 |  |  |  | (166 | ) |  |  | 115,895 |
Asset-backed securities |  |  | 9,887 |  |  |  | 9 |  |  |  | — |  |  |  | 9,896 |
Total short-term investments |  |  | 255,902 |  |  |  | 162 |  |  |  | (166 | ) |  |  | 255,898 |
Long-term investments: |  |  |  |  |  |  |  |  |  |  |  |
Corporate notes |  |  | 19,150 |  |  |  | — |  |  |  | (130 | ) |  |  | 19,020 |
Total long-term investments |  |  | 19,150 |  |  |  | — |  |  |  | (130 | ) |  |  | 19,020 |
Total investments |  | $ | 275,052 |  |  | $ | 162 |  |  | $ | (296 | ) |  | $ | 274,918 |
The following table summarizes Cullinan’s investments by security type at December 31, 2025 (in thousands):
|  | Amortized Cost |  |  | Gross Unrealized Gains |  |  | Gross Unrealized Losses |  |  | Estimated Fair Value |
Short-term investments: |  |  |  |  |  |  |  |  |  |  |  |
U.S. government notes |  | $ | 159,632 |  |  | $ | 683 |  |  | $ | — |  |  | $ | 160,315 |
Corporate notes |  |  | 119,368 |  |  |  | 119 |  |  |  | (7 | ) |  |  | 119,480 |
Asset-backed securities |  |  | 9,717 |  |  |  | 52 |  |  |  | — |  |  |  | 9,769 |
Total short-term investments |  |  | 288,717 |  |  |  | 854 |  |  |  | (7 | ) |  |  | 289,564 |
Long-term investments: |  |  |  |  |  |  |  |  |  |  |  |
Corporate notes |  |  | 48,134 |  |  |  | 90 |  |  |  | (2 | ) |  |  | 48,222 |
U.S. government notes |  |  | 9,963 |  |  |  | 85 |  |  |  | — |  |  |  | 10,048 |
Total long-term investments |  |  | 58,097 |  |  |  | 175 |  |  |  | (2 | ) |  |  | 58,270 |
Total investments |  | $ | 346,814 |  |  | $ | 1,029 |  |  | $ | (9 | ) |  | $ | 347,834 |
Summary of Fair Value of Financial Assets Measured on Recurring Basis | The following table sets forth the fair value of Cullinan’s financial assets that were measured at fair value on a recurring basis as of June 30, 2026 (in thousands):
|  | Level 1 |  |  | Level 2 |  |  | Level 3 |  |  | Total |
Short-term investments: |  |  |  |  |  |  |  |  |  |  |  |
U.S. government notes |  | $ | — |  |  | $ | 130,107 |  |  | $ | — |  |  | $ | 130,107 |
Corporate notes |  |  | — |  |  |  | 115,895 |  |  |  | — |  |  |  | 115,895 |
Asset-backed securities |  |  | — |  |  |  | 9,896 |  |  |  | — |  |  |  | 9,896 |
Total short-term investments |  |  | — |  |  |  | 255,898 |  |  |  | — |  |  |  | 255,898 |
Long-term investments: |  |  |  |  |  |  |  |  |  |  |  |
Corporate notes |  |  | — |  |  |  | 19,020 |  |  |  | — |  |  |  | 19,020 |
Total long-term investments |  |  | — |  |  |  | 19,020 |  |  |  | — |  |  |  | 19,020 |
Total investments |  | $ | — |  |  | $ | 274,918 |  |  | $ | — |  |  | $ | 274,918 |
The following table sets forth the fair value of the Company’s financial assets that were measured at fair value on a recurring basis as of December 31, 2025 (in thousands):
|  | Level 1 |  |  | Level 2 |  |  | Level 3 |  |  | Total |
Short-term investments |  |  |  |  |  |  |  |  |  |  |  |
U.S. government notes |  | $ | — |  |  | $ | 160,315 |  |  | $ | — |  |  | $ | 160,315 |
Corporate notes |  |  | — |  |  |  | 119,480 |  |  |  | — |  |  |  | 119,480 |
Asset-backed securities |  |  | — |  |  |  | 9,769 |  |  |  | — |  |  |  | 9,769 |
Total short-term investments |  |  | — |  |  |  | 289,564 |  |  |  | — |  |  |  | 289,564 |
Long-term investments |  |  |  |  |  |  |  |  |  |  |  |
Corporate notes |  |  | — |  |  |  | 48,222 |  |  |  | — |  |  |  | 48,222 |
U.S. government notes |  |  | — |  |  |  | 10,048 |  |  |  | — |  |  |  | 10,048 |
Total long-term investments |  |  | — |  |  |  | 58,270 |  |  |  | — |  |  |  | 58,270 |
Total investments |  | $ | — |  |  | $ | 347,834 |  |  | $ | — |  |  | $ | 347,834 |

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