both equity-based and cash-based incentive awards, including: (i) stock options (both incentive stock options and nonqualified stock options), (ii) stock appreciation rights, (iii) restricted stock awards, (iv) restricted stock units, or RSUs, and (v) cash or other stock-based awards. Incentive stock options may be granted only to employees. All other types of awards may be issued to employees, directors, consultants, and other service providers.
As of March 31, 2022, the aggregate number of shares of common stock of the Company that may be issued under the Plan is 3,625,897. The number of shares reserved for issuance under the 2021 Plan increased automatically on January 1, 2022 pursuant to an evergreen provision therein by 1,111,502 shares, representing 5% of total common shares outstanding at December 31, 2021. The aggregate number of shares will increase each anniversary of such date prior to the termination of the 2021 Plan, equal to the lesser of (i) 5% of our shares of common stock issued and outstanding on the last day of the immediately preceding fiscal year and (ii) such smaller number of shares as determined by the Company’s board of directors or the compensation committee. No more than 7,543,185 shares of common stock may be issued under the 2021 Plan through incentive stock options. Shares subject to the 2017 Plan or the 2007 Equity Incentive Plan (the “2007 Plan” and collectively with the 2017 Plan, the “Prior Plans”) that expire, terminate or are cancelled or forfeited for any reason after the effectiveness of the 2021 Plan will be added (or added back) to the shares available for issuance under the 2021 Plan. The total number of shares underlying the Prior Plan awards that may be recycled into the 2021 Plan will not exceed 4,334,131 shares.
2017 Equity Incentive Plan
On September 15, 2017, the Company’s board of directors approved the 2017 Plan, which provides for the granting of incentive stock options, non-qualified stock options and stock awards to employees, certain consultants and directors. The Board, or its designated committee, has the sole authority to select the individuals to whom awards are granted and determine the terms of each award, including the number of shares and the schedule upon which the award becomes exercisable. Upon the effectiveness of the 2021 Plan, no further awards will be granted under the 2017 Plan.
The aggregate number of shares of common stock of the Company that may be issued under the 2017 Plan is 4,334,131 (taking into account shares of common stock that may become issuable pursuant to Section 3(b) of the 2017 Plan in respect of shares of common stock reserved under the Company’s Amended and Restated 2007 Equity Incentive Plan). The 2021 Plan allows for a provision for shares granted under the Prior Plans which are cancelled, forfeited, exchanged or surrendered without having been exercised to subsequently be available for reissuance under the 2021 Plan.
Employee Stock Purchase Plan
The Company’s board of directors approved the Employee Stock Purchase Plan (the “ESPP”) prior to the closing of the IPO. Under the ESPP, the Company may provide employees and employees of the Subsidiary with an opportunity to purchase shares of the Company’s common stock at a discounted purchase price. As of March 31, 2022, subject to adjustment as provided in the ESPP, a total of 209,532 shares of common stock are authorized and reserved for issuance under the ESPP.
Subject to prior approval by the board of directors in each instance, on or about January 1, 2022 and each anniversary of such date thereafter prior to the termination of the ESPP, the number of shares of common stock authorized and reserved for issuance under the ESPP will be increased by a number of shares of common stock equal to the least of (i) 1,000,000 shares of the Company’s common stock, (ii) 1% of the shares of common stock outstanding on the final day of the immediately preceding calendar year, and (iii) such smaller number of shares of common stock as determined by the Company’s board of directors. Such shares of common stock may be newly issued shares, treasury shares or shares acquired on the open market. In the event that any dividend or other distribution (whether in the form of cash, our common stock, or other property), recapitalization, stock split, reverse stock split, reorganization, merger, consolidation, split-up, spin-off, or exchange of common stock or other securities, or other change in the structure affecting common stock occurs, then in order to prevent dilution or enlargement of the benefits or potential benefits intended to be made available under the ESPP, the compensation committee will, in such manner as it deems equitable, adjust the number of shares and class of common stock that may be delivered under the ESPP, the purchase price per