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Equity Incentive Plans (Tables) | 6 Months Ended
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Jun. 30, 2025
Equity Incentive Plans |
Schedule of stock option activity under the Equity Plans | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ |  | ​ | ​ |  | Weighted |  | ​ | ​ |  | ​
​ | ​ | ​ | ​ |  | Average |  | Weighted | ​ |  | Aggregate
​ | ​ | ​ | ​ |  | Exercise Price |  | Average Remaining | ​ |  | Intrinsic
​ |  | Options | ​ |  | Per Share |  | Life in Years | ​ |  | Value
Outstanding at December 31, 2024 |  | 6,416,744 | ​ | $ | 8.43 |  | 8.43 | ​ | $ | 1,937
Exercised | ​ | (6,667) | ​ | $ | 2.40 | ​ | ​ | ​ | ​ | ​
Forfeited |  | (1,378,104) | ​ | $ | 7.55 |  | ​ | ​ | ​ | ​
Outstanding at June 30, 2025 |  | 5,031,973 | ​ | $ | 8.68 |  | 6.00 | ​ | $ | —
Options exercisable at June 30, 2025 |  | 3,639,701 | ​ | $ | 10.98 |  | 4.94 | ​ | ​ | ​
Options vested and expected to vest at June 30, 2025 |  | 5,031,973 | ​ | $ | 8.68 |  | 6.00 | ​ | $ | —
Schedule of assumptions used to determine grant-date fair value of stock options | ​
​ | ​ | ​ | ​
​ | ​ | Six Months Ended June 30, | ​
​ |  | 2024 | ​
​ | ​ | ​ | ​
Expected volatility | ​ | 92.84 | %
Weighted average risk-free interest rate | ​ | 4.00 | %
Expected dividend yield | ​ | 0.00 | %
Expected term (in years) | ​ | 6.44 | ​
Schedule of RSU activity under the 2016 Plan | ​
​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | ​ | Weighted
​ | ​ | ​ | ​ | Average Grant
​ |  | Number of Shares |  | Date Fair Value
Outstanding at December 31, 2024 |  | 220,000 | ​ | $ | 19.40
Vested | ​ | (220,000) | ​ | $ | 19.40
Outstanding at June 30, 2025 |  | — | ​ | $ | —
Schedule of recognized stock-based compensation expense related to the issuance of stock option awards and RSUs to employees and non-employees in the condensed consolidated statements of operations | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Three Months Ended June 30, | ​ | Six Months Ended June 30,
​ |  | 2025 |  | 2024 |  | 2025 |  | 2024
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Research and development |  | $ | 387 | ​ | $ | 729 | ​ | $ | 1,021 | ​ | $ | 1,356
General and administrative |  | ​ | 476 | ​ |  | 641 | ​ | ​ | 1,046 | ​ |  | 1,262
Restructuring charges | ​ | ​ | 626 | ​ | ​ | — | ​ | ​ | 626 | ​ | ​ | —
Total | ​ | $ | 1,489 | ​ | $ | 1,370 | ​ | $ | 2,693 | ​ | $ | 2,618
​

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- Definition Tabular disclosure of allocation of amount expensed and capitalized for award under share-based payment arrangement to statement of income or comprehensive income and statement of financial position. Includes, but is not limited to, corresponding line item in financial statement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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- Definition Tabular disclosure of the number and weighted-average grant date fair value for restricted stock units that were outstanding at the beginning and end of the year, and the number of restricted stock units that were granted, vested, or forfeited during the year. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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- Definition Tabular disclosure for stock option plans. Includes, but is not limited to, outstanding awards at beginning and end of year, grants, exercises, forfeitures, and weighted-average grant date fair value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -SubTopic 10 -Topic 718 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (e) -SubTopic 10 -Topic 718 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 718 -SubTopic 10 -Subparagraph (f)(2) -Name Accounting Standards Codification -Paragraph 2 -Section 50 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
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