Stock-Based Compensation | Note 9. Stock-Based Compensation 2017 Equity Incentive Plan The Company’s 2017 Equity Incentive Plan (the “2017 Plan”) became effective in August 2017. Following the effective date of the Company's 2020 Plan (as defined below), the Company ceased granting awards under the 2017 Plan, however, the terms and conditions of the 2017 Plan continue to govern any outstanding awards granted thereunder. 2020 Incentive Award Plan The Company’s 2020 Plan was approved and became effective at the Company’s 2020 annual meeting of Shareholders on May 20, 2020 and unless, earlier terminated by the Board of Directors, will remain in effect until March 26, 2030. The 2020 Plan originally authorized for issuance the sum of (i) 911 shares of the Company’s common stock authorized for issuance and (ii) 233 shares of the Company’s common stock, which represents the number of shares that remained available for issuance under the 2017 Plan as of immediately prior to the approval of the 2020 Plan by the Company’s shareholders. Any shares of Common Stock which, as of immediately prior to the approval of the 2020 Plan by the Company’s stockholders, were subject to awards granted under the 2017 Plan that are forfeited or lapse unexercised and are not issued under the 2017 Plan will increase the number of shares of common stock available for grant under the 2020 Plan. In addition, the number of shares available for issuance under the 2020 Plan will increase on the first day of each calendar year beginning January 1, 2021 and ending on and including January 1, 2030 by a number of shares equal to the lesser of (A) 4% of the aggregate number of shares of the Company’s common stock outstanding on the final day of the immediately preceding calendar year and (B) such smaller number of shares of common stock as determined by the Board of Directors. On January 1, 2021, the shares available for issuance under the 2020 Plan increased by 977 shares and on January 1, 2022, the shares available for issuance under the 2020 Plan increased by 1,119 additional shares pursuant to this provision. Options granted under the 2020 Plan have a term of ten years with the vesting schedule determined by the Board of Directors, which is generally four years. As of December 31, 2021, there were 648 shares available to be granted under the 2020 Plan. A summary of the status of the Company’s stock option activity for the year ended December 31, 2021 is presented below (in thousands, except per share amounts): Number Weighted Average of Exercise Shares Price per Share Outstanding as of January 1, 2021 3,798 $ 16.15 Granted 869 $ 37.26 Forfeited (364) $ 43.04 Cancelled (19) $ 55.38 Exercised (284) $ 5.12 Outstanding as of December 31, 2021 4,000 $ 18.89 Options vested and exercisable as of December 31, 2021 2,684 $ 9.58 As of December 31, 2021, the intrinsic value of options outstanding was $41,120. The intrinsic value for stock options is calculated based on the difference between the exercise prices of the underlying awards and the quoted stock price of the Company’s common stock as of the reporting date. The total intrinsic value of stock options exercised for the years ended December 31, 2021 and 2020 was $11,942 and $11,629, respectively. The total intrinsic value of stock options exercisable for the years ended December 31, 2021 and 2020 was $39,794 and $99,054, respectively. The weighted average grant date fair value of options granted in 2021 and 2020 was $28.81 and $32.71, respectively. The weighted average grant date fair value of options vested at December 31, 2021 was $7.05. The weighted average remaining contractual life is 6.3 years for options exercisable. The weighted average remaining contractual life is 8.8 years for options outstanding. Stock-Based Compensation The fair value of options granted during the years ended December 31, 2021 and 2020 was estimated using the Black-Scholes option-pricing model with the following assumptions. For the For the Year Ended Year Ended December 31, 2021 December 31, 2020 Expected Term 5.50 years - 6.25 years 5.50 years - 6.25 years Expected stock price volatility 95.00 % - 98.00 % 79.02 % - 86.71 % Risk-free rate of interest 0.96 % - 1.37 % 0.33 % - 2.34 % Expected dividend 0.0 % - 0.0 % 0.0 % - 0.0 % Prior to the Company’s IPO, it did not have a history of market prices of its common stock and, as such, volatility is estimated using historical volatilities of similar public companies. In 2021, the Company began using a combination of the historical volatility of similar public companies and the limited historical information related to the Company’s common stock. The expected term of the employee awards is estimated based on the simplified method, which calculates the expected term based upon the midpoint of the term of the award and the vesting period. The Company uses the simplified method because it does not have sufficient option exercise data to provide a reasonable basis upon which to estimate the expected term. The expected dividend yield is 0% as the Company has no history of paying dividends nor does management expect to pay dividends over the contractual terms of these options. The risk-free interest rates are based on the United States Treasury yield curve in effect at the time of grant, with maturities approximating the expected term of the stock options. The fair value of the underlying common stock is generally determined as the closing price of the Company’s common stock on the Nasdaq Capital Market on the grant date, with consideration of whether there is material nonpublic information that could impact that estimated fair value when it is released. The Company recognized stock-based compensation expense under the 2017 Plan and the 2020 Plan of $19,455 and $14,611 for the years ended December 31, 2021 and 2020, respectively. Unrecognized compensation expense related to unvested awards as of December 31, 2021 was $18,738 and will be recognized over the remaining vesting periods of the underlying awards. The weighted-average period over which such compensation is expected to be recognized is 1.7 years. Total stock-based compensation charges were approximately $19,455 and $14,611 for the years ended December 31, 2021 and 2020, respectively. The Company charged $6,657 and $12,798 to research and development and general and administrative expense for the year ended December 31, 2021, respectively. The Company charged $6,020 and $8,591 to research and development and general and administrative expense for the year ended December 31, 2020, respectively. 2020 Employee Stock Purchase Plan The Company’s 2020 Employee Stock Purchase Plan (the “ESPP”) was also approved and became effective at the Company’s 2020 annual meeting of Shareholders on May 20, 2020. The ESPP is designed to assist eligible employees of the Company with the opportunity to purchase the Company’s common stock at a discount through accumulated payroll deductions during successive offering periods. The aggregate number of Shares that may be issued pursuant to rights granted under the ESPP is |