Stockholders' Equity and Stock-Based Compensation | 8. Stockholders’ Equity and Stock-Based Compensation As of September 30, 2023, there were 2,345,395 shares available for future issuance under the 2020 Equity Incentive Plan and 241,091 shares available for future issuance under the 2022 Inducement Equity Incentive Plan. The 2020 Equity Incentive Plan provides for the grants of stock options and other equity-based awards to employees, non-employee directors and consultants of the Company. The 2022 Inducement Equity Incentive Plan provides for the grants of equity-based awards to individuals not previously employees or non-employee directors of the Company. The table below summarizes the total stock-based compensation expense included in the Company’s statements of operations and comprehensive loss for the periods presented (in thousands): Three Months Ended Nine Months Ended 2023 2022 2023 2022 Research and development $ 1,610 $ 1,280 $ 4,662 $ 4,435 General and administrative 2,254 2,013 6,641 6,895 Total stock-based compensation expense $ 3,864 $ 3,293 $ 11,303 $ 11,330 Stock Options On June 21, 2022, the Company filed with the SEC a Tender Offer Statement on Schedule TO defining the terms and conditions of a one-time voluntary stock option exchange of certain eligible options for its employees (the Option Exchange). On July 20, 2022, the completion date of the Option Exchange, stock options covering an aggregate of 4,406,732 sh ares of common stock were tendered by eligible employees, and the Company granted new options at an exercise price of $ 4.36 , the Company’s closing stock price on July 20, 2022, covering an aggregate of 4,406,732 shares of common stock under the 2020 Equity Incentive Plan in exchange for the tendered options. As a result of the Option Exchange, the Company will recognize incremental stock-based compensation expense of $ 3.7 million over the requisite service period of the new stock options, which is three or four years. The Company will recognize the sum of the incremental stock-based compensation expense and the remaining unrecognized compensation expense for the original awards on the modification date, over the requisite service period of the new stock options. The following table summarizes the stock option activity for the nine months ended September 30, 2023: Options Weighted- Weighted- Aggregate Outstanding at December 31, 2022 6,690,492 $ 4.27 Granted 1,979,690 $ 6.07 Exercised ( 7,185 ) $ 4.23 Forfeited and cancelled ( 43,445 ) $ 4.97 Outstanding at September 30, 2023 8,619,552 $ 4.68 8.2 $ 15,217 Exercisable at September 30, 2023 3,379,551 $ 4.18 6.9 $ 9,273 The fair value of stock option awards to employees, executives, directors, and other service providers was estimated at the date of grant using the Black-Scholes-Merton option pricing model with the following assumptions: Nine Months Ended 2023 2022 Risk-free interest rate 3.45 % - 4.28 % 1.47 % - 3.37 % Expected volatility 86.06 % - 87.68 % 82.98 % - 87.60 % Expected term (in years) 5.50 - 6.08 5.50 - 6.08 Expected dividend yield 0 % 0 % The Company recognized stock-based compensation expense related to the vesting of stock options of $ 3.2 million and $ 3.0 million during the three months ended September 30, 2023 and 2022 , respectively, and $ 9.5 million an d $ 10.5 million during the nine months ended September 30, 2023 and 2022, respectively. Total unrecognized compensation expense related to outstanding unvested stock-option awards as of September 30, 2023, was $ 32.6 million, which is expected to be recognized over a weighted-average remaining service period of 2.7 years. Restricted Stock Units The following table summarizes the restricted stock unit activity for the nine months ended September 30, 2023: Number of Shares Weighted- Outstanding at December 31, 2022 191,925 $ 7.83 Granted 310,763 $ 6.05 Vested ( 12,345 ) $ 4.57 Forfeited ( 4,515 ) $ 6.14 Outstanding at September 30, 2023 485,828 $ 6.79 The Company recognized stock-based compensation expense related to the vesting of restricted stock units of $ 0.4 million and $ 0.2 million during the three months ended September 30, 2023 and 2022 , respectively, and $ 1.0 million and $ 0.5 million during the nine months ended September 30, 2023 and 2022, respectively. Total unrecognized compensation expense related to restricted stock units as of September 30, 2023, was $ 2.3 million, which is expected to be recognized over a weighted-average remaining service period of 1.9 years. Employee Stock Purchase Plan The Company recognized stock-based compensation expense related to the Employee Stock Purchase Plan (ESPP) of $ 0.3 million and $ 0.1 million during the three months ended September 30, 2023 and 2022 , respectively, and $ 0.8 million and $ 0.3 million during the nine months ended September 30, 2023 and 2022, respectively. Pre-funded Warrants In June 2023, the Company completed a private placement, in which it sold 9,285,710 shares of common stock together with pre-funded warrants to purchase 2,857,142 shares of common stock with an exercise price of $ 0.0001 per share. Each pre-funded warrant was immediately exercisable and will remain exercisable until exercised in full. The Company performed an assessment upon issuance of the pre-funded warrants to determine proper classification in the financial statements based on the specific terms of the pre-funded warrants. The Company determined the pre-funded warrants met all the criteria for equity classification and recorded them in additional paid-in capital. All pre-funded warrants remained outstanding as of September 30, 2023 . Net Loss per Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding, including pre-funded warrants issued, during the period, without consideration of potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares, including pre-funded warrants issued, and potentially dilutive securities outstanding for the period. As the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods. The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive: Three Months Ended September 30, Nine Months Ended September 30, 2023 2022 2023 2022 Options to purchase common stock 8,619,552 6,597,373 8,619,552 6,597,373 Non-vested restricted stock units 485,828 239,991 485,828 239,991 Total 9,105,380 6,837,364 9,105,380 6,837,364 |