| Summary of stock option activity |
| | | | | | | | | | | | | | | Weighted | | | | | | | | | average | | | | | | | | | remaining | | Aggregate | | | Number of | | Weighted average | | contractual | | intrinsic | | | options | | exercise price (US$) | | life (years) | | value (US$) | Outstanding at January 1, 2022 | | 22,226,338 | | 0.80 | | 7.41 | | 26,813 | Granted | | 1,010,000 | | 1.10 | | — | | — | Forfeited | | (2,537,466) | | 0.98 | | — | | — | Exercised | | (956,256) | | 0.44 | | — | | — | Outstanding at December 31, 2022 | | 19,742,616 | | 0.81 | | 6.49 | | 22,974 | Granted | | — | | — | | — | | — | Forfeited | | (5,047,307) | | 0.78 | | — | | — | Exercised | | (176,883) | | 0.03 | | — | | — | Outstanding at December 31, 2023 | | 14,518,426 | | 0.83 | | 5.58 | | 15,553 | Granted | | 11,920,000 | | 0.11 | | — | | — | Forfeited | | (1,642,047) | | 0.54 | | — | | — | Exercised | | (355,543) | | 0.04 | | — | | — | Outstanding at December 31, 2024 | | 24,440,836 | | 0.51 | | 11.43 | | 19,794 | Exercisable as of December 31, 2024 | | 11,504,836 | | 0.79 | | 4.31 | | 13,460 | Expected to vest as of December 31, 2024 | | 11,642,400 | | 0.26 | | 17.77 | | 5,700 |
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