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Equity Incentive Plans, Equity Inducement Plans, Employee Stock Purchase Plan and Stock-Based Compensation (Tables) | 9 Months Ended
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Sep. 30, 2023
Share-Based Payment Arrangement [Abstract] |
Summary of Option Activity | The following table summarizes option activity under the Company’s 2004 Plan, 2018 Plan and 2021 Plan:
|  | Shares |  |  | Weighted- Average Exercise Price |
Stock options outstanding at December 31, 2022 |  |  | 7,310,611 |  |  | $ | 12.68 |
Granted |  |  | 1,562,500 |  |  |  | 5.43 |
Exercised |  |  | (53,060 | ) |  |  | 5.92 |
Canceled and forfeited |  |  | (899,490 | ) |  |  | 12.69 |
Stock options outstanding at September 30, 2023 |  |  | 7,920,561 |  |  |  | 11.30 |
Stock options exercisable at September 30, 2023 |  |  | 5,484,791 |  |  | $ | 12.56 |
Summary of Status and Activity of Non-vested RSUs | A summary of the status and activity of non-vested RSUs during the nine months ended September 30, 2023 is as follows:
|  | Number of shares |  |  | Weighted Average Grant-Date Fair Value |
Non-vested December 31, 2022 |  |  | 3,958,478 |  |  | $ | 11.70 |
Granted |  |  | 2,629,225 |  |  |  | 5.58 |
Vested and released |  |  | (1,046,519 | ) |  |  | 12.51 |
Canceled and forfeited |  |  | (327,936 | ) |  |  | 10.24 |
Non-vested September 30, 2023 |  |  | 5,213,248 |  |  | $ | 8.55 |
Schedule of Stock-Based Compensation Expense Recognized | Total stock-based compensation expense recognized was as follows:
|  | Three Months Ended |  |  | Nine Months Ended |
|  | September 30, |  |  | September 30, |
|  | 2023 |  |  | 2022 |  |  | 2023 |  |  | 2022 |
|  | (in thousands) |  |  | (in thousands) |
Research and development expense: |  | $ | 2,877 |  |  | $ | 2,630 |  |  | $ | 8,825 |  |  | $ | 7,514 |
General and administrative expense: |  |  | 3,126 |  |  |  | 4,152 |  |  |  | 9,860 |  |  |  | 12,938 |
Total |  | $ | 6,003 |  |  | $ | 6,782 |  |  | $ | 18,685 |  |  | $ | 20,452 |

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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 -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 + Details
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