Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation (Tables)
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9 Months Ended |
Sep. 30, 2020 |
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| Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] |
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| Summary of Option Activity |
The following table summarizes option activity under the Company’s 2004 Plan and 2018 Plan:
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|
|
Shares
|
|
|
Weighted-
Average
Exercise Price
|
|
|
Weighted-
Average
Remaining
Contract Term
(Years)
|
|
|
Aggregate
Intrinsic Value
(in thousands)
|
|
|
Stock options outstanding at December 31, 2019
|
|
|
3,872,664
|
|
|
$
|
12.89
|
|
|
|
7.88
|
|
|
$
|
2,119
|
|
|
Granted
|
|
|
1,655,078
|
|
|
$
|
8.96
|
|
|
|
|
|
|
|
|
|
|
Exercised
|
|
|
(26,502
|
)
|
|
$
|
6.49
|
|
|
|
|
|
|
|
|
|
|
Canceled and forfeited
|
|
|
(112,989
|
)
|
|
$
|
10.45
|
|
|
|
|
|
|
|
|
|
|
Stock options outstanding at September 30, 2020
|
|
|
5,388,251
|
|
|
$
|
11.77
|
|
|
|
7.82
|
|
|
$
|
3,425
|
|
|
Stock options exercisable at September 30, 2020
|
|
|
2,482,870
|
|
|
$
|
12.48
|
|
|
|
6.69
|
|
|
$
|
1,389
|
|
|
| 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:
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Nine Months Ended
|
|
|
|
|
September 30,
|
|
|
|
|
2020
|
|
|
2019
|
|
|
Expected term (in years)
|
|
5.06-7.01
|
|
|
5.07-7.01
|
|
|
Expected volatility
|
|
73.15%-84.24%
|
|
|
72.89%-74.89%
|
|
|
Risk-free interest rate
|
|
0.16%-1.62%
|
|
|
1.42%-2.55%
|
|
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Expected dividend
|
|
|
–
|
|
|
|
–
|
|
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| Summary of Status and Activity of Non-vested RSUs |
A summary of the status and activity of non-vested RSUs at September 30, 2020 is as follows:
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Number of
shares
|
|
|
Weighted
Average
Grant-Date
Fair Value
|
|
|
Non-vested December 31, 2019
|
|
|
335,799
|
|
|
$
|
13.49
|
|
|
Granted
|
|
|
505,250
|
|
|
$
|
8.21
|
|
|
Vested and released
|
|
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(151,976
|
)
|
|
$
|
14.03
|
|
|
Canceled and forfeited
|
|
|
(36,898
|
)
|
|
$
|
9.10
|
|
|
Non-vested September 30, 2020
|
|
|
652,175
|
|
|
$
|
9.52
|
|
|
| Schedule of Fair Value of ESPP Shares Using Option Pricing Model |
For the nine months ended September 30, 2020, the fair value of ESPP shares was estimated using the following assumptions:
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Nine Months Ended
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|
September 30,
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|
|
|
2020
|
|
|
2019
|
|
|
Expected term (in years)
|
0.5
|
|
|
0.5
|
|
|
Expected volatility
|
|
94.10
|
%
|
|
|
63.04
|
%
|
|
Risk-free interest rate
|
|
0.38
|
%
|
|
|
1.92
|
%
|
|
Expected dividend
|
|
–
|
|
|
|
–
|
|
|
| Schedule of Stock-Based Compensation Expense Recognized |
Total stock-based compensation expense recognized was as follows:
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|
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Three Months Ended
|
|
|
Nine Months Ended
|
|
|
|
|
September 30,
|
|
|
September 30,
|
|
|
|
|
2020
|
|
|
2019
|
|
|
2020
|
|
|
2019
|
|
|
|
|
(in thousands)
|
|
|
(in thousands)
|
|
|
Research and development expense:
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|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Stock options
|
|
$
|
403
|
|
|
$
|
259
|
|
|
$
|
987
|
|
|
$
|
732
|
|
|
Restricted stock units
|
|
|
210
|
|
|
|
190
|
|
|
|
617
|
|
|
|
493
|
|
|
ESPP
|
|
|
148
|
|
|
|
218
|
|
|
|
368
|
|
|
|
295
|
|
|
Subtotal
|
|
|
761
|
|
|
|
667
|
|
|
|
1,972
|
|
|
|
1,520
|
|
|
General and administrative expense:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Stock options
|
|
|
1,799
|
|
|
|
1,766
|
|
|
|
5,257
|
|
|
|
4,920
|
|
|
Restricted stock units
|
|
|
532
|
|
|
|
381
|
|
|
|
1,521
|
|
|
|
1,095
|
|
|
ESPP
|
|
|
20
|
|
|
|
66
|
|
|
|
80
|
|
|
|
94
|
|
|
Subtotal
|
|
|
2,351
|
|
|
|
2,213
|
|
|
|
6,858
|
|
|
|
6,109
|
|
|
Total
|
|
$
|
3,112
|
|
|
$
|
2,880
|
|
|
$
|
8,830
|
|
|
$
|
7,629
|
|
|
|
|
|
|
|
|
|
|
|
|
|
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|
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|
| Summary of the Status of Call Options |
A summary of the status of the call options at September 30, 2020 and at December 31, 2019 is as follows:
|
|
|
September 30,
|
|
|
December 31,
|
|
|
|
|
2020
|
|
|
2019
|
|
|
|
|
Shares
|
|
|
Shares
|
|
|
Options vested and exercised
|
|
|
191,153
|
|
|
|
191,153
|
|
|
Options vested and outstanding
|
|
|
66,681
|
|
|
|
-
|
|
|
Options unvested and outstanding
|
|
|
8,890
|
|
|
|
75,571
|
|
|
Total options granted
|
|
|
266,724
|
|
|
|
266,724
|
|
|