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Stockholders' Equity (Tables) | 9 Months Ended
--- | ---
Sep. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Summary of Stock Option Activities | The following table summarizes stock option activities for the nine months ended September 30, 2023: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | ​ | ​ |  | Weighted Average
​ | ​ | ​ | ​ | ​ | ​ | ​ | Remaining
​ | ​ | ​ | ​ | Weighted Average | ​ | Contractual Life (in
​ | ​ | Stock Options | ​ | Exercise Price | ​ | years)
Outstanding at December 31, 2022 |  | 76,112 | ​ | $ | 59.09 |  | 4.31
Outstanding at September 30, 2023 |  | 76,112 | ​ | $ | 59.09 |  | 3.56
Options vested and exercisable at September 30, 2023 |  | 47,570 | ​ | $ | 59.09 |  | 3.56
Schedule of Stock-Based Compensation Expense | The following table summarizes stock-based compensation expense for the three and nine months ended September 30, 2023 and 2022 (in thousands): ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | For the three months ended September 30, | ​ | For the nine months ended September 30,
​ |  | 2023 |  | 2022 |  | 2023 |  | 2022
General and administrative | ​ | $ | 119 | ​ | $ | 194 | ​ | $ | 381 | ​ | $ | 549
Research and development (1) | ​ |  | (19) | ​ |  | 302 | ​ |  | (1) | ​ |  | 1,261
Total stock-based compensation expense | ​ | $ | 100 | ​ | $ | 496 | ​ | $ | 380 | ​ | $ | 1,810
​ (1) The credit in research and development stock-based compensation expense reflects the reversal of expense related to Restricted Stock Unit forfeitures during the three and nine months ended September 30, 2023.
Summary of Warrant Activities | A summary of warrant activities for the nine months ended September 30, 2023, is presented below: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | ​ | ​ |  | Weighted Average
​ | ​ | ​ | ​ | ​ | ​ | ​ | Remaining
​ | ​ | ​ | ​ | Weighted Average | ​ | Contractual Life (in
​ | ​ | Warrants | ​ | Exercise Price | ​ | years)
Outstanding as of December 31, 2022 |  | 70,195 | ​ | $ | 22.80 |  | 8.29
Exercised |  | (93) | ​ |  | — |  | —
Outstanding as of September 30, 2023 |  | 70,102 | ​ | $ | 22.80 |  | 7.55
Restricted Stock Awards [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Schedules of Restricted Stock and Restricted Stock Unit Activity | The following table summarizes restricted stock award activities for the nine months ended September 30, 2023: ​
​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Weighted Average
​ | ​ | ​ | ​ | Grant Date Fair
​ | ​ | Number of Shares | ​ | Value
Nonvested at December 31, 2022 |  | 34,016 | ​ | $ | 22.20
Granted |  | 36,230 | ​ |  | 6.90
Vested | ​ | (5,540) | ​ | ​ | 46.20
Nonvested at September 30, 2023 |  | 64,706 | ​ | $ | 11.59
Restricted Stock Units [Member] |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
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, 2023: ​
​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ |  | Weighted Average
​ | ​ | ​ | ​ | Grant Date Fair
​ | ​ | Number of Units | ​ | Value
Nonvested at December 31, 2022 |  | 165,912 | ​ | $ | 27.60
Granted |  | 29,732 | ​ |  | 5.13
Forfeited | ​ | (46,172) | ​ | ​ | 27.93
Vested |  | (43,372) | ​ |  | 32.82
Nonvested at September 30, 2023 |  | 106,100 | ​ | $ | 19.03

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