XML 27 R15.htm IDEA: XBRL DOCUMENT
v3.24.2.u1

Stock-based Compensation | 6 Months Ended
--- | ---
Jun. 30, 2024
Share-Based Payment Arrangement [Abstract] |
Stock-based Compensation | 8. Stock-based Compensation 2017 Stock Incentive Plan In December 2017, we adopted the 2017 Stock Incentive Plan (as amended and restated, the “2017 Plan”), under which we could grant incentive stock options (“ISOs”), non-qualified stock options, restricted stock awards (“RSAs”), restricted stock units (“RSUs”), stock appreciation rights and other stock-based awards to eligible employees, officers, directors and consultants. The terms of stock options and RSAs, including vesting requirements, were determined by our board of directors, subject to the provisions of the 2017 Plan. 2021 Stock Incentive Plan In April 2021, our board of directors adopted and our stockholders approved the 2021 Stock Incentive Plan (the “2021 Plan”), which became effective immediately prior to the effectiveness of our initial public offering (“IPO”). As a result of the adoption of the 2021 Plan, no further awards will be made under the 2017 Plan. The 2021 Plan provides for the grant of ISOs, non-qualified stock options, RSAs, RSUs, stock appreciation rights and other stock-based awards. Our employees, officers, directors, consultants and advisors are eligible to receive awards under the 2021 Plan. The terms of awards, including vesting requirements, are determined by our board of directors, subject to the provisions of the 2021 Plan. We initially registered 3,352,725 shares of common stock under the 2021 Plan, pursuant to a Registration Statement on Form S-8 filed with the SEC on April 30, 2021, which was comprised of (i) 2,843,116 shares of common stock reserved for issuance under the 2021 Plan, (ii) 31,884 shares of common stock originally reserved for issuance under the 2017 Plan that became available for issuance under the 2021 Plan upon the completion of the IPO, and (iii) 477,725 shares of unvested restricted stock subject to repurchase by us that may become issuable under the 2021 Plan following such repurchase. The 2021 Plan also provides that an additional number of shares will be added annually to the shares authorized for issuance under the 2021 Plan on the first day of each fiscal year, beginning with the fiscal year ended December 31, 2022 and continuing until, and including, the fiscal year ending December 31, 2031. The number of shares added each year will be equal to the lesser of (i) 5% of the number of outstanding common stock on such date and (ii) such amount as determined by our board of directors. As of June 30, 2024, a total of 4,911,502 additional shares have been added to the total shares authorized for issuance under the 2021 Plan in accordance with these terms. 2021 Employee Stock Purchase Plan The 2021 ESPP permits eligible employees to purchase shares of our common stock at a discount and consists of consecutive six-month offering periods, each containing a single six-month purchase period. On the first day of each offering period, each employee who is enrolled in the 2021 ESPP will automatically receive an option to purchase up to a whole number of shares of our common stock. The purchase price of each of the shares purchased, in a given purchase period, will be equal to 85% of the lesser of the closing price of a share of our common stock on (i) the first day of the offering period, or (ii) the last day of the offering period. During the six months ended June 30, 2024 and 2023, 35,180 shares and 28,739 shares, respectively, of our common stock were purchased by participants of the 2021 ESPP. Stock-Based Compensation Expense Total stock-based compensation expense recognized in the condensed consolidated statements of operations was as follows:
| Three Months Ended June 30, |  | Six Months Ended June 30,
| 2024 |  | 2023 |  | 2024 |  | 2023
| (in thousands)
Research and development | $ | 1,516 |  |  | $ | 1,019 |  |  | $ | 2,698 |  |  | $ | 2,039 |
General and administrative | 1,086 |  |  | 911 |  |  | 2,209 |  |  | 1,999 |
Total stock-based compensation | $ | 2,602 |  |  | $ | 1,930 |  |  | $ | 4,907 |  |  | $ | 4,038 |
RSA Activity We may, at our discretion, repurchase unvested shares of restricted stock issued pursuant to the 2017 Plan at the initial purchase price if the employees or non-employees terminate their service relationship with us. The shares are recorded in stockholders’ deficit as they vest. As of December 31, 2023, all RSAs granted to employees or non-employees had become fully vested or had been previously forfeited. No RSAs were granted during the six months ended June 30, 2024. Accordingly, we had no unrecognized stock-based compensation expense related to unvested RSAs as of June 30, 2024. The aggregate fair value of RSAs that vested during the three and six months ended June 30, 2023, based upon the fair values of the stock underlying the RSAs on the date of vesting, was $0.1 million and $0.2 million, respectively. RSU Activity We have granted RSUs to our employees under the 2021 Plan. The following table summarizes RSU activity during the six months ended June 30, 2024:
