7.  Stock-Based Compensation

As of December 31, 2022, an aggregate of 6,018,136 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 December 31, 2022, 935,495 common shares were available for future grants under the 2019 Plan. As of December 31, 2022, 291,667 shares of common stock were authorized under the Company’s 2016 Consolidated Stock Incentive Plan (the “2016 Plan”) and 228,041 common shares 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 December 31, 2022 and 2021:

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Stock-based compensation expense for the three months ended December 31, 2022 and 2021 includes the reversal of expense previously recognized for unvested stock options of $0.8 million that were forfeited during the period. The stock-based compensation expense benefit included in the Research and development expense category is primarily the result of stock options forfeited in connection with the Company’s restructuring, see Note 8.

Stock Options

Below is a table summarizing the options issued and outstanding as of and for the three months ended December 31, 2022:

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As of December 31, 2022, unrecognized compensation costs associated with the stock options of $1.4 million will be recognized over an estimated weighted average amortization period of 1.1 years.

The intrinsic value of options exercised during the three months ended December 31, 2021 was $0.1 million. No options were exercised during the three months ended December 31, 2022.

The weighted average grant date fair value of options granted during the three months ended December 31, 2022 and 2021 was $0.19 and $2.33, respectively.

Key assumptions used to estimate the fair value of the stock options granted during the three months ended December 31, 2022 and 2021 included:

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