Equity Incentive Plans and Stock Based Compensation (Tables)
|
12 Months Ended |
Dec. 31, 2022 |
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
|
Summary of Stock Option Activity Under Equity Incentive Plan |
The following table summarizes information about stock option activity for years ended December 31, 2022 and 2021:
|
|
Outstanding Options
Number of Shares
|
|
|
Weighted Average
Exercise Price
|
|
|
Weighted Average
Remaining
Contractual Term
|
|
|
Aggregate Intrinsic
Value (in millions):
|
|
Balances, December 31, 2020
|
|
|
6,697,927
|
|
|
$
|
9.13
|
|
|
|
7.76
|
|
|
$
|
13.79
|
|
Granted
|
|
|
2,683,818
|
|
|
$
|
12.84
|
|
|
|
|
|
|
|
|
|
Exercised
|
|
|
(320,716
|
)
|
|
$
|
5.05
|
|
|
|
|
|
|
|
|
|
Cancelled
|
|
|
(1,206,556
|
)
|
|
$
|
11.46
|
|
|
|
|
|
|
|
|
|
Balances, December 31, 2021
|
|
|
7,854,473
|
|
|
$
|
10.21
|
|
|
|
6.72
|
|
|
$
|
0.95
|
|
Granted
|
|
|
2,920,189
|
|
|
$
|
2.21
|
|
|
|
|
|
|
|
|
|
Exercised
|
|
|
(46,598
|
)
|
|
$
|
0.71
|
|
|
|
|
|
|
|
|
|
Cancelled
|
|
|
(2,281,601
|
)
|
|
$
|
9.44
|
|
|
|
|
|
|
|
|
|
Balances, December 31, 2022
|
|
|
8,446,463
|
|
|
$
|
7.70
|
|
|
|
7.09
|
|
|
$
|
-
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Vested and expected to vest, December 31, 2022
|
|
|
8,446,463
|
|
|
$
|
7.70
|
|
|
|
7.09
|
|
|
$
|
-
|
|
Exercisable at December 31, 2022
|
|
|
4,852,746
|
|
|
$
|
8.91
|
|
|
|
6.07
|
|
|
$
|
-
|
|
|
Stock Options Outstanding and Exercisable by Exercise Price |
At December 31, 2022, stock options outstanding and exercisable by exercise price were as follows:
|
|
|
Options Outstanding
|
|
|
Options Exercisable
|
|
Range of
Exercise
Prices
|
|
Number
Outstanding
|
|
|
Weighted
Average
Remaining
Contractual
Life (Years)
|
|
|
Weighted
Average
Exercise
Price
|
|
|
Number
Exercisable
|
|
|
Weighted
Average
Exercise
Price
|
|
$
|
0.33-1.27
|
|
|
1,058,749
|
|
|
|
7.43
|
|
|
$
|
0.92
|
|
|
|
298,909
|
|
|
$
|
1.27
|
|
$
|
1.70-2.35
|
|
|
87,053
|
|
|
|
8.97
|
|
|
$
|
2.30
|
|
|
|
3,453
|
|
|
$
|
1.85
|
|
$
|
2.77-2.77
|
|
|
1,643,051
|
|
|
|
8.63
|
|
|
$
|
2.77
|
|
|
|
232,303
|
|
|
$
|
2.77
|
|
$
|
3.08-5.81
|
|
|
815,521
|
|
|
|
6.29
|
|
|
$
|
4.71
|
|
|
|
733,059
|
|
|
$
|
4.75
|
|
$
|
6.31-6.31
|
|
|
913,037
|
|
|
|
5.41
|
|
|
$
|
6.31
|
|
|
|
913,037
|
|
|
$
|
6.31
|
|
$
|
6.52-9.40
|
|
|
1,082,012
|
|
|
|
6.08
|
|
|
$
|
8.80
|
|
|
|
945,395
|
|
|
$
|
8.95
|
|
$
|
10.78-13.99
|
|
|
454,814
|
|
|
|
6.04
|
|
|
$
|
12.35
|
|
|
|
310,753
|
|
|
$
|
12.39
|
|
$
|
14.05-14.05
|
|
|
1,259,793
|
|
|
|
7.63
|
|
|
$
|
14.05
|
|
|
|
584,120
|
|
|
$
|
14.05
|
|
$
|
14.50-14.94
|
|
|
961,442
|
|
|
|
7.08
|
|
|
$
|
14.57
|
|
|
|
685,157
|
|
|
$
|
14.57
|
|
$
|
15.43-61.27
|
|
|
170,991
|
|
|
|
7.12
|
|
|
$
|
16.79
|
|
|
|
146,560
|
|
|
$
|
16.89
|
|
$
|
0.33-61.27
|
|
|
8,446,463
|
|
|
|
7.09
|
|
|
$
|
7.70
|
|
|
|
4,852,746
|
|
|
$
|
8.91
|
|
|
Stock-Based Compensation Expense |
Stock-based compensation expense, which consists of the compensation cost for employee stock options and the value of options issued to non-employees for services rendered, was allocated to research and development and general and administrative in the consolidated statements of operations as follows (in thousands):
|
|
Year Ended
December 31,
|
|
|
|
2022
|
|
|
2021
|
|
Research and development
|
|
$
|
6,096
|
|
|
$
|
8,839
|
|
General and administrative
|
|
|
5,813
|
|
|
|
7,792
|
|
Total stock-based compensation
|
|
$
|
11,909
|
|
|
$
|
16,631
|
|
|
Weighted-Average Fair Value Valuation Assumptions |
The fair value of employee stock options was estimated using the following weighted-average assumptions:
|
|
Year Ended
December 31,
|
|
|
|
2022
|
|
|
2021
|
|
Employee Stock Options:
|
|
|
|
|
|
|
|
|
Risk-free interest rate
|
|
|
2.35
|
%
|
|
|
0.93
|
%
|
Expected term (in years)
|
|
|
6.08
|
|
|
|
6.08
|
|
Dividend yield
|
|
|
—
|
|
|
|
—
|
|
Volatility
|
|
|
88.59
|
%
|
|
|
113.25
|
%
|
Weighted-average fair value of stock options granted
|
|
$
|
1.65
|
|
|
$
|
10.81
|
|
|