Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation (Tables)
|
6 Months Ended |
Jun. 30, 2022 |
|---|
| Share-Based Payment Arrangement [Abstract] |
|
| Summary of Option Activity |
The following table summarizes option activity under the Company’s 2004 Plan, 2018 Plan and 2021 Plan:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Shares |
|
|
Weighted-
Average
Exercise Price |
|
|
Weighted-
Average
Remaining
Contract Term
(Years) |
|
|
Aggregate
Intrinsic Value
(in thousands) |
|
Stock options outstanding at December 31, 2021 |
|
|
6,512,086 |
|
|
$ |
13.86 |
|
|
|
7.39 |
|
|
$ |
14,955 |
|
Granted |
|
|
1,302,500 |
|
|
$ |
7.17 |
|
|
|
|
|
|
|
Exercised |
|
|
(32,795 |
) |
|
$ |
5.56 |
|
|
|
|
|
|
|
Canceled and forfeited |
|
|
(274,360 |
) |
|
$ |
14.79 |
|
|
|
|
|
|
|
Stock options outstanding at June 30, 2022 |
|
|
7,507,431 |
|
|
$ |
12.70 |
|
|
|
7.40 |
|
|
$ |
252 |
|
Stock options exercisable at June 30, 2022 |
|
|
4,524,709 |
|
|
$ |
13.13 |
|
|
|
6.48 |
|
|
$ |
10 |
|
|
| Schedule of Employee Stock Options Valuation |
For determining stock-based compensation expense, the fair-value-based measurement of each employee stock option was estimated as of the date of grant using the Black-Scholes option-pricing model with assumptions as follows:
|
|
|
|
|
|
|
|
|
|
|
Six Months Ended |
|
|
|
June 30, |
|
|
|
2022 |
|
|
2021 |
|
Expected term (in years) |
|
5.3-6.1 |
|
|
5.3-6.1 |
|
Expected volatility |
|
81.8%-83.4% |
|
|
84.6%-84.9% |
|
Risk-free interest rate |
|
1.7%-3.4% |
|
|
0.6%-1.1% |
|
Expected dividend |
|
|
– |
|
|
|
– |
|
|
| Summary of Status and Activity of Non-vested RSUs |
A summary of the status and activity of non-vested RSUs during the six months ended June 30, 2022 is as follows:
|
|
|
|
|
|
|
|
|
|
|
Number of
shares |
|
|
Weighted
Average
Grant-Date
Fair Value |
|
Non-vested December 31, 2021 |
|
|
2,403,826 |
|
|
$ |
18.43 |
|
Granted |
|
|
2,083,500 |
|
|
|
7.85 |
|
Vested and released |
|
|
(497,106 |
) |
|
|
17.75 |
|
Canceled and forfeited |
|
|
(252,275 |
) |
|
|
15.57 |
|
Non-vested June 30, 2022 |
|
|
3,737,945 |
|
|
$ |
12.82 |
|
|
| Schedule of Fair Value of ESPP Shares Using Option Pricing Model |
The fair value of the ESPP shares is estimated using the Black-Scholes option pricing model. For the six months ended June 30, 2022 and 2021, the fair value of ESPP shares was estimated using the following assumptions:
|
|
|
|
|
|
|
|
|
Six Months Ended |
|
|
June 30, |
|
|
2022 |
|
|
2021 |
|
Expected term (in years) |
0.5 |
|
|
0.5 |
|
Expected volatility |
65.9%-66.3% |
|
|
72.5%-111.4% |
|
Risk-free interest rate |
0.1%-0.9% |
|
|
|
0.1 |
% |
Expected dividend |
|
– |
|
|
|
– |
|
|
| Schedule of Stock-Based Compensation Expense Recognized |
Total stock-based compensation expense recognized was as follows:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Three Months Ended |
|
|
Six Months Ended |
|
|
|
June 30, |
|
|
June 30, |
|
|
|
2022 |
|
|
2021 |
|
|
2022 |
|
|
2021 |
|
|
|
(in thousands) |
|
|
(in thousands) |
|
Research and development expense: |
|
$ |
2,271 |
|
|
$ |
1,845 |
|
|
$ |
4,884 |
|
|
$ |
2,949 |
|
General and administrative expense: |
|
|
4,425 |
|
|
|
4,062 |
|
|
|
8,786 |
|
|
|
6,910 |
|
Total |
|
$ |
6,696 |
|
|
$ |
5,907 |
|
|
$ |
13,670 |
|
|
$ |
9,859 |
|
|