Stockholders’ Equity and Stock-Based Compensation (Tables)
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12 Months Ended |
Dec. 31, 2022 |
| Equity [Abstract] |
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| Schedule of Warrant Activity |
A summary of the Company’s warrant activity for the year ended December 31, 2022 was as follows: | | | | | | | | | | | | | | | | | | | | | | | | | Shares of Stock under Warrants | | Weighted- Average Exercise Price | | Weighted- Average Remaining Contractual Term | | Aggregate Intrinsic Value | Outstanding at January 1, 2021 | 15,174,000 | | | $ | 2.34 | | | 3.76 | | $ | 26,841,000 | | | Granted | — | | | — | | | | | — | | | Exercised | (10,794,000) | | | 0.88 | | | | | 58,191,000 | | | Canceled | (24,000) | | | 3.29 | | | | | — | | Outstanding at December 31, 2021 | 4,356,000 | | | $ | 5.96 | | | 1.76 | | $ | 785,000 | | | Granted | — | | | — | | | | | — | | | Exercised | — | | | — | | | | | — | | | Canceled | — | | | — | | | | | — | | Outstanding at December 31, 2022 | 4,356,000 | | | $ | 5.96 | | | 0.76 | | $ | 273,000 | |
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| Summary of Stock Option Activity Under 2018 Plan and 2006 Plan |
A summary of the Company’s stock option activity is as follows: | | | | | | | | | | | | | | | | | | | | | | | | | Shares of Stock under Stock Options | | Weighted- Average Exercise Price | | Weighted- Average Remaining Contractual Term | | Aggregate Intrinsic Value | Outstanding at January 1, 2022 | 12,765,000 | | $ | 4.97 | | | 8.9 | | $ | 7,891,000 | | | Granted | 16,148,000 | | 2.12 | | | | | | | Exercised | (467,000) | | 0.74 | | | | | 580,000 | | | Canceled | (4,424,000) | | 4.18 | | | | | | Outstanding at December 31, 2022 | 24,022,000 | | 3.28 | | 8.5 | | 2,068,000 | | Vested and exercisable at December 31, 2022 | 7,791,000 | | $ | 3.79 | | | 7.5 | | $ | 1,513,000 | |
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| Share-based Payment Arrangement, Restricted Stock Unit, Activity |
Restricted stock activity was as follows: | | | | | | | | | | | | | Stock Units | | Weighted- Average Grant Date Fair Value per Share | Outstanding at January 1, 2022 | 361,000 | | $ | 4.74 | | | Granted | — | | — | | Released | (265,000) | | 4.74 | | Forfeited | — | | — | | Outstanding at December 31, 2022 | 96,000 | | $ | 4.74 |
Performance stock activity was as follows: | | | | | | | | | | | | | Stock Units | | Weighted- Average Grant Date Fair Value per Share | Outstanding at January 1, 2022 | 290,000 | | $ | 4.74 | | | Granted | — | | — | | Released | — | | — | | Forfeited | — | | — | Outstanding at December 31, 2022 | 290,000 | | $ | 4.74 |
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| Summary of Recognized Stock-Based Compensation Expense |
The Company recognized stock-based compensation expense for the years ended December 31, 2022 and 2021 was as follows: | | | | | | | | | | | | | Years Ended December 31, | | 2022 | | 2021 | | Research and development | $ | 13,402,000 | | | $ | 3,531,000 | | | General and administrative | 9,015,000 | | | 6,188,000 | | | Total stock-based compensation expense | $ | 22,417,000 | | | $ | 9,719,000 | |
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| Schedule of Weighted-Average Assumptions in Black -Scholes Option Pricing Model |
The weighted-average assumptions used in the Black-Scholes-Merton option pricing model to determine the fair value of the employee stock option grants were as follows: | | | | | | | | | | | | | Years Ended December 31, | | 2022 | | 2021 | | Risk-free interest rate | 2.4% | | 1.1% | | Expected volatility | 68.0% | | 76.2% | | Expected term (in years) | 5.8 | | 6.0 | | Expected dividend yield | 0.0% | | 0.0% |
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