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Stock-Based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2023
Share-Based Payment Arrangement [Abstract] |
Schedule of stock-based compensation expense | The Company recorded stock-based compensation expense in the following expense categories of its accompanying audited statements of operations and comprehensive loss (in thousands):
| Year Ended December 31,
| 2023 |  | 2022
Research and development | $ | 3,462 |  |  | $ | 3,574 |
General and administrative | 3,477 |  |  | 2,888 |
Total stock-based compensation | $ | 6,939 |  |  | $ | 6,462 |
Schedule of option activity | The following table summarizes option activity under the 2020 Plan:
| Options |  | Weighted Average Exercise Price |  | Weighted Average Remaining Life (Years)
Balance at December 31, 2022 | 4,209,255 |  |  | $ | 8.29 |  |  | 8.07
Granted | 1,462,535 |  |  | 3.41 |  |  |
Exercised | (135,254) |  |  | 3.26 |  |  |
Forfeited | (594,372) |  |  | 6.41 |  |  |
Balance at December 31, 2023 | 4,942,164 |  |  | $ | 7.21 |  |  | 7.62
Vested and expected to vest | 4,787,518 |  |  | $ | 7.27 |  |  | 7.47
Exercisable at the end of the period | 2,696,018 |  |  | $ | 8.34 |  |  | 6.47
Schedule of RSU activities | The following table summarizes employee RSU activity for the year ended December 31, 2023:
| Awards |  | Weighted Average Grant Date Fair Value
Unvested RSUs at December 31, 2022 | 309,477 |  |  | $ | 7.22 |
Granted | 460,925 |  |  | 3.54 |
Vested | (77,312) |  |  | 7.22 |
Forfeited | (102,687) |  |  | 4.62 |
Balance at December 31, 2023 | 590,403 |  |  | $ | 4.80 |
Schedule of valuation assumptions | The grant-date fair value of options calculated using the Black-Scholes option pricing model granted under the Company’s 2020 Plan were estimated using the following weighted-average assumptions:
| Year Ended December 31,
| 2023 | 2022
2020 Plan |  |
Expected term - years | 6.08 | 6.08
Expected volatility | 84.8 | % | 82.4 | %
Risk-free interest rate | 3.6 | % | 2.4 | %
Expected dividends | — |  | — |
The grant-date fair value of options calculated using the Monte Carlo option pricing model granted under the Company’s 2020 Plan were estimated using the following assumptions:
| Year Ended December 31,
| 2023 | 2022
2020 Plan |  |
Expected term - years | 4.00 | 4.00
Expected volatility | 80.0 | % | 80.0 | %
Risk-free interest rate | 3.6 | % | 1.4 | %
Expected dividends | — |  | — |
The grant-date fair value of shares issued calculated using the Black-Scholes option pricing model under the Company’s 2020 ESPP were estimated using the following weighted-average assumptions:
| Year Ended December 31,
| 2023 | 2022
2020 ESPP |  |
Expected term - years | 0.5 | 0.5
Expected volatility | 85.5 | % | 82.9 | %
Risk-free interest rate | 4.0 | % | 2.5 | %
Expected dividends | — |  | — |

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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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