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Stock-based Compensation (Tables) | 3 Months Ended
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Mar. 31, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] |
Summary of Stock Option Activity | A summary of the Company’s stock option activity under the 2021 Plan and 2018 Plan is as follows (in thousands, except share and per share data and years):
|  |  |  |  |  |  |  | Weighted- |  |  |  |
|  |  |  |  | Weighted- |  |  | average remaining |  |  | Aggregate |
|  |  |  |  | average |  |  | contractual |  |  | intrinsic |
|  | Shares |  |  | exercise price |  |  | term (years) |  |  | value |
Outstanding at December 31, 2022 |  |  | 17,393,396 |  |  | $ | 5.84 |  |  |  | 8.20 |  |  | $ | 18,295 |
Granted |  |  | 9,025,337 |  |  |  | 4.00 |  |  |  |  |  |  |
Exercised |  |  | (199,344 | ) |  |  | 0.92 |  |  |  |  |  |  |
Canceled |  |  | (327,118 | ) |  |  | 5.48 |  |  |  |  |  |  |
Outstanding at March 31, 2023 |  |  | 25,892,271 |  |  | $ | 5.24 |  |  |  | 8.61 |  |  | $ | 8,752 |
Options exercisable at March 31, 2023 |  |  | 8,166,304 |  |  | $ | 4.45 |  |  |  | 7.54 |  |  | $ | 6,553 |
Schedule of Stock-based Compensation Expense | The allocation of stock-based compensation for all stock awards was as follows (in thousands):
|  | Three Months Ended March 31, |
|  | 2023 |  |  | 2022 |
Research and development |  | $ | 3,880 |  |  | $ | 2,732 |
General and administrative |  |  | 2,965 |  |  |  | 1,710 |
Total |  | $ | 6,845 |  |  | $ | 4,442 |
Summary of Common Stock Reserved for Future Issuance | Common stock reserved for future issuance consisted of the following as of March 31, 2023 and December 31, 2022:
|  | March 31, |  |  | December 31, |
|  | 2023 |  |  | 2022 |
Stock options issued and outstanding |  |  | 25,892,271 |  |  |  | 17,393,396 |
Awards available for future grant |  |  | 14,846,946 |  |  |  | 16,022,747 |
Shares available for purchase under the ESPP |  |  | 2,469,614 |  |  |  | 965,131 |
Total |  |  | 43,208,831 |  |  |  | 34,381,274 |
Stock Options |
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] |
Assumptions used to Determine Fair Value of Stock Option Grants and Stock to be Purchased under ESPP | The assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee and nonemployee stock option grants were as follows:
|  | Three Months Ended March 31,
|  | 2023 |  | 2022
Risk-free interest rate |  | 3.46%-4.22% |  | 1.46%-1.74%
Expected volatility |  | 85.52%-85.81% |  | 85.86%-85.99%
Expected term (in years) |  | 6.02-6.07 |  | 5.99-6.08
Expected dividend yield |  | --% |  | --%

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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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