In connection with the Closing, the Company adopted the 2021 Equity Incentive Plan (the “2021 Plan”) and the 2021 Employee Stock Purchase Plan (“2021 ESPP”). The number of shares available for issuance under the 2021 Plan is increased on the first day of each fiscal year, beginning on January 1, 2022, in an amount as provided in the 2021 Plan. Pursuant to this automatic increase feature of the 2021 Plan, 7,183,969 shares were added as available for issuance thereunder on January 1, 2023. As of March 31, 2023, 11,984,656 shares were available for issuance under the 2021 Plan.

The number of shares available for issuance under the 2021 ESPP is increased on the first day of each fiscal year, beginning on January 1, 2022, in an amount as provided in the 2021 ESPP. Pursuant to this automatic increase feature of the 2021 ESPP, 1,436,793 shares were added as available for issuance thereunder on January 1, 2023. As of March 31, 2023, 5,495,955 shares were available for issuance under the 2021 ESPP.

The following table summarizes stock option activity under our equity compensation plans:

The Company received no cash proceeds from options exercised during the three months ended March 31, 2023 and received $638 in cash proceeds from options exercised during the three months ended March 31, 2022. There were no options granted during the three months ended March 31, 2023 and 2022.

For RSUs with service-based vesting conditions, the fair value is calculated based upon the Company’s closing stock price on the date of grant, and the stock-based compensation expense is recognized over the four-year vesting period.

As of March 31, 2023, there was $28,107 of total unrecognized compensation expense related to options and RSUs expected to be recognized over a weighted average-period of 2.25 years.