Stock-based Compensation | Stock-based Compensation 2013 Stock Option and Grant Plan In February 2013, the board of directors adopted and the Company’s stockholders approved the 2013 Stock Option and Grant Plan (the “2013 Plan”), as amended and restated, under which it could grant incentive stock options (“ISOs”), non-qualified stock options, restricted stock awards (“RSAs”) and restricted stock units (“RSUs”) to eligible employees, officers, directors, and consultants. The 2013 Plan was subsequently amended in January 2015, April 2015, July 2015, March 2016 and October 2016 to allow for the issuance of additional shares of common stock. 2017 Stock Option and Incentive Plan In January 2017, the board of directors adopted and the Company’s stockholders approved the 2017 Stock Option and Incentive Plan (the “2017 Plan”). Upon the adoption of the 2017 Plan, no further awards will be granted under the 2013 Plan. The 2017 Plan provides for the grant of ISOs, non-qualified stock options, RSAs, RSUs, stock appreciation rights and other stock-based awards. The Company’s employees, officers, directors and consultants and advisors are eligible to receive awards under the 2017 Plan. The terms of awards, including vesting requirements, are determined by the board of directors, subject to the provisions of the 2017 Plan. The Company initially registered on Form S-8 1,753,758 shares of common stock under the 2017 Plan, which was comprised of (i) 1,510,000 shares of common stock reserved for issuance under the 2017 Plan, plus (ii) 243,758 shares of common stock originally reserved for issuance under the 2013 Plan that became available for issuance under the 2017 Plan upon the completion of the Company’s IPO. The 2017 Plan also provides that an additional number of shares will automatically be added to the shares authorized for issuance under the 2017 Plan on January 1, 2018 and each January 1 st thereafter. The number of shares added each year will be equal to the lesser of (i) 4% of the outstanding shares on the immediately preceding December 31 st or (ii) such amount as determined by the compensation committee of the board of directors. Effective January 1, 2021 and 2022, 1,669,162 and 2,050,601 additional shares, respectively, were automatically added to the shares authorized for issuance under the 2017 Plan. As of September 30, 2022, there were 1,733,603 shares available for future issuance under the 2017 Plan. Inducement Stock Options The Company may grant, upon approval by the compensation committee of the board of directors, awards, including options to purchase shares of common stock, as an inducement to employment in accordance with Nasdaq Listing Rule 5635(c)(4). The securities are issued pursuant to Section 4(a)(2) under the Securities Act of 1933, as amended, relating to transactions by an issuer not involving any public offering. These options are subject to substantially the same terms as options issued pursuant to the 2017 Plan. During the second quarter of 2021, the Company granted an option to purchase 225,000 shares of common stock as an inducement award. 2017 Employee Stock Purchase Plan In January 2017, the board of directors adopted and the Company’s stockholders approved the 2017 Employee Stock Purchase Plan (the “2017 ESPP”). The Company initially reserved 302,000 shares of common stock for future issuance under the 2017 ESPP. The 2017 ESPP also provides that an additional number of shares will automatically be added to the shares authorized for issuance under the 2017 ESPP on January 1, 2018 and each January 1 st thereafter through January 1, 2027. The number of shares added each year will be equal to the lesser of (i) 1% of the outstanding shares on the immediately preceding December 31 st , (ii) 603,000 shares or (iii) such amount as determined by the compensation committee of the board of directors. Effective January 1, 2021 and 2022, 417,291 and 512,650 additional shares, respectively, were automatically added to the shares authorized for issuance under the 2017 ESPP. No offering periods under the 2017 ESPP had been initiated as of September 30, 2022. Stock-based Compensation Expense Total stock-based compensation expense recognized in the condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2022 and 2021 was as follows (in thousands): Three Months Ended Nine Months Ended 2022 2021 2022 2021 Research and development $ 1,254 $ 1,628 $ 3,913 $ 4,129 General and administrative 1,306 1,298 3,919 4,557 Total stock-based compensation expense $ 2,560 $ 2,926 $ 7,832 $ 8,686 RSU Activity The Company has also granted RSUs to its employees under the 2017 Plan. The following table summarizes RSU activity for the nine months ended September 30, 2022 (in thousands, except per share amounts): RSUs Weighted-Average Grant Date Fair Value per Share Unvested as of December 31, 2021 833 $ 9.13 Issued 670 $ 7.25 Vested (358) $ 8.15 Cancelled (129) $ 8.59 Unvested as of September 30, 2022 1,016 $ 8.31 The aggregate fair value of RSUs that vested during the three and nine months ended September 30, 2022, based upon the fair values of the stock underlying the RSUs on the day of vesting, was less than $0.1 million and $2.7 million, respectively. The aggregate fair value of RSUs that vested during the three and nine months ended September 30, 2021, based upon the fair values of the stock underlying the RSUs on the day of vesting, was less than $0.1 million and $1.5 million, respectively. As of September 30, 2022, there was unrecognized stock-based compensation expense related to unvested RSUs of $5.5 million, which the Company expects to recognize over a weighted-average period of approximately 1.7 years. Stock Option Activity The fair value of stock options granted during the three and nine months ended September 30, 2022 and 2021 was calculated on the date of grant using the following weighted-average assumptions: Three Months Ended Nine Months Ended 2022 2021 2022 2021 Risk-free interest rate 2.9 % 1.0 % 2.0 % 0.8 % Expected dividend yield — % — % — % — % Expected term (in years) 6.1 6.1 6.0 6.0 Expected volatility 80.7 % 82.0 % 80.9 % 81.9 % Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the three months ended September 30, 2022 and 2021 was $2.20 per share and $4.24 per share, respectively. The weighted-average grant date fair value of stock options granted during the nine months ended September 30, 2022 and 2021 was $4.57 per share and $7.22 per share, respectively. The following table summarizes stock option activity during the nine months ended September 30, 2022 (in thousands, except per share amounts): Options Weighted-Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value Outstanding at December 31, 2021 7,629 $ 8.87 6.4 $ 16,881 Granted 1,747 $ 6.57 Exercised (71) $ 5.49 Cancelled (713) $ 9.29 Outstanding at September 30, 2022 8,592 $ 8.39 6.4 $ 1,255 Exercisable at September 30, 2022 5,751 $ 8.77 5.1 $ 1,255 No stock options were exercised during the three months ended September 30, 2022. The aggregate intrinsic value of stock options exercised during the three months ended September 30, 2021 was less than $0.1 million. The aggregate intrinsic value of stock options exercised during the nine months ended September 30, 2022 and 2021 was $0.1 million and $2.9 million, respectively. As of September 30, 2022, there was unrecognized stock-based compensation expense related to unvested stock options of $13.5 million, which the Company expects to recognize over a weighted-average period of approximately 2.5 years. |