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Stock Options, Restricted Stock and Stock-Based Compensation (Tables) | 3 Months Ended
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Mar. 31, 2024
Share-Based Payment Arrangement [Abstract] |
Schedule of Stock Option Activity | Stock option activity is summarized a s follows:
|  | NUMBER OF STOCK OPTIONS |  |  | WEIGHTED- AVERAGE EXERCISE PRICE |  |  | WEIGHTED- AVERAGE REMAINING CONTRACTUAL TERM (IN YEARS) |  |  | AGGREGATE INTRINSIC VALUE (IN THOUSANDS) |
Outstanding as of December 31, 2023 |  |  | 5,666,621 |  |  | $ | 2.47 |  |  |  | 6.61 |  |  |  |
Granted |  |  | 67,500 |  |  |  | 1.59 |  |  |  |  |  |  |
Exercised |  |  | (146,964 | ) |  |  | 1.54 |  |  |  |  |  |  |
Cancelled, forfeited or expired |  |  | (474,484 | ) |  |  | 3.42 |  |  |  |  |  |  |
Outstanding as of March 31, 2024 |  |  | 5,112,673 |  |  | $ | 2.40 |  |  |  | 6.66 |  |  | $ | 378 |
Exercisable as of March 31, 2024 |  |  | 3,500,102 |  |  | $ | 2.41 |  |  |  | 5.80 |  |  | $ | 133 |
Unvested as of March 31, 2024 |  |  | 1,612,571 |  |  | $ | 2.37 |  |  |  | 8.53 |  |  | $ | 245 |
Schedule of Fair Value of Stock Options Granted Was Estimated on Black-Scholes Options | The fair value of stock options granted was estimated on the grant date using the Black-Scholes option pricing model based on the following assumptions:
|  | THREE MONTHS ENDED MARCH 31, |
|  | 2024 |  |  | 2023 |
Expected option life (years) |  |  | 6.08 |  |  |  | 6.08 |
Risk-free interest rate |  | 4.21% - 4.27% |  |  | 3.58% - 4.13% |
Expected volatility |  | 99.30% - 99.45% |  |  | 91.33% - 92.25% |
Expected dividend yield |  |  | 0 | % |  |  | 0 | %
Summary of Restricted Stock Activity | Restricted stock activity is summarized as follows:
|  | NUMBER OF SHARES |  |  | WEIGHTED- AVERAGE GRANT DATE FAIR VALUE |
Unvested at December 31, 2023 |  |  | 2,526,432 |  |  | $ | 1.06 |
Granted |  |  | — |  |  | $ | — |
Vested |  |  | — |  |  | $ | — |
Forfeited |  |  | (219,543 | ) |  | $ | 1.13 |
Unvested at March 31, 2024 |  |  | 2,306,889 |  |  | $ | 1.06 |
Schedule of Stock-based Compensation Expense | Stock-based compensation expense for th e three months ended March 31, 2024 and 2023 was classified in the condensed consolidated statements of operations and comprehensive loss as follows (in thousands):
|  | THREE MONTHS ENDED MARCH 31, |
|  | 2024 |  |  | 2023 |
Research and development |  | $ | 553 |  |  | $ | 311 |
General and administrative |  |  | 490 |  |  |  | 422 |
Total stock-based compensation expense |  | $ | 1,043 |  |  | $ | 733 |

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- Definition Tabular disclosure of the changes in outstanding nonvested restricted stock shares. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Subparagraph (c) -Paragraph 2 -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 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 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 -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -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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