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Stockholders' Equity (Tables) | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2024 | Dec. 31, 2023
Stockholders' Equity |  |
Summary of Stock Option Activities | The following table summarizes stock option activities for the nine months ended September 30, 2024: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | ​ | ​ |  | Weighted Average
​ | ​ | ​ | ​ | ​ | ​ | ​ | Remaining
​ | ​ | ​ | ​ | Weighted Average | ​ | Contractual Life (in
​ | ​ | Stock Options | ​ | Exercise Price | ​ | years)
Outstanding at December 31, 2023 |  | 1,521 | ​ | $ | 4,297.50 |  | 3.31
Outstanding at September 30, 2024 |  | 1,521 | ​ | $ | 4,297.50 |  | 2.56
Options vested and exercisable at September 30, 2024 |  | 951 | ​ | $ | 4,297.50 |  | 2.56
| The following table summarizes stock option activities for the years ended December 31, 2023 and 2022: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | ​ | ​ |  | Weighted Average
​ | ​ | ​ | ​ | ​ | ​ | ​ | Remaining
​ | ​ | ​ | ​ | Weighted Average | ​ | Contractual Life (in
​ | ​ | Stock Options | ​ | Exercise Price | ​ | years)
Outstanding at December 31, 2021 |  | 1,521 | ​ | $ | 4,297.50 |  | 5.31
Outstanding at December 31, 2022 |  | 1,521 | ​ | $ | 4,297.50 |  | 4.31
Outstanding at December 31, 2023 |  | 1,521 | ​ | $ | 4,297.50 |  | 3.31
Options vested and exercisable at December 31, 2023 |  | 951 | ​ | $ | 4,297.50 |  | 3.31
Schedule of Stock-Based Compensation Expense | The following table summarizes stock-based compensation expense for the three and nine months ended September 30, 2024 and 2023 (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | For the three months ended September 30, | ​ | For the nine months ended September 30,
​ |  | 2024 |  | 2023 |  | 2024 |  | 2023
General and administrative | ​ | $ | 52 | ​ | $ | 119 | ​ | $ | 150 | ​ | $ | 381
Research and development | ​ |  | (10) | ​ |  | (19) | ​ |  | (650) | ​ |  | (1)
Total stock-based compensation expense | ​ | $ | 42 | ​ | $ | 100 | ​ | $ | (500) | ​ | $ | 380
​ | The following table summarizes stock-based compensation expense for the years ended December 31, 2023 and 2022 (in thousands). ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | For the year ended December 31,
​ |  | 2023 |  | 2022
General and administrative | ​ | $ | 436 | ​ | $ | 700
Research and development | ​ |  | 132 | ​ |  | 1,583
Total stock-based compensation expense | ​ | $ | 568 | ​ | $ | 2,283
Summary of Warrant Activities | A summary of warrant activities for the nine months ended September 30, 2024, is presented below: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | ​ | ​ |  | Weighted Average
​ | ​ | ​ | ​ | ​ | ​ | ​ | Remaining
​ | ​ | ​ | ​ | Weighted Average | ​ | Contractual Life (in
​ | ​ | Warrants | ​ | Exercise Price | ​ | years)
Outstanding as of December 31, 2023 |  | 89,618 | ​ | $ | 67.16 |  | 5.34
Exercised |  | (409,816) | ​ |  | 0.01 |  | —
Granted |  | 1,539,314 | ​ |  | 9.75 |  | 2.50
Outstanding as of September 30, 2024 |  | 1,219,116 | ​ | $ | 14.39 |  | 2.73
| A summary of warrant activities for years ended December 31, 2023 and 2022, is presented below: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | ​ | ​ |  | Weighted Average
​ | ​ | ​ | ​ | ​ | ​ | ​ | Remaining
​ | ​ | ​ | ​ | Weighted Average | ​ | Contractual Life (in
​ | ​ | Warrants | ​ | Exercise Price | ​ | years)
Outstanding as of December 31, 2021 |  | 4,393 | ​ | $ | 6,036.53 |  | 0.73
Expired | ​ | (4,003) | ​ | ​ | 6,375.00 | ​ | —
Granted |  | 997 | ​ |  | 601.58 |  | 9.18
Outstanding as of December 31, 2022 |  | 1,387 | ​ | $ | 1,152.94 |  | 8.29
Exercised |  | (1) | ​ |  | 0.08 |  | —
Granted |  | 88,232 | ​ |  | 50.09 |  | 5.29
Outstanding as of December 31, 2023 |  | 89,618 | ​ | $ | 67.16 |  | 5.34
Restricted stock award |  |
Stockholders' Equity |  |
Schedules of Restricted Stock and Restricted Stock Unit Activity | The following table summarizes restricted stock award activities for the nine months ended September 30, 2024: ​
​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Weighted Average
​ | ​ | ​ | ​ | Grant Date Fair
​ | ​ | Number of Shares | ​ | Value
Nonvested at December 31, 2023 |  | 1,285 | ​ | $ | 577.50
Vested | ​ | (90) | ​ | ​ | 2,722.50
Nonvested at September 30, 2024 |  | 1,195 | ​ | $ | 415.95
| Certain employees and directors have been awarded restricted stock. The restricted stock vesting consists of milestone and time-based vesting. The following table summarizes restricted stock award activities for the years ended December 31, 2023 and 2022: ​
​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Weighted Average
​ | ​ | ​ | ​ | Grant Date Fair
​ | ​ | Number of Shares | ​ | Value
Nonvested at December 31, 2021 |  | 369 | ​ | $ | 3,034.04
Granted | ​ | 475 | ​ | ​ | 523.50
Vested | ​ | (169) | ​ | ​ | 3,671.23
Nonvested at December 31, 2022 |  | 675 | ​ | $ | 1,107.83
Granted |  | 720 | ​ |  | 345.00
Vested | ​ | (110) | ​ | ​ | 2,310.00
Nonvested at December 31, 2023 |  | 1,285 | ​ | $ | 577.50
Restricted stock units |  |
Stockholders' Equity |  |
Schedules of Restricted Stock and Restricted Stock Unit Activity | Certain employees and consultants have been awarded restricted stock units with time-based vesting. The following table summarizes restricted stock units’ activities for the nine months ended September 30, 2024: ​
​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Weighted Average
​ | ​ | ​ | ​ | Grant Date Fair
​ | ​ | Number of Units | ​ | Value
Nonvested at December 31, 2023 |  | 1,911 | ​ | $ | 948.25
Forfeited | ​ | (1,313) | ​ | ​ | 912.15
Vested |  | (365) | ​ |  | 1,205.20
Nonvested at September 30, 2024 |  | 233 | ​ | $ | 749.14
| The following table summarizes restricted stock units’ activities for the year ended December 31, 2023 and 2022: ​
​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Weighted Average
​ | ​ | ​ | ​ | Grant Date Fair
​ | ​ | Number of Units | ​ | Value
Nonvested at December 31, 2021 |  | 3,108 | ​ | $ | 2,311.00
Granted |  | 1,943 | ​ |  | 565.63
Forfeited | ​ | (689) | ​ | ​ | 1,906.78
Vested | ​ | (1,059) | ​ | ​ | 2,239.62
Nonvested at December 31, 2022 |  | 3,303 | ​ | $ | 1,391.48
Granted |  | 577 | ​ |  | 256.51
Forfeited | ​ | (1,027) | ​ | ​ | 1,374.25
Vested |  | (942) | ​ |  | 1,614.25
Nonvested at December 31, 2023 |  | 1,911 | ​ | $ | 948.25

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