| Shares/Units |  | Weighted-Average Grant Date Fair Value Per Share
| (in thousands)
Unvested at December 31, 2023 | 361,500 |  |  | $ | 3.92 |
Granted | — |  |  | $ | — |
Vested | (211,500) |  |  | $ | 4.97 |
Forfeited | — |  |  | $ | — |
Unvested at June 30, 2024 | 150,000 |  |  | $ | 2.45 |
As of June 30, 2024, we had unrecognized stock-based compensation expense related to unvested RSUs of $0.2 million, which we expect to recognize over a weighted-average period of approximately 0.4 years. The aggregate fair value of RSUs that vested during the three and six months ended June 30, 2024, was $0.7 million based upon the fair value of the stock underlying the RSUs on the day of vesting. No RSUs vested during the three and six months ended June 30, 2023. Stock Option Activity During the year ended December 31, 2022, we granted performance-based stock options to certain executive officers for the purchase of an aggregate of 883,352 shares of common stock with a grant date fair value of $3.36 per share. These stock options would have vested only upon achievement of specified performance targets related to certain business objectives on or before December 31, 2023. As of June 30, 2023, none of these options were vested because none of the specified performance targets had been achieved. Because achievement of the specified performance targets was not deemed probable as of June 30, 2023, we did not record any expense for these stock options during the three or six months ended June 30, 2023. As of December 31, 2023, the specified performance targets had not been achieved, and accordingly, all outstanding performance-based stock options expired without vesting. No additional performance-based stock options have been granted during the three or six months ended June 30, 2024. The fair value of stock options granted during the three and six months ended June 30, 2024 and 2023 was calculated on the date of grant using the following weighted-average assumptions:
| Three Months Ended June 30, |  | Six Months Ended June 30,
| 2024 |  | 2023 |  | 2024 |  | 2023
Risk-free interest rate | 4.5 | % |  | 3.8 | % |  | 4.0 | % |  | 3.9 | %
Expected term (in years) | 5.5 |  | 5.7 |  | 6.0 |  | 6.0
Expected annual dividend yield | — | % |  | — | % |  | — | % |  | — | %
Expected volatility | 92.6 | % |  | 82.6 | % |  | 92.6 | % |  | 82.6 | %
Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the three months ended June 30, 2024 and 2023 was $3.68 and $2.24 per share, respectively. Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the six months ended June 30, 2024 and 2023 was $3.60 and $1.55 per share, respectively. The following table summarizes stock option activity during the six months ended June 30, 2024:
| Options Outstanding
| Number of Options |  | Weighted-Average Exercise Price per Share |  | Weighted-Average Remaining Contractual Life (in years) |  | Aggregate Intrinsic Value (in millions)
Outstanding at December 31, 2023 | 5,700,070 |  |  | $ | 6.89 |  |  |  |  |
Granted | 2,205,112 |  |  | $ | 4.66 |  |  |  |  |
Exercised | (6,099) |  |  | $ | 2.05 |  |  |  |  |
Cancelled | (389,050) |  |  | $ | 5.06 |  |  |  |  |
Outstanding at June 30, 2024 | 7,510,033 |  |  | $ | 6.33 |  |  | 7.85 |  | $ | 0.8 |
Exercisable at June 30, 2024 | 4,100,266 |  |  | $ | 7.25 |  |  | 7.09 |  | $ | 0.5 |
The aggregate intrinsic fair value of stock options exercised during the three and six months ended June 30, 2024 and 2023 was nominal for each period. As of June 30, 2024, we had unrecognized stock-based compensation expense related to unvested stock options of $12.4 million, which we expect to recognize over a weighted-average period of approximately 2.5 years.

X
- Definition The entire disclosure for share-based payment arrangement. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org/718/tableOfContent Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (h)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (h)(2)(i) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Topic 718 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (l) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480429/718-10-50-2 + Details
Name: | us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration