7.  Stock-Based Compensation

As of March 31, 2023, an aggregate of 7,338,482 shares of common stock were authorized under the Company’s 2019 Stock Incentive Plan (the “2019 Plan”), subject to an “evergreen” provision that will automatically increase the maximum number of shares of common stock that may be issued under the term of the 2019 Plan. As of March 31, 2023, 2,068,551 shares of common stock were available for future grants under the 2019 Plan. As of March 31, 2023, 291,667 shares of common stock were authorized under the Company’s 2016 Consolidated Stock Incentive Plan (the “2016 Plan”) and 228,041 shares of common stock were available for future grants under the 2016 Plan.

The Company recorded stock-based compensation expense in the following expense categories of its unaudited condensed consolidated statements of operations for the three months ended March 31, 2023 and 2022:

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Stock Options

Below is a table summarizing the options issued and outstanding as of and for the three months ended March 31, 2023:

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As of March 31, 2023, unrecognized compensation costs associated with the stock options of $1.1 million will be recognized over an estimated weighted average amortization period of 1.5 years.

The intrinsic value of options exercised during the three months ended March 31, 2023 and 2022 was $0.1 million and $0.1 million, respectively.

The weighted average grant date fair value of options granted during the three months ended March 31, 2023 and 2022 was $0.16 and $1.40, respectively.

Key assumptions used to estimate the fair value of the stock options granted during the three months ended March 31, 2023 and 2022 included:

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Restricted Stock Units

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Below is a table summarizing the restricted stock units granted and outstanding as of and for the three months ended March 31, 2023:

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