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Equity (Tables) | 6 Months Ended
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Jun. 30, 2025
Summary of warrants outstanding | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Warrants | ​ | Pre-Funded Warrants(1)
(in thousands, except per share data) | ​ | Number | ​ | Wtd. Avg. Exercise Price | ​ | Wtd. Avg. Remaining Life (in years) | ​ | Aggregate Intrinsic Value | ​ | Number | ​ | Wtd. Avg. Exercise Price | ​ | Aggregate Intrinsic Value
Beginning Balance | ​ | 21,295 | $ | 1.0535 | ​ | 4.74 | $ | 8,230 | ​ | 4,499 | $ | 0.0001 | $ | 6,478
Granted | ​ | — | ​ | — | ​ | ​ | ​ | ​ | ​ | — | ​ | — | ​ | ​
Exercised | ​ | (23) | ​ | 1.0500 | ​ | ​ | ​ | ​ | ​ | (1,703) | ​ | 0.0001 | ​ | ​
Forfeited/Expired | ​ | — | ​ | — | ​ | ​ | ​ | ​ | ​ | — | ​ | — | ​ | ​
Outstanding at Period End | ​ | 21,272 | $ | 1.0535 | ​ | 4.24 | $ | — | ​ | 2,796 | $ | 0.0001 | $ | 1,565
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
(1) Pre-funded warrants have no expiration date and only expire when exercised in full. | ​ | ​
Schedule of outstanding, reserved and authorized shares under share-based compensation plans | ​
​ | ​ | ​ | ​ | ​
​ | ​ | June 30, | ​ | December 31,
(in thousands) |  | 2025 |  | 2024
Outstanding options and restricted stock units |  | 3,474 |  | 3,316
Reserved but unissued shares under the Plan | ​ | 1,692 | ​ | 1,858
Reserved but unissued shares at end of period |  | 5,166 |  | 5,174
Schedule of stock option activity | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | June 30,
​ | ​ | 2025
(in thousands, except per share data) | ​ | Options to Purchase Common Stock | ​ | Weighted Average Exercise Price | ​ | Weighted Average Remaining Contractual Life (in years) | ​ | Aggregate Intrinsic Value
Outstanding at beginning of year |  | 2,452 | ​ | $ | 2.04 |  | 4.92 | $ | 496
Granted |  | — | ​ | $ | — |  | ​ | ​ | ​
Exercised |  | — | ​ | $ | — |  | ​ | ​ | ​
Forfeited/Expired |  | (55) | ​ | $ | 2.56 |  | ​ | ​ | ​
Outstanding at end of period |  | 2,397 | ​ | $ | 2.03 |  | 4.18 | $ | —
Exercisable at end of period |  | 1,872 | ​ | $ | 1.70 |  | 3.78 | $ | —
Schedule of restricted stock unit activity | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | June 30,
​ | ​ | 2025
(in thousands, except per share data) | ​ | Number of Shares | ​ | Weighted Average Grant Date Fair Value | ​ | Weighted Average Contractual Life (in years) (1)
Nonvested at beginning of year |  | 865 | ​ | $ | 0.99 | ​ | 0.88
Granted |  | 393 | ​ | $ | 0.91 | ​ | ​
Vested |  | (121) | ​ | $ | 0.91 | ​ | ​
Forfeited | ​ | (60) | ​ | $ | 0.92 | ​ | ​
Nonvested at end of period |  | 1,077 | ​ | $ | 0.97 | ​ | 1.36
Schedule of share-based compensation activity | ​
​ | ​ | ​ | ​ | ​
​ | ​ | June 30, | ​
(in thousands) |  | 2025 |
Reserved but unissued shares at beginning of period | ​ | ​ | 264 | ​
Increases in the number of authorized shares | ​ | ​ | 21 | ​
Grants | ​ | ​ | (7) | ​
Reserved but unissued shares at end of period | ​ |  | 278 | ​
Restricted Stock Units |
Schedule of compensation expense | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | For the Three Months Ended | ​ | For the Six Months Ended
​ | June 30, | ​ | June 30,
(in thousands, except per share data) | 2025 | 2024 | ​ | 2025 |  | 2024
Share-based compensation expense | $ | 34 | $ | 306 | ​ | $ | 66 | $ | 342 | ​
Weighted average value per share | $ | 0.89 | $ | 1.36 | ​ | $ | 0.89 | $ | 1.32 | ​
Equity Incentive Plan |
Schedule of compensation expense | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | 2025 | ​ | 2024
(in thousands, except per share data) | ​ | Number of Shares |  | Fair Value | ​ | Weighted Average per Share | ​ | Number of Shares |  | Fair Value | ​ | Weighted Average per Share
Fair value of stock payments in accrued compensation | ​ | 326 | ​ | $ | 279 | ​ | $ | 0.85 | ​ | 307 | ​ | $ | 326 | ​ | $ | 1.06
Consultant Stock Plan |
Schedule of compensation expense | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | For the Three Months Ended | ​ | For the Six Months Ended
​ | June 30, | ​ | June 30,
(in thousands, except per share data) | 2025 |  | 2024 |  | 2025 |  | 2024
Share-based compensation expense | $ | 3 | ​ | $ | 3 | ​ | $ | 7 | ​ | $ | 6
Weighted average value per share | $ | 0.94 | ​ | $ | 0.81 | ​ | $ | 0.94 | ​ | $ | 0.81
​
Non-Qualified Stock Option |
Schedule of stock option activity | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | June 30,
​ | ​ | 2025
(in thousands, except per share data) | ​ | Options to Purchase Common Stock | ​ | Weighted Average Exercise Price | ​ | Weighted Average Remaining Contractual Life (in years) | ​ | Aggregate Intrinsic Value
Outstanding at beginning of year |  | 491 | ​ | $ | 1.53 |  | 3.04 | $ | 119
Granted |  | — | ​ | $ | — |  | ​ | ​ | ​
Exercised |  | — | ​ | $ | — |  | ​ | ​ | ​
Forfeited/Expired |  | — | ​ | $ | — |  | ​ | ​ | ​
Outstanding at end of period |  | 491 | ​ | $ | 1.53 |  | 2.55 | $ | —
Exercisable at end of period |  | 441 | ​ | $ | 1.60 |  | 2.79 | $ | —

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