14. Stock-based Compensation

2014 Equity Incentive Plan

In 2014, the Board of Directors and a majority of the stockholders adopted the 2014 Equity Incentive Plan, or the 2014 Plan, allowing for the issuance of 137 shares of common stock. The 2014 Plan has since been amended and restated with approval by the stockholders to increase the maximum number of shares issuable, as shown in the table below:

As of December 31, 2023, the total shares authorized for grant under the 2014 Plan was 3,724, of which 277 were available for future grants. The 2014 Plan expired on January 31, 2024. Following such expiration, no grants may be made under the 2014 Plan, but the  grants in effect prior to such termination were not impacted by the termination. 

Under the terms of the 2014 Plan, the Board of Directors may award stock options, restricted stock, restricted stock units, stock appreciation rights and dividend equivalent rights having either a fixed or variable price related to the fair market value of the shares and with an exercise or conversion privilege related to the passage of time, the occurrence of one or more events, or the satisfaction of performance criteria or other conditions or any other security with the value derived from the value of the shares.

Shares available for future grant as of December 31, 2023 under the 2014 Plan was as follows:

Stock Options

The Board of Directors may grant stock options under the 2014 Plan at a price of not less than 100% of the fair market value of the Company’s common stock on the date the option is granted. The maximum term of an incentive stock option granted to participants may not exceed ten years. Subject to the limitations discussed above, the Board of Directors determines the term and exercise or purchase price of other awards granted under the 2014 Plan. The Board of Directors also determines the terms and conditions of awards, including the vesting schedule and any forfeiture provisions. Options granted under the 2014 Plan vest upon the passage of time, generally four years, or upon the attainment of certain performance criteria established by the Board of Directors. The Company may grant options to purchase common stock to non-employees for advisory and consulting services. Upon exercise of a stock option, the Company issues new shares of common stock.

A summary of the stock option activity during the year ended December 31, 2023 is presented below:

No stock options were exercised during the years ended December 31, 2023 and 2022.

As no stock options were granted during the years ended December 31, 2023 and December 31, 2022, there was no related weighted-average grant date fair value. The total grant date fair value of stock options vested during the years ended  December 31, 2023 and 2022 was $58 and $428, respectively.

As of December 31, 2023, total unrecognized compensation cost related to unvested stock options was de minimus. 

The following table summarizes information about stock options outstanding as of December 31, 2023:

The Company recognizes compensation expense using the straight-line method over the requisite service period.

Restricted Stock Units

The Company issues time-based RSUs and PSUs to employees and non-employee members of the Board. Each RSU and PSU represents the right to receive one share of the Company’s common stock upon vesting and subsequent settlement. PSUs vest upon achievement of performance targets based on the Company's annual operating plan. The fair values of RSUs and PSUs are determined based on the closing price of the Company’s common stock on the date of grant.

Combined RSU and PSU activity for the year ended December 31, 2023 is summarized below:

The total grant-date fair value of RSUs and PSUs that vested during the year ended December 31, 2023 was $1,612. As of December 31, 2023, $1,383 of total unrecognized compensation expense related to unvested RSUs and PSUs was expected to be recognized over a weighted average period of 1.38 years.

Compensation Expense

Stock-based compensation is included in the consolidated statements of operations and comprehensive loss in general and administrative, research and development, or sales and marketing expenses, depending upon the nature of services provided. Stock-based compensation expense related to stock options, RSUs and PSUs was recorded as follows:

Employee Stock Purchase Plan

The Company has an Employee Stock Purchase Plan, or ESPP. Under the ESPP, the Company has 33 shares of common stock reserved for issuance, subject to adjustment in the event of a stock split, stock dividend, combination or reclassification or similar event. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 25% of their eligible compensation, subject to any plan limitations. The ESPP provides for six-month offering periods. At the end of each offering period, employees can purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last trading day of the offering period. As of December 31, 2023, the Company had not initiated employee enrollment to the plan.