Equity Incentive Plans and Stock Based Compensation (Tables)
|
12 Months Ended |
Dec. 31, 2021 |
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, 2021 and 2020:
|
|
Outstanding Options
Number of Shares
|
|
|
Weighted Average
Exercise Price
|
|
|
Weighted Average
Remaining
Contractual Term
|
|
|
Aggregate Intrinsic
Value (in millions):
|
|
Balances, December 31, 2019
|
|
|
4,763,062
|
|
|
$
|
6.36
|
|
|
|
8.10
|
|
|
$
|
36.63
|
|
Granted
|
|
|
2,453,506
|
|
|
$
|
14.06
|
|
|
|
|
|
|
|
|
|
Exercised
|
|
|
(261,260
|
)
|
|
$
|
3.99
|
|
|
|
|
|
|
|
|
|
Cancelled
|
|
|
(257,381
|
)
|
|
$
|
9.99
|
|
|
|
|
|
|
|
|
|
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
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Vested and expected to vest, December 31, 2021
|
|
|
7,854,473
|
|
|
$
|
10.21
|
|
|
|
6.72
|
|
|
$
|
0.95
|
|
Exercisable at December 31, 2021
|
|
|
4,289,745
|
|
|
$
|
8.75
|
|
|
|
5.81
|
|
|
$
|
0.95
|
|
|
Stock Options Outstanding and Exercisable by Exercise Price |
At December 31, 2021, 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
|
|
$
|
0.71-4.66
|
|
|
1,118,437
|
|
|
|
4.88
|
|
|
$
|
3.55
|
|
|
|
844,087
|
|
|
$
|
3.23
|
|
$
|
4.74-5.81
|
|
|
315,322
|
|
|
|
5.94
|
|
|
$
|
5.08
|
|
|
|
224,149
|
|
|
$
|
5.08
|
|
$
|
6.31-6.31
|
|
|
1,056,037
|
|
|
|
5.71
|
|
|
$
|
6.31
|
|
|
|
951,933
|
|
|
$
|
6.31
|
|
$
|
6.52-9.40
|
|
|
1,312,396
|
|
|
|
7.20
|
|
|
$
|
8.53
|
|
|
|
828,210
|
|
|
$
|
8.86
|
|
$
|
10.78-13.99
|
|
|
795,418
|
|
|
|
6.87
|
|
|
$
|
12.09
|
|
|
|
398,615
|
|
|
$
|
12.08
|
|
$
|
14.05-14.05
|
|
|
1,742,811
|
|
|
|
7.97
|
|
|
$
|
14.05
|
|
|
|
289,148
|
|
|
$
|
14.05
|
|
$
|
14.50-14.50
|
|
|
1,106,337
|
|
|
|
6.75
|
|
|
$
|
14.50
|
|
|
|
513,928
|
|
|
$
|
14.50
|
|
$
|
14.94-42.57
|
|
|
404,079
|
|
|
|
7.78
|
|
|
$
|
15.74
|
|
|
|
236,039
|
|
|
$
|
15.86
|
|
$
|
61.27-61.27
|
|
|
1,818
|
|
|
|
1.37
|
|
|
$
|
61.27
|
|
|
|
1,818
|
|
|
$
|
61.27
|
|
$
|
70.29-70.29
|
|
|
1,818
|
|
|
|
0.37
|
|
|
$
|
70.29
|
|
|
|
1,818
|
|
|
$
|
70.29
|
|
$
|
0.71-70.29
|
|
|
7,854,473
|
|
|
|
6.72
|
|
|
$
|
10.21
|
|
|
|
4,289,745
|
|
|
$
|
8.75
|
|
|
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,
|
|
|
|
2021
|
|
|
2020
|
|
Research and development
|
|
$
|
8,839
|
|
|
$
|
6,387
|
|
General and administrative
|
|
|
7,792
|
|
|
|
5,430
|
|
Total stock-based compensation
|
|
$
|
16,631
|
|
|
$
|
11,817
|
|
|
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,
|
|
|
|
2021
|
|
|
2020
|
|
Employee Stock Options:
|
|
|
|
|
|
|
|
|
Risk-free interest rate
|
|
|
0.93
|
%
|
|
|
1.44
|
%
|
Expected term (in years)
|
|
|
6.08
|
|
|
|
6.08
|
|
Dividend yield
|
|
|
—
|
|
|
|
—
|
|
Volatility
|
|
|
113.25
|
%
|
|
|
110.90
|
%
|
Weighted-average fair value of stock options granted
|
|
$
|
10.81
|
|
|
$
|
11.75
|
|
|