9. Stock-based compensation

Stock-Based Compensation Expense

Total compensation cost recognized for all stock-based compensation awards in the condensed consolidated statements of operations and comprehensive (loss) income was as follows:

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Stock-based compensation expense by type of award included within the condensed consolidated statements of operations and comprehensive (loss) income was as follows:

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Restricted Stock Units

A summary of the status of and changes in unvested restricted stock unit activity under the Company’s equity award plans for the three months ended March 31, 2024 was as follows:

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Stock-based compensation of restricted stock units is based on the fair value of the Company’s common stock on the date of grant and is recognized over the vesting period. Restricted stock units granted by the Company typically vest in equal amounts, annually over three years. All of the restricted stock units granted in the three months ended March 31, 2024 vest in equal amounts, annually over three years. The stock-based compensation expense related to restricted stock units and awards was $1.1 million and $0.8 million for the three months ended March 31, 2024 and 2023, respectively.

As of March 31, 2024, the Company had unrecognized stock-based compensation expense related to its unvested restricted stock units of $10.9 million, which is expected to be recognized over the remaining average vesting period of 2.4 years.

Stock Options

The following is a summary of stock option activity for the three months ended March 31, 2024:

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As of March 31, 2024, the Company had unrecognized stock-based compensation expense related to its unvested stock options of $23.2 million which is expected to be recognized over the remaining weighted-average vesting period of 3.0 years.