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Equity Incentive Plans (Tables) | 6 Months Ended
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Jun. 30, 2023
Share-Based Payment Arrangement [Abstract] |
Summary of Stock Option Activity | The following table presents stock option activity under the Plans for the period:
|  | Number of Shares |  |  | Weighted- Average Exercise Price Per Share |  |  | Weighted- Average Remaining Contractual Term (in years) |  |  | Aggregate Intrinsic Value (in thousands) |
Balances as of December 31, 2022 |  |  | 8,152,093 |  |  | $ | 11.92 |  |  |  | 8.09 |  |  | $ | 3,329 |
Stock options granted |  |  | 2,013,450 |  |  | $ | 5.82 |  |  |  |  |  |  |
Stock options exercised |  |  | (55,888 | ) |  | $ | 1.99 |  |  |  |  |  |  |
Stock options forfeited |  |  | (922,562 | ) |  | $ | 10.93 |  |  |  |  |  |  |
Balances as of June 30, 2023 |  |  | 9,187,093 |  |  | $ | 10.74 |  |  |  | 7.98 |  |  | $ | 798 |
Exercisable as of June 30, 2023 |  |  | 4,290,985 |  |  | $ | 12.20 |  |  |  | 6.97 |  |  | $ | 610 |
Summary of RSU Activity under 2020 Plan | A summary of RSU activity under the 2020 Plan and related information is as follows:
|  | Number of Shares |  |  | Weighted-Average Grant Date Fair Value Per Share |
Unvested as of December 31, 2022 |  |  | 550,236 |  |  | $ | 5.58 |
Granted |  |  | 249,615 |  |  |  | 5.95 |
Vested |  |  | (73,058 | ) |  |  | 6.94 |
Cancelled |  |  | (66,762 | ) |  |  | 5.43 |
Unvested as of June 30, 2023 |  |  | 660,031 |  |  | $ | 5.59 |
Summary of Stock-Based Compensation Expense | The total stock-based compensation expense related to all equity-based awards recognized in the period was as follows (in thousands):
|  | Three Months Ended June 30, |  |  | Six Months Ended June 30, |
|  | 2023 |  |  | 2022 |  |  | 2023 |  |  | 2022 |
Research and development |  | $ | 2,307 |  |  | $ | 2,117 |  |  | $ | 4,558 |  |  | $ | 4,076 |
General and administrative |  |  | 2,353 |  |  |  | 2,403 |  |  |  | 4,709 |  |  |  | 4,696 |
Total stock-based compensation expense |  | $ | 4,660 |  |  | $ | 4,520 |  |  | $ | 9,267 |  |  | $ | 8,772 |
Summary of Fair Value of Each Award Issued Estimated on the Date of Grant Using the Black-Scholes Option Pricing Model | The fair value of each award issued was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions:
|  | Three Months Ended June 30, |  | Six Months Ended June 30,
|  | 2023 |  | 2022 |  | 2023 |  | 2022
Expected term (in years) |  | 5.50 - 6.08 |  | 5.50 - 6.08 |  | 5.50 - 6.08 |  | 5.50 - 6.08
Expected volatility |  | 81.50% - 82.40% |  | 81.20% - 82.80% |  | 81.20% - 82.40% |  | 78.80% - 82.80%
Risk-free interest rate |  | 3.47% - 3.86% |  | 2.80% - 3.37% |  | 3.47% - 4.02% |  | 1.49% - 3.37%
Dividend yield |  | — |  | — |  | — |  | —

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- Definition Tabular disclosure of the changes in outstanding nonvested restricted stock units. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + 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 -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (e) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + 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 -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
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