v3.19.3.a.u2

Stock-Based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2019
Share-based Payment Arrangement [Abstract] |
Options Activity | The following table summarizes our option activity as of December 31, 2019 and 2018:
|  | Number of Options |  | Weighted Average Exercise Price per Share |  | Weighted Average Grant Date Fair Value per Share |  | Weighted- Average Remaining Contractual Term |  | Aggregate Intrinsic Value (1) (in thousands)
Outstanding at December 31, 2018 |  | 50,821,132 |  |  | 12.16 |  |  | 6.59 |  |  | 7.1 years |  | 220,434 |
Granted |  | 7,354,268 |  |  | 19.58 |  |  | 11.35 |  |  |  |  |
Exercised |  | (6,945,306 | ) |  | 6.86 |  |  | 4.47 |  |  |  |  |
Canceled/forfeited |  | (5,693,179 | ) |  | 15.17 |  |  | 8.67 |  |  |  |  |
Outstanding at December 31, 2019 |  | 45,536,915 |  |  | 13.82 |  |  | 7.35 |  |  | 7.2 years |  | 286,310 |
Exercisable at December 31, 2019 |  | 22,872,221 |  |  | 10.13 |  |  | 4.86 |  |  | 5.9 years |  | 216,241 |
Expected to vest at December 31, 2019 |  | 22,664,694 |  |  | 17.54 |  |  | 9.86 |  |  | 8.6 years |  | 70,069 |
_______ (1)Aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of common stock for those options in the money as of December 31, 2019.
Restricted Common Stock Activity | The following table summarizes our restricted stock activity during the year ended December 31, 2019:
| Number of Shares |  | Weighted Average Grant Date Price per Share
Outstanding, non-vested at December 31, 2018 | 198,597 |  |  | $ | 12.15 |
Issued | — |  |  | — |
Vested | (162,717 | ) |  | 12.15 |
Canceled/forfeited | (35,880 | ) |  | 12.15 |
Outstanding, non-vested at December 31, 2019 | — |  |  | — |
Restricted Common Stock Units Activity | The following table summarizes our restricted stock unit activity during the year ended December 31, 2019:
| Number of Units |  | Weighted Average Grant Date Price per Unit
Outstanding, non-vested at December 31, 2018 | 458,715 |  |  | $ | 11.93 |
Issued | 1,283,662 |  |  | 19.12 |
Vested | (57,344 | ) |  | 11.93 |
Canceled/forfeited | (106,413 | ) |  | 20.25 |
Vested in prior year and settled during the period | (401,371 | ) |  | 11.93 |
Outstanding, non-vested at December 31, 2019 | 1,177,249 |  |  | 19.01 |
Weighted-Average Assumptions Used to Estimate the Fair Value of Options Granted | The weighted-average assumptions used to estimate the fair value of options granted and ESPP for the years ended December 31, 2019, 2018 and 2017 are as follows:
|  | Weighted Average
|  | Years Ended December 31,
|  | 2019 |  | 2018 |  | 2017
Options: |  |  |  |  |  |
Risk-free interest rate |  | 2.29 | % |  | 2.76 | % |  | 2.02 | %
Expected term |  | 6.07 years |  |  | 6.27 years |  |  | 6.21 years |
Expected volatility |  | 61 | % |  | 63 | % |  | 63 | %
Expected dividends |  | — | % |  | — | % |  | — | %
Weighted average fair value per share |  | $ | 11.35 |  |  | $ | 9.33 |  |  | $ | 7.96 |
ESPP: |  |  |  |  |  |
Risk-free interest rate |  | 1.95 | % |  | * |  | *
Expected term |  | 0.50 years |  |  | * |  | *
Expected volatility |  | 53 | % |  | * |  | *
Expected dividends |  | — | % |  | * |  | *
Weighted average fair value per share |  | $ | 5.98 |  |  | * |  | *
_________ * - Not applicable
Stock-Based Compensation Expense | The following table presents the components and classification of stock-based compensation expense for the years ended December 31, 2019, 2018 and 2017 as follows (in thousands):
| Years Ended December 31,
| 2019 |  | 2018 |  | 2017
Options | $ | 74,780 |  |  | $ | 63,288 |  |  | $ | 31,724 |
Restricted common stock and units | 5,125 |  |  | 9,277 |  |  | 8,331 |
Employee stock purchase plan | 1,217 |  |  | — |  |  | — |
Total | $ | 81,122 |  |  | $ | 72,565 |  |  | $ | 40,055 |
Research and development | $ | 48,259 |  |  | $ | 37,659 |  |  | $ | 21,679 |
General and administrative | 32,863 |  |  | 34,906 |  |  | 18,376 |
Total | $ | 81,122 |  |  | $ | 72,565 |  |  | $ | 40,055 |

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