v3.6.0.2

Income Taxes (Tables) | 12 Months Ended
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Dec. 31, 2016
Income Taxes |
Schedule of effective tax rates differing from U.S. federal statutory rate |
|  | December 31, |
|  | 2016 |  |  | 2015 |
|  | (in thousands, except percentages) |
U.S. federal taxes (benefit) at statutory rate |  | $ | (32,277) |  | (34.0) | % |  | $ | (24,375) |  | (34.00) | %
State tax expense |  |  | (2,842) |  | (2.99) | % |  |  | (2,428) |  | (3.39) | %
Research and development credits |  |  | (1,449) |  | (1.53) | % |  |  | (751) |  | (1.05) | %
Stock-based compensation |  |  | 1,275 |  | 1.34 | % |  |  | 1,683 |  | 2.35 | %
Mark to market fair value adjustments |  |  | 49 |  | 0.05 | % |  |  | 504 |  | 0.70 | %
Other nondeductible items |  |  | 933 |  | 0.99 | % |  |  | 841 |  | 1.17 | %
Change in valuation allowance |  |  | 34,453 |  | 36.29 | % |  |  | 24,526 |  | 34.21 | %
Provision for income taxes |  | $ | 142 |  | 0.15 | % |  | $ | — |  | — | %
Schedule of tax effects of temporary differences that give rise to significant portions of the deferred tax assets |
|  | December 31, |
|  | 2016 |  | 2015 |
|  | (in thousands) |
Deferred tax assets |  |  |  |  |  |  |
Net operating loss carryforwards |  | $ | 68,504 |  | $ | 41,451 |
Research and development tax credit carryforwards |  |  | 8,634 |  |  | 4,794 |
Reserves and accruals |  |  | 5,719 |  |  | 3,108 |
Stock-based compensation |  |  | 3,220 |  |  | 2,206 |
Total deferred tax assets before valuation allowance |  |  | 86,077 |  |  | 51,559 |
Less: valuation allowance |  |  | (85,606) |  |  | (51,153) |
|  |  | 471 |  |  | 406 |
Deferred tax liabilities |  |  |  |  |  |  |
Property and equipment |  |  | (471) |  |  | (406) |
Net deferred tax assets |  | $ | — |  | $ | — |
Schedule of reconciliation of the beginning and ending amount of gross unrecognized tax benefits |
|  | December 31, |
|  | 2016 |  | 2015 |
|  | (in thousands) |
Balance at beginning of year |  | $ | 2,405 |  | $ | 1,360 |
Additions based on tax positions related to the current year |  |  | 1,836 |  |  | 1,045 |
Additions for tax positions of prior years |  |  | 52 |  |  | — |
Balance at end of year |  | $ | 4,293 |  | $ | 2,405 |

